Publications by authors named "Rama R Amara"

35 Publications

The C3/465 glycan hole cluster in BG505 HIV-1 envelope is the major neutralizing target involved in preventing mucosal SHIV infection.

PLoS Pathog 2021 Feb 8;17(2):e1009257. Epub 2021 Feb 8.

Emory Vaccine Center, Emory University, Atlanta, Georgia, United States of America.

Stabilized HIV-1 envelope (Env) trimers elicit tier 2 autologous neutralizing antibody (nAb) responses in immunized animals. We previously demonstrated that BG505 SOSIP.664.T332N gp140 (BG505 SOSIP) immunization of rhesus macaques (RM) provided robust protection against autologous intra-vaginal simian-human immunodeficiency virus (SHIV) challenge that was predicted by high serum nAb titers. Here, we show that nAb in these protected RM targeted a glycan hole proximal to residue 465 in gp120 in all cases. nAb also targeted another glycan hole at residues 241/289 and an epitope in V1 at varying frequencies. Non-neutralizing antibodies directed at N611-shielded epitopes in gp41 were also present but were more prevalent in RM with low nAb titers. Longitudinal analysis demonstrated that nAb broadened in some RM during sequential immunization but remained focused in others, the latter being associated with increases in nAb titer. Thirty-eight monoclonal antibodies (mAbs) isolated from a protected RM with an exceptionally high serum neutralization titer bound to the trimer in ELISA, and four of the mAbs potently neutralized the BG505 Env pseudovirus (PV) and SHIV. The four neutralizing mAbs were clonally related and targeted the 465 glycan hole to varying degrees, mimicking the serum. The data demonstrate that the C3/465 glycan hole cluster was the dominant neutralization target in high titer protected RM, despite other co-circulating neutralizing and non-neutralizing specificities. The isolation of a neutralizing mAb family argues that clonotype expansion occurred during BG505 SOSIP immunization, leading to high titer, protective nAb and setting a desirable benchmark for HIV vaccines.
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http://dx.doi.org/10.1371/journal.ppat.1009257DOI Listing
February 2021

Clinical and whole genome characterization of SARS-CoV-2 in India.

PLoS One 2021 2;16(2):e0246173. Epub 2021 Feb 2.

Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad, Hyderabad, India.

We report clinical profile of hundred and nine patients with SARS CoV-2 infection, and whole genome sequences (WGS) of seven virus isolates from the first reported cases in India, with various international travel histories. Comorbidities such as diabetes, hypertension, and cardiovascular disease were frequently associated with severity of the disease. WBC and neutrophil counts showed an increase, while lymphocyte counts decreased in patients with severe infection suggesting a possible neutrophil mediated organ damage, while immune activity may be diminished with decrease in lymphocytes leading to disease severity. Increase in SGOT, SGPT and blood urea suggests the functional deficiencies of liver, heart, and kidney in patients who succumbed to the disease when compared to the group of recovered patients. The WGS analysis showed that these isolates were classified into two clades: I/A3i, and A2a (four according to GISAID: O, L, GR, and GH). Further, WGS phylogeny and travel history together indicate possible transmission from Middle East and Europe. Three S protein variants: Wuhan reference, D614G, and Y28H were identified predicted to possess different binding affinities to host ACE2.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0246173PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7853523PMC
February 2021

Ex vivo rectal explant model reveals potential opposing roles of Natural Killer cells and Marginal Zone-like B cells in HIV-1 infection.

Sci Rep 2020 11 19;10(1):20154. Epub 2020 Nov 19.

Division of Infectious Disease, The Hope Clinic of the Emory Vaccine Center, Emory University School of Medicine, Decatur, GA, 30030, USA.

Our understanding of innate immune responses in human rectal mucosal tissues (RM) and their contributions to promoting or restricting HIV transmission is limited. We defined the RM composition of innate and innate-like cell subsets, including plasmacytoid dendritic cells; CD1c + myeloid DCs; neutrophils; macrophages; natural killer cells (NK); Marginal Zone-like B cells (MZB); γδ T cells; and mucosal-associated invariant T cells in RM from 69 HIV-negative men by flow cytometry. Associations between these cell subsets and HIV-1 replication in ex vivo RM explant challenge experiments revealed an inverse correlation between RM-NK and p24 production, in contrast to a positive association between RM-MZB and HIV replication. Comparison of RM and blood-derived MZB and NK illustrated qualitative and quantitative differences between tissue compartments. Additionally, 22 soluble molecules were measured in a subset of explant cultures (n = 26). Higher production of IL-17A, IFN-γ, IL-10, IP-10, GM-CSF, sFasL, Granzyme A, Granzyme B, Granulysin, and Perforin following infection positively correlated with HIV replication. These data show novel associations between MZB and NK cells and p24 production in RM and underscore the importance of inflammatory cytokines in mucosal HIV infection, demonstrating the likely critical role these innate immune responses play in early mucosal HIV replication in humans.
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http://dx.doi.org/10.1038/s41598-020-76976-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7677325PMC
November 2020

Systematic Assessment of Antiviral Potency, Breadth, and Synergy of Triple Broadly Neutralizing Antibody Combinations against Simian-Human Immunodeficiency Viruses.

J Virol 2021 Jan 13;95(3). Epub 2021 Jan 13.

Duke Human Vaccine Institute, Duke University, Durham, North Carolina, USA

Daily burden and clinical toxicities associated with antiretroviral therapy (ART) emphasize the need for alternative strategies to induce long-term human immunodeficiency virus (HIV) remission upon ART cessation. Broadly neutralizing antibodies (bNAbs) can both neutralize free virions and mediate effector functions against infected cells and therefore represent a leading immunotherapeutic approach. To increase potency and breadth, as well as to limit the development of resistant virus strains, it is likely that bNAbs will need to be administered in combination. It is therefore critical to identify bNAb combinations that can achieve robust polyfunctional antiviral activity against a high number of HIV strains. In this study, we systematically assessed the abilities of single bNAbs and triple bNAb combinations to mediate robust polyfunctional antiviral activity against a large panel of cross-clade simian-human immunodeficiency viruses (SHIVs), which are commonly used as tools for validation of therapeutic strategies targeting the HIV envelope in nonhuman primate models. We demonstrate that most bNAbs are capable of mediating both neutralizing and nonneutralizing effector functions against cross-clade SHIVs, although the susceptibility to V3 glycan-specific bNAbs is highly strain dependent. Moreover, we observe a strong correlation between the neutralization potencies and nonneutralizing effector functions of bNAbs against the transmitted/founder SHIV CH505. Finally, we identify several triple bNAb combinations comprising of CD4 binding site-, V2-glycan-, and gp120-gp41 interface-targeting bNAbs that are capable of mediating synergistic polyfunctional antiviral activities against multiple clade A, B, C, and D SHIVs. Optimal bNAb immunotherapeutics will need to mediate multiple antiviral functions against a broad range of HIV strains. Our systematic assessment of triple bNAb combinations against SHIVs will identify bNAbs with synergistic, polyfunctional antiviral activity that will inform the selection of candidate bNAbs for optimal combination designs. The identified combinations can be validated in future passive immunization studies using the SHIV challenge model.
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http://dx.doi.org/10.1128/JVI.01667-20DOI Listing
January 2021

Author Correction: Distribution of Functional CD4 and CD8 T cell Subsets in Blood and Rectal Mucosal Tissues.

Sci Rep 2020 Jun 17;10(1):10096. Epub 2020 Jun 17.

The Hope Clinic of the Emory Vaccine Research Center, Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Decatur, GA, 30030, United States.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s41598-020-67062-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7297809PMC
June 2020

T cell-inducing vaccine durably prevents mucosal SHIV infection even with lower neutralizing antibody titers.

Nat Med 2020 06 11;26(6):932-940. Epub 2020 May 11.

Institute for Immunity, Transplantation and Infection, Stanford University School of Medicine, Stanford University, Stanford, CA, USA.

Recent efforts toward an HIV vaccine focus on inducing broadly neutralizing antibodies, but eliciting both neutralizing antibodies (nAbs) and cellular responses may be superior. Here, we immunized macaques with an HIV envelope trimer, either alone to induce nAbs, or together with a heterologous viral vector regimen to elicit nAbs and cellular immunity, including CD8 tissue-resident memory T cells. After ten vaginal challenges with autologous virus, protection was observed in both vaccine groups at 53.3% and 66.7%, respectively. A nAb titer >300 was generally associated with protection but in the heterologous viral vector + nAb group, titers <300 were sufficient. In this group, protection was durable as the animals resisted six more challenges 5 months later. Antigen stimulation of T cells in ex vivo vaginal tissue cultures triggered antiviral responses in myeloid and CD4 T cells. We propose that cellular immune responses reduce the threshold of nAbs required to confer superior and durable protection.
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http://dx.doi.org/10.1038/s41591-020-0858-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303014PMC
June 2020

Impact of T1 CD4 Follicular Helper T Cell Skewing on Antibody Responses to an HIV-1 Vaccine in Rhesus Macaques.

J Virol 2020 02 28;94(6). Epub 2020 Feb 28.

The Center for Immunology and Infectious Diseases, UC Davis, Davis, California, USA

Generating durable humoral immunity through vaccination depends upon effective interactions of follicular helper T (T) cells with germinal center (GC) B cells. T1 polarization of T cells is an important process shaping the success of T-GC B cell interactions by influencing costimulatory and cytokine-dependent T help to B cells. However, the question remains as to whether adjuvant-dependent modulation of T cells enhances HIV-1 vaccine-induced antienvelope (anti-Env) antibody responses. We investigated whether an HIV-1 vaccine platform designed to increase the number of T1-polarized T cells enhances the magnitude and quality of anti-Env antibodies. Utilizing a novel interferon-induced protein 10 (IP-10)-adjuvanted HIV-1 DNA prime followed by a monophosphoryl lipid A and QS-21 (MPLA+QS-21)-adjuvanted Env protein boost (D P) in macaques, we observed higher anti-Env serum IgG titers with greater cross-clade reactivity, specificity for V1V2, and effector functions than in macaques primed with DNA lacking IP-10 and boosted with MPLA-plus-alum-adjuvanted Env protein (DP) The D P vaccine regimen elicited higher anti-Env IgG1 and lower IgG4 antibody levels in serum, showing for the first time that adjuvants can dramatically impact the IgG subclass profile in macaques. The D P regimen also increased vaginal and rectal IgA antibodies to a greater extent. Within lymph nodes, we observed augmented GC B cell responses and the promotion of T1 gene expression profiles in GC T cells. The frequency of GC T cells correlated with both the magnitude and avidity of anti-Env serum IgG. Together, these data suggest that adjuvant-induced stimulation of T1-T cells is an effective strategy for enhancing the magnitude and quality of anti-Env antibody responses. The results of the RV144 trial demonstrated that vaccination could prevent HIV transmission in humans and that longevity of anti-Env antibodies may be key to this protection. Efforts to improve upon the prime-boost vaccine regimen used in RV144 have indicated that booster immunizations can increase serum anti-Env antibody titers but only transiently. Poor antibody durability hampers efforts to develop an effective HIV-1 vaccine. This study was designed to identify the specific elements involved in the immunological mechanism necessary to produce robust HIV-1-specific antibodies in rhesus macaques. By clearly defining immune-mediated pathways that improve the magnitude and functionality of the anti-HIV-1 antibody response, we will have the foundation necessary for the rational development of an HIV-1 vaccine.
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http://dx.doi.org/10.1128/JVI.01737-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7158739PMC
February 2020

Distribution of Functional CD4 and CD8 T cell Subsets in Blood and Rectal Mucosal Tissues.

Sci Rep 2019 05 6;9(1):6951. Epub 2019 May 6.

The Hope Clinic of the Emory Vaccine Research Center, Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Decatur, GA, 30030, United States.

A better understanding of the distribution and functional capacity of CD4 T helper (Th) and CD8 T cytotoxic (Tc) cell subsets in the rectal mucosa (RM), a major site for HIV acquisition and replication, in adults is needed. In this study, we compared the distribution of Th and Tc cell subsets between blood and RM compartments in 62 HIV negative men, focusing primarily on IL-17-producing CD4 and CD8 T cells due to their importance in establishing and maintaining mucosal defenses, and examined associations between the frequencies of Th17 and Tc17 cell subsets and the availability of highly HIV-susceptible target cells in the RM. The RM exhibited a distinct immune cell composition comprised of higher frequencies of Th2, Th17, and Tc17 cells compared to the peripheral blood. The majority of Tc17 cells in RM were quadruple-cytokine producers (IL-17A, IFN-γ, TNF-α, and IL4), whereas most Th17 cells in blood and RM were single IL-17A producers or dual-cytokine producers (IL-17ATNF-α). In a separate cohort of 21 HIV positive men, we observed similar tissue distributions of Th and Tc cell subsets, although Tc17 cell frequencies in both blood and tissues were very low. Higher frequencies of multi-cytokine-producing Th17 and Tc17 cells in RM of HIV negative men positively correlated with increased mucosal HIV target cells, suggesting a need to further characterize the effector functions of these cells and their role in HIV acquisition and pathogenesis.
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http://dx.doi.org/10.1038/s41598-019-43311-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6502862PMC
May 2019

Vaccine induction of antibodies and tissue-resident CD8+ T cells enhances protection against mucosal SHIV-infection in young macaques.

JCI Insight 2019 02 21;4(4). Epub 2019 Feb 21.

Departments of Pathology, and Microbiology & Immunology, Institute for Immunity, Transplantation and Infection, Stanford University, Stanford, California, USA.

Antibodies and cytotoxic T cells represent 2 arms of host defense against pathogens. We hypothesized that vaccines that induce both high-magnitude CD8+ T cell responses and antibody responses might confer enhanced protection against HIV. To test this hypothesis, we immunized 3 groups of nonhuman primates: (a) Group 1, which includes sequential immunization regimen involving heterologous viral vectors (HVVs) comprising vesicular stomatitis virus, vaccinia virus, and adenovirus serotype 5-expressing SIVmac239 Gag; (b) Group 2, which includes immunization with a clade C HIV-1 envelope (Env) gp140 protein adjuvanted with nanoparticles containing a TLR7/8 agonist (3M-052); and (c) Group 3, which includes a combination of both regimens. Immunization with HVVs induced very high-magnitude Gag-specific CD8+ T cell responses in blood and tissue-resident CD8+ memory T cells in vaginal mucosa. Immunization with 3M-052 adjuvanted Env protein induced robust and persistent antibody responses and long-lasting innate responses. Despite similar antibody titers in Groups 2 and 3, there was enhanced protection in the younger animals in Group 3, against intravaginal infection with a heterologous SHIV strain. This protection correlated with the magnitude of the serum and vaginal Env-specific antibody titers on the day of challenge. Thus, vaccination strategies that induce both CD8+ T cell and antibody responses can confer enhanced protection against infection.
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http://dx.doi.org/10.1172/jci.insight.126047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478416PMC
February 2019

Novel Modified Vaccinia Virus Ankara Vector Expressing Anti-apoptotic Gene Delays Apoptosis and Enhances Humoral Responses.

J Virol 2019 03 19;93(5). Epub 2019 Feb 19.

Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA

Modified vaccinia virus Ankara (MVA), an attenuated poxvirus, has been developed as a potential vaccine vector for use against cancer and multiple infectious diseases, including human immunodeficiency virus (HIV). MVA is highly immunogenic and elicits strong cellular and humoral responses in preclinical models and humans. However, there is potential to further enhance the immunogenicity of MVA, as MVA-infected cells undergo rapid apoptosis, leading to faster clearance of recombinant antigens and potentially blunting a greater response. Here, we generated MVA- by replacing the fragmented / genes of MVA with a functional anti-apoptotic gene, , and confirmed its anti-apoptotic function against chemically induced apoptosis In addition, MVA- showed a significant delay in induction of apoptosis in muscle cells derived from mice and humans, as well as in plasmacytoid dendritic cells (pDCs) and CD141 DCs from rhesus macaques, compared to the induction of apoptosis in MVA-infected cells. MVA- expressing simian immunodeficiency virus (SIV) Gag and Pol and HIV envelope (SHIV) (MVA-/SHIV) produced higher levels of envelope in the supernatants than MVA/SHIV-infected DF-1 cells Immunization of BALB/c mice showed induction of higher levels of envelope-specific antibody-secreting cells and memory B cells, higher IgG antibody titers, and better persistence of antibody titers with MVA-/SHIV than with MVA/SHIV. Gene set enrichment analysis of draining lymph node cells from day 1 after immunization showed negative enrichment for interferon responses in MVA-/SHIV-immunized mice compared to the responses in MVA/SHIV-immunized mice. Taken together, these results demonstrate that restoring functionality in MVA significantly delays MVA-induced apoptosis in muscle and antigen-presenting cells and augments vaccine-induced humoral immunity in mice. MVA is an attractive viral vector for vaccine development due to its safety and immunogenicity in multiple species and humans even under conditions of immunodeficiency. Here, to further improve the immunogenicity of MVA, we developed a novel vector, MVA-, by replacing the fragmented anti-apoptotic genes / with a functional version derived from vaccinia virus, Our results show that MVA- significantly delays apoptosis in antigen-presenting cells and muscle cells and augments vaccine-induced humoral immunity in mice, leading to the development of a novel vector for vaccine development against infectious diseases and cancer.
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http://dx.doi.org/10.1128/JVI.01648-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6384055PMC
March 2019

Oral Coadministration of an Intramuscular DNA/Modified Vaccinia Ankara Vaccine for Simian Immunodeficiency Virus Is Associated with Better Control of Infection in Orally Exposed Infant Macaques.

AIDS Res Hum Retroviruses 2019 03 27;35(3):310-325. Epub 2018 Nov 27.

1 Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

The majority of human immunodeficiency virus (HIV) type 1 infections in infants are acquired orally through breastfeeding. Toward development of a pediatric HIV vaccine to prevent breastmilk transmission, we tested the efficacy of a simultaneous oral and intramuscular (IM) vaccination regimen for preventing oral simian immunodeficiency virus (SIV) transmission in infant rhesus macaques. Two groups of neonatal macaques were immunized with DNA encoding SIV virus-like particles (DNA-SIV) on weeks 0 and 3, then boosted with modified vaccinia Ankara (MVA) virus expressing SIV antigens (MVA-SIV) on weeks 6 and 9. One group was prime/boosted by the IM route only. Another group was immunized with DNA by both the IM and topical oral (O) buccal routes, and boosted with MVA-SIV by both the IM and sublingual (SL) routes. A third group of control animals received saline by O + IM routes on weeks 0 and 3, and empty MVA by SL + IM routes on weeks 6 and 9. On week 12, infants were orally challenged once weekly with SIV until infected. The vaccine regimen that included oral routes resulted in reduced peak viremia. The rate of infection acquisition in vaccinated infants was found to be associated with prechallenge intestinal immunoglobulin G (IgG) responses to SIV gp120 and V1V2. Peak viremia was inversely correlated with postinfection intestinal IgG responses to gp120, gp41, and V1V2. These results suggest that codelivery of a pediatric HIV vaccine by an oral route may be superior to IM-only regimens for generating mucosal antibodies and preventing HIV breastmilk transmission in neonates.
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http://dx.doi.org/10.1089/AID.2018.0180DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6434602PMC
March 2019

Combination anti-PD-1 and antiretroviral therapy provides therapeutic benefit against SIV.

JCI Insight 2018 09 20;3(18). Epub 2018 Sep 20.

Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA.

Therapeutic strategies that augment antiviral immunity and reduce the viral reservoir are critical to achieving durable remission of HIV. The coinhibitory receptor programmed death-1 (PD-1) regulates CD8+ T cell dysfunction during chronic HIV and SIV infections. We previously demonstrated that in vivo blockade of PD-1 during chronic SIV infection improves the function of antiviral CD8+ T cells and B cells. Here, we tested the immunological and virological effects of PD-1 blockade combined with antiretroviral therapy (ART) in rhesus macaques. Administration of anti-PD-1 antibody 10 days prior to ART initiation rapidly enhanced antiviral CD8+ T cell function and diminished IFN-stimulated genes. This resulted in faster viral suppression in plasma and better Th17 cell reconstitution in the rectal mucosa following ART initiation. PD-1 blockade during ART resulted in lower levels of cell-associated replication-competent virus. Following ART interruption, PD-1 antibody-treated animals showed markedly higher expansion of proliferating CXCR5+perforin+granzyme B+ effector CD8+ T cells and lower regulatory T cells that resulted in better control of viremia. Our results show that PD-1 blockade can be administered safely with ART to augment antiviral CD8+ T cell function and reduce the viral reservoir, leading to improved control of viral rebound after ART interruption.
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http://dx.doi.org/10.1172/jci.insight.122940DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237231PMC
September 2018

A simultaneous oral and intramuscular prime/sublingual boost with a DNA/Modified Vaccinia Ankara viral vector-based vaccine induces simian immunodeficiency virus-specific systemic and mucosal immune responses in juvenile rhesus macaques.

J Med Primatol 2018 10 11;47(5):288-297. Epub 2018 Sep 11.

Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.

Background: A pediatric vaccine to prevent breast milk transmission of human immunodeficiency virus (HIV) may generate greater immune responses at viral entry sites if given by an oral route.

Methods: We compared immune responses induced in juvenile macaques by prime/boosting with simian immunodeficiency virus (SIV)-expressing DNA/modified vaccinia Ankara virus (MVA) by the intramuscular route (IM), the oral (O)/tonsillar routes (T), the O/sublingual (SL) routes, and O+IM/SL routes.

Results: O/T or O/SL immunization generated SIV-specific T cells in mucosal tissues but failed to induce SIV-specific IgA in saliva or stool or IgG in plasma. IM/IM or O+IM/SL generated humoral and cellular responses to SIV. IM/IM generated greater frequencies of T in spleen, but O+IM/SL animals had higher avidity plasma IgG and more often demonstrated mucosal IgA responses.

Conclusion: These results suggest that codelivery of HIV DNA/MVA vaccines by the oral and IM routes might be optimal for generating both systemic and mucosal antibodies.
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http://dx.doi.org/10.1111/jmp.12372DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6158111PMC
October 2018

Effect of Chronic Social Stress on Prenatal Transfer of Antitetanus Immunity in Captive Breeding Rhesus Macaques ().

J Am Assoc Lab Anim Sci 2018 07 15;57(4):357-367. Epub 2018 May 15.

Divisions of Animal Resources, Developmental and Cognitive Neurosciences, Yerkes National Primate Research Center, Emory University School of Medicine, Atlanta, Georgia, Departments of Pathology and Laboratory Medicine, Emory University School of Medicine, Atlanta, Georgia;, Email:

Because tetanus can cause significant morbidity and mortality in NHP, colonywide vaccination with tetanus toxoid is recommended for outdoor breeding colonies of rhesus macaques, with primary immunizations commonly given to infants at 6 mo of age followed by booster vaccines every 10 y. Maternal antibodies are thought to offer protective immunity to infants younger than 6 mo. However, historical colony data from the Yerkes National Primate Research Center show a higher incidence of tetanus among infants (≤ 6 mo old) born to subordinate dams. Whether this higher incidence of infantile tetanus is due to a higher incidence of trauma among subordinate animals or is a stress-induced impairment of maternal antibody protection is unknown. Studies in other NHP species suggest that chronic exposure to social stressors interferes with the receptor-mediated transplacental transfer of IgG. Therefore, the primary aim of this study was to determine whether chronic stress associated with social subordination impairs prenatal transfer of antitetanus immunity in breeding female rhesus macaques. Subjects included 26 high- and 26 low-ranking adult female rhesus macaques that were nearly 5 or 10 y after their initial immunization and their nonimmunized infants. We hypothesized that infants born to subordinate dams that were nearly 10 y after immunization would have the lowest infant-to-dam antibody ratios and thus would be at greatest risk for infection. Results revealed no significant intergroup differences in infant antitetanus IgG levels. However, infant-to-dam IgG ratios against tetanus were significantly lower among subordinate animals compared with dominant macaques, after accounting for the number of years since the dam's initial vaccination. In addition, higher maternal hair cortisol levels predicted lower infantto-dam tetanus toxoid IgG ratios. Together, these findings suggest that chronic social stress in female rhesus macaques may hamper the prenatal transfer of antitetanus immunity to offspring.
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http://dx.doi.org/10.30802/AALAS-JAALAS-17-000102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6059219PMC
July 2018

Correlates of Protection Against SIV Infection in Rhesus Macaques Immunized With Chimpanzee-Derived Adenovirus Vectors.

EBioMedicine 2018 May 4;31:25-35. Epub 2018 Mar 4.

Wistar Institute, Philadelphia, PA, United States. Electronic address:

We report on prime-boost vaccine regimens with two simian adenovirus (Ad) vectors (SAdV) or two human serotype Ad vectors (HAdV) expressing Gag and gp160 of simian immunodeficiency virus (SIV) tested in HAdV-seropositive rhesus macaques (RMs) repeatedly challenged rectally with low doses of SIV Both vaccine regimens reduced set point and peak viral loads (PVL) and accelerated viral clearance. In SAdV-vaccinated controller genotype RMs resistance against infection correlated with levels of envelope (Env)-specific antibody (Ab) titers. In both vaccine groups CD8T cells controlled viral loads (VL) upon infection. Circulating CD4 and CD8 T cells showed significant changes in their transcriptome over time following vaccination, which differed between the vaccine groups. T cells from SIV-resistant RMs had unique transcriptional profiles indicating that both follicular T helper (T) cell responses and highly activated CD8 T cells may play a role in protection.
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http://dx.doi.org/10.1016/j.ebiom.2018.02.025DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6013748PMC
May 2018

Intragastric Administration of Lactobacillus plantarum and 2,2'-Dithiodipyridine-Inactivated Simian Immunodeficiency Virus (SIV) Does Not Protect Indian Rhesus Macaques from Intrarectal SIV Challenge or Reduce Virus Replication after Transmission.

J Virol 2018 05 27;92(10). Epub 2018 Apr 27.

Emory Vaccine Center, Emory University, Atlanta, Georgia, USA

A major obstacle to development of an effective AIDS vaccine is that along with the intended beneficial responses, the immunization regimen may activate CD4 T cells that can facilitate acquisition of human immunodeficiency virus (HIV) by serving as target cells for the virus. Lu et al. (W. Lu et al., Cell Rep 1736-1746, 2012, https://doi.org/10.1016/j.celrep.2012.11.016) reported that intragastric administration of chemically inactivated simian immunodeficiency virus SIV and (iSIV-) protected 15/16 Chinese-origin rhesus macaques (RMs) from high-dose intrarectal SIV challenge at 3 months postimmunization. They attributed the observed protection to induction of immune tolerance, mediated by "MHC-Ib/E-restricted CD8 regulatory T cells that suppressed SIV-harboring CD4 T cell activation and SIV replication in 15/16 animals without inducing SIV-specific antibodies or cytotoxic T." J.-M. Andrieu et al. (Front Immunol 5:297, 2014, https://doi.org/10.3389/fimmu.2014.00297) subsequently reported protection from infection in 23/24 RMs immunized intragastrically or intravaginally with iSIV and BCG, , or , which they ascribed to the same tolerogenic mechanism. Using vaccine materials obtained from our coauthors, we conducted an immunization and challenge experiment with 54 Indian RMs and included control groups receiving iSIV only or only as well as unvaccinated animals. Intrarectal challenge with SIV resulted in rapid infection in all groups of vaccinated RMs as well as unvaccinated controls. iSIV-vaccinated animals that became SIV infected showed viral loads similar to those observed in animals receiving iSIV only or only or in unvaccinated controls. The protection from SIV transmission conferred by intragastric iSIV- administration reported previously for Chinese-origin RMs was not observed when the same experiment was conducted in a larger cohort of Indian-origin animals. Despite an increased understanding of immune responses against HIV, a safe and effective AIDS vaccine is not yet available. One obstacle is that immunization may activate CD4 T cells that may act as target cells for acquisition of HIV. An alternative strategy may involve induction of a tolerance-inducing response that limits the availability of activated CD4 T cells, thus limiting the ability of virus to establish infection. In this regard, exciting results were obtained for Chinese-origin rhesus macaques by using a "tolerogenic" vaccine, consisting of intragastric administration of and 2,2'-dithiodipyridine-inactivated SIV, which showed highly significant protection from virus transmission. In the present study, we administered iSIV- to Indian-origin rhesus macaques and failed to observe any protective effect on virus acquisition in this experimental setting. This work is important because it contributes to the overall assessment of the clinical potential of a new candidate AIDS vaccine platform based on iSIV-.
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http://dx.doi.org/10.1128/JVI.02030-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5923080PMC
May 2018

Characteristics of HIV target CD4 T cells collected using different sampling methods from the genital tract of HIV seronegative women.

PLoS One 2017 1;12(6):e0178193. Epub 2017 Jun 1.

Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, Georgia, United States of America.

Background: Understanding the immune profile of CD4 T cells, the primary targets for HIV, in the female genital tract (FGT) is critical for evaluating and developing effective biomedical HIV prevention strategies in women. However, longitudinal investigation of HIV susceptibility markers expressed by FGT CD4 T cells has been hindered by low cellular yield and risk of sampling-associated trauma. We investigated three minimally invasive FGT sampling methods to characterize and compare CD4 T cell yield and phenotype with the goal of establishing feasible sampling strategies for immune profiling of mucosal CD4 T cells.

Methods And Results: FGT samples were collected bimonthly from 12 healthy HIV negative women of reproductive age in the following order: 1) Cervicovaginal lavage (CVL), 2) two sequential endocervical flocked swabs (FS), and 3) two sequential endocervical cytobrushes (CB1, CB2). Cells were isolated and phentoyped via flow cytometry. CD4 T cell recovery was highest from each individual CB compared to either CVL or FS (p < 0.0001). The majority of CD4 T cells within the FGT, regardless of sampling method, expressed CCR5 relative to peripheral blood (p < 0.01). Within the CB, CCR5+ CD4 T cells expressed significantly higher levels of α4β7, CD69, and low levels of CD27 relative to CCR5- CD4 T cells (all p < 0.001). We also identified CD4 Treg lineage cells expressing CCR5 among CB samples.

Conclusions: Using three different mucosal sampling methods collected longitudinally we demonstrate that CD4 T cells within the FGT express CCR5 and α4β7 and are highly activated, attributes which could act in concert to facilitate HIV acquisition. FS and CB sampling methods can allow for investigation of strategies to reduce HIV target cells in the FGT and could inform the design and interpretation microbicide and vaccine studies in women.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0178193PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5453484PMC
September 2017

Dynamics of SIV-specific CXCR5+ CD8 T cells during chronic SIV infection.

Proc Natl Acad Sci U S A 2017 02 3;114(8):1976-1981. Epub 2017 Feb 3.

Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322;

A significant challenge to HIV eradication is the elimination of viral reservoirs in germinal center (GC) T follicular helper (Tfh) cells. However, GCs are considered to be immune privileged for antiviral CD8 T cells. Here, we show a population of simian immunodeficiency virus (SIV)-specific CD8 T cells express CXCR5 (C-X-C chemokine receptor type 5, a chemokine receptor required for homing to GCs) and expand in lymph nodes (LNs) following pathogenic SIV infection in a cohort of vaccinated macaques. This expansion was greater in animals that exhibited superior control of SIV. The CXCR5+ SIV-specific CD8 T cells demonstrated enhanced polyfunctionality, restricted expansion of antigen-pulsed Tfh cells in vitro and possessed a unique gene expression pattern related to Tfh and Th2 cells. The increase in CXCR5+ CD8 T cells was associated with the presence of higher frequencies of SIV-specific CD8 T cells in the GC. Following TCR-driven stimulation in vitro, CXCR5+ but not CXCR5- CD8 T cells generated both CXCR5+ as well as CXCR5- cells. However, the addition of TGF-β to CXCR5- CD8 T cells induced a population of CXCR5+ CD8 T cells, suggesting that this cytokine may be important in modulating these CXCR5+ CD8 T cells in vivo. Thus, CXCR5+ CD8 T cells represent a unique subset of antiviral CD8 T cells that expand in LNs during chronic SIV infection and may play a significant role in the control of pathogenic SIV infection.
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http://dx.doi.org/10.1073/pnas.1621418114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338410PMC
February 2017

Adjuvanting a Simian Immunodeficiency Virus Vaccine with Toll-Like Receptor Ligands Encapsulated in Nanoparticles Induces Persistent Antibody Responses and Enhanced Protection in TRIM5α Restrictive Macaques.

J Virol 2017 02 31;91(4). Epub 2017 Jan 31.

Emory Vaccine Center/Yerkes National Primate Research Center at Emory University, Atlanta, Georgia, USA

Our previous work has shown that antigens adjuvanted with ligands specific for Toll-like receptor 4 (TLR4) and TLR7/8 encapsulated in poly(lactic-co-glycolic) acid (PLGA)-based nanoparticles (NPs) induce robust and durable immune responses in mice and macaques. We investigated the efficacy of these NP adjuvants in inducing protective immunity against simian immunodeficiency virus (SIV). Rhesus macaques (RMs) were immunized with NPs containing TLR4 and TLR7/8 agonists mixed with soluble recombinant SIVmac239-derived envelope (Env) gp140 and Gag p55 (protein) or with virus-like particles (VLPs) containing SIVmac239 Env and Gag. NP-adjuvanted vaccines induced robust innate responses, antigen-specific antibody responses of a greater magnitude and persistence, and enhanced plasmablast responses compared to those achieved with alum-adjuvanted vaccines. NP-adjuvanted vaccines induced antigen-specific, long-lived plasma cells (LLPCs), which persisted in the bone marrow for several months after vaccination. NP-adjuvanted vaccines induced immune responses that were associated with enhanced protection against repeated low-dose, intravaginal challenges with heterologous SIVsmE660 in animals that carried TRIM5α restrictive alleles. The protection induced by immunization with protein-NP correlated with the prechallenge titers of Env-specific IgG antibodies in serum and vaginal secretions. However, no such correlate was apparent for immunization with VLP-NP or alum as the adjuvant. Transcriptional profiling of peripheral blood mononuclear cells isolated within the first few hours to days after primary vaccination revealed that NP-adjuvanted vaccines induced a molecular signature similar to that induced by the live attenuated yellow fever viral vaccine. This systems approach identified early blood transcriptional signatures that correlate with Env-specific antibody responses in vaginal secretions and protection against infection. These results demonstrate the adjuvanticity of the NP adjuvant in inducing persistent and protective antibody responses against SIV in RMs with implications for the design of vaccines against human immunodeficiency virus (HIV).

Importance: The results of the RV144 HIV vaccine trial, which demonstrated a rapid waning of protective immunity with time, have underscored the need to develop strategies to enhance the durability of protective immune responses. Our recent work in mice has highlighted the capacity of nanoparticle-encapsulated TLR ligands (NP) to induce potent and durable antibody responses that last a lifetime in mice. In the present study, we evaluated the ability of these NP adjuvants to promote robust and durable protective immune responses against SIV in nonhuman primates. Our results demonstrate that immunization of rhesus macaques with NP adjuvants mixed with soluble SIV Env or a virus-like particle form of Env (VLP) induces potent and durable Env-specific antibody responses in the serum and in vaginal secretions. These responses were superior to those induced by alum adjuvant, and they resulted in enhanced protection against a low-dose intravaginal challenge with a heterologous strain of SIV in animals with TRIM5a restrictive alleles. These results highlight the potential for such NP TLR L adjuvants in promoting robust and durable antibody responses against HIV in the next generation of HIV immunogens currently being developed.
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http://dx.doi.org/10.1128/JVI.01844-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5286877PMC
February 2017

INTIMATE PARTNER VIOLENCE IS ASSOCIATED WITH INCREASED CD4 T-CELL ACTIVATION AMONG HIV-NEGATIVE HIGH-RISK WOMEN.

Pathog Immun 2016 ;1(1):193-213

University of Michigan School of Nursing, Department of Health Behavior and Biological Sciences, Ann Arbor, MI.

Background: Biological pathways mediating the link between intimate partner violence (IPV) and increased HIV risk remain unexplored. We hypothesized that IPV-induced stress negatively affects HIV systemic immune defenses and aimed to evaluate whether IPV was associated with immune profiles linked to HIV susceptibility: CD4 activation and diminished regulatory T-cell (Treg) frequency.

Methods: Seventy-five HIV-negative high-risk women were surveyed regarding their IPV experience. They provided blood, urine, and (if present) genital ulcer samples for cortisol, immune assays, and STI testing. Using flow cytometry, we assessed activated CD4 T-cell (%HLA-DR/CD38) and Treg (%CD4CD25FoxP3) frequencies and phenotyping. Nonparametric tests evaluated the association between IPV and immune outcomes. Multivariate regression explored confounding and moderation of the IPV-CD4 activation pathway.

Results: Lifetime IPV was associated with increased CD4 activation (r = 0.331, = 0.004), a shift in CD4 phenotype from naïve to effector memory (r = 0.343, = 0.003), and a decrease in naive (%HLA-DR/CD45RA) Treg frequency (r = -0.337, = 0.003). Experiencing IPV over the past year had similar trends. After controlling for sexual IPV, lifetime physical and psychological abuse remained significantly associated with CD4 activation ( = 0.004 and = 0.033, respectively). After controlling for race (the only covariate linked to activation), the lifetime IPV-CD4 activation association remained significant ( = 0.012). Alcohol use and depression were identified as potential pathway moderators.

Conclusion: Our data is the first to suggest an immune link between IPV and HIV, and may help explain differences at the individual level in HIV susceptibility and response to biological HIV prevention strategies. The association of psychological and physical abuse with CD4 activation independent of sexual abuse further supports the existence of a stress-induced immune pathway.
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http://dx.doi.org/10.20411/pai.v1i1.120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5034930PMC
January 2016

Differences in expression of gut-homing receptors on CD4+ T cells in black and white HIV-negative men who have sex with men.

AIDS 2016 05;30(8):1305-8

aDivision of Infectious Diseases, Department of Medicine, Emory University School of Medicine bDepartment of Epidemiology, Rollins School of Public Health, Emory University cYerkes National Primate Research Center and the Emory Vaccine Center, Emory University dHubert Department of Global Health, Rollins School of Public Health, Emory University School of Medicine, Atlanta, Georgia, USA.

HIV incidence rates are higher among black men who have sex with men (BMSM) as compared with MSM of other race/ethnicities in the USA. We found that blood memory CD4 cells from BMSM express higher levels of α4β7, the gut-homing integrin, compared with white MSM. Higher expression of α4β7 on blood CD4 cells correlated with higher percentage of proliferating CD4α4β7 cells in rectal tissue suggesting increased trafficking of potential HIV target cells to rectal mucosa could increase HIV susceptibility among BMSM.
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http://dx.doi.org/10.1097/QAD.0000000000001062DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851564PMC
May 2016

Signatures in Simian Immunodeficiency Virus SIVsmE660 Envelope gp120 Are Associated with Mucosal Transmission but Not Vaccination Breakthrough in Rhesus Macaques.

J Virol 2016 02 16;90(4):1880-7. Epub 2015 Dec 16.

Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA Emory Vaccine Center, Emory University, Atlanta, Georgia, USA Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, USA

Unlabelled: Mucosal surfaces are vulnerable to human immunodeficiency virus (HIV)/simian immunodeficiency virus (SIV) infection and thus are key sites for eliciting vaccine-mediated protection. Vaccine protocols carried out at the Yerkes Primate Research Center utilized SIVmac239-based immunization strategies with intrarectal and intravaginal SIVsmE660 challenge of rhesus macaques. We investigated whether there were genetic signatures associated with SIVsmE660 intrarectal and intravaginal transmissions in vaccinated and unvaccinated monkeys. When transmitted/founder (T/F) envelope (Env) sequences from 49 vaccinated and 15 unvaccinated macaques were compared to each other, we were unable to identify any vaccine breakthrough signatures. In contrast, when the vaccinated and control T/F Envs were combined and compared to the challenge stock, residues at gp120 positions 23, 45, 47, and 70 (Ile-Ala-Lys-Asn [I-A-K-N]) emerged as signatures of mucosal transmission. However, T/F Envs derived from intrarectal and intravaginal infections were not different. Our data suggest that the vaginal and rectal mucosal environments both imposed a strong selection bias for SIVsmE660 variants carrying I-A-K-N that was not further enhanced by immunization. These findings, combined with the strong conservation of A-K-N in most HIV-2/SIVsmm isolates and the analogous residues in HIV-1/SIVcpz isolates, suggest that these residues confer increased transmission fitness to SIVsmE660.

Importance: Most HIV-1 infections occur across a mucosal barrier, and it is therefore important to understand why these sites are vulnerable and how to protect them with a vaccine. To gain insight into these questions, we studied rhesus macaques that were vaccinated with SIVmac239 and unvaccinated controls to determine whether the SIVsmE660 viral variants that infected these two groups were different. We did not find differences between viral variants in the absence versus presence of vaccination-induced immunity, but we did find that the SIVsmE660 viral variants that infected the monkeys, regardless of vaccination, were different from the dominant population found in the viral challenge inoculum. Our data suggest that the mucosal environments of the vagina and rectum both impose a strong selection for the SIVsmE660 variants in the challenge inoculum that are most like SIV and HIVs that circulate in nature.
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http://dx.doi.org/10.1128/JVI.02711-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734005PMC
February 2016

Decreased T Follicular Regulatory Cell/T Follicular Helper Cell (TFH) in Simian Immunodeficiency Virus-Infected Rhesus Macaques May Contribute to Accumulation of TFH in Chronic Infection.

J Immunol 2015 Oct 21;195(7):3237-47. Epub 2015 Aug 21.

Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA30329;

T follicular helper cells (TFH) are critical for the development and maintenance of germinal center (GC) and humoral immune responses. During chronic HIV/SIV infection, TFH accumulate, possibly as a result of Ag persistence. The HIV/SIV-associated TFH expansion may also reflect lack of regulation by suppressive follicular regulatory CD4(+) T cells (TFR). TFR are natural regulatory T cells (TREG) that migrate into the follicle and, similar to TFH, upregulate CXCR5, Bcl-6, and PD1. In this study, we identified TFR as CD4(+)CD25(+)FOXP3(+)CXCR5(+)PD1(hi)Bcl-6(+) within lymph nodes of rhesus macaques (RM) and confirmed their localization within the GC by immunohistochemistry. RNA sequencing showed that TFR exhibit a distinct transcriptional profile with shared features of both TFH and TREG, including intermediate expression of FOXP3, Bcl-6, PRDM1, IL-10, and IL-21. In healthy, SIV-uninfected RM, we observed a negative correlation between frequencies of TFR and both TFH and GC B cells, as well as levels of CD4(+) T cell proliferation. Post SIV infection, the TFR/TFH ratio was reduced with no change in the frequency of TREG or TFR within the total CD4(+) T cell pool. Finally, we examined whether higher levels of direct virus infection of TFR were responsible for their relative depletion post SIV infection. We found that TFH, TFR, and TREG sorted from SIV-infected RM harbor comparable levels of cell-associated viral DNA. Our data suggest that TFR may contribute to the regulation and proliferation of TFH and GC B cells in vivo and that a decreased TFR/TFH ratio in chronic SIV infection may lead to unchecked expansion of both TFH and GC B cells.
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http://dx.doi.org/10.4049/jimmunol.1402701DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4575868PMC
October 2015

Breakthrough of SIV strain smE660 challenge in SIV strain mac239-vaccinated rhesus macaques despite potent autologous neutralizing antibody responses.

Proc Natl Acad Sci U S A 2015 Aug 10;112(34):10780-5. Epub 2015 Aug 10.

Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329; Emory Vaccine Center, Emory University, Atlanta, GA 30329; Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30329;

Although the correlates of immunological protection from human immunodeficiency virus or simian immunodeficiency virus infection remain incompletely understood, it is generally believed that medium to high titers of serum neutralizing antibodies (nAbs) against the challenge virus will prevent infection. This paradigm is based on a series of studies in which passive transfer of HIV-specific nAbs protected rhesus macaques (RMs) from subsequent mucosal challenge with a chimeric human/simian immunodeficiency virus. However, it is unknown whether nAb titers define protection in the setting of active immunization. Here we determined serum nAb titers against breakthrough transmitted/founder (T/F) SIVsmE660-derived envelope glycoprotein (Env) variants from 14 RMs immunized with SIVmac239-based DNA-prime/modified vaccinia virus Ankara-boost vaccine regimens that included GM-CSF or CD40L adjuvants and conferred significant but incomplete protection against repeated low-dose intrarectal challenge. A single Env variant established infection in all RMs except one, with no identifiable genetic signature associated with vaccination breakthrough compared with T/F Envs from four unvaccinated monkeys. Breakthrough T/F Env pseudoviruses were potently neutralized in vitro by heterologous pooled serum from chronically SIVsmE660-infected monkeys at IC50 titers exceeding 1:1,000,000. Remarkably, the T/F Env pseudoviruses from 13 of 14 monkeys were also susceptible to neutralization by autologous prechallenge serum at in vitro IC50 titers ranging from 1:742-1:10,832. These titers were similar to those observed in vaccinated RMs that remained uninfected. These data suggest that the relationship between serum nAb titers and protection from mucosal SIV challenge in the setting of active immunization is more complex than previously recognized, warranting further studies into the balance between immune activation, target cell availability, and protective antibody responses.
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http://dx.doi.org/10.1073/pnas.1509731112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4553804PMC
August 2015

Characterization and Implementation of a Diverse Simian Immunodeficiency Virus SIVsm Envelope Panel in the Assessment of Neutralizing Antibody Breadth Elicited in Rhesus Macaques by Multimodal Vaccines Expressing the SIVmac239 Envelope.

J Virol 2015 Aug 27;89(16):8130-51. Epub 2015 May 27.

Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA Emory Vaccine Center, Emory University, Atlanta, Georgia, USA Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, USA

Unlabelled: Antibodies that can neutralize diverse viral strains are likely to be an important component of a protective human immunodeficiency virus type 1 (HIV-1) vaccine. To this end, preclinical simian immunodeficiency virus (SIV)-based nonhuman primate immunization regimens have been designed to evaluate and enhance antibody-mediated protection. However, these trials often rely on a limited selection of SIV strains with extreme neutralization phenotypes to assess vaccine-elicited antibody activity. To mirror the viral panels used to assess HIV-1 antibody breadth, we created and characterized a novel panel of 14 genetically and phenotypically diverse SIVsm envelope (Env) glycoproteins. To assess the utility of this panel, we characterized the neutralizing activity elicited by four SIVmac239 envelope-expressing DNA/modified vaccinia virus Ankara vector- and protein-based vaccination regimens that included the immunomodulatory adjuvants granulocyte-macrophage colony-stimulating factor, Toll-like receptor (TLR) ligands, and CD40 ligand. The SIVsm Env panel exhibited a spectrum of neutralization sensitivity to SIV-infected plasma pools and monoclonal antibodies, allowing categorization into three tiers. Pooled sera from 91 rhesus macaques immunized in the four trials consistently neutralized only the highly sensitive tier 1a SIVsm Envs, regardless of the immunization regimen. The inability of vaccine-mediated antibodies to neutralize the moderately resistant tier 1b and tier 2 SIVsm Envs defined here suggests that those antibodies were directed toward epitopes that are not accessible on most SIVsm Envs. To achieve a broader and more effective neutralization profile in preclinical vaccine studies that is relevant to known features of HIV-1 neutralization, more emphasis should be placed on optimizing the Env immunogen, as the neutralization profile achieved by the addition of adjuvants does not appear to supersede the neutralizing antibody profile determined by the immunogen.

Importance: Many in the HIV/AIDS vaccine field believe that the ability to elicit broadly neutralizing antibodies capable of blocking genetically diverse HIV-1 variants is a critical component of a protective vaccine. Various SIV-based nonhuman primate vaccine studies have investigated ways to improve antibody-mediated protection against a heterologous SIV challenge, including administering adjuvants that might stimulate a greater neutralization breadth. Using a novel SIV neutralization panel and samples from four rhesus macaque vaccine trials designed for cross comparison, we show that different regimens expressing the same SIV envelope immunogen consistently elicit antibodies that neutralize only the very sensitive tier 1a SIV variants. The results argue that the neutralizing antibody profile elicited by a vaccine is primarily determined by the envelope immunogen and is not substantially broadened by including adjuvants, resulting in the conclusion that the envelope immunogen itself should be the primary consideration in efforts to elicit antibodies with greater neutralization breadth.
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http://dx.doi.org/10.1128/JVI.01221-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4524250PMC
August 2015

Vaccine-Induced Linear Epitope-Specific Antibodies to Simian Immunodeficiency Virus SIVmac239 Envelope Are Distinct from Those Induced to the Human Immunodeficiency Virus Type 1 Envelope in Nonhuman Primates.

J Virol 2015 Aug 27;89(16):8643-50. Epub 2015 May 27.

Duke Human Vaccine Institute, Duke University Medical Center, Durham, North Carolina, USA Department of Immunology, Duke University Medical Center, Durham, North Carolina, USA Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA Department of Surgery, Duke University Medical Center, Durham, North Carolina, USA

To evaluate antibody specificities induced by simian immunodeficiency virus (SIV) versus human immunodeficiency virus type 1 (HIV-1) envelope antigens in nonhuman primate (NHP), we profiled binding antibody responses to linear epitopes in NHP studies with HIV-1 or SIV immunogens. We found that, overall, HIV-1 Env IgG responses were dominated by V3, with the notable exception of the responses to the vaccine strain A244 Env that were dominated by V2, whereas the anti-SIVmac239 Env responses were dominated by V2 regardless of the vaccine regimen.
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http://dx.doi.org/10.1128/JVI.03635-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4524233PMC
August 2015

DNA/MVA Vaccines for HIV/AIDS.

Vaccines (Basel) 2014 Feb 28;2(1):160-78. Epub 2014 Feb 28.

Emory Vaccine Center, Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA.

Since the initial proof-of-concept studies examining the ability of antigen-encoded plasmid DNA to serve as an immunogen, DNA vaccines have evolved as a clinically safe and effective platform for priming HIV-specific cellular and humoral responses in heterologous "prime-boost" vaccination regimens. Direct injection of plasmid DNA into the muscle induces T- and B-cell responses against foreign antigens. However, the insufficient magnitude of this response has led to the development of approaches for enhancing the immunogenicity of DNA vaccines. The last two decades have seen significant progress in the DNA-based vaccine platform with optimized plasmid constructs, improved delivery methods, such as electroporation, the use of molecular adjuvants and novel strategies combining DNA with viral vectors and subunit proteins. These innovations are paving the way for the clinical application of DNA-based HIV vaccines. Here, we review preclinical studies on the DNA-prime/modified vaccinia Ankara (MVA)-boost vaccine modality for HIV. There is a great deal of interest in enhancing the immunogenicity of DNA by engineering DNA vaccines to co-express immune modulatory adjuvants. Some of these adjuvants have demonstrated encouraging results in preclinical and clinical studies, and these data will be examined, as well.
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http://dx.doi.org/10.3390/vaccines2010160DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4494194PMC
February 2014

Identification of novel markers for mouse CD4(+) T follicular helper cells.

Eur J Immunol 2013 Dec 14;43(12):3219-32. Epub 2013 Oct 14.

Emory Vaccine Center, Emory University School of Medicine, Atlanta, GA, USA; Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA, USA.

CD4(+) T follicular helper (TFH) cells are central for generation of long-term B-cell immunity. A defining phenotypic attribute of TFH cells is the expression of the chemokine R CXCR5, and TFH cells are typically identified by co-expression of CXCR5 together with other markers such as PD-1, ICOS, and Bcl-6. Herein, we report high-level expression of the nutrient transporter folate R 4 (FR4) on TFH cells in acute viral infection. Distinct from the expression profile of conventional TFH markers, FR4 was highly expressed by naive CD4(+) T cells, was downregulated after activation and subsequently re-expressed on TFH cells. Furthermore, FR4 expression was maintained, albeit at lower levels, on memory TFH cells. Comparative gene expression profiling of FR4(hi) versus FR4(lo) Ag-specific CD4(+) effector T cells revealed a molecular signature consistent with TFH and TH1 subsets, respectively. Interestingly, genes involved in the purine metabolic pathway, including the ecto-enzyme CD73, were enriched in TFH cells compared with TH1 cells, and phenotypic analysis confirmed expression of CD73 on TFH cells. As there is now considerable interest in developing vaccines that would induce optimal TFH cell responses, the identification of two novel cell surface markers should be useful in characterization and identification of TFH cells following vaccination and infection.
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http://dx.doi.org/10.1002/eji.201343469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3947211PMC
December 2013

DNA and virus particle vaccination protects against acquisition and confers control of viremia upon heterologous simian immunodeficiency virus challenge.

Proc Natl Acad Sci U S A 2013 Feb 28;110(8):2975-80. Epub 2013 Jan 28.

Human Retrovirus Section, Vaccine Branch, Center for Cancer Research, Frederick National Laboratory for Cancer Research, Frederick, MD 21702, USA.

We have previously shown that macaques vaccinated with DNA vectors expressing SIVmac239 antigens developed potent immune responses able to reduce viremia upon high-dose SIVmac251 challenge. To further improve vaccine-induced immunity and protection, we combined the SIVmac239 DNA vaccine with protein immunization using inactivated SIVmac239 viral particles as protein source. Twenty-six weeks after the last vaccination, the animals were challenged intrarectally at weekly intervals with a titrated dose of the heterologous SIVsmE660. Two of DNA-protein coimmunized macaques did not become infected after 14 challenges, but all controls were infected by 11 challenges. Vaccinated macaques showed modest protection from SIVsmE660 acquisition compared with naïve controls (P = 0.050; stratified for TRIM5α genotype). Vaccinees had significantly lower peak (1.6 log, P = 0.0048) and chronic phase viremia (P = 0.044), with 73% of the vaccinees suppressing viral replication to levels below assay detection during the 40-wk follow-up. Vaccine-induced immune responses associated significantly with virus control: binding antibody titers and the presence of rectal IgG to SIVsmE660 Env correlated with delayed SIVsmE660 acquisition; SIV-specific cytotoxic T cells, prechallenge CD4(+) effector memory, and postchallenge CD8(+) transitional memory cells correlated with control of viremia. Thus, SIVmac239 DNA and protein-based vaccine protocols were able to achieve high, persistent, broad, and effective cellular and humoral immune responses able to delay heterologous SIVsmE660 infection and to provide long-term control of viremia. These studies support a role of DNA and protein-based vaccines for development of an efficacious HIV/AIDS vaccine.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3581900PMC
http://dx.doi.org/10.1073/pnas.1215393110DOI Listing
February 2013