Publications by authors named "Sailaja Gangadhara"

25 Publications

  • Page 1 of 1

A modified vaccinia Ankara vector-based vaccine protects macaques from SARS-CoV-2 infection, immune pathology, and dysfunction in the lungs.

Immunity 2021 Feb 4. Epub 2021 Feb 4.

Emory Vaccine Center, Division of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA; Department of Microbiology and Immunology, Emory School of Medicine, Emory University, Atlanta, GA 30322, USA. Electronic address:

A combination of vaccination approaches will likely be necessary to fully control the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we show that modified vaccinia Ankara (MVA) vectors expressing membrane-anchored pre-fusion stabilized spike (MVA/S) but not secreted S1 induced strong neutralizing antibody responses against SARS-CoV-2 in mice. In macaques, the MVA/S vaccination induced strong neutralizing antibodies and CD8 T cell responses, and conferred protection from SARS-CoV-2 infection and virus replication in the lungs as early as day 2 following intranasal and intratracheal challenge. Single-cell RNA sequencing analysis of lung cells on day 4 after infection revealed that MVA/S vaccination also protected macaques from infection-induced inflammation and B cell abnormalities and lowered induction of interferon-stimulated genes. These results demonstrate that MVA/S vaccination induces neutralizing antibodies and CD8 T cells in the blood and lungs and is a potential vaccine candidate for SARS-CoV-2.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.immuni.2021.02.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7859620PMC
February 2021

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1371/journal.ppat.1009257DOI Listing
February 2021

Cutting Edge: Mouse SARS-CoV-2 Epitope Reveals Infection and Vaccine-Elicited CD8 T Cell Responses.

J Immunol 2021 03 13;206(5):931-935. Epub 2021 Jan 13.

Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN 55455;

The magnitude of SARS-CoV-2-specific T cell responses correlates inversely with human disease severity, suggesting T cell involvement in primary control. Whereas many COVID-19 vaccines focus on establishing humoral immunity to viral spike protein, vaccine-elicited T cell immunity may bolster durable protection or cross-reactivity with viral variants. To better enable mechanistic and vaccination studies in mice, we identified a dominant CD8 T cell SARS-CoV-2 nucleoprotein epitope. Infection of human ACE2 transgenic mice with SARS-CoV-2 elicited robust responses to H2-D/N, and 40% of HLA-A*02 COVID-19 PBMC samples isolated from hospitalized patients responded to this peptide in culture. In mice, i.m. prime-boost nucleoprotein vaccination with heterologous vectors favored systemic CD8 T cell responses, whereas intranasal boosting favored respiratory immunity. In contrast, a single i.v. immunization with recombinant adenovirus established robust CD8 T cell memory both systemically and in the respiratory mucosa.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.2001400DOI Listing
March 2021

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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41591-020-0858-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7303014PMC
June 2020

Strong T1-biased CD4 T cell responses are associated with diminished SIV vaccine efficacy.

Sci Transl Med 2019 11;11(519)

Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329, USA.

Activated CD4 T cells are a major target of HIV infection. Results from the STEP HIV vaccine trial highlighted a potential role for total activated CD4 T cells in promoting HIV acquisition. However, the influence of vaccine insert-specific CD4 T cell responses on HIV acquisition is not known. Here, using the data obtained from four macaque studies, we show that the DNA prime/modified vaccinia Ankara boost vaccine induced interferon γ (IFNγ) CD4 T cells [T helper 1 (T1) cells] rapidly migrate to multiple tissues including colon, cervix, and vaginal mucosa. These mucosal T1 cells persisted at higher frequencies and expressed higher density of CCR5, a viral coreceptor, compared to cells in blood. After intravaginal or intrarectal simian immunodeficiency virus (SIV)/simian-human immunodeficiency virus (SHIV) challenges, strong vaccine protection was evident only in animals that had lower frequencies of vaccine-specific T1 cells but not in animals that had higher frequencies of T1 cells, despite comparable vaccine-induced humoral and CD8 T cell immunity in both groups. An RNA transcriptome signature in blood at 7 days after priming immunization from one study was associated with induction of fewer T1-type CD4 cells and enhanced protection. These results demonstrate that high and persisting frequencies of HIV vaccine-induced T1-biased CD4 T cells in the intestinal and genital mucosa can mitigate beneficial effects of protective antibodies and CD8 T cells, highlighting a critical role of priming immunization and vaccine adjuvants in modulating HIV vaccine efficacy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scitranslmed.aav1800DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7227795PMC
November 2019

Human Immunodeficiency Virus C.1086 Envelope gp140 Protein Boosts following DNA/Modified Vaccinia Virus Ankara Vaccination Fail To Enhance Heterologous Anti-V1V2 Antibody Response and Protection against Clade C Simian-Human Immunodeficiency Virus Challenge.

J Virol 2019 10 30;93(20). Epub 2019 Sep 30.

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

The RV144 human immunodeficiency virus type 1 (HIV-1) vaccine trial showed a strong association between anti-gp70 V1V2 scaffold (V1V2) and anti-V2 hot spot peptide (V2 HS) antibody responses and reduced risk of HIV infection. Accordingly, a primary goal for HIV vaccines is to enhance the magnitude and breadth of V1V2 and V2 HS antibody responses in addition to neutralizing antibodies. Here, we tested the immunogenicity and efficacy of HIV-1 C.1086 gp140 boosts administered sequentially after priming with CD40L-adjuvanted DNA/simian-human immunodeficiency virus (SHIV) and boosting with modified vaccinia virus Ankara (MVA)-SHIV vaccines in rhesus macaques. The DNA/MVA vaccination induced robust vaccine-specific CD4 and CD8 T cell responses with a polyfunctional profile. Two gp140 booster immunizations induced very high levels (∼2 mg/ml) of gp140 binding antibodies in serum, with strong reactivity directed against the homologous (C.1086) V1V2, V2 HS, V3, and gp41 immunodominant (ID) proteins. However, the vaccine-induced antibody showed 10-fold (peak) and 32-fold (prechallenge) weaker binding to the challenge virus (SHIV1157ipd3N4) V1V2 and failed to bind to the challenge virus V2 HS due to a single amino acid change. Point mutations in the immunogen V2 HS to match the V2 HS in the challenge virus significantly diminished the binding of vaccine-elicited antibodies to membrane-anchored gp160. Both vaccines failed to protect from infection following repeated SHIV1157ipd3N4 intrarectal challenges. However, only the protein-boosted animals showed enhanced viral control. These results demonstrate that C.1086 gp140 protein immunizations administered following DNA/MVA vaccination do not significantly boost heterologous V1V2 and V2 HS responses and fail to enhance protection against heterologous SHIV challenge. HIV, the virus that causes AIDS, is responsible for millions of infections and deaths annually. Despite intense research for the past 25 years, there remains no safe and effective vaccine available. The significance of this work is in identifying the pros and cons of adding a protein boost to an already well-established DNA/MVA HIV vaccine that is currently being tested in the clinic. Characterizing the effects of the protein boost can allow researchers going forward to design vaccines that generate responses that will be more effective against HIV. Our results in rhesus macaques show that boosting with a specific HIV envelope protein does not significantly boost antibody responses that were identified as immune correlates of protection in a moderately successful RV144 HIV vaccine trial in humans and highlight the need for the development of improved HIV envelope immunogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.00934-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6798111PMC
October 2019

Clade C HIV-1 Envelope Vaccination Regimens Differ in Their Ability To Elicit Antibodies with Moderate Neutralization Breadth against Genetically Diverse Tier 2 HIV-1 Envelope Variants.

J Virol 2019 04 21;93(7). Epub 2019 Mar 21.

Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Georgia, USA

The goals of preclinical HIV vaccine studies in nonhuman primates are to develop and test different approaches for their ability to generate protective immunity. Here, we compared the impact of 7 different vaccine modalities, all expressing the HIV-1 1086.C clade C envelope (Env), on (i) the magnitude and durability of antigen-specific serum antibody responses and (ii) autologous and heterologous neutralizing antibody capacity. These vaccination regimens included immunization with different combinations of DNA, modified vaccinia virus Ankara (MVA), soluble gp140 protein, and different adjuvants. Serum samples collected from 130 immunized monkeys at two key time points were analyzed using the TZM-bl cell assay: at 2 weeks after the final immunization (week 40/41) and on the day of challenge (week 58). Key initial findings were that inclusion of a gp140 protein boost had a significant impact on the magnitude and durability of Env-specific IgG antibodies, and addition of 3M-052 adjuvant was associated with better neutralizing activity against the SHIV1157ipd3N4 challenge virus and a heterologous HIV-1 CRF01 Env, CNE8. We measured neutralization against a panel of 12 tier 2 Envs using a newly described computational tool to quantify serum neutralization potency by factoring in the predetermined neutralization tier of each reference Env. This analysis revealed modest neutralization breadth, with DNA/MVA immunization followed by gp140 protein boosts in 3M-052 adjuvant producing the best scores. This study highlights that protein-containing regimens provide a solid foundation for the further development of novel adjuvants and inclusion of trimeric Env immunogens that could eventually elicit a higher level of neutralizing antibody breadth. Despite much progress, we still do not have a clear understanding of how to elicit a protective neutralizing antibody response against HIV-1 through vaccination. There have been great strides in the development of envelope immunogens that mimic the virus particle, but less is known about how different vaccination modalities and adjuvants contribute to shaping the antibody response. We compared seven different vaccines that were administered to rhesus macaques and that delivered the same envelope protein through various modalities and with different adjuvants. The results demonstrate that some vaccine components are better than others at eliciting neutralizing antibodies with breadth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01846-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6430525PMC
April 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.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01648-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6384055PMC
March 2019

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-.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.02030-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5923080PMC
May 2018

Vaccination with Combination DNA and Virus-Like Particles Enhances Humoral and Cellular Immune Responses upon Boost with Recombinant Modified Vaccinia Virus Ankara Expressing Human Immunodeficiency Virus Envelope Proteins.

Vaccines (Basel) 2017 Dec 19;5(4). Epub 2017 Dec 19.

Center for Inflammation, Immunity & Infection, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA 30303, USA.

Heterologous prime boost with DNA and recombinant modified vaccinia virus Ankara (rMVA) vaccines is considered as a promising vaccination approach against human immunodeficiency virus (HIV-1). To further enhance the efficacy of DNA-rMVA vaccination, we investigated humoral and cellular immune responses in mice after three sequential immunizations with DNA, a combination of DNA and virus-like particles (VLP), and rMVA expressing HIV-1 89.6 gp120 envelope proteins (Env). DNA prime and boost with a combination of VLP and DNA vaccines followed by an rMVA boost induced over a 100-fold increase in Env-specific IgG antibody titers compared to three sequential immunizations with DNA and rMVA. Cellular immune responses were induced by VLP-DNA and rMVA vaccinations at high levels in CD8 T cells, CD4 T cells, and peripheral blood mononuclear cells secreting interferon (IFN)-γ, and spleen cells producing interleukin (IL)-2, 4, 5 cytokines. This study suggests that a DNA and VLP combination vaccine with MVA is a promising strategy in enhancing the efficacy of DNA-rMVA vaccination against HIV-1.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/vaccines5040052DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5748618PMC
December 2017

High Doses of GM-CSF Inhibit Antibody Responses in Rectal Secretions and Diminish Modified Vaccinia Ankara/Simian Immunodeficiency Virus Vaccine Protection in TRIM5α-Restrictive Macaques.

J Immunol 2016 11 28;197(9):3586-3596. Epub 2016 Sep 28.

Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329;

We tested, in rhesus macaques, the effects of a 500-fold range of an admixed recombinant modified vaccinia Ankara (MVA) expressing rhesus GM-CSF (MVA/GM-CSF) on the immunogenicity and protection elicited by an MVA/SIV macaque 239 vaccine. High doses of MVA/GM-CSF did not affect the levels of systemic envelope (Env)-specific Ab, but it did decrease the expression of the gut-homing receptor α4β7 on plasmacytoid dendritic cells (p < 0.01) and the magnitudes of Env-specific IgA (p = 0.01) and IgG (p < 0.05) in rectal secretions. The protective effect of the vaccine was evaluated using 12 weekly rectal challenges in rhesus macaques subgrouped by tripartite motif-containing protein 5α (TRIM5α) genotypes that are restrictive or permissive for infection by the challenge virus SIVsmE660. Eight of nine TRIM5α-restrictive animals receiving no or the lowest dose (1 × 10 PFU) of MVA/GM-CSF resisted all 12 challenges. In the comparable TRIM5α-permissive group, only 1 of 12 animals resisted all 12 challenges. In the TRIM5α-restrictive animals, but not in the TRIM5α-permissive animals, the number of challenges to infection directly correlated with the magnitudes of Env-specific rectal IgG (r = +0.6) and IgA (r = +0.6), the avidity of Env-specific serum IgG (r = +0.5), and Ab dependent cell-mediated virus inhibition (r = +0.6). Titers of neutralizing Ab did not correlate with protection. We conclude that 1) protection elicited by MVA/SIVmac239 is strongly dependent on the presence of TRIM5α restriction, 2) nonneutralizing Ab responses contribute to protection against SIVsmE660 in TRIM5α-restrictive animals, and 3) high doses of codelivered MVA/GM-CSF inhibit mucosal Ab responses and the protection elicited by MVA expressing noninfectious SIV macaque 239 virus-like particles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1600629DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5101171PMC
November 2016

Induction of Th1-Biased T Follicular Helper (Tfh) Cells in Lymphoid Tissues during Chronic Simian Immunodeficiency Virus Infection Defines Functionally Distinct Germinal Center Tfh Cells.

J Immunol 2016 09 1;197(5):1832-42. Epub 2016 Aug 1.

Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, GA 30329; Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30322; and

Chronic HIV infection is associated with accumulation of germinal center (GC) T follicular helper (Tfh) cells in the lymphoid tissue. The GC Tfh cells can be heterogeneous based on the expression of chemokine receptors associated with T helper lineages, such as CXCR3 (Th1), CCR4 (Th2), and CCR6 (Th17). However, the heterogeneous nature of GC Tfh cells in the lymphoid tissue and its association with viral persistence and Ab production during chronic SIV/HIV infection are not known. To address this, we characterized the expression of CXCR3, CCR4, and CCR6 on GC Tfh cells in lymph nodes following SIVmac251 infection in rhesus macaques. In SIV-naive rhesus macaques, only a small fraction of GC Tfh cells expressed CXCR3, CCR4, and CCR6. However, during chronic SIV infection, the majority of GC Tfh cells expressed CXCR3, whereas the proportion of CCR4(+) cells did not change, and CCR6(+) cells decreased. CXCR3(+), but not CXCR3(-), GC Tfh cells produced IFN-γ (Th1 cytokine) and IL-21 (Tfh cytokine), whereas both subsets expressed CD40L following stimulation. Immunohistochemistry analysis demonstrated an accumulation of CD4(+)IFN-γ(+) T cells within the hyperplastic follicles during chronic SIV infection. CXCR3(+) GC Tfh cells also expressed higher levels of ICOS, CCR5, and α4β7 and contained more copies of SIV DNA compared with CXCR3(-) GC Tfh cells. However, CXCR3(+) and CXCR3(-) GC Tfh cells delivered help to B cells in vitro for production of IgG. These data demonstrate that chronic SIV infection promotes expansion of Th1-biased GC Tfh cells, which are phenotypically and functionally distinct from conventional GC Tfh cells and contribute to hypergammaglobulinemia and viral reservoirs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1600143DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4992610PMC
September 2016

Virus-Like Particles Displaying Trimeric Simian Immunodeficiency Virus (SIV) Envelope gp160 Enhance the Breadth of DNA/Modified Vaccinia Virus Ankara SIV Vaccine-Induced Antibody Responses in Rhesus Macaques.

J Virol 2016 10 12;90(19):8842-54. Epub 2016 Sep 12.

Department of Microbiology and Immunology, Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA

Unlabelled: The encouraging results of the RV144 vaccine trial have spurred interest in poxvirus prime-protein boost human immunodeficiency virus (HIV) vaccine modalities as a strategy to induce protective immunity. Because vaccine-induced protective immunity is critically determined by HIV envelope (Env) conformation, significant efforts are directed toward generating soluble trimeric Env immunogens that assume native structures. Using the simian immunodeficiency virus (SIV)-macaque model, we tested the immunogenicity and efficacy of sequential immunizations with DNA (D), modified vaccinia virus Ankara (MVA) (M), and protein immunogens, all expressing virus-like particles (VLPs) displaying membrane-anchored trimeric Env. A single VLP protein boost displaying trimeric gp160 adjuvanted with nanoparticle-encapsulated Toll-like receptor 4/7/8 (TLR4/7/8) agonists, administered 44 weeks after the second MVA immunization, induced up to a 3-fold increase in Env-specific IgG binding titers in serum and mucosa. Importantly, the VLP protein boost increased binding antibody against scaffolded V1V2, antibody-dependent phagocytic activity against VLP-coated beads, and antibody breadth and neutralizing antibody titers against homologous and heterologous tier 1 SIVs. Following 5 weekly intrarectal SIVmac251 challenges, two of seven DNA/MVA and VLP (DM+VLP)-vaccinated animals were completely protected compared to productive infection in all seven DM-vaccinated animals. Vaccinated animals demonstrated stronger acute viral pulldown than controls, but a trend for higher acute viremia was observed in the DM+VLP group, likely due to a slower recall of Gag-specific CD8 T cells. Our findings support immunization with VLPs containing trimeric Env as a strategy to augment protective antibody but underscore the need for optimal engagement of CD8 T cells to achieve robust early viral control.

Importance: The development of an effective HIV vaccine remains a global necessity for preventing HIV infection and reducing the burden of AIDS. While this goal represents a formidable challenge, the modest efficacy of the RV144 trial indicates that multicomponent vaccination regimens that elicit both cellular and humoral immune responses can prevent HIV infection in humans. However, whether protein immunizations synergize with DNA prime-viral vector boosts to enhance cellular and humoral immune responses remains poorly understood. We addressed this question in a nonhuman primate model, and our findings show benefit for sequential protein immunization combined with a potent adjuvant in boosting antibody titers induced by a preceding DNA/MVA immunization. This promising strategy can be further developed to enhance neutralizing antibody responses and boost CD8 T cells to provide robust protection and viral control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01163-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5021426PMC
October 2016

Strong, but Age-Dependent, Protection Elicited by a Deoxyribonucleic Acid/Modified Vaccinia Ankara Simian Immunodeficiency Virus Vaccine.

Open Forum Infect Dis 2016 Jan 11;3(1):ofw034. Epub 2016 Feb 11.

Yerkes National Primate Research Center, Emory University , Atlanta, Georgia.

Background.  In this study, we analyzed the protective efficacy of a simian immunodeficiency virus (SIV) macaque 239 (SIVmac239) analogue of the clinically tested GOVX-B11 deoxyribonucleic acid (DNA)/modified vaccinia Ankara (MVA) human immunodeficiency virus vaccine. Methods.  The tested vaccine used a DNA immunogen mutated to mimic the human vaccine and a regimen with DNA deliveries at weeks 0 and 8 and MVA deliveries at weeks 16 and 32. Twelve weekly rectal challenges with 0.3 animal infectious doses of SIV sootey mangabey E660 (SIVsmE660) were administered starting at 6 months after the last immunization. Results.  Over the first 6 rectal exposures to SIVsmE660, <10-year-old tripartite motif-containing protein 5 (TRIM5)α-permissive rhesus macaques showed an 80% reduction in per-exposure risk of infection as opposed to a 46% reduction in animals over 10 years old; and, over the 12 challenges, they showed a 72% as opposed to a 10% reduction. Analyses of elicited immune responses suggested that higher antibody responses in the younger animals had played a role in protection. Conclusions.  The simian analogue of the GOVX-B11 HIV provided strong protection against repeated rectal challenges in young adult macaques.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/ofid/ofw034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4800464PMC
January 2016

Codelivery of Envelope Protein in Alum with MVA Vaccine Induces CXCR3-Biased CXCR5+ and CXCR5- CD4 T Cell Responses in Rhesus Macaques.

J Immunol 2015 Aug 26;195(3):994-1005. Epub 2015 Jun 26.

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

The goal of an HIV vaccine is to generate robust and durable protective Ab. Vital to this goal is the induction of CD4(+) T follicular helper (TFH) cells. However, very little is known about the TFH response to HIV vaccination and its relative contribution to magnitude and quality of vaccine-elicited Ab titers. In this study, we investigated these questions in the context of a DNA/modified vaccinia virus Ankara SIV vaccine with and without gp140 boost in aluminum hydroxide in rhesus macaques. In addition, we determined the frequency of vaccine-induced CD4(+) T cells coexpressing chemokine receptor, CXCR5 (facilitates migration to B cell follicles) in blood and whether these responses were representative of lymph node TFH responses. We show that booster modified vaccinia virus Ankara immunization induced a distinct and transient accumulation of proliferating CXCR5(+) and CXCR5(-) CD4 T cells in blood at day 7 postimmunization, and the frequency of the former but not the latter correlated with TFH and B cell responses in germinal centers of the lymph node. Interestingly, gp140 boost induced a skewing toward CXCR3 expression on germinal center TFH cells, which was strongly associated with longevity, avidity, and neutralization potential of vaccine-elicited Ab response. However, CXCR3(+) cells preferentially expressed the HIV coreceptor CCR5, and vaccine-induced CXCR3(+)CXCR5(+) cells showed a moderate positive association with peak viremia following SIV251 infection. Taken together, our findings demonstrate that vaccine regimens that elicit CXCR3-biased TFH cell responses favor Ab persistence and avidity but may predispose to higher acute viremia in the event of breakthrough infections.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1500083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4506863PMC
August 2015

CD40L-adjuvanted DNA/modified vaccinia virus Ankara simian immunodeficiency virus (SIV) vaccine enhances protection against neutralization-resistant mucosal SIV infection.

J Virol 2015 Apr 4;89(8):4690-5. Epub 2015 Feb 4.

Emory Vaccine Center, Department of Microbiology and Immunology, and Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA

Here, we show that a CD40L-adjuvanted DNA/modified vaccinia virus Ankara (MVA) simian immunodeficiency virus (SIV) vaccine enhances protection against a pathogenic neutralization-resistant mucosal SIV infection, improves long-term viral control, and prevents AIDS. Analyses of serum IgG antibodies to linear peptides of SIV Env revealed a strong response to V2, with targeting of fewer epitopes in the immunodominant region of gp41 (gp41-ID) and the V1 region as a correlate for enhanced protection. Greater expansion of antiviral CD8 T cells in the gut correlated with long-term viral control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.03527-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4442387PMC
April 2015

CD40L-adjuvanted DNA/modified vaccinia virus Ankara simian immunodeficiency virus SIV239 vaccine enhances SIV-specific humoral and cellular immunity and improves protection against a heterologous SIVE660 mucosal challenge.

J Virol 2014 Sep 11;88(17):9579-89. Epub 2014 Jun 11.

Emory Vaccine Center, Department of Microbiology and Immunology, Yerkes National Primate Research Center, Emory University, Atlanta, Georgia, USA

Unlabelled: It remains a challenge to develop a successful human immunodeficiency virus (HIV) vaccine that is capable of preventing infection. Here, we utilized the benefits of CD40L, a costimulatory molecule that can stimulate both dendritic cells (DCs) and B cells, as an adjuvant for our simian immunodeficiency virus (SIV) DNA vaccine in rhesus macaques. We coexpressed the CD40L with our DNA/SIV vaccine such that the CD40L is anchored on the membrane of SIV virus-like particle (VLP). These CD40L containing SIV VLPs showed enhanced activation of DCs in vitro. We then tested the potential of DNA/SIV-CD40L vaccine to adjuvant the DNA prime of a DNA/modified vaccinia virus Ankara (MVA) vaccine in rhesus macaques. Our results demonstrated that the CD40L adjuvant enhanced the functional quality of anti-Env antibody response and breadth of anti-SIV CD8 and CD4 T cell responses, significantly delayed the acquisition of heterologous mucosal SIV infection, and improved viral control. Notably, the CD40L adjuvant enhanced the control of viral replication in the gut at the site of challenge that was associated with lower mucosal CD8 immune activation, one of the strong predictors of disease progression. Collectively, our results highlight the benefits of CD40L adjuvant for enhancing antiviral humoral and cellular immunity, leading to enhanced protection against a pathogenic SIV. A single adjuvant that enhances both humoral and cellular immunity is rare and thus underlines the importance and practicality of CD40L as an adjuvant for vaccines against infectious diseases, including HIV-1.

Importance: Despite many advances in the field of AIDS research, an effective AIDS vaccine that can prevent infection remains elusive. CD40L is a key stimulator of dendritic cells and B cells and can therefore enhance T cell and antibody responses, but its overly potent nature can lead to adverse effects unless used in small doses. In order to modulate local expression of CD40L at relatively lower levels, we expressed CD40L in a membrane-bound form, along with SIV antigens, in a nucleic acid (DNA) vector. We tested the immunogenicity and efficacy of the CD40L-adjuvanted vaccine in macaques using a heterologous mucosal SIV infection. The CD40L-adjuvanted vaccine enhanced the functional quality of anti-Env antibody response and breadth of anti-SIV T cell responses and improved protection. These results demonstrate that VLP-membrane-bound CD40L serves as a novel adjuvant for an HIV vaccine.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.00975-14DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4136340PMC
September 2014

Deletion of specific immune-modulatory genes from modified vaccinia virus Ankara-based HIV vaccines engenders improved immunogenicity in rhesus macaques.

J Virol 2012 Dec 12;86(23):12605-15. Epub 2012 Sep 12.

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

Modified vaccinia virus Ankara (MVA) is a safe, attenuated orthopoxvirus that is being developed as a vaccine vector but has demonstrated limited immunogenicity in several early-phase clinical trials. Our objective was to rationally improve the immunogenicity of MVA-based HIV/AIDS vaccines via the targeted deletion of specific poxvirus immune-modulatory genes. Vaccines expressing codon-optimized HIV subtype C consensus Env and Gag antigens were generated from MVA vector backbones that (i) harbor simultaneous deletions of four viral immune-modulatory genes, encoding an interleukin-18 (IL-18) binding protein, an IL-1β receptor, a dominant negative Toll/IL-1 signaling adapter, and CC-chemokine binding protein (MVAΔ4-HIV); (ii) harbor a deletion of an additional (fifth) viral gene, encoding uracil-DNA glycosylase (MVAΔ5-HIV); or (iii) represent the parental MVA backbone as a control (MVA-HIV). We performed head-to-head comparisons of the cellular and humoral immune responses that were elicited by these vectors during homologous prime-boost immunization regimens utilizing either high-dose (2 × 10(8) PFU) or low-dose (1 × 10(7) PFU) intramuscular immunization of rhesus macaques. At all time points, a majority of the HIV-specific T cell responses, elicited by all vectors, were directed against Env, rather than Gag, determinants, as previously observed with other vector systems. Both modified vectors elicited up to 6-fold-higher frequencies of HIV-specific CD8 and CD4 T cell responses and up to 25-fold-higher titers of Env (gp120)-specific binding (nonneutralizing) antibody responses that were relatively transient in nature. While the correlates of protection against HIV infection remain incompletely defined, our results indicate that the rational deletion of specific genes from MVA vectors can positively alter their cellular and humoral immunogenicity profiles in nonhuman primates.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.00246-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3497691PMC
December 2012

Expanding the repertoire of Modified Vaccinia Ankara-based vaccine vectors via genetic complementation strategies.

PLoS One 2009 6;4(5):e5445. Epub 2009 May 6.

Emory Vaccine Center, Emory University, Atlanta, GA, USA.

Background: Modified Vaccinia virus Ankara (MVA) is a safe, highly attenuated orthopoxvirus that is being developed as a recombinant vaccine vector for immunization against a number of infectious diseases and cancers. However, the expression by MVA vectors of large numbers of poxvirus antigens, which display immunodominance over vectored antigens-of-interest for the priming of T cell responses, and the induction of vector-neutralizing antibodies, which curtail the efficacy of subsequent booster immunizations, remain as significant impediments to the overall utility of such vaccines. Thus, genetic approaches that enable the derivation of MVA vectors that are antigenically less complex may allow for rational improvement of MVA-based vaccines.

Principal Findings: We have developed a genetic complementation system that enables the deletion of essential viral genes from the MVA genome, thereby allowing us to generate MVA vaccine vectors that are antigenically less complex. Using this system, we deleted the essential uracil-DNA-glycosylase (udg) gene from MVA and propagated this otherwise replication-defective variant on a complementing cell line that constitutively expresses the poxvirus udg gene and that was derived from a newly identified continuous cell line that is permissive for growth of wild type MVA. The resulting virus, MVADeltaudg, does not replicate its DNA genome or express late viral gene products during infection of non-complementing cells in culture. As proof-of-concept for immunological 'focusing', we demonstrate that immunization of mice with MVADeltaudg elicits CD8+ T cell responses that are directed against a restricted repertoire of vector antigens, as compared to immunization with parental MVA. Immunization of rhesus macaques with MVADeltaudg-gag, a udg(-) recombinant virus that expresses an HIV subtype-B consensus gag transgene, elicited significantly higher frequencies of Gag-specific CD8 and CD4 T cells following both primary (2-4-fold) and booster (2-fold) immunizations as compared to the udg(+) control virus MVA-gag, as determined by intracellular cytokine assay. In contrast, levels of HIV Gag-specific antibodies were elicited similarly in macaques following immunization with MVADeltaudg-gag and MVA-gag. Furthermore, both udg(-) and udg(+) MVA vectors induced comparatively similar titers of MVA-specific neutralizing antibody responses following immunization of mice (over a 4-log range: 10(4)-10(8) PFU) and rhesus macaques. These results suggest that the generation of MVA-specific neutralizing antibody responses are largely driven by input MVA antigens, rather than those that are synthesized de novo during infection, and that the processes governing the generation of antiviral antibody responses are more readily saturated by viral antigen than are those that elicit CD8+ T cell responses.

Significance: Our identification of a spontaneously-immortalized (but not transformed) chicken embryo fibroblast cell line (DF-1) that is fully permissive for MVA growth and that can be engineered to stably express MVA genes provides the basis for a genetic system for MVA. DF-1 cells (and derivatives thereof) constitute viable alternatives, for the manufacture of MVA-based vaccines, to primary CEFs -- the conventional cell substrate for MVA vaccines that is not amenable to genetic complementation strategies due to these cells' finite lifespan in culture. The establishment of a genetic system for MVA, as illustrated here to allow udg deletion, enables the generation of novel replication-defective MVA mutants and expands the repertoire of genetic viral variants that can now be explored as improved vaccine vectors.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0005445PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2674217PMC
June 2009

Immunogenicity of virus-like particles containing modified human immunodeficiency virus envelope proteins.

Vaccine 2007 May 15;25(19):3841-50. Epub 2007 Feb 15.

Department of Microbiology and Immunology, and Emory Vaccine Center, Emory University School of Medicine, 1510 Clifton Rd, Atlanta, GA 30322, United States.

Extensive glycosylation and variable loops of the HIV envelope protein (Env) are reported to shield some neutralizing epitopes. Here, we investigated the immunogenicity of mutated HIV Envs presented in virus-like particles (VLPs). We immunized mice with simian human immunodeficiency virus (SHIV) VLPs containing mutant HIV Env with reduced glycosylation (3G), variable loop-deleted mutations (dV1V2), or combinations of both types of mutations (3G-dV2-1G), and evaluated immune responses. Immune sera from mice that received VLPs with modified HIV Envs (3G or dV1V2) showed higher neutralizing activities against the homologous HIV 89.6 virus as well as heterologous viruses when compared with wild type SHIV VLP-immunized mice. Lymphocytes from immunized mice produced HIV Env-specific cytokines, with the 3G-dV2-1G mutant producing high levels of cytokines. Interestingly, both dendritic cells and B cells were found to interact with VLPs suggesting that VLPs are effective immunogens. Therefore, this study suggests that VLPs containing modified HIV Env have the potential to be developed as candidate vaccines capable of inducing cellular and humoral immune responses including neutralizing activities.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.vaccine.2007.01.107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1973151PMC
May 2007

Human immunodeficiency virus-like particles activate multiple types of immune cells.

Virology 2007 Jun 5;362(2):331-41. Epub 2007 Feb 5.

Emory Vaccine Center and Department of Microbiology and Immunology, Rollins Research Center 3086, Emory University School of Medicine, 1510 Clifton Road, Atlanta, GA 30322, USA.

The rapid spread of human immunodeficiency virus (HIV) worldwide makes it a high priority to develop an effective vaccine. Since live attenuated or inactivated HIV is not likely to be approved as a vaccine due to safety concerns, HIV virus like particles (VLPs) offer an attractive alternative because they are safe due to the lack of a viral genome. Although HIV VLPs have been shown to induce humoral and cellular immune responses, it is important to understand the mechanisms by which they induce such responses and to improve their immunogenicity. We generated HIV VLPs, and VLPs containing Flt3 ligand (FL), a dendritic cell growth factor, to target VLPs to dendritic cells, and investigated the roles of these VLPs in the initiation of adaptive immune responses in vitro and in vivo. We found that HIV-1 VLPs induced maturation of dendritic cells and monocyte/macrophage populations in vitro and in vivo, with enhanced expression of maturation markers and cytokines. Dendritic cells pulsed with VLPs induced activation of splenocytes resulting in increased production of cytokines. VLPs containing FL were found to increase dendritic cells and monocyte/macrophage populations in the spleen when administered to mice. Administration of VLPs induced acute activation of multiple types of cells including T and B cells as indicated by enhanced expression of the early activation marker CD69 and down-regulation of the homing receptor CD62L. VLPs containing FL were an effective form of antigen in activating immune cells via dendritic cells, and immunization with HIV VLPs containing FL resulted in enhanced T helper type 2-like immune responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.virol.2006.12.014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1974898PMC
June 2007

Incorporation of glycosylphosphatidylinositol-anchored granulocyte- macrophage colony-stimulating factor or CD40 ligand enhances immunogenicity of chimeric simian immunodeficiency virus-like particles.

J Virol 2007 Feb 15;81(3):1083-94. Epub 2006 Nov 15.

Department of Microbiology and Immunology and Emory Vaccine Center, Emory University School of Medicine, 1510 Clifton Rd., Atlanta, GA 30322, USA.

The rapid worldwide spread of human immunodeficiency virus (HIV) mandates the development of successful vaccination strategies. Since live attenuated HIV is not accepted as a vaccine due to safety concerns, virus-like particles (VLPs) offer an attractive safe alternative because they lack the viral genome yet they are perceived by the immune system as a virus particle. We hypothesized that adding immunostimulatory signals to VLPs would enhance their efficacy. To accomplish this we generated chimeric simian immunodeficiency virus (SIV) VLPs containing either glycosylphosphatidylinositol (GPI)-anchored granulocyte-macrophage colony-stimulating factor (GM-CSF) or CD40 ligand (CD40L) and investigated their biological activity and ability to enhance immune responses in vivo. Immunization of mice with chimeric SIV VLPs containing GM-CSF induced SIV Env-specific antibodies as well as neutralizing activity at significantly higher levels than those induced by standard SIV VLPs, SIV VLPs containing CD40L, or standard VLPs mixed with soluble GM-CSF. In addition, mice immunized with chimeric SIV VLPs containing either GM-CSF or CD40L showed significantly increased CD4(+)- and CD8(+)-T-cell responses to SIV Env, compared to standard SIV VLPs. Taken together, these results demonstrate that the incorporation of immunostimulatory molecules enhances humoral and cellular immune responses. We propose that anchoring immunostimulatory molecules into SIV VLPs can be a promising approach to augmenting the efficacy of VLP antigens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/JVI.01692-06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1797543PMC
February 2007

Augmenting the immunogenicity of DNA vaccines: role of plasmid-encoded Flt-3 ligand, as a molecular adjuvant in genetic vaccination.

Virology 2006 May 24;348(2):277-88. Epub 2006 Mar 24.

Emory Vaccine Center, Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, GA 30329, USA.

In this study, we have taken advantage of the unique property of a potent dendritic cell (DC) growth factor, Flt-3 ligand (FL), which could act as a vaccine adjuvant. Accordingly, a single injection of plasmid DNA coding for soluble FL (FLex) was shown to induce large numbers of DCs in various tissue compartments and was critical for generating high frequencies of antigen-specific (HIV gp120 and LCMV NP) immune responses in mice. Interestingly, this enhanced level of immune response is strictly dependent on the co-delivery (i.m.) of the DNA vaccines and hFLex DNA to mice harboring large numbers of DCs. The high frequencies of antigen-specific CD8(+) T cells were largely associated with the expansion phase of DCs in vivo. However, DC expansion and immune enhancement have not reciprocally maintained a linear correlation, suggesting that other factors, cytokines/chemokines, which have the potential to modulate the microenvironment of DCs, could influence immunological outcome in this vaccination modality.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.virol.2006.02.016DOI Listing
May 2006

Enhancement of gp120-specific immune responses by genetic vaccination with the human immunodeficiency virus type 1 envelope gene fused to the gene coding for soluble CTLA4.

J Virol 2003 Oct;77(20):10850-61

Department of Microbiology and Immunology, Emory Vaccine Center, Emory University School of Medicine, Emory University, Atlanta, Georgia 30329, USA.

DNA vaccines exploit the inherent abilities of professional antigen-presenting cells to prime the immune system and to elicit immunity against diverse pathogens. In this study, we explored the possibility of augmenting human immunodeficiency virus type 1 gp120-specific immune responses by a DNA vaccine coding for a fusion protein, CTLA4:gp120, in mice. In vitro binding studies revealed that secreted CTLA4:gp120 protein induced a mean florescence intensity shift, when incubated with Raji B cells, indicating its binding to B7 proteins on Raji B cells. Importantly, we instituted three different vaccination regimens to test the efficacy of DNA vaccines encoding gp120 and CTLA4:gp120 in the induction of both cellular (CD8(+)) and antibody responses. Each of the vaccination regimens incorporated a single intramuscular (i.m.) injection of the DNA vaccines to prime the immune system, followed by two booster injections. The i.m.-i.m.-i.m. regimen induced only modest levels of gp120-specific CD8(+) T cells, but the antibody response by CTLA4:gp120 DNA was nearly 16-fold higher than that induced by gp120 DNA. In contrast, using the i.m.-subcutaneous (s.c.)-i.m. regimen, it was found that gp120 and CTLA4:gp120 DNAs were capable of inducing significant levels of gp120-specific CD8(+) T cells (3.5 and 11%), with antibody titers showing a modest twofold increase for CTLA4:gp120 DNA. In the i.m.-gene gun (g.g.)-g.g. regimen, the mice immunized with gp120 and CTLA4:gp120 harbored gp120-specific CD8(+) T cells at frequencies of 0.9 and 2.9%, with the latter showing an eightfold increase in antibody titers. Thus, covalent antigen modification and the routes of genetic vaccination have the potential to modulate antigen-specific immune responses in mice.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC224956PMC
http://dx.doi.org/10.1128/jvi.77.20.10850-10861.2003DOI Listing
October 2003

Long-term maintenance of gp120-specific immune responses by genetic vaccination with the HIV-1 envelope genes linked to the gene encoding Flt-3 ligand.

J Immunol 2003 Mar;170(5):2496-507

Department of Microbiology and Immunology, Emory University School of Medicine, Emory Vaccine Center at Yerkes, Atlanta, GA 30329, USA.

DNA vaccines target dendritic cells (DC) to induce Ag-specific immune responses in animals. Potent HIV-specific immunity could be achieved by efficient priming of the immune system by DNA vaccines. We investigated a novel DNA vaccine approach based on the role of growth factors in DC expansion and differentiation. To this end, we constructed chimeric genes encoding the HIV envelope glycoproteins physically linked to the extracellular domain of Fms-like tyrosine kinase receptor-3 ligand (FLex; a DC growth factor; both mouse (m)FLex and human (h)FLex). These chimeric gene constructs synthesized biologically active, oligomeric FLex:gp120 fusion proteins and induced DC expansion (CD11c(+)CD11b(+)) when injected i.v. into mice. This DC expansion is comparable to that achieved by FLex DNA encoding native FLex protein. When delivered intramuscularly as DNA vaccines, hFLex:gp120 induced high frequencies of gp120-specific CD8(+) T cells in the presence or absence of FLex DNA-induced DC expansion, but gp120 and mFLex:gp120 elicited only low to moderate levels of Ag-specific CD8(+) T cells. In contrast, mFLex:gp120 induced high levels of anti-gp120 Abs under identical conditions of DNA vaccination. However, the Ab levels in mice immunized with DNA vaccines encoding hFLex:gp120 and gp120 proteins were low without DC expansion, but reached high levels comparable to that elicited by mFLex:gp120 only after the second boost in the presence of DC expansion. Importantly, the gp120-specific CD8(+) T cells persisted at high frequency for 114 days (16 wk) after a booster injection. These experiments provide insight into the importance of modulating DC function in vivo for effective genetic vaccination in animals.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.170.5.2496DOI Listing
March 2003