As a follow-up to yesterday's post, here is a quick round up of the published data relating to immune responses generated by the Merck and VRC HIV vaccine candidates. I've also added the recent conference presentations that I could find, but note that this almost certainly omits some additional presentations for which the abstracts are not accessible online (e.g. the annual Keystone HIV vaccine conference). A full comparative analysis will have to await a future post but a few things jump out immediately:
- The Merck vaccine appears to have been surprisingly poor at inducing HIV-specific CD4 T cell responses. During initial talks about the vaccine, my recollection is that the rates of CD4 T cell responses were said to be comparable to CD8 T cell responses, but according to the CROI abstract from 2005, only ~30% of people with detectable HIV-specific CD8 T cells also displayed HIV-specific CD4 T cells. This raises a number of questions about the functionality of the HIV-specific CD8 T cell response in people who lacked detectable CD4 T cells (CD4 T cell help is required for the efficient generation and secondary expansion of CD8 T cells) and also whether the activation of pre-existing Ad5-specific CD4 T cell responses by the vector somehow interfered with the development of CD4 T cell responses to the HIV proteins encoded by the vaccine.
- The limited polyfunctionality data presented by Merck at the AIDS Vaccines 2007 conference does appear to support the contention that the VRC construct induces a more polyfunctional CD8 T cell response than the Merck HIV vaccine.
- Given the importance of the topic, the HIV vaccine field urgently needs more comprehensive published data than the limited amount that is currently available; it should not be necessary to try and read immunological tea leaves when considering the implications of the Merck vaccine failure for other candidates such as the VRC's.
Merck – published papers:
J Acquir Immune Defic Syndr. 2007 May 1;45(1):20-7.
Detection of HIV vaccine-induced cell-mediated immunity in HIV-seronegative clinical trial participants using an optimized and validated enzyme-linked immunospot assay.
Dubey S, Clair J, Fu TM, Guan L, Long R, Mogg R, Anderson K, Collins KB, Gaunt C, Fernandez VR, Zhu L, Kierstead L, Thaler S, Gupta SB, Straus W, Mehrotra D, Tobery TW, Casimiro DR, Shiver JW.
Department of Vaccine and Biologics Research, Merck Research Laboratories, West Point, PA 19486, USA.
An effective vaccine for HIV is likely to require induction of T-cell-mediated immune responses, and the interferon-gamma (IFNgamma) enzyme-linked immunospot (ELISPOT) assay has become the most commonly used assay for measuring these responses in vaccine trials. We optimized and validated the HIV ELISPOT assay using an empirical method to establish positivity criteria that results in a < or =1% false-positive rate. Using this assay, we detected a broad range of HIV-specific ELISPOT responses to peptide pools of overlapping 20mers, 15mers, or 9mers in study volunteers receiving DNA- or adenovirus vector-based HIV vaccines and in HIV-seropositive donors. We found that 15mers generally had higher response magnitudes than 20mers and lower false-positive rates than 9mers. These studies show that our validated ELISPOT assay using 15mer peptide pools and the positivity criteria of > or =55 spots per 10(6) cells and > or =4-fold over mock (negative control) is a sensitive and specific assay for the detection of HIV vaccine-induced cell-mediated immunity.
AIDS Res Hum Retroviruses. 2006 Nov;22(11):1081-90.
A comparison of standard immunogenicity assays for monitoring HIV type 1 gag-specific T cell responses in Ad5 HIV Type 1 gag vaccinated human subjects.
Tobery TW, Dubey SA, Anderson K, Freed DC, Cox KS, Lin J, Prokop MT, Sykes KJ, Mogg R, Mehrotra DV, Fu TM, Casimiro DR, Shiver JW.
Department of Vaccines and Biologics Research, Merck Research Laboratories, West Point, Pennsylvania 19486, USA.
Currently, there are numerous candidate HIV vaccines aimed at inducing T-cell mediated immune responses against HIV. To assess the immunogenicity of such vaccines, a reliable T cell assay must be utilized and typically one of the following assays is chosen for this purpose: bulk culture CTL, MHC I tetramer staining, IFN-gamma ELISPOT, or IFN-gamma intracellular cytokine staining. In this paper we report a comparison of the T cell responses detected by each assay in a large cohort of healthy normal volunteers vaccinated with adenovirus serotype 5 expressing HIV gag. Using stringently validated formats of each of these assays and pools of overlapping HIV gag peptides, we demonstrate that there is a high degree of correlation between all four of the common T cell assays, but inherent differences in the sensitivity of each assay to detect responders. In this study, the ELISPOT assay is shown to have the greatest sensitivity in detecting vaccine responses, while the ICS assay, although less sensitive, has the advantage of providing additional information on the phenotype of the responding cells.
AIDS Res Hum Retroviruses. 2007 Jan;23(1):86-92
Enhanced rates and magnitude of immune responses detected against an HIV vaccine: effect of using an optimized process for isolating PBMC.
Kierstead LS, Dubey S, Meyer B, Tobery TW, Mogg R, Fernandez VR, Long R, Guan L, Gaunt C, Collins K, Sykes KJ, Mehrotra DV, Chirmule N, Shiver JW, Casimiro DR.
Vaccine and Biologics Research, Merck Research Laboratories, West Point and Wayne, PA 19087, USA.
Quantitative analysis of cell-mediated immune responses induced by candidate HIV vaccines requires robust procedures for collecting and processing human peripheral mononuclear blood cells (PBMCs). We evaluated several parameters in order to optimize a sample handling process that would be suitable for a multicenter clinical trial. Among the findings, systematic increases in the magnitude of IFN-gamma ELISpot responses were observed when the time from blood collection to PBMC freezing was reduced to <12 h. By implementing these improvements within an ongoing clinical trial, the estimated immunologic response rates to an adenovirus- based HIV vaccine increased by more than 20 percentage points to approximately 80% of the vaccine recipients against any of the vaccine antigens and the average levels of T cell response improved more than 3-fold. These studies establish the importance of optimal conditions for PBMC collection and handling to the success of a clinical development program.
Merck – conference presentations:
AIDS Vaccines 2007
http://www.hivvaccineenterprise.org/_dwn/Oral_Sessions.pdf
OA08-02
Safety and immunogenicity of the MRKAd5 gag HIV-1 vaccine in a worldwide phase I study of healthy adults (Merck V520-018/HVTN 050)
S Hammer5, M Miller12, J Pape10, P Pitisuttithum11, V Suriyanon3, S Nitayaphan1, J Sanchez2, E Kallas6, C Harro9, G Gray4, M Cardinali7, K Turner8, X Sun12, D Mehrotra12 and E Quirk12
1 Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand; 2 Asociación Civil Impacta Salud y Educación, Lima, Peru; 3 Chiang Mai University, Chiang Mai, Thailand; 4 Chris Hani Baragwanath Hospital, Johannesburg, South Africa; 5 Columbia University, New York, NY, USA; 6 Federal University of Sao Paulo, Sao Paolo, Brazil; 7 Henry M. Jackson Foundation at the Division of AIDS, NIAID, Bethesda, MD, USA; 8 HIV Vaccine Trials Network, Seattle, WA, USA; 9 Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA; 10 Les Centres GHESKIO, Port-au- Prince, Haiti; 11 Mahidol University, Bangkok, Thailand; 12 Merck Research Laboratories, West Point, PA, USA
Background: Phase I studies indicate the monovalent MRKAd5 HIV-1 gag vaccine is well tolerated and immunogenic in N. American populations. High prevalence of preexisting immunity to adenovirus type 5 (Ad5) may affect vaccine response rates. Aim: We analyzed the preliminary data through Week 30 of this international Phase I study testing the safety and immunogenicity of an Ad5 HIV vaccine candidate. Methods: Healthy adults aged 18-50 at low risk for HIV infection were randomized 1:3:3 to receive placebo, 1x109 or 1x1010 viral particles (vp) of the MRKAd5 HIV-1 gag vaccine at Day 1, Week 4 and Week 26 in a dose-escalating staged study in 24 centers in Africa, Asia, Caribbean, N. and S. America. Enrollment was not stratified by baseline Ad5 titer. Adverse events (AE) and lab values were assessed after each dose. Immunogenicity was evaluated using an IFN-γ ELISPOT gag 15-mer assay. Positive ELISPOT responses were defined as >55 SFC/106 PBMC and ≥4-fold over mock control. Results: 360 people (55% male, median age 30) were enrolled (87 each in Asia and N. and S.America; 75 in the Caribbean; 24 in Africa). The vaccine was generally well tolerated at both doses. The most common AEs were injection site reaction, headache, fever, and diarrhea. At Week 30, pooled ELISPOT responses were 57/133 (43%) in the 1x109 vp group and 108/139 (78%) in the 1x1010 vp group. Overall, responses to 1x1010 vp were 85% and 68% in subjects with low (≤200, n=75) and high (>200, n=62) baseline Ad5 titers, respectively. Response rates among subjects with high baseline Ad5 titers who received 1x1010 vp were: 23/26 (88%) in Asia, 2/7 (29%) in N. America, 10/13 (77%) in S. America, 7/12 (58%) in the Caribbean, and 0/4 in Africa. Conclusion: The MRKAd5 HIV-1 gag vaccine was generally well tolerated and immunogenic in diverse world regions. The 1x1010 vp dose was generally more immunogenic than 1x109 vp. Although there may be a modest effect of high baseline Ad5 titers on ELISPOT responses, overall most subjects with high levels of preexisting Ad5 immunity had positive ELISPOT responses to 1x1010 vp. These data indicate that the MRKAd5 HIV-1 gag vaccine may be immunogenic in regions with high prevalence of Ad5 immunity. This international study of the MRKAd5 gag vaccine supports ongoing Phase II test-of-concept trials of a next generation MRKAd5 trivalent gag/pol/nef vaccine.
http://www.hivvaccineenterprise.org/_dwn/Poster_Sessions.pdf
P06-29
Evaluation of multi-functional T cell responses elicited by the Merck trivalent Ad5gag/pol/nef vaccine using a qualified 9 color flow cytometric assay
KS Cox, JH Clair, MT Prokop, S Dubey, J Shiver and D Casimiro
Merck Research Laboratories, West Point, PA, USA
Background: Cellular immunity has been shown to play a critical role in the control of HIV-1 infections. To date, the most commonly measured T cell response in HIV vaccine programs is IFN-gamma (IFN-γ) production. Recently, there has been increased interest in the examination of additional T cell markers to measure the quality and breadth of the immune response, which may be important in HIV viral control. Although these types of multi-color flow cytometeric assays have been emerging across various laboratories, data sets have not been generated using a statistically qualified assay, which is critical for the accurate interpretation of results. Objective: To qualify a multi-color intracellular cytokine staining (ICS) assay to determine the positivity criteria, false positive rates, and the repeatability of positive responses and utilize this assay to measure the immune responses in a cohort of forty HIV clinical trial vaccinees. Methods: A flow based assay was developed to simultaneously examine five T cell functions (CD107a, IFN-γ, IL-2, MIP1-β, and TNFα). This analysis results in 31 subsets each for the CD8 and CD4 populations. To qualify the assay, 10 HIV gag responders were repeated in 4 assay runs, and 10 HIV seronegative subjects were each run twice with HIV gag, nef and pol 15 mer peptide pools. After statistical analysis of the qualification data set, a cohort of forty HIV seronegative clinical trial participants who were vaccinated with 3 x1010 v.p. of the Merck Trivalent Adenovirus type 5 vaccine (MRKAd5 HIV-1 gag/pol/nef) were tested. The pre-vaccination samples from the same cohort were tested for clinical confirmation of the false positive rates. Results: Assay qualification demonstrated that a two-dimensional positivity cut-off of >90 antigen-specific events per million lymphocytes and >3-fold over background (no antigen) would result in false positive rate of <5% per subset of responses. When the qualified assay was used to evaluate responses in the 40 vaccinees, we observed positive responses in 9 of the 31 CD8 subsets and 10 of the 31 CD4 subsets. Conclusion: A data set from MRKAd5 HIV-1 gag/pol/nef vaccinees was generated using a qualified multi-color ICS assay. The vaccine elicited multifunctional T cell responses to HIV gag, pol and nef in both the CD8 and CD4 T cell populations.
P08-17
Flow cytometric analysis of T cell proliferation using a CFSE dye assay
KJ Sykes, S Dubey, Y Wang, Shiver and D Casimiro
Merck and Co., West Point, PA, USA
Background: Greater understanding of the role of HIV-specific immunity remains fundamental to current and future therapies to prevent and treat HIV infection. Very early in HIV infection, prior to a decrease in absolute CD4 cell number, functional defects in HIV-specific CD4+ T helper cells become apparent, including the ability of the CD4+ peripheral blood mononuclear cells (PBMCs) to proliferate in response to HIV antigens. A flow cytometrybased proliferation assay using CFSE has become a widely used method to measure proliferation in samples from HIV infected patients and in HIV vaccine recipients. However, high backgrounds and low sensitivity have often been observed with this assay, prompting further optimization and characterization in order for it to be a useful tool in vaccine studies. Objective: To assess the proliferative capacity of HIV seropositive donors and HIV seronegative vaccinees using an optimized CFSE flow cytometric assay measuring CD4 and CD8 T cell proliferation. Methods: The CFSE assay was optimized by comparing serum sources, cell concentrations and culturing conditions using frozen-thawed PBMC. Using the optimized CFSE assay, data was collected from 39 HIV seropositive individuals and 10 HIV seronegative vaccinees who received Adenovirus-5 HIV gag vaccine (Ad5 gag). CFSE labeled cells were cultured in 96-deep well plates in the presence or absence of Gag 15mer peptide for 7 days. After 7 days, cells were stained using CD3, CD4 and CD8 monoclonal antibodies and run on a BD FACsCalibur. Data was analyzed using FlowJo software. Results: The assay was successfully optimized to give low backgrounds and measurable proliferation in both cohorts analyzed. Proliferation in HIV seropositive individuals ranged from 1.0% to 4.5% for CFSElowCD8highand 1.5% to 2.0% for CFSElowCD4high. HIV seronegative vaccinees showed gagspecific proliferation at similar yet higher levels compared to HIV-infected donors, with post vaccination proliferation ranging from 2.0% to 8.0% for CFSElowCD8highand 1.0% to 6.0% for CFSElowCD4high. Conclusion: Optimizing the CFSE assay has allowed detection of proliferation in HIV-infected donors and in seronegative HIV gag vaccinees. This optimized assay shows that the Merck Ad5 gag vaccine induces HIV-specific proliferation in our vaccine recipients.
CROI 2005 Abstract #506
Detailed Characterization of the Cellular Immune Responses in Healthy Volunteers Immunized with Replication-defective Adenovirus HIV Vaccines
Danilo Casimiro*, S Dubey, T Tobery, L Kierstead, J Condra, A Finnefrock, R Isaacs, M Robertson, R Leavitt, R Mogg, D Mehrotra, J Kublin, J Shiver, and V520 Merck Study Group
Merck & Co, West Point, PA, USA
Background: We have recently been developing replication-defective adenovirus type 5 (MRKAd5)-based vaccines that express reasonably conserved viral antigens (gag, pol, nef) of the B clade in several phase I studies. It is important to assess the potential of this vaccine to elicit potent cytotoxic activity as well as to provide broad coverage against viruses both intraclade and interclade.
Methods: Peripheral mononuclear cells (PBMC) were obtained from subjects in 3 phase I studies, each evaluating a different MRKAd5-based vaccine. MRKAd5 HIV-1 gag and the trivalent MRKAd5 gag/pol/nef vaccines were independently tested in healthy adults at low risk of HIV infection (18 to 50 years of age). HIV-specific T-cell responses were evaluated by IFN-γ ELISpot and intracellular cytokine staining (ICS) against full antigen peptide pools. The responses were also dissected by testing PBMC against series of smaller pools of the gag, pol, or nef peptides. PBMC from responders were also analyzed for cross-reactivity against peptide pools representing near-consensus sequences of clade A and C antigens.
Results: The MRKA5 vaccines elicited predominantly antigen-specific CD8+ T cells; a smaller fraction (20 to 30%) of patients with positive ICS responses contained detectable levels of virus-specific helper T cells. Cross-clade gag- and nef-specific responses were evaluated using the ELIspot method; cross-clade responses against pol were not evaluated because of its high protein sequence conservation (90% across clades vs 80% for gag and 70% for nef). About 66% of individuals (73 of 110 receiving either the MRKAd5 gag or MRKAd5 trivalent vaccine) with responses to the vaccine CAM1 HIV-1 gag (clade B) peptide pool cross-reacted with either clade A gag or clade C gag sequences. Of those receiving the MRKAd5 trivalent vaccine who had responses against JRFL HIV-1 nef (clade B), 38% (10 of 26) were able to respond to the clade A nef pool, while 19% (5 of 26) cross-reacted with clade C nef. PBMC were also assayed against a series of smaller pools (mini-pools) each consisting of 8 sequence-consecutive 9-aa peptides from gag, pol, and nef. The median numbers of positive mini-pools for clade B gag, pol, and nef were 2, 2, and 1, respectively
Conclusions: The MRKAd5 vaccines are potent in eliciting CD8+ and to a lesser degree CD4+ T cells in human clinical trials. The vaccine antigens exhibited levels of immune coverage across multiple clades although at varying levels depending on the antigen.
VRC - published papers:
Vaccine. 2007 May 16;25(20):4085-92. Epub 2007 Mar 7.
Phase I clinical evaluation of a six-plasmid multiclade HIV-1 DNA candidate vaccine.
Catanzaro AT, Roederer M, Koup RA, Bailer RT, Enama ME, Nason MC, Martin JE, Rucker S, Andrews CA, Gomez PL, Mascola JR, Nabel GJ, Graham BS; VRC 007 Study Team.
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 40 Convent Drive, Building 40, Bethesda, MD 20892-3017, USA.
Needle-free delivery of a six-plasmid HIV-1 DNA vaccine encoding EnvA, EnvB, EnvC, and subtype B Gag, Pol, and Nef underwent open-label evaluation in 15 subjects; 14 completed the 0, 1, 2 month vaccination schedule. T cell responses to HIV-specific peptide pools were detected by intracellular cytokine staining of CD4(+) [13/14 (93%)] and CD8(+) [5/14 (36%)], and by ELISpot in 11/14 (79%). Ten of 14 (71%) had ELISA antibody responses to Env proteins. Compared to a four-plasmid product, Gag- and Nef-specific T cell responses were improved, while Env-specific responses were maintained. This candidate vaccine has now advanced to Phase II evaluation.
J Acquir Immune Defic Syndr. 2007 Apr 15;44(5):601-5.
Safety and immunogenicity of a Gag-Pol candidate HIV-1 DNA vaccine administered by a needle-free device in HIV-1-seronegative subjects.
Tavel JA, Martin JE, Kelly GG, Enama ME, Shen JM, Gomez PL, Andrews CA, Koup RA, Bailer RT, Stein JA, Roederer M, Nabel GJ, Graham BS.
Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
OBJECTIVE: To evaluate the safety and immunogenicity of a candidate HIV DNA vaccine administered using a needle-free device. DESIGN: In this phase 1, dose escalation, double-blind, placebo-controlled clinical trial, 21 healthy adults were randomized to receive placebo or 0.5, 1.5, or 4 mg of a single plasmid expressing a Gag/Pol fusion protein. Each participant received repeat immunizations at days 28 and 56 after the first inoculation. Safety and immunogenicity data were collected. RESULTS: The vaccine was well tolerated, with most adverse events being mild injection site reactions, including pain, tenderness, and erythema. No dose-limiting toxicities occurred. HIV-specific antibody response was not detected in any vaccinee by enzyme-linked immunosorbent assay. HIV-specific T-cell responses to Gag or Pol as measured by enzyme-linked immunospot assay and intracellular cytokine staining were of low frequency and magnitude. CONCLUSIONS: This candidate HIV DNA vaccine was safe and well tolerated. No HIV-specific antibody responses were detected, and only low-magnitude HIV-specific T-cell responses were detected in 8 (53%) of 15 vaccinees. This initial product led to the development of a 4-plasmid multiclade HIV DNA Vaccine Research Center vaccine candidate in which envelope genes expressing Env from clades A, B, and C and a Nef gene from clade B have been added.
J Infect Dis. 2006 Dec 15;194(12):1650-60. Epub 2006 Nov 8.
Comment in:
J Infect Dis. 2006 Dec 15;194(12):1625-7.
Phase 1 safety and immunogenicity evaluation of a multiclade HIV-1 DNA candidate vaccine. (free full text access)
Graham BS, Koup RA, Roederer M, Bailer RT, Enama ME, Moodie Z, Martin JE, McCluskey MM, Chakrabarti BK, Lamoreaux L, Andrews CA, Gomez PL, Mascola JR, Nabel GJ; Vaccine Research Center 004 Study Team.
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-3017, USA.
BACKGROUND: Gene-based vaccine delivery is an important strategy in the development of a preventive vaccine for acquired immunodeficiency syndrome (AIDS). Vaccine Research Center (VRC) 004 is the first phase 1 dose-escalation study of a multiclade HIV-1 DNA vaccine. METHODS: VRC-HIVDNA009-00-VP is a 4-plasmid mixture encoding subtype B Gag-Pol-Nef fusion protein and modified envelope (Env) constructs from subtypes A, B, and C. Fifty healthy, uninfected adults were randomized to receive either placebo (n=10) or study vaccine at 2 mg (n=5), 4 mg (n=20), or 8 mg (n=15) by needle-free intramuscular injection. Humoral responses (measured by enzyme-linked immunosorbant assay, Western blotting, and neutralization assay) and T cell responses (measured by enzyme-linked immunospot assay and intracellular cytokine staining after stimulation with antigen-specific peptide pools) were measured. RESULTS: The vaccine was well tolerated and induced cellular and humoral responses. The maximal CD4(+) and CD8(+) T cell responses occurred after 3 injections and were in response to Env peptide pools. The pattern of cytokine expression by vaccine-induced HIV-specific T cells evolved over time, with a diminished frequency of interferon- gamma -producing T cells and an increased frequency of interleukin-2-producing T cells at 1 year. CONCLUSIONS: DNA vaccination induced antibody to and T cell responses against 3 major HIV-1 subtypes and will be further evaluated as a potential component of a preventive AIDS vaccine regimen.
J Infect Dis. 2006 Dec 15;194(12):1638-49. Epub 2006 Nov 8.
Comment in:
J Infect Dis. 2006 Dec 15;194(12):1625-7.
Phase 1 safety and immunogenicity evaluation of a multiclade HIV-1 candidate vaccine delivered by a replication-defective recombinant adenovirus vector. (free full text access)
Catanzaro AT, Koup RA, Roederer M, Bailer RT, Enama ME, Moodie Z, Gu L, Martin JE, Novik L, Chakrabarti BK, Butman BT, Gall JG, King CR, Andrews CA, Sheets R, Gomez PL, Mascola JR, Nabel GJ, Graham BS; Vaccine Research Center 006 Study Team.
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-3017, USA.
BACKGROUND: The development of an effective human immunodeficiency virus (HIV) vaccine is a high global priority. Here, we report the safety, tolerability, and immunogenicity of a replication-defective recombinant adenovirus serotype 5 (rAd5) vector HIV-1 candidate vaccine. METHODS: The vaccine is a mixture of 4 rAd5 vectors that express HIV-1 subtype B Gag-Pol fusion protein and envelope (Env) from subtypes A, B, and C. Healthy, uninfected adults were randomized to receive 1 intramuscular injection of placebo (n=6) or vaccine at dose levels of 10(9) (n=10), 10(10) (n=10), or 10(11) (n=10) particle units and were followed for 24 weeks to assess immunogenicity and safety. RESULTS: The vaccine was well tolerated but was associated with more reactogenicity at the highest dose. At week 4, vaccine antigen-specific T cell responses were detected in 28 (93.3%) and 18 (60%) of 30 vaccine recipients for CD4(+) and CD8(+) T cells, respectively, by intracellular cytokine staining assay and in 22 (73%) of 30 vaccine recipients by enzyme-linked immunospot assay. Env-specific antibody responses were detected in 15 (50%) of 30 vaccine recipients by enzyme-linked immunosorbant assay and in 28 (93.3%) of 30 vaccine recipients by immunoprecipitation followed by Western blotting. No neutralizing antibody was detected. CONCLUSIONS: A single injection induced HIV-1 antigen-specific CD4(+) T cell, CD8(+) T cell, and antibody responses in the majority of vaccine recipients. This multiclade rAd5 HIV-1 vaccine is now being evaluated in combination with a multiclade HIV-1 DNA plasmid vaccine.
VRC – conference presentations:
AIDS Vaccines 2007
http://www.hivvaccineenterprise.org/_dwn/Oral_Sessions.pdf
OA08-01
Adenoviral HIV-1 vaccine elicits durable CD8+ and CD4+ HIV specific responses in HIV-1 uninfected adults without pre-existing Ad5 antibodies, HVTN 054
C Morgan2, L Peiperl4, Z Moodie2, D Carter2, S De Rosa2, N Russell1,
B Graham3 and N HIV Vaccine Trials Network2
1 Bill and Melinda Gates Foundation, Seattle, WA, USA; 2 Fred Hutchinson Cancer Research Center, Seattle, WA, USA; 3 NIAID Vaccine Research Center, Bethesda, MD, USA; 4 University of California San Francisco, San Francisco, CA, USA
Objective: To evaluate the safety and immunogenicity of the NIAID Vaccine Research Center adenoviral vector HIV gag-polB/envA/envB/envC vaccine (rAd5-HIV) delivered IM at 2 doses in adults with undetectable levels of preexisting adenovirus type 5 (Ad5) neutralizing antibodies (nAb). Methods: The NIAID HIV Vaccine Trials Network enrolled 48 participants: 20 received 1 dose of 1010 PU rAd5-HIV (T1), 20 1011 PU rAd5-HIV (T2), and 8 placebo (C). Participants were monitored for reactogenicity and adverse events. PBMC were evaluated by IFN-γ ELISpot and CD4/CD8, IFN-γ/IL-2 intracellular cytokine staining (ICS) assays. These assays utilized potential T cell epitope peptide pools for Gag, Pol, and Env, representing peptides present in at least 15% of HIV-1 isolates in the Los Alamos Database. HIV antibody testing was performed using Abbot HIVAB HIV 1/2, BioRad Genetic Systems HIV 1/2 Plus O, and/or bioMerieux Vironostika HIV-1 EIAs. Results: The vaccine appeared safe in participants without prior Ad5 nAb (presented at AIDS Vaccine 2006). IFN-γ ELISpot response rates to any of the 3 antigens at 4 weeks post injection (D28) were 0/7C, 14/16 T1 and 17/20 T2 with magnitudes up to 3200 SFC/106 PBMC to a peptide pool. 53% of vacinees recognized all 3 antigens, 22% recognized 2, 11% recognized 1, and 14% recognized 0. One year post vaccination the IFN-γ ELISpot response rates were 15/22 T1 and 13/20 T2. Response rates to any of the 3 antigens for CD4+ or CD8+ T cells by ICS for IFN-γ and/or IL-2 at D28 were 0/8 C, 17/19 T1, and 17/20 T2 with up to 4.2% of T cells responding to a peptide pool. 0/8 C, 12/19 T1, and 10/20 T2 had HIV-specific CD4+ T cell responses. 0/8 C, 15/18 T1, and 16/20 T2 had HIV-specific CD8+ T cell responses. One year post vaccination, 0/8 C, 18/19 T1, and 15/19 T2 tested positive for vaccine induced HIV antibodies by 1 or more EIA. Conclusion: One dose of this rAd5-HIV vaccine elicited high frequency and magnitude of CD8+ T cell responses to HIV antigens in Ad5 nAb seronegative persons. These responses were discernible for up to one year, perhaps related to the associated CD4+ T cell responses. 75% of vaccinees recognized epitopes in 2 or more antigens. 87% of uninfected vaccinees developed antibodies detected by commercial HIV antibody tests. To date, these are the most potent vaccine induced HIV-1 responses reported in humans.
OA08-03
Safety and immunogenicity of VRC multiclade HIV-1 adenoviral vector vaccine alone or with VRC multiclade HIV-1 DNA plasmid vaccine in African adults
W Jaoko4, K Kayitenkore6, GO Manyonyi3, E Karita6, C Schmidt2, P Fast2, W Komaroff2, A Cooper1, M Boaz1, J Gilmour1, L Dally7, M Ho7, C Smith7 and B Graham5
1 IAVI Core Laboratory, London, United Kingdom (Great Britain); 2 International AIDS Vaccine Initiative (IAVI), New York, NY, USA; 3 Kenya AIDS Vaccine Initiative (KAVI), Nairobi, Kenya; 4 Kenya AIDS Vaccine Initiative (KAVI), University of Nairobi, Nairobi, Kenya; 5 NIH Vaccine Research Centre (VRC), Bethesda, MD, USA; 6 Project San Francisco (PSF), Kigali, Rwanda; 7 The EMMES Corporation, Rockville, MD, USA
Methods: Healthy adults aged 18-50 in Kigali, Rwanda and Nairobi, Kenya were randomized to either i) one intramuscular injection of 1x1010 or 1x1011 particle units of VRC multiclade HIV-1 recombinant adenoviral vector vaccine (rAd5, n=35) or placebo, or ii) 3 doses 4mg VRC multiclade HIV-1 DNA vaccine (DNA) followed by 1 dose rAd5 1x1010 or 1x1011 as boost or placebo (n=79) (vaccine:placebo 3:1). Safety and tolerability were assessed clinically and by routine lab tests. Immunogenicity was evaluated by Ad5-specific neutralization (NT) assay and IFN-γ ELISpot on frozen PBMC with matched peptides reported as spot forming cells (SFC)/million PBMC. Results: The study is ongoing; preliminary safety and group unblinded immunogenicity data are presented. Local reactions were experienced by approx. 75% of volunteers following any rAd5/placebo and almost all volunteers following any DNA/placebo, most events were mild. Systemic symptoms were reported by 67-72% following any rAd5/placebo and 89% of volunteers following any DNA/placebo, most events were mild. 342 adverse events, mostly mild, were reported within 28 days of any vaccination. There were no vaccine related serious adverse events. Immune responses by ELISpot were detected in 6/13 (46%) and 7/13 (54%) recipients of rAd5 1010 and rAd5 1011 respectively, and in 0/9 placebo recipients. Median SFC were 85 and 77 per million PBMC respectively (range 39-297). Following 3 DNA/placebo there were 27/55 (49%) vaccinees and 1/20 placebo recipients with positive IFN-y ELISpot responses. Median SFC were 92 (range 44-598). Following rAd5 1010 and rAd5 1011 boost, there were 18/25 (72%) and 18/26 (69%) responders respectively. Median SFC were 106 and 105 (range 41-1707). At baseline, 74% of all volunteers had detectable Ad5 NT antibodies (Ab). In either DNA prime/rAd5 boost arms the impact of Ad5 NT Ab on immunogenicity amongst vaccine recipients was modest. In rAd5 alone arms numbers were too small to assess effect. Conclusion: Vaccination with rAd5 either alone or as boost in combination with corresponding DNA vaccine appears safe and well tolerated. Data from African volunteers indicates good immunogenicity of DNA prime/rAd5 boost regimen, appears equivalent at the different rAd5 boost doses and only modestly affected by baseline Ad5 NT Ab. Future trials will focus on larger sample sizes and those at risk for HIV.
OA08-04
A phase IIA trial to evaluate a multiclade HIV-1 DNA vaccine followed by a multiclade rAd5 HIV-1 vaccine boost in HIV-1 uninfected adults (HVTN 204)
MC Keefer7, C Morgan3, G Churchyard1, E Adams2, J Hural3, B Graham5, Z Moodie3, G Gray8, L Bekker6, L Baden4 and M McElrath3
1 Aurum Institute for Health Research, Klerksdorp, South Africa; 2 Division of AIDS, NIAID, Bethesda, MD, USA; 3 Fred Hutchinson Cancer Research Center, Seattle, WA, USA; 4 Harvard University Medical School, Boston, MA, USA; 5 NIAID Vaccine Research Center, Bethesda, MD, USA; 6 University of Cape Town, Cape Town, South Africa; 7 University of Rochester School of Medicine and Dentistry, Rochester, NY, USA; 8 University of Witwatersrand, Johannesburg, South Africa
Background: The NIAID HIV Vaccine Trials Network (HVTN) has undertaken a prospective, randomized, double-blind, placebo-controlled phase IIA clinical trial of the NIAID Vaccine Research Center’s (VRC) 6-plasmid candidate DNA HIV-1 (envA, envB, envC, gagB, polB, nefB) (DNA-HIV) and rAd5 HIV- 1 (envA, envB, envC, gagB, polB) vaccine (Ad5-HIV) in healthy uninfected people in diverse geographic locations. Methods: A total of 480 participants (ppts) were enrolled irrespective of their baseline Ad5 titer; 240 in the Americas (US, Brazil, Jamaica & Haiti) and 240 in South Africa. Half in each region received DNA-HIV (4 mg IM by Biojector) at 0, 1 and 2 months, followed by Ad5-HIV (1010 PU IM by needle/syringe) at 6 months; the other half received placebo injections on the same schedule. Ppts were monitored for reactogenicity and adverse events throughout the 12- month trial; sera and PBMCs were evaluated by humoral (binding/neutralizing antibody) and cellular (bulk IFN-γ ELISpot and IFN-γ /IL-2 intracellular cytokine staining, using global Potential T cell Epitope [PTE] peptide pools) immune assays. Results: At the US sites, the 180 allotted ppts completed enrollment on 7 Apr 06 while enrollment was completed in South Africa on 18 Dec 06 and in the Caribbean/South American region on 20 Mar 07. Preliminary blinded safety and immunogenicity results are available for the US cohort. Both vaccines were well-tolerated. DNA-HIV/placebo caused more local reactions; moderate pain in 10% of participants after 1st vaccination, decreasing with subsequent injections, while Ad5-HIV/placebo caused more systemic reactions; selflimited moderate malaise and/or fatigue in 9.3%. At days 0 and 210 (6 weeks after the rAd5-HIV boost), IFN-γ ELISpot assays were positive in 1.6% and 37.8% of study ppts (half of whom received placebo), respectively. Of those that were positive, responses to Env and Gag peptides were most frequent, seen in 73.2% and 80.4% of responders, respectively. Conclusion: These preliminary interim data indicate acceptable safety and suggest that IFN-γ ELISpot responses using the PTE peptide pools could be positive in up to 75% of vaccine recipients. If further study data confirm these findings and results are favorable from other related protocols, evaluation of this regimen in a phase IIB efficacy trial will be proposed, and would be conducted by the Partnership for AIDS Vaccine Evaluation (PAVE) in distinct regions with diverse HIV-1 epidemics.
http://www.hivvaccineenterprise.org/_dwn/Poster_Sessions.pdf
P06-16
DNA prime followed by adenoviral vector boost elicits HIV-1 specific CD8+ T cell responses in healthy HIV-1 uninfected adults (HVTN 052 and 057)
C Morgan2, L Peiperl4, M McElrath2, Z Moodie2, S De Rosa2, D Carter2, N Russell1, B Graham3 and N HIV Vaccine Trials Network2
1 Bill and Melinda Gates Foundation, Seattle, WA, USA; 2 Fred Hutchinson Cancer Research Center, Seattle, WA, USA; 3 NIAID Vaccine Research Center, Bethesda, MD, USA; 4 University of California San Francisco, San Francisco, CA, USA
Objective: To evaluate the safety and immunogenicity of 2 or 3 doses of a 4-plasmid DNA (envA, envB, envC, gagB-polB-nefB) HIV-1 prime (DNA) followed by a recombinant adenoviral vector (envA, envB, envC, gagB-polB) HIV-1 boost (rAd5) in healthy, HIV-1 uninfected adults. Methods: The NIAID HIV Vaccine Trials Network enrolled 180 participants (ppts) in HVTN 052 where ppts received 4mg DNA x 3 at 0, 1 and 2 mos (N=60; T1), 4mg DNA x 2 at 0, 2 mos (N=60; T2) or placebo (N=10; C). Seventy of these ppts rolled over into HVTN 057 and received 1 dose of 1010PU rAd5 6-9 mos after completing the DNA prime (N=30 in T1 and T2, N=10 in C). Ppts were monitored for reactogenicity and adverse events. PBMC were collected and shipped overnight prior to cryopreservation. PBMC were evaluated by IFN-γ ELISpot and CD4/CD8, IFN-γ/IL-2 intracellular cytokine staining (ICS) assays. These assays utilized global potential T cell epitope peptide pools for Gag, Pol, and Env, representing peptides present in at least 15% of HIV-1 clades A, B, C and non-A,B,C isolates in the Los Alamos Database. Results: There were no notable untoward safety events attributable to vaccine (presented at AIDS Vaccine 2005). The response rates to any of the 3 HIV antigens by IFN-γ ELISpot 2 weeks after the last DNA prime were 2/52 (4%) C, 28/56 (50%) T1, and 12/53 (23%) T2. By ICS the response rates to any of the 3 antigens by CD4+ or CD8+ T cells and IFN-γ and/or IL-2 secretion were 1/10 (10%) C, 11/30 (37%) T1, and 9/29 (31%) T2. 1/10 (10%) C, 8/27 (30%) T1, and 8/28 (29%) T2 were CD4+. 0/9 (0%) C, 4/30 (13%) T1, and 1/29 (3%) T2 were CD8+. Four weeks after the boost, the response rates by IFN-γ ELISpot were 0/8 (0%) C, 7/12 (58%) T1, and 10/21 (48%) T2. ICS assays were positive in 1/10 (10%) C, 12/25 (48%) T1, and 9/28 (32%) T2. 1/10 (0%) C, 4/23 (17%) T1, and 4/28 (14%) T2 were CD4+. 0/10 (0%) C, 11/25 (44%) T1, and 8/28 (29%) T2 were CD8+. The rAd5 boost elicited more responses to Gag and Pol than DNA alone. Conclusion: The DNA vaccine primarily elicited CD4+ HIV-specific T cells while the rAd5 boost elicited primarily CD8+ responses and broadened the responses to Gag and Pol. The 3rd dose of DNA may have skewed the response more towards a CD8+ response. We anticipate that the response frequencies will increase in future protocols with the evaluation of PBMC cryopreserved on the same day as venipuncture.
P06-19
Evaluation of candidate DNA HIV-1 vaccine delivery by biojector or needle and syringe in healthy adults (VRC 008)
BS Graham, JE Martin, I Gordon, M Nason, M Enama, R Koup, M Roederer, P Gomez, J Mascola and G Nabel
Vaccine Research Center, NIAID, NIH, Bethesda, MD, USA
Objective: To compare safety and immunogenicity of the NIAID Vaccine Research Center (VRC) candidate DNA HIV-1 vaccine delivered by either needle-free injection device Biojector or needle & syringe (N/S), and its ability to prime for a response to boosting with the VRC candidate recombinant replication-defective adenoviral serotype 5 HIV-1 vaccine vector (rAd5) given at a dose of 1010 or 1011 particle units (PU) in volunteers with either high or low preexisting Ad5 antibody. Methods: 40 healthy adults age 18-50 were randomized to receive 3 injections of 4 mg of the VRC multiclade DNA IM at 0, 1, and 2 months by Biojector or N/S. All subjects received rAd5 at month 6 IM by N/S at either 1010 or 1011 PU. Equal numbers in each subgroup had low (≤500) or high (>500) reciprocal titers of preexisting Ad5 95% neutralizing antibody. Cryopreserved PBMCs were evaluated by ELISpot and intracellular cytokine staining (ICS). Results: 120 DNA and 39 rAd5 injections were given; 36 subjects had a 4 week sample collected after the boost. The vaccine regimen was well tolerated for each delivery approach and dose level. Biojector resulted in occasional bruising, and routinely caused small papules or scabs (less than 1 X 1 cm) at the injection site. The lesions were observed by clinician exam after 38/60 (63%) Biojector injections, but were reported by subject diary cards in only 11/60 (18%). Lesions were never pustular or vesicular and resolved without treatment. Neither clinicians nor subjects reported any papules or scabs after any of the 60 DNA N/S injections. IFN-γ ELISpot response rates for any peptide pool at 4 weeks post rAd5 boost were 17/19 (89%) for Biojector and 13/17 (76%) for N/S delivery. The cumulative median ELISpot response (sum of highest Env+Gag+Pol+Nef responses) was 3-fold higher in the Biojector recipients than those receiving N/S. Response rates and magnitude for CD8+ T cells by ICS were similar to the patterns seen for ELISpot, but CD4+ T cell response frequencies and magnitudes by ICS were the same with use of either delivery method. Conclusion: Biojector delivery of DNA results in slightly greater local reactogenicity than N/S, but is associated with improved ELISpot and CD8+ T cell responses post boosting with rAd5. These data support continued evaluation of Biojector for DNA vaccine delivery and exploration of alternative delivery approaches to improve vaccine-induced immune responses.
P06-20
Functional profiles and epitope specificities of HIVspecific T cells induced by Ad5 HIV vaccination in Ad5- naïve, HIV-uninfected participants
H Horton1, DP Friedrich1, EC Jalbert1, SC DeRosa1, L Peiperl2, G Nabel3 and JM McElrath1
1 Fred Hutchinson Cancer Research Center, Seattle, WA, USA; 2 San Francisco Department of Public Health, San Francisco, CA, USA; 3 Vaccine Research Center, Bethesda, MD, USA
Background: We recently reported that in natural infection, the functional capabilities of HIV-specific T cells differ depending on their epitope specificities and MHC restriction. To determine if this response pattern occurs following vaccination in immunocompetent persons, we analyzed epitope specificities and functional capabilities of T cells induced by a single dose (either 1010 or 1011 PU) recombinant adenoviral vector expressing Clade B Gag/Pol and Clades A,B,C Env in 48 healthy HIV-1-uninfected adults with undetectable preexisting Ad5 neutralizing antibodies. Methods: HIV-specific vaccine-induced T cell responses were de-convoluted by IFN-γ ELISpot to determine the 9-15mer peptide recognized. In addition, functional profiling of responses was performed, including examining cytokine secretion (IFN-γ, IL-2 and TNF-α), degranulation (CD107a) and proliferation (CFSE dilution) in response to cognate epitopes. Results: A total of 66 epitopic peptides were recognized in 30 participants: 39 distinct epitopes in pol, 8 in gag and 19 in env. A median of 3 epitopes were recognized per participant (mean = 4; range 1-22). The sum of epitopespecific T cell magnitudes per individual ranged from 71-20,778 SFC/106 PBMC (median= 972; mean = 1,778). Forty-six CD8+ T cell responses were mapped to the optimal epitope in 21 individuals. Eight of these individuals (38%) possessed T cells that recognized multiple variants of 14 different epitopes. Since each volunteer was HLA typed we can infer that these epitopes were restricted by 12 different MHC alleles. Responses restricted by HLA-B27 (present at 10% in this population), -B57 (6%), -B14 (15%) and B35 (15%) were dominant (86-100% individuals expressing these alleles possessed vaccine-induced responses restricted by them). However, responses restricted by HLA-A02 and -B07 were seen very infrequently despite these alleles being present at high frequency in these subjects (A02: 48%; B07: 21%). Conclusion: Our findings indicate that immunocompetent vaccinees mount broad high magnitude CD8+ T cell responses to this candidate vaccine. Furthermore, a substantial proportion of vaccine-induced CD8+ T cells recognize multiple epitope variants present in circulating viral sequences. Finally, this study suggests that CD8+ T cell responses induced in individuals with low pre-existing Ad5 neutralizing antibody can be predicted based on HLA and that certain HLA alleles dominate vaccine-induced responses.
http://www.hivvaccineenterprise.org/_dwn/Late_Breaker_Abstracts.pdf
P06-43
Cellular immune responses in HIV-1 uninfected adult Tanzanian volunteers enrolled in a phase I/II multiclade HIV-1 DNA plasmid vaccine
A Schuetz4, A Haule3, A Mwalongo3, C Kiwole3, K Schindler3, M Schunk3, A Kroidl3, M Hoelscher2, L Maganga3, L Maboko3, M Robb5, N Michael5, B Graham6, J Cox5 and M de Souza1
1 Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand; 2 Department of Infectious Diseases and Tropical Medicine, Munich, Germany; 3 Mbeya Medical Research Programme, Mbeya, Tanzania, United Republic of; 4 USMHRP / Henry M. Jackson Foundation, Mbeya, Tanzania, United Republic of; 5 USMHRP / Henry M. Jackson Foundation, Rockville, MD, USA; 6 Vaccine Research Center / NIH, Bethesda, MD, USA
Objective: To determine the frequency of T cell responses in Tanzanian seronegative participants in a multiclade phase I/II HIV-1 DNA plasmid vaccine / Adenovirus-5 vector boost vaccine trial. Methods: Sixty participants were enrolled in a phase I/II randomised, double- blind, placebo controlled trial to assess the safety and immunogenicity of a multiclade (A, B and C) HIV-1 DNA plasmid vaccine, boosted with a clade- matched HIV-1 recombinant Adenovirus-5 vector (Vaccine Research Center, NIH, USA). The vaccine:placebo ratio was 1:1. DNA was administered at weeks 0, 4 and 8 and the adenovirus boost at week 24. Cellular immunogenicity assays were conducted on a random subset of participants using an interferon-gamma (IFN- γ) ELISpot assay with freshly isolated peripheral blood mononuclear cells (PBMC). Assays were conducted at weeks 0, 6, 10, 26 and 30 to HIV-1 Env (clades A and B), Pol and Nef (clade B) peptide pools. A positive IFN- γ ELISpot response was defined as at least 55 SFC/106 PBMC and 4 times the media treated wells. Results: Forty of the 60 participants were tested by IFN- γ ELISpot. All results are blinded and include placebo controls. There were no positive IFN- γ ELISpot responses to HIV peptides prior to immunization. Positive immune responses were initially observed in volunteers at 2 weeks following the second injection against Env (5/40) and Pol (1/40). Point prevalence two weeks following the third DNA injection was 23% (9/40), with all responding against Env, 5% (2/40) against Pol and 13% (5/40) against Nef. Two weeks after the adenoviral boost 35% (14/40) of subjects demonstrated a HIV- specific immune response, all against Env, 5% (2/40) against Pol and 3% (1/40) against Nef. However, six weeks after the adenoviral boost 10/39 (26%) participants reacted against Env, 1/39 (3%) against Pol and 1/39 against Nef (3%). The cumulative frequency of positive responses 6 weeks following the completion of immunization is 16/40 (40%), with 15/40 (38 %) reacting against Env, 3/40 (8%) against Pol and 5/40 (13%) against Nef. Twelve of the 16 (75%) positive responders were positive at more than one time-point. Conclusion: This multiclade DNA/adenovirus vaccine combination induced HIV-specific cellular immune responses as measured by IFN- ELIspot assay, and these responses were sustained in a large number of study participants.
P06-44
Cellular immune responses in HIV-1 uninfected Ugandans enrolled in a phase II multiclade HIV-1 DNA plasmid/adenovirus-5 vector boost vaccine trial
L Eller1, M Eller1, P Naluyima1, D Kyabaggu1, M Robb2, H Kibuuka1, F Wabwire-Mangen1, B Graham3, N Michael2, M deSouza2 and J Cox2
1 Makerere University Walter Reed Project, Kampala, Uganda; 2 U.S. Military HIV Research Program, Rockville, MD, USA; 3 Vaccine Research Center, NIH, Bethesda, MD, USA
Objective: To determine the frequency of cellular immune responses by intracellular cytokine staining (ICS) in freshly isolated peripheral blood mononuclear cells (PBMC) derived from Ugandan HIV seronegative recipients of a multiclade HIV-1 DNA/ Adenovirus-5 (Ad5) vector vaccine combination. Methods: Sixty adult volunteers were enrolled in a randomized, double blind, placebo controlled trial to assess the safety and immunogenicity of multiclade (A,B,C) HIV-1 DNA plasmid vaccine (VRC-HIVDNA016-00-VP) boosted with HIV-1 recombinant Ad5 vector (VRC-HIVADV014-00-VP) vaccine (Vaccine Research Center, NIH Bethesda). The ratio of vaccine to placebo recipients was 1:1. DNA vaccine was administered at weeks 0, 4 and 8, with Ad5 boosting at week 24. A standard intracellular cytokine staining assay (ICS) was performed at weeks 0, 6, 10, 26 and 30 on fresh PBMC stimulated with HIV Env (clades A and B), Pol and Nef (clade B) peptide pools and analyzed for interferon-gamma (IFN-g) and interleukin 2 (IL-2) using 4-color flow cytometry. A positive response was defined as greater than or equal to 0.05 (corrected for unstimulated background) and greater than 3 times background. All assays were conducted on blinded samples. Results: Reactivity to HIV peptides was detectable in 8% (5/60) of volunteers prior to immunization. To date, cumulative positive ICS responses to HIV peptides have been observed in 58% (35/60) of volunteers in this blinded study that includes placebo controls. Cytokine production was measured in both CD4 (53%; 32/60 volunteers) and CD8 (38%; 23/60 volunteers) T cells. ICS responses were seen following the second immunization in some volunteers. 74% (26/35) of ICS responders were positive at multiple timepoints and 71% (25/35) had responses to multiple peptide pools. 77% (27/35) had responses to clade A Env, 60% (21/35) to clade B Env, 29% (10/35) to Pol, and 43% (15/35) to Nef. Conclusion: A multiclade HIV-1 DNA vaccine boosted with Ad5 vector induced CD4 and CD8 T cell immune responses to a wide range of HIV antigens. The response rate in this urban Ugandan population looks similar to that seen in the U.S. and other trials of the Vaccine Research Center’s DNA/Ad5 vaccine. The results of this trial will help with the decision to undertake phase IIb trials of this vaccine in East Africa.
P06-47
Safety and immunogenicity of the NIAID VRC multiclade HIV-1 DNA plasmid/multiclade rAd5 vector vaccine boost (HVTN 204) in South African participants
G Churchyard1, M Keefer8, C Morgan3, E Adams6, J Hural3, Z Moodie3, B Graham5, L Gu3, M McElrath3, L Bekker2, G Gray7, E Vardas7 and HIV Vaccine Trials Network4
1 Aurum Institute for Health Research, Marshalltown, St. Helena; 2 Desmond Tutu HIV Foundation, University of Cape Town, Cape Town, South Africa; 3 Fred Hutchinson Cancer Research Center, Seattle, WA, USA; 4 NIAID HIV Vaccine Trials Network, Seattle, WA, USA; 5 NIAID Vaccine Research Center, Bethesda, MD, USA; 6 NIAID, Division of AIDS, Bethesda, MD, USA; 7 Perinatal HIV Research Unit, University of the Witwatersrand, Soweto, South Africa; 8 University of Rochester Medical Center, Rochester, NY, USA
Background: Results from primate and humans studies suggest that prior immunity to adenovirus, particularly high-titer neutralizing Ad5 antibody (NAb), reduces the immune response to recombinant Ad5 HIV vaccines and may be associated with less reactogenicity. South African (SA) participants (ppts) have higher neutralizing Ad5 titers than United States (US) ppts (Ad5 NAb titers>1:1000 [Merck assay]: SA; 23.1% vs US; 12.2%). A multi- country, randomized, double-blind, placebo-controlled phase IIA clinical trial of the NIAID Vaccine Research Center’s 6-plasmid candidate DNA HIV-1 (envA, envB, envC, gagB, polB, nefB) (DNA-HIV) given IM by biojector at 0,1 and 2 months, and boosted with rAd5 HIV-1 (envA, envB, envC, gagB, polB) vaccine (Ad5-HIV) given IM at 6 months was conducted in healthy uninfected ppts. Preliminary safety and immunogenicity data for SA ppts are described. Methods: 240 SA ppts were enrolled irrespective of their baseline Ad5 titer. Half received placebo. Ppts were monitored for reactogenicity and adverse events. PBMCs were evaluated by IFN- γ ELISpot, using global Potential T cell Epitope peptide pools 6 weeks after the Ad5-HIV boost. Results: Median (range) age: 24 (18-47) years. 45% Male, 98% black. The proportion receiving vaccinations with product/placebo at 0, 1, 2 and 6 months were 100%, 96%, 93% and 88% respectively. Compared to placebo, DNA-HIV caused more local reactions (≥ mild), decreasing with subsequent injections (DNA-HIV; 70%, 47.7%, 43.2%; placebo: 42.5%, 31.3%, 33.6%), but not more systemic reactions. Ad5-HIV caused more local (≥ mild) reactions than placebo (40.6% vs 20.8%) and a similar rate of systemic reactions (3.1% vs 2.8%). Preliminary IFN- γ ELISpot data suggest acceptable responses. Conclusion: Both vaccines were well tolerated. Ad5-HIV associated systemic reactions are lower than that observed in US ppts. Preliminary IFN- γ ELISpot data suggest that the product is comparably immunogenic in South African ppts compared to US ppts.
AIDS Vaccines 2005
Safety and Immunogenicity of a Multiclade HIV-1 Recombinant Adenovirus Vaccine Boost in Prior Recipients of a Multiclade HIV-1 DNA Vaccine
Barney S. Graham, Mario Roederer, Richard A. Koup, Robert Bailer, Phillip L. Gomez, Martha Nason, Julie E. Martin, Mary E. Enama, John Mascola, Gary J. Nabel, for The VRC Clinical Trials Core, The VRC Vector Core, The VRC Vaccine Production Program and The VRC Immunology Core Lab. Vaccine Research Center, NIAID, NIH, DHHS, Bethesda, MD
Induction of HIV-1-specific T cell and antibody responses to diverse subtypes is a major goal of current vaccine efforts. We have developed a heterologous DNA prime-recombinant adenovirus vector boost approach, priming subjects with 3 doses of a 4-plasmid DNA expressing clade B gag/pol/nef and clades A, B, and C envelope constructs and boosting with 4 recombinant adenovirus serotype 5 vectors (rAd5) expressing matching genes except for the absence of nef. Subjects received 4 mg (N=4) or 8 mg (N=4) of DNA. All subjects were boosted with 1010 PU of rAd5 at a boost interval ranging from 79 to 104 weeks. Three subjects had moderate systemic symptoms, including myalgia and 1 had mild fever within 24 hours following rAd5. CD4 and CD8 T cell responses were measured by IFN-gamma ELISpot and intracellular cytokine staining for IL- 2 or IFN-gamma. Preliminary analysis showed that 6 of 8 subjects had >3-fold increase (range 3-21) in Env-specific ELISpot responses, and all subjects had robust antibody responses after rAd5 boosting. Both T cell and antibody responses were up to 30-fold higher than seen previously in rAd5 only recipients. Priming with the VRC DNA vaccine followed by the rAd5 vector was well tolerated in this small cohort of subjects. With a 20-26 month interval between prime and boost, significant T cell and antibody responses are induced by the rAd5 that exceed the highest values seen to date in subjects immunized with rAd5 alone.
Keystone Meeting 2006 (from the GenVec website) Speaker Abstract 029
Update on VRC Clinical Trials
Barney S. Graham, M.D., Ph.D.
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892
The Vaccine Research Center (VRC) in the National Institute of Allergy and Infectious Diseases (vrc.nih.gov) is devoted to developing a vaccine for HIV. The program is mission-oriented and develops vaccine candidates for viral diseases from basic research through production and analysis of Phase I clinical trials. The initial VRC HIV vaccine candidate is based on gene delivery of vaccine antigens (clade B Gag, Pol, and Nef, and clades A, B, and C Envelope) using a combination of plasmid DNA for priming and replication-defective recombinant adenoviral vectors (rAd5) for boosting. CD4+ and CD8+ T cell responses are measured by peptide pool stimulation of PBMCs followed by IFN-(ELISpot and flow cytometric detection of intracellular IL-2 or IFN-(production. The vaccine is designed to induce T cell responses against multiple HIV proteins to diminish immune escape, and includes sequences from multiple clades to be relevant for large portion of the global epidemic. Several Phase I studies have evaluated plasmid DNA vaccine candidates, rAd5 vectors, or a combined prime-boost regimen delivered by needless injection device or needle syringe. Both DNA and rAd5 vaccines are immunogenic alone, and the combined prime-boost schedule induces HIV-specific T cell responses up to 5-10 fold higher and antibody responses several orders of magnitude higher than either modality alone. The product has now advanced into Phase II evaluation in collaboration with the HIV Vaccine Trials Network (HVTN), the U.S. Military HIV Research Program (USMHRP), and the International AIDS Vaccine Initiative (IAVI) at sites in the Americas, Caribbean, South Africa, and East Africa.
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