Publications by authors named "David A Hokey"

33 Publications

Multidimensional analyses reveal modulation of adaptive and innate immune subsets by tuberculosis vaccines.

Commun Biol 2020 10 9;3(1):563. Epub 2020 Oct 9.

South African Tuberculosis Vaccine Initiative, Institute of Infectious Disease & Molecular Medicine and Division of Immunology, Department of Pathology, University of Cape Town, Cape Town, South Africa.

We characterize the breadth, function and phenotype of innate and adaptive cellular responses in a prevention of Mycobacterium tuberculosis infection trial. Responses are measured by whole blood intracellular cytokine staining at baseline and 70 days after vaccination with H4:IC31 (subunit vaccine containing Ag85B and TB10.4), Bacille Calmette-Guerin (BCG, a live attenuated vaccine) or placebo (n = ~30 per group). H4:IC31 vaccination induces Ag85B and TB10.4-specific CD4 T cells, and an unexpected NKT subset, that expresses IFN-γ, TNF and/or IL-2. BCG revaccination increases frequencies of CD4 T cell subsets that either express Th1 cytokines or IL-22, and modestly increases IFNγ-producing NK cells. In vitro BCG re-stimulation also triggers responses by donor-unrestricted T cells, which may contribute to host responses against mycobacteria. BCG, which demonstrated efficacy against sustained Mycobacterium tuberculosis infection, modulates multiple immune cell subsets, in particular conventional Th1 and Th22 cells, which should be investigated in discovery studies of correlates of protection.
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http://dx.doi.org/10.1038/s42003-020-01288-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547090PMC
October 2020

Transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to animals: an updated review.

J Transl Med 2020 09 21;18(1):358. Epub 2020 Sep 21.

Pathobiology Department, Faculty of Veterinary Medicine, Science and Research Branch, Islamic Azad University, Tehran, Iran.

COVID-19 caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originated in Wuhan (Hubei province, China) during late 2019. It has spread across the globe affecting nearly 21 million people with a toll of 0.75 million deaths and restricting the movement of most of the world population during the past 6 months. COVID-19 became the leading health, economic, and humanitarian challenge of the twenty-first century. In addition to the considerable COVID-19 cases, hospitalizations, and deaths in humans, several cases of SARS-CoV-2 infections in animal hosts (dog, cat, tiger, lion, and mink) have been reported. Thus, the concern of pet owners is increasing. Moreover, the dynamics of the disease requires further explanation, mainly concerning the transmission of the virus from humans to animals and vice versa. Therefore, this study aimed to gather information about the reported cases of COVID-19 transmission in animals through a literary review of works published in scientific journals and perform genomic and phylogenetic analyses of SARS-CoV-2 isolated from animal hosts. Although many instances of transmission of the SARS-CoV-2 have been reported, caution and further studies are necessary to avoid the occurrence of maltreatment in animals, and to achieve a better understanding of the dynamics of the disease in the environment, humans, and animals. Future research in the animal-human interface can help formulate and implement preventive measures to combat the further transmission of COVID-19.
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http://dx.doi.org/10.1186/s12967-020-02534-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7503431PMC
September 2020

CD4+ T cell cytokine responses to the DAR-901 booster vaccine in BCG-primed adults: A randomized, placebo-controlled trial.

PLoS One 2019 23;14(5):e0217091. Epub 2019 May 23.

Geisel School of Medicine, Hanover, NH, United States of America.

Background: DAR-901 is an inactivated whole cell tuberculosis booster vaccine, prepared using a new scalable, broth-grown method from the master cell bank of SRL172, a vaccine previously shown to prevent tuberculosis. This study examined whether DAR-901 (a) induces CD4+ T cell cytokine profiles previously proposed as correlates of protection and (b) has a specific vaccine-induced immunological signature compared to BCG or placebo.

Methods: We analysed CD4+ T cell cytokine immune responses from 10 DAR-901 recipients, 9 BCG recipients and 9 placebo recipients from the Phase I DAR-901 MDES trial. In that study, HIV-negative, IGRA-negative participants with prior BCG immunization were randomized (double-blind) to receive three intradermal injections of DAR-901 or saline placebo or two injections of saline placebo followed by an intradermal injection of BCG. Antigen-specific functional and phenotypic CD4+ T cell responses along with effector phenotype of responder cells were measured by intracellular cytokine staining.

Results: DAR-901 recipients exhibited increased DAR-901 antigen-specific polyfunctional or bifunctional T cell responses compared to baseline. Vaccine specific CD4+ IFNγ, IL2, TNFα and any cytokine responses peaked at 7 days post-dose 3. Th1 responses predominated, with most responder cells exhibiting a polyfunctional effector memory phenotype. BCG induced greater CD4+ T cell responses than placebo while the more modest DAR-901 responses did not differ from placebo. Neither DAR-901 nor BCG induced substantial or sustained Th17 /Th22 cytokine responses.

Conclusion: DAR-901, a TB booster vaccine grown from the master cell bank of SRL 172 which was shown to prevent TB, induced low magnitude polyfunctional effector memory CD4+ T cell responses. DAR-901 responses were lower than those induced by BCG, a vaccine that has been shown ineffective as a booster to prevent tuberculosis disease. These results suggest that induction of higher levels of CD4+ cytokine stimulation may not be a critical or pre-requisite characteristic for candidate TB vaccine boosters.

Trial Registration: ClinicalTrials.gov NCT02063555.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0217091PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6532882PMC
January 2020

Prevention of M. tuberculosis Infection with H4:IC31 Vaccine or BCG Revaccination.

N Engl J Med 2018 07;379(2):138-149

From the South African Tuberculosis Vaccine Initiative, Institute of Infectious Disease and Molecular Medicine and Division of Immunology, Department of Pathology (E.N., H.G., V.R., F.R., N.B., S.M., L.M., M.E., A.T., H.M., W.A.H., T.J.S., M.H.), and Desmond Tutu HIV Foundation (L.-G.B.), University of Cape Town, Cape Town, South Africa; Aeras, Rockville, MD (K.T.R., T.E., R.D.E., B.L., D.A.H., R.H., A.M.G.); Statistical Center for HIV Research, Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle (S.G.S.); Sanofi Pasteur, Swiftwater, PA (R.R., S.G., C.A.D.); and Center for Vaccine Research, Statens Serum Institut, Copenhagen (P.A., I.K.).

Background: Recent Mycobacterium tuberculosis infection confers a predisposition to the development of tuberculosis disease, the leading killer among global infectious diseases. H4:IC31, a candidate subunit vaccine, has shown protection against tuberculosis disease in preclinical models, and observational studies have indicated that primary bacille Calmette-Guérin (BCG) vaccination may offer partial protection against infection.

Methods: In this phase 2 trial, we randomly assigned 990 adolescents in a high-risk setting who had undergone neonatal BCG vaccination to receive the H4:IC31 vaccine, BCG revaccination, or placebo. All the participants had negative results on testing for M. tuberculosis infection on the QuantiFERON-TB Gold In-tube assay (QFT) and for the human immunodeficiency virus. The primary outcomes were safety and acquisition of M. tuberculosis infection, as defined by initial conversion on QFT that was performed every 6 months during a 2-year period. Secondary outcomes were immunogenicity and sustained QFT conversion to a positive test without reversion to negative status at 3 months and 6 months after conversion. Estimates of vaccine efficacy are based on hazard ratios from Cox regression models and compare each vaccine with placebo.

Results: Both the BCG and H4:IC31 vaccines were immunogenic. QFT conversion occurred in 44 of 308 participants (14.3%) in the H4:IC31 group and in 41 of 312 participants (13.1%) in the BCG group, as compared with 49 of 310 participants (15.8%) in the placebo group; the rate of sustained conversion was 8.1% in the H4:IC31 group and 6.7% in the BCG group, as compared with 11.6% in the placebo group. Neither the H4:IC31 vaccine nor the BCG vaccine prevented initial QFT conversion, with efficacy point estimates of 9.4% (P=0.63) and 20.1% (P=0.29), respectively. However, the BCG vaccine reduced the rate of sustained QFT conversion, with an efficacy of 45.4% (P=0.03); the efficacy of the H4:IC31 vaccine was 30.5% (P=0.16). There were no clinically significant between-group differences in the rates of serious adverse events, although mild-to-moderate injection-site reactions were more common with BCG revaccination.

Conclusions: In this trial, the rate of sustained QFT conversion, which may reflect sustained M. tuberculosis infection, was reduced by vaccination in a high-transmission setting. This finding may inform clinical development of new vaccine candidates. (Funded by Aeras and others; C-040-404 ClinicalTrials.gov number, NCT02075203 .).
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http://dx.doi.org/10.1056/NEJMoa1714021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5937161PMC
July 2018

The Cross-Species Mycobacterial Growth Inhibition Assay (MGIA) Project, 2010-2014.

Clin Vaccine Immunol 2017 Sep 5;24(9). Epub 2017 Sep 5.

Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.

The development of a functional biomarker assay in the tuberculosis (TB) field would be widely recognized as a major advance in efforts to develop and to test novel TB vaccine candidates efficiently. We present preliminary studies using mycobacterial growth inhibition assays (MGIAs) to detect BCG vaccine responses across species, and we extend this work to determine whether a standardized MGIA can be applied in characterizing new TB vaccines. The comparative MGIA studies reviewed here aimed to evaluate robustness, reproducibility, and ability to reflect responses. In doing so, they have laid the foundation for the development of a MGIA that can be standardized and potentially qualified. A major challenge ahead lies in better understanding the relationships between protection, growth inhibition, and the immune mechanisms involved. The final outcome would be a MGIA that could be used with confidence in TB vaccine trials. We summarize data arising from this project, present a strategy to meet the goals of developing a functional assay for TB vaccine testing, and describe some of the challenges encountered in performing and transferring such assays.
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http://dx.doi.org/10.1128/CVI.00142-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585695PMC
September 2017

Safety and immunogenicity of an inactivated whole cell tuberculosis vaccine booster in adults primed with BCG: A randomized, controlled trial of DAR-901.

PLoS One 2017 12;12(5):e0175215. Epub 2017 May 12.

Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States of America.

Background: Development of a tuberculosis vaccine to boost BCG is a major international health priority. SRL172, an inactivated whole cell booster derived from a non-tuberculous mycobacterium, is the only new vaccine against tuberculosis to have demonstrated efficacy in a Phase 3 trial. In the present study we sought to determine if a three-dose series of DAR-901 manufactured from the SRL172 master cell bank by a new, scalable method was safe and immunogenic.

Methods: We performed a single site, randomized, double-blind, controlled, Phase 1 dose escalation trial of DAR-901 at Dartmouth-Hitchcock Medical Center in the United States. Healthy adult subjects age 18-65 with prior BCG immunization and a negative interferon-gamma release assay (IGRA) were enrolled in cohorts of 16 subjects and randomized to three injections of DAR-901 (n = 10 per cohort), or saline placebo (n = 3 per cohort), or two injections of saline followed by an injection of BCG (n = 3 per cohort; 1-8 x 106 CFU). Three successive cohorts were enrolled representing DAR-901 at 0.1, 0.3, and 1 mg per dose. Randomization was performed centrally and treatments were masked from staff and volunteers. Subsequent open label cohorts of HIV-negative/IGRA-positive subjects (n = 5) and HIV-positive subjects (n = 6) received three doses of 1 mg DAR-901. All subjects received three immunizations at 0, 2 and 4 months administered as 0.1 mL injections over the deltoid muscle alternating between right and left arms. The primary outcomes were safety and immunogenicity. Subjects were followed for 6 months after dose 3 for safety and had phlebotomy performed for safety studies and immune assays before and after each injection. Immune assays using peripheral blood mononuclear cells included cell-mediated IFN-γ responses to DAR-901 lysate and to Mycobacterium tuberculosis (MTB) lysate; serum antibody to M. tuberculosis lipoarabinomannan was assayed by ELISA.

Results: DAR-901 had an acceptable safety profile and was well-tolerated at all dose levels in all treated subjects. No serious adverse events were reported. Median (range) 7-day erythema and induration at the injection site for 1 mg DAR-901 were 10 (4-20) mm and 10 (4-16) mm, respectively, and for BCG, 30 (10-107) mm and 38 (15-55) mm, respectively. Three mild AEs, all headaches, were considered possibly related to DAR-901. No laboratory or vital signs abnormalities were related to immunization. Compared to pre-vaccination responses, three 1 mg doses of DAR-901 induced statistically significant increases in IFN-γ response to DAR-901 lysate and MTB lysate, and in antibody responses to M. tuberculosis lipoarabinomannan. Ten subjects who received 1 mg DAR-901 remained IFN-γ release assay (IGRA) negative after three doses of vaccine.

Conclusions: A three-injection series of DAR-901 was well-tolerated, had an acceptable safety profile, and induced cellular and humoral immune responses to mycobacterial antigens. DAR-901 is advancing to efficacy trials.

Trial Registration: ClinicalTrials.gov NCT02063555.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0175215PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5429024PMC
September 2017

Safety and immunogenicity of the novel H4:IC31 tuberculosis vaccine candidate in BCG-vaccinated adults: Two phase I dose escalation trials.

Vaccine 2017 03 17;35(12):1652-1661. Epub 2017 Feb 17.

Center for Infectious Medicine (CIM), Karolinska Institutet, Stockholm, Sweden. Electronic address:

Background: Novel vaccine strategies are required to provide protective immunity in tuberculosis (TB) and prevent development of active disease. We investigated the safety and immunogenicity of a novel TB vaccine candidate, H4:IC31 (AERAS-404) that is composed of a fusion protein of M. tuberculosis antigens Ag85B and TB10.4 combined with an IC31® adjuvant.

Methods: BCG-vaccinated healthy subjects were immunized with various antigen (5, 15, 50, 150μg) and adjuvant (0, 100, 500nmol) doses of the H4:IC31 vaccine (n=106) or placebo (n=18) in two randomized, double-blind, placebo-controlled phase I studies conducted in a low TB endemic setting in Sweden and Finland. The subjects were followed for adverse events and CD4 T cell responses.

Results: H4:IC31 vaccination was well tolerated with a safety profile consisting of mostly mild to moderate self-limited injection site pain, myalgia, arthralgia, fever and post-vaccination inflammatory reaction at the screening tuberculin skin test injection site. The H4:IC31 vaccine elicited antigen-specific CD4 T cell proliferation and cytokine production that persisted 18weeks after the last vaccination. CD4 T cell expansion, IFN-γ production and multifunctional CD4 Th1 responses were most prominent after two doses of H4:IC31 containing 5, 15, or 50μg of H4 in combination with the 500nmol IC31 adjuvant dose.

Conclusions: The novel TB vaccine candidate, H4:IC31, demonstrated an acceptable safety profile and was immunogenic, capable of triggering multifunctional CD4 T cell responses in previously BCG-vaccinated healthy individuals. These dose-escalation trials provided evidence that the optimal antigen-adjuvant dose combinations are 5, 15, or 50μg of H4 and 500nmol of IC31.

Trial Registration: ClinicalTrials.gov, NCT02066428 and NCT02074956.
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http://dx.doi.org/10.1016/j.vaccine.2017.01.055DOI Listing
March 2017

Safety and Immunogenicity of Adenovirus 35 Tuberculosis Vaccine Candidate in Adults with Active or Previous Tuberculosis. A Randomized Trial.

Am J Respir Crit Care Med 2017 05;195(9):1171-1180

1 University of Cape Town Lung Institute, Division of Pulmonology, Department of Medicine.

Rationale: Administration of tuberculosis (TB) vaccines in participants with previous or current pulmonary TB may have the potential for causing harmful postvaccination immunologic (Koch-type) reactions.

Objectives: To assess the safety and immunogenicity of three dose levels of the AERAS-402 live, replication-deficient adenovirus 35-vectored TB candidate vaccine, containing three mycobacterial antigens, in individuals with current or previous pulmonary TB.

Methods: We performed a phase II randomized, placebo-controlled, double-blinded dose-escalation study in an HIV-negative adult South African cohort (n = 72) with active pulmonary TB (on treatment for 1-4 mo) or pulmonary TB treated at least 12 months before study entry and considered cured. Safety endpoints included clinical assessment, flow volume curves, diffusing capacity of the lung for carbon monoxide, pulse oximetry, chest radiograph, and high-resolution thoracic computerized tomography scans. Cytokine expression by CD4 and CD8 T cells, after stimulation with Ag85A, Ag85B, and TB10.4 peptide pools, was examined by intracellular cytokine staining.

Measurements And Main Results: No apparent temporal or dose-related changes in clinical status (specifically acute, Koch phenomenon-like reactions), lung function, or radiology attributable to vaccine were observed. Injection site reactions were mild or moderate. Hematuria (by dipstick only) occurred in 25 (41%) of 61 AERAS-402 recipients and 3 (27%) of 11 placebo recipients, although no gross hematuria was reported. AERAS-402 induced robust CD8 and moderate CD4 T-cell responses, mainly to Ag85B in both vaccine groups.

Conclusions: Administration of the AERAS-402 candidate TB vaccine to participants with current or previous pulmonary TB induced a robust immune response and is not associated with clinically significant pulmonary complications. Clinical trial registered with www.clinicaltrials.gov (NCT 02414828) and in the South African National Clinical Trials Register ( www.sanctr.gov.za DOH 27-0808-2060).
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http://dx.doi.org/10.1164/rccm.201603-0654OCDOI Listing
May 2017

A new tool for tuberculosis vaccine screening: Ex vivo Mycobacterial Growth Inhibition Assay indicates BCG-mediated protection in a murine model of tuberculosis.

BMC Infect Dis 2016 08 12;16:412. Epub 2016 Aug 12.

London School of Hygiene and Tropical Medicine, London, UK.

Background: In the absence of a validated animal model and/or an immune correlate which predict vaccine-mediated protection, large-scale clinical trials are currently the only option to prove efficacy of new tuberculosis candidate vaccines. Tools to facilitate testing of new tuberculosis (TB) vaccines are therefore urgently needed.

Methods: We present here an optimized ex vivo mycobacterial growth inhibition assay (MGIA) using a murine Mycobacterium tuberculosis infection model. This assay assesses the combined ability of host immune cells to inhibit mycobacterial growth in response to vaccination. C57BL/6 mice were immunized with Bacillus Calmette-Guérin (BCG) and growth inhibition of mycobacteria by splenocytes was assessed. Mice were also challenged with Mycobacterium tuberculosis Erdman, and bacterial burden was assessed in lungs and spleen.

Results: Using the growth inhibition assay, we find a reduction in BCG CFU of 0.3-0.8 log10 after co-culture with murine splenocytes from BCG vaccinated versus naïve C57BL/6 mice. BCG vaccination in our hands led to a reduction in bacterial burden after challenge with Mycobacterium tuberculosis of approx. 0.7 log10 CFU in lung and approx. 1 log10 CFU in spleen. This effect was also seen when using Mycobacterium smegmatis as the target of growth inhibition. An increase in mycobacterial numbers was found when splenocytes from interferon gamma-deficient mice were used, compared to wild type controls, indicating that immune mechanisms may also be investigated using this assay.

Conclusions: We believe that the ex vivo mycobacterial growth inhibition assay could be a useful tool to help assess vaccine efficacy in future, alongside other established methods. It could also be a valuable tool for determination of underlying immune mechanisms.
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http://dx.doi.org/10.1186/s12879-016-1751-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4983071PMC
August 2016

Safety and Immunogenicity of the Recombinant BCG Vaccine AERAS-422 in Healthy BCG-naïve Adults: A Randomized, Active-controlled, First-in-human Phase 1 Trial.

EBioMedicine 2016 May 19;7:278-86. Epub 2016 Apr 19.

Division of Pediatric Infectious Diseases, Columbia University, United States.

Background: We report a first-in-human trial evaluating safety and immunogenicity of a recombinant BCG, AERAS-422, over-expressing TB antigens Ag85A, Ag85B, and Rv3407 and expressing mutant perfringolysin.

Methods: This was a randomized, double-blind, dose-escalation trial in HIV-negative, healthy adult, BCG-naïve volunteers, negative for prior exposure to Mtb, at one US clinical site. Volunteers were randomized 2:1 at each dose level to receive a single intradermal dose of AERAS-422 (>10(5)-<10(6)CFU=low dose, ≥10(6)-<10(7)CFU=high dose) or non-recombinant Tice BCG (1-8×10(5)CFU). Randomization used an independently prepared randomly generated sequence of treatment assignments. The primary and secondary outcomes were safety and immunogenicity, respectively, assessed in all participants through 182days post-vaccination. ClinicalTrials.gov registration number: NCT01340820.

Findings: Between Nov 2010 and Aug 2011, 24 volunteers were enrolled (AERAS-422 high dose, n=8; AERAS-422 low dose, n=8; Tice BCG, n=8); all were included in the safety and immunogenicity analyses. All 24 subjects had at least one adverse event, primarily expected local reactions. High dose AERAS-422 vaccination induced Ag85A- and Ag85B-specific lymphoproliferative responses and marked anti-mycobacterial activity in a whole blood bactericidal activity culture assay (WBA), but was associated with varicella zoster virus (VZV) reactivation in two vaccinees. These volunteers displayed high BCG-specific IFN-γ responses pre- and post-vaccination possibly predisposing them to autocrine/paracrine negative regulation of immune control of latent VZV. A systems biology transcriptomal approach identified positive correlations between post-vaccination T cell expression modules and WBA, and negative correlations between post-vaccination monocyte expression modules and WBA. The expression of one key macrophage marker (F4/80) was constitutively elevated in the two volunteers with zoster.

Interpretation: The unexpected development of VZV in two of eight healthy adult vaccine recipients resulted in discontinuation of AERAS-422 vaccine development. Immunological and transcriptomal data identified correlations with the development of TB immunity and VZV that require further investigation.

Funding: Aeras, FDA, Bill and Melinda Gates Foundation.
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http://dx.doi.org/10.1016/j.ebiom.2016.04.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4909487PMC
May 2016

A Phase I, Open-Label Trial, Evaluating the Safety and Immunogenicity of Candidate Tuberculosis Vaccines AERAS-402 and MVA85A, Administered by Prime-Boost Regime in BCG-Vaccinated Healthy Adults.

PLoS One 2015 3;10(11):e0141687. Epub 2015 Nov 3.

The Jenner Institute, University of Oxford, Oxford, OX3 7DQ, United Kingdom.

Background: MVA85A and AERAS-402 are two clinically advanced viral vectored TB vaccine candidates expressing Mycobacterium tuberculosis antigens designed to boost BCG-induced immunity. Clinical trials with candidate malaria vaccines have demonstrated that adenoviral vector based priming immunisation, followed by MVA vector boost, induced high levels of immunity. We present the safety and immunogenicity results of the first clinical trial to evaluate this immunisation strategy in TB.

Methods: In this phase 1, open-label trial, 40 healthy previously BCG-vaccinated participants were enrolled into three treatment groups and vaccinated with 1 or 2 doses of AERAS-402 followed by MVA85A; or 3 doses of AERAS-402.

Results: Most related adverse events (AEs) were mild and there were no vaccine related serious AEs. Boosting AERAS-402 with MVA85A significantly increased Ag85A-specific T-cell responses from day of vaccination. Two priming doses of AERAS-402 followed by MVA85A boost, resulted in a significantly higher AUC post-peak Ag85A response compared to three doses of AERAS-402 and historical data with MVA85A vaccination alone. The frequency of CD8+ T-cells producing IFN-γ, TNF-α and IL-2 was highest in the group receiving two priming doses of AERAS-402 followed by MVA85A.

Conclusions: Vaccination with AERAS-402 followed by MVA85A was safe and increased the durability of antigen specific T-cell responses and the frequency and polyfunctionality of CD8+ T-cells, which may be important in protection against TB. Further clinical trials with adenoviral prime-MVA85A boost regimens are merited to optimise vaccination intervals, dose and route of immunisation and to evaluate this strategy in the target population in TB high burden countries.

Trial Registration: ClinicalTrials.gov NCT01683773.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0141687PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631471PMC
June 2016

TB Vaccines: The (Human) Challenge Ahead.

Authors:
David A Hokey

Mycobact Dis 2014 Aug;4(4):e128

Department of Immunology, Aeras, Rockville, Maryland, USA.

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http://dx.doi.org/10.4172/2161-1068.1000e128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262929PMC
August 2014

A novel liposomal adjuvant system, CAF01, promotes long-lived Mycobacterium tuberculosis-specific T-cell responses in human.

Vaccine 2014 Dec 30;32(52):7098-107. Epub 2014 Oct 30.

Statens Serum Institut, Department of Infectious Disease Immunology, Artillerivej 5, Copenhagen 2300s, Denmark. Electronic address:

Here, we report on a first-in-man trial where the tuberculosis (TB) vaccine Ag85B-ESAT-6 (H1) was adjuvanted with escalating doses of a novel liposome adjuvant CAF01. On their own, protein antigens cannot sufficiently induce immune responses in humans, and require the addition of an adjuvant system to ensure appropriate delivery and concomitant immune activation. To date no approved adjuvants are available for induction of cellular immunity, which seems essential for a number of vaccines, including vaccines against TB. We vaccinated four groups of human volunteers: a non-adjuvanted H1 group, followed by three groups with escalating doses of CAF01-adjuvanted H1 vaccine. All subjects were vaccinated at 0 and 8 weeks and followed up for 150 weeks. Vaccination did not cause local or systemic adverse effects besides transient soreness at the injection site. Two vaccinations elicited strong antigen-specific T-cell responses which persisted after 150 weeks follow-up, indicating the induction of a long-lasting memory response in the vaccine recipients. These results show that CAF01 is a safe and tolerable, Th1-inducing adjuvant for human TB vaccination trials and for vaccination studies in general where cellular immunity is required.
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http://dx.doi.org/10.1016/j.vaccine.2014.10.036DOI Listing
December 2014

A nonhuman primate toxicology and immunogenicity study evaluating aerosol delivery of AERAS-402/Ad35 vaccine: Evidence for transient t cell responses in peripheral blood and robust sustained responses in the lungs.

Hum Vaccin Immunother 2014 ;10(8):2199-210

a Aeras; Rockville, MD USA.

Bacille Calmette-Guérin (BCG), the only licensed vaccine for the prevention of tuberculosis (TB), provides only limited protection against certain forms of Mycobacterium tuberculosis (Mtb) infection. While infection with Mtb can be treated with antibiotics, the therapy is expensive, toxic, and requires several months for treatment. In addition, the emergence of drug resistant strains limits the impact of antibiotics and underlines the importance of developing a more effective vaccine to control this disease. Given that pulmonary TB is the most common form of the disease, a vaccine capable of inducing lung-resident immunity may be advantageous for combating this infection. New advances in pulmonary delivery make this route of vaccination feasible and affordable. Here, we evaluate the safety and immunogenicity of an aerosolized Ad35-based vaccine, AERAS-402, delivered to the lungs in nonhuman primates as part of a GLP acute and chronic toxicology and safety study. In this study, animals received three high doses (1 x 10(11) vp) of AERAS-402 by inhalation via a nebulizer at 1-week intervals. Aerosol delivery of AERAS-402 resulted in an increase in relative lung weights as well as microscopic findings in the lungs, mediastinal lymph nodes, bronchus-associated lymphatic tissue, and the naso-oropharynx that were consistent with the induction of an immune response during the acute phase. These findings resolved by the chronic phase and were considered to be non-adverse. Furthermore, we observed transient vaccine-specific immune responses in the peripheral blood as well as sustained high-level polyfunctional CD4(+) and CD8(+) T cell responses in the bronchoalveolar lavage fluid of vaccinated nonhuman primates. The data suggest that pulmonary delivery of Ad35-based vaccines can be safe and can induce potent lung-resident immunity.
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http://dx.doi.org/10.4161/hv.29108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4896762PMC
July 2015

The novel tuberculosis vaccine, AERAS-402, is safe in healthy infants previously vaccinated with BCG, and induces dose-dependent CD4 and CD8T cell responses.

Vaccine 2014 Oct 10;32(45):5908-17. Epub 2014 Sep 10.

South African Tuberculosis Vaccine Initiative (SATVI), Institute of Infectious Disease and Molecular Medicine and Department of Paediatrics and Child Health, University of Cape Town, Cape Town, South Africa; Bill and Melinda Gates Foundation, Seattle, WA, USA. Electronic address:

Background: Efforts to reduce risk of tuberculosis disease in children include development of effective vaccines. Our aim was to test safety and immunogenicity of the new adenovirus 35-vectored tuberculosis vaccine candidate AERAS-402 in infants, administered as a boost following a prime with the Bacille Calmette-Guerin vaccine.

Methods: In a phase 1 randomised, double-blind, placebo-controlled, dose-escalation trial, BCG-vaccinated infants aged 6-9 months were sequentially assigned to four study groups, then randomized to receive an increasing dose-strength of AERAS-402, or placebo. The highest dose group received a second dose of vaccine or placebo 56 days after the first. The primary study outcome was safety. Whole blood intracellular cytokine staining assessed immunogenicity.

Results: Forty-two infants received AERAS-402 and 15 infants received placebo. During follow-up of 182 days, an acceptable safety profile was shown with no serious adverse events or discontinuations related to the vaccine. AERAS-402 induced a specific T cell response. A single dose of AERAS-402 induced CD4T cells predominantly expressing single IFN-γ whereas two doses induced CD4T cells predominantly expressing IFN-γ, TNF-α and IL-2 together. CD8T cells were induced and were more likely to be present after 2 doses of AERAS-402.

Conclusions: AERAS-402 was safe and immunogenic in healthy infants previously vaccinated with BCG at birth. Administration of the highest dose twice may be the most optimal vaccination strategy, based on the induced immunity. Multiple differences in T cell responses when infants are compared with adults vaccinated with AERAS-402, in the same setting and using the same whole blood intracellular cytokine assay, suggest specific strategies may be important for vaccination for each population.
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http://dx.doi.org/10.1016/j.vaccine.2014.09.001DOI Listing
October 2014

Aerosol vaccination with AERAS-402 elicits robust cellular immune responses in the lungs of rhesus macaques but fails to protect against high-dose Mycobacterium tuberculosis challenge.

J Immunol 2014 Aug 14;193(4):1799-811. Epub 2014 Jul 14.

Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892;

Development of a vaccine against pulmonary tuberculosis may require immunization strategies that induce a high frequency of Ag-specific CD4 and CD8 T cells in the lung. The nonhuman primate model is essential for testing such approaches because it has predictive value for how vaccines elicit responses in humans. In this study, we used an aerosol vaccination strategy to administer AERAS-402, a replication-defective recombinant adenovirus (rAd) type 35 expressing Mycobacterium tuberculosis Ags Ag85A, Ag85B, and TB10.4, in bacillus Calmette-Guérin (BCG)-primed or unprimed rhesus macaques. Immunization with BCG generated low purified protein derivative-specific CD4 T cell responses in blood and bronchoalveolar lavage. In contrast, aerosolized AERAS-402 alone or following BCG induced potent and stable Ag85A/b-specific CD4 and CD8 effector T cells in bronchoalveolar lavage that largely produced IFN-γ, as well as TNF and IL-2. Such responses induced by BCG, AERAS-402, or both failed to confer overall protection following challenge with 275 CFUs M. tuberculosis Erdman, although vaccine-induced responses associated with reduced pathology were observed in some animals. Anamnestic T cell responses to Ag85A/b were not detected in blood of immunized animals after challenge. Overall, our data suggest that a high M. tuberculosis challenge dose may be a critical factor in limiting vaccine efficacy in this model. However, the ability of aerosol rAd immunization to generate potent cellular immunity in the lung suggests that using different or more immunogens, alternative rAd serotypes with enhanced immunogenicity, and a physiological challenge dose may achieve protection against M. tuberculosis.
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http://dx.doi.org/10.4049/jimmunol.1400676DOI Listing
August 2014

The frequencies of IFNγ+IL2+TNFα+ PPD-specific CD4+CD45RO+ T-cells correlate with the magnitude of the QuantiFERON® gold in-tube response in a prospective study of healthy indian adolescents.

PLoS One 2014 3;9(7):e101224. Epub 2014 Jul 3.

Centre for Immune Regulation and Department of Pathology, Oslo University Hospital - Rikshospitalet and the University of Oslo, Oslo, Norway.

Background: QuantiFERON-TB Gold In-Tube (QFT) is an IFNγ-release assay used in the diagnosis of Mycobacterium tuberculosis (MTB) infection. The risk of TB progression increases with the magnitude of the MTB-specific IFNγ-response. QFT reversion, also associated with low Tuberculin Skin Test responses, may therefore represent a transient immune response with control of M. tuberculosis infection. However, studies at the single cell level have suggested that the quality (polyfunctionality) of the T-cell response is more important than the quantity of cytokines produced.

Objective: To explore the quality and/or magnitude of mycobacteria-specific T-cell responses associated with QFT reversion and persistent QFT-positivity.

Methods: Multi-color flowcytometry on prospectively collected peripheral blood mononuclear cells was applied to assess mycobacteria-specific T-cell responses in 42 QFT positive Indian adolescents of whom 21 became QFT negative (reverters) within one year. Ten QFT consistent negatives were also included as controls.

Results: There was no difference in the qualitative PPD-specific CD4+ T-cell response between QFT consistent positives and reverters. However, compared with QFT consistent positives, reverters displayed lower absolute frequencies of polyfunctional (IFNγ+IL2+TNFα+) CD4+ T-cells at baseline, which were further reduced to the point where they were not different to QFT negative controls one year later. Moreover, absolute frequencies of these cells correlated well with the magnitude of the QFT-response.

Conclusion: Whereas specific polyfunctional CD4+ T-cells have been suggested to protect against TB progression, our data do not support that higher relative or absolute frequencies of PPD-specific polyfunctional CD4+ T-cells in peripheral blood can explain the reduced risk of TB progression observed in QFT reverters. On the contrary, absolute frequencies of these cells correlated with the QFT-response, suggesting that this readout reflects antigenic load.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0101224PLOS
October 2015

OMIP-022: Comprehensive assessment of antigen-specific human T-cell functionality and memory.

Cytometry A 2014 Jul 27;85(7):576-9. Epub 2014 May 27.

Aeras, Rockville, Maryland USA.

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http://dx.doi.org/10.1002/cyto.a.22478DOI Listing
July 2014

The current state of tuberculosis vaccines.

Hum Vaccin Immunother 2013 Oct 21;9(10):2142-6. Epub 2013 Jun 21.

Aeras; Rockville, MD USA.

Tuberculosis continues to persist despite widespread use of BCG, the only licensed vaccine to prevent TB. BCG's limited efficacy coupled with the emergence of drug-resistant strains of Mycobacterium tuberculosis emphasizes the need for a more effective vaccine for combatting this disease. However, the development of a TB vaccine is hindered by the lack of immune correlates, suboptimal animal models, and limited funding. An adolescent/adult vaccine would have the greatest public health impact, but effective delivery of such a vaccine will require a better understanding of global TB epidemiology, improved infrastructure, and engagement of public health leaders and global manufacturers. Here we discuss the current state of tuberculosis vaccine research and development, including our understanding of the underlying immunology as well as the challenges and opportunities that may hinder or facilitate the development of a new and efficacious vaccine.
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http://dx.doi.org/10.4161/hv.25427DOI Listing
October 2013

Immune modulation through 4-1BB enhances SIV vaccine protection in non-human primates against SIVmac251 challenge.

PLoS One 2011 15;6(9):e24250. Epub 2011 Sep 15.

University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.

Costimulatory molecules play a central role in the development of cellular immunity. Understanding how costimulatory pathways can be directed to positively influence the immune response may be critical for the generation of an effective HIV vaccine. Here, we evaluated the ability of intravenous administration of a blocking monoclonal antibody (mAb) directed against the negative costimulatory molecule CTLA-4, and an agonist mAb directed against the positive costimulatory molecule 4-1BB, either alone or in combination, to augment intramuscular SIV DNA immunizations. We then tested the ability these of these responses to impact a high-dose SIVmac251 challenge. Following immunization, the groups infused with the anti-4-1BB mAb exhibited enhanced IFN-γ responses compared to the DNA vaccine only group. Interestingly, although CTLA-4 blockade alone did not enhance IFN-γ responses it did increase the proliferative capacity of the CD4(+) and CD8(+) T cells. The combination of both mAbs enhanced the magnitude of the polyfunctional CD8(+) T cell response. Following challenge, the group that received both mAbs exhibited a significant, ∼2.0 log, decrease in plasma viral load compared to the naïve group the included complete suppression of viral load in some animals. Furthermore, the use of the CTLA-4 blocking antibody resulted in significantly higher viral loads during chronic infection compared to animals that received the 4-1BB mAb, likely due to the higher CD4(+) T cell proliferative responses which were driven by this adjuvant following immunization. These novel studies show that these adjuvants induce differential modulation of immune responses, which have dramatically different consequences for control of SIV replication, suggesting important implications for HIV vaccine development.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0024250PLOS
February 2012

Aerosol vaccines for tuberculosis: a fine line between protection and pathology.

Tuberculosis (Edinb) 2011 Jan 9;91(1):82-5. Epub 2010 Nov 9.

Aeras Global TB Vaccine Foundation, Vaccine Assessment, 1405 Research Boulevard, Suite 300, Rockville, MD 20850, USA.

Pulmonary delivery of vaccines against airborne infection is being investigated worldwide, but there is limited effort directed at developing inhaled vaccines for tuberculosis (TB). This review addresses some of the challenges confronting vaccine development for TB and attempts to link these challenges to the promises of mucosal immunity offered by pulmonary delivery. There are several approaches working toward this goal including subunit vaccines, recombinant strains, a novel vaccine strain Mycobacterium w, and DNA vaccine approaches. While it is clear that lung-resident adaptive immunity is an attainable goal, vaccine platforms must ensure that damage to the lung is limited during both vaccination and when memory cells respond to pathogenic infection.
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http://dx.doi.org/10.1016/j.tube.2010.09.007DOI Listing
January 2011

Ki-67 staining for determination of rhesus macaque T cell proliferative responses ex vivo.

Cytometry A 2010 Mar;77(3):275-84

Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.

The capacity for robust proliferation upon re-infection is a hallmark of adaptive immunity and the basis of vaccination. A widely used animal model for the study of human disease is the rhesus macaque (RM), where capacity for proliferation can be assessed ex vivo using carboxyfluorescein succinimidyl ester (CFSE)-based dilution assays. However, we show over the course of the standard ex vivo proliferation assay that CFSE-labeling at commonly used dye concentrations induces significant cell death, but that this phenomenon is dose-dependent. Here, we describe an alternative semiquantitative method for estimating T cell proliferative responses that avoids the putative biases associated with chemical modification. RM peripheral blood mononuclear cells were stimulated ex vivo with cognate peptides for 5 days, immunostained for intracellular Ki-67, and then analyzed by flow cytometry. We describe a gating strategy using Ki-67 and side light scatter, also a marker of blastogenesis, which correlates strongly with data from CFSE dilution. We show that this method is a valid tool for measuring RM antigen-specific cellular proliferation ex vivo and can be used as an alternative to CFSE dilution assays.
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http://dx.doi.org/10.1002/cyto.a.20857DOI Listing
March 2010

Novel SIVmac DNA vaccines encoding Env, Pol and Gag consensus proteins elicit strong cellular immune responses in cynomolgus macaques.

Vaccine 2009 May 5;27(25-26):3260-6. Epub 2009 Feb 5.

Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.

Cellular immunity plays an important role in controlling HIV-1 replication. One of the major challenges in developing an HIV-1 DNA vaccine is to generate broader and more potent cellular responses. In this study, we constructed three novel constructs expressing SIVmac antigens Env, Pol and Gag, respectively, with the goal of increasing anti-SIV cellular immunity. The results demonstrate that these constructs can induce strong cellular immune responses in a murine model. Moreover, when applied to cynomolgus macaques, these constructs are not only able to elicit robust IFN-gamma effector responses, but also induce SIV antigen-specific CD8(+) T cells that have high proliferative capacity. These data suggest that such DNA immunogens deserve further examination for their potential to control viral replication.
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http://dx.doi.org/10.1016/j.vaccine.2009.01.065DOI Listing
May 2009

CLTA-4 blockade in vivo promotes the generation of short-lived effector CD8 T cells and a more persistent central memory CD4 T cell response.

J Med Primatol 2008 Dec;37 Suppl 2:62-8

Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA.

Background: Previously, we examined the effects of in vivo CTLA-4 blockade using a fully human monoclonal antibody as a part of a DNA vaccination regimen in cynomolgus macaques (Macaca fascicularis). We observed that while the antibody had little effect on the IFN-gamma ELISpot response, CTLA-4 blockade enhanced antigen-specific cellular proliferation in both CD4(+) and CD8(+)T-cell compartments.

Methods: We examine the specific effects of CTLA-4 blockade on memory T-cell compartments following the third immunization and 10 months following a fourth immunization, during the memory phase of the immune response.

Results: CLTA-4 blockade enhanced CD4(+) and CD8(+) central memory (CD28(hi), CD95(hi)) T-cell responses as well as a short-lived CD8(+) effector (CD28(lo), CD95(hi)) T-cell response.

Conclusions: These data suggest differing effects of CTLA-4 blockade on CD4(+) and CD8(+) T cells with implications on the clinical use of anti-CTLA-4 antibodies for enhancement of vaccine strategies or treatment of human disease.
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http://dx.doi.org/10.1111/j.1600-0684.2008.00324.xDOI Listing
December 2008

Induction of antitumor immunity in vivo following delivery of a novel HPV-16 DNA vaccine encoding an E6/E7 fusion antigen.

Vaccine 2009 Jan 18;27(3):431-40. Epub 2008 Nov 18.

Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.

Human papillomavirus type 16 (HPV-16) infection is associated with a majority of cervical cancers and a significant proportion of head and neck cancers. Here, we describe a novel-engineered DNA vaccine that encodes a HPV-16 consensus E6/E7 fusion gene (pConE6E7) with the goal of increasing its antitumor cellular immunity. Compared to an early stage HPV-16 E7 DNA vaccine (pE7), this construct was up to five times more potent in driving E7-specific cellular immune responses. Prophylactic administration of this vaccine resulted in 100% protection against HPV E6 and E7-expressing tumors. Therapeutic studies indicated that vaccination with pConE6E7 prevented or delayed the growth of tumors. Moreover, immunization with pConE6E7 could also partially overcome immune tolerance in E6/E7 transgenic mice. Such DNA immunogens are interesting candidates for further study to investigate mechanisms of tumor immune rejection in vivo.
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http://dx.doi.org/10.1016/j.vaccine.2008.10.078DOI Listing
January 2009

Combined effects of IL-12 and electroporation enhances the potency of DNA vaccination in macaques.

Vaccine 2008 Jun 11;26(25):3112-20. Epub 2008 Mar 11.

Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, 422 Curie Boulevard, 505 SCL, Philadelphia, PA 19104, United States.

DNA vaccines are a promising technology. Historically, however, the ability of DNA vaccines to induce high response rates and strong immune responses, especially antibody responses, in non-human primates and human clinical trials has proven suboptimal. Here, we performed a pilot study in rhesus macaques to evaluate whether we could improve the immunogenicity of DNA vaccines through the use of adjuvant technology and improved delivery systems. The study consisted of four groups of animals that received: DNA by intramuscular (IM) injection, DNA with plasmid-encoded IL-12 by IM injection, DNA by IM injection with in vivo electroporation (EP), and DNA with IL-12 by IM EP. Each group was immunized three times with optimized HIV gag and env constructs. Vaccine immunogenicity was assessed by IFNgamma ELISpot, CFSE proliferation, polyfunctional flow cytometry, and antibody ELISA. Similar to previous studies, use of IL-12 as an adjuvant increased the gag and env-specific cellular responses. The use of EP to enhance plasmid delivery resulted in dramatically higher cellular as well as humoral responses. Interestingly, the use of EP to administer the DNA and IL-12 adjuvant combination resulted in the induction of higher, more efficient responses such that a 10-fold increase in antigen-specific IFNgamma(+) cells compared to IM DNA immunization was observed after a single immunization. In addition to increases in the magnitude of IFNgamma production in the initial and memory responses, the combined approach resulted in enhancements in the proliferative capacity of antigen-specific CD8(+) T cells and the amount of polyfunctional cells capable of producing IL-2 and TNFalpha in addition to IFNgamma. These data suggest that adjuvant and improved delivery methods may be able to overcome previous immunogenicity limitations in DNA vaccine technology.
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http://dx.doi.org/10.1016/j.vaccine.2008.02.036DOI Listing
June 2008

Activation drives PD-1 expression during vaccine-specific proliferation and following lentiviral infection in macaques.

Eur J Immunol 2008 May;38(5):1435-45

Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.

Recent data supports that increased expression of PD-1, a negative regulator of immune function, is associated with T cell exhaustion during chronic viral infection. However, PD-1 expression during acute infection and vaccination has not been studied in great detail in primates. Here, we examine PD-1 expression on CD3(+) T cells following DNA vaccination or lentiviral infection of macaques. Ex vivo peptide stimulation of PBMC from DNA-vaccinated uninfected macaques revealed a temporal increase in PD-1 expression in proliferating antigen-specific CD8(+) T cells. Following the initial increase, PD-1 expression steadily declined as proliferation continued, with a concomitant increase in IFN-gamma secretion. Subsequent examination of PD-1 expression on T cells from uninfected and lentivirus-infected non-vaccinated macaques revealed a significant increase in PD-1 expression with lentiviral infection, consistent with previous reports. PD-1 expression was highest on cells with activated memory and effector phenotypes. Despite their decreased telomere length, PD-1(hi) T cell populations do not appear to have statistically significant uncapped telomeres, typically indicative of proliferative exhaustion, suggesting a different mechanistic regulation of proliferation by PD-1. Our data indicate that PD-1 expression is increased as a result of T cell activation during a primary immune response as well as during persistent immune activation in macaques.
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http://dx.doi.org/10.1002/eji.200737857DOI Listing
May 2008

Augmentation of SIV DNA vaccine-induced cellular immunity by targeting the 4-1BB costimulatory molecule.

Vaccine 2008 Jun 22;26(25):3121-34. Epub 2008 Feb 22.

Research Institute for Genetic and Human Therapy, Ploiclinico S. Matteo, 27100 Pavia, Italy.

DNA vaccines are effective at inducing antigen-specific cellular immune responses. Approaches to improve these responses, however, are needed. We examined the effect of stimulating 4-1BB, an activation-inducible T-cell costimulatory receptor, by intravenously co-administering anti-human 4-1BB monoclonal antibody (mAb) in DNA-immunized cynomolgus macaques. Three groups of six cynomolgus macaques were immunized intramuscularly with a DNA vaccine encoding SIV Gag antigen (pSIVgag) at weeks 0, 4 and 8. At days 12, 15, and 19, six macaques received anti-4-1BB 4E9 mAb and six macaques received anti-4-1BB 10C7 mAb. Treatment with 10C7 mAb led to a significant augmentation of SIV Gag-specific IFN-gamma, granzyme B and perforin responses. Treatment with humanized 4E9 mAb also resulted in an enhancement of SIV Gag-specific cellular responses but the magnitude was lower compared to animals receiving 10C7 mAb. These responses persisted up to week 40 and were mostly mediated by CD8(+) T cells. Treatment with anti-4-1BB mAb was more effective in driving the CD8(+) T cells toward a more differentiated CCR7(-)/CD45RA(+) effector state. This study demonstrates that targeting the 4-1BB molecule in vivo results in an enhanced and long-lasting cellular immune response. 4-1BB stimulation may be a promising approach to enhance the effectiveness of DNA vaccines.
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http://dx.doi.org/10.1016/j.vaccine.2008.02.017DOI Listing
June 2008

Protection against simian/human immunodeficiency virus (SHIV) 89.6P in macaques after coimmunization with SHIV antigen and IL-15 plasmid.

Proc Natl Acad Sci U S A 2007 Nov 13;104(47):18648-53. Epub 2007 Nov 13.

Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, 422 Curie Boulevard, Philadelphia, PA 19104, USA.

The cell-mediated immune profile induced by a recombinant DNA vaccine was assessed in the simian/HIV (SHIV) and macaque model. The vaccine strategy included coimmunization of a DNA-based vaccine alone or in combination with an optimized plasmid encoding macaque IL-15 (pmacIL-15). We observed strong induction of vaccine-specific IFN-gamma-producing CD8(+) and CD4(+) effector T cells in the vaccination groups. Animals were subsequently challenged with 89.6p. The vaccine groups were protected from ongoing infection, and the IL-15 covaccinated group showed a more rapidly controlled infection than the group treated with DNA vaccine alone. Lymphocytes isolated from the group covaccinated with pmacIL-15 had higher cellular proliferative responses than lymphocytes isolated from the macaques that received SHIV DNA alone. Vaccine antigen activation of lymphocytes was also studied for a series of immunological molecules. Although mRNA for IFN-gamma was up-regulated after antigen stimulation, the inflammatory molecules IL-8 and MMP-9 were down-regulated. These observed immune profiles are potentially reflective of the ability of the different groups to control SHIV replication. This study demonstrates that an optimized IL-15 immune adjuvant delivered with a DNA vaccine can impact the cellular immune profile in nonhuman primates and lead to enhanced suppression of viral replication.
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http://dx.doi.org/10.1073/pnas.0709198104DOI Listing
November 2007

Phagocytosis induces lysosome remodeling and regulated presentation of particulate antigens by activated dendritic cells.

J Immunol 2006 Dec;177(12):8493-503

Department of Dermatology, Center for Biologic Imaging, University of Pittsburgh School of Medicine, Pittsburgh, PA 15217, USA.

Immunization with particulate Ag effectively induces antitumor and antiviral T cell-mediated immunity. Immature dendritic cells (DCs) efficiently internalize, process, and present a variety of particulate Ags; however, previously published data suggest that both the uptake of soluble Ag through micropinocytosis, and phagocytosis of particulates are significantly curtailed in activated DC populations. In this study, we demonstrate that although macropinocytosis of soluble Ag is diminished following DC activation, subsets of DCs in activated DC populations retain the ability to actively phagocytose particulate Ags. Live cell imaging of activated DCs reveals that phagocytosis of particulates can result in cytoskeletal remodeling and perinuclear lysosome cluster disruption in a time-dependent manner. Interestingly, our results suggest that in activated DC populations, presentation of phagocytosed particulate Ags is dependent on the nature of the activation signal. These results provide direct evidence of functional heterogeneity in DC populations and contribute to the development of particle-based immunization strategies.
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http://dx.doi.org/10.4049/jimmunol.177.12.8493DOI Listing
December 2006
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