Phase 1 Safety and Immunogenicity Evaluation of
ADVAX, a Multigenic, DNA-Based Clade C/B’ HIV-1
Sandhya Vasan1,2*, Sarah J. Schlesinger1,2, Yaoxing Huang1,2, Arlene Hurley1,2, Angela Lombardo3,
Zhiwei Chen1,2¤a, Soe Than3¤b, Phumla Adesanya3¤c, Catherine Bunce4, Mark Boaz3¤d, Rosanne Boyle3,
Eddy Sayeed3, Lorna Clark5, Daniel Dugin1, Claudia Schmidt3, Yang Song1, Laura Seamons5, Len Dally6,
Martin Ho6, Carol Smith6, Martin Markowitz1,2, Josephine Cox5, Dilbinder K. Gill5, Jill Gilmour5,
Michael C. Keefer4, Patricia Fast3, David D. Ho1,2
1Aaron Diamond AIDS Research Center, New York, New York, United States of America, 2The Rockefeller University, New York, New York, United States of America,
3International AIDS Vaccine Initiative, New York, New York, United States of America, 4University of Rochester Medical Center, Rochester, New York, United States of
America, 5International AIDS Vaccine Initiative Core Laboratory, Imperial College, London, United Kingdom, 6EMMES Corporation, Rockville, Maryland, United States of
Background: We conducted a Phase I dose escalation trial of ADVAX, a DNA-based candidate HIV-1 vaccine expressing
Clade C/B’ env, gag, pol, nef, and tat genes. Sequences were derived from a prevalent circulating recombinant form in
Yunnan, China, an area of high HIV-1 incidence. The objective was to evaluate the safety and immunogenicity of ADVAX in
Methodology/Principal Findings: ADVAX or placebo was administered intramuscularly at months 0, 1 and 3 to 45 healthy
volunteers not at high risk for HIV-1. Three dosage levels [0.2 mg (low), 1.0 mg (mid), and 4.0 mg (high)] were tested. Twelve
volunteers in each dosage group were assigned to receive ADVAX and three to receive placebo in a double-blind design.
Subjects were followed for local and systemic reactogenicity, adverse events, and clinical laboratory parameters. Study follow up
was 18 months. Humoral immunogenicity was evaluated by anti-gp120 binding ELISA. Cellular immunogenicity was assessed by
a validated IFNc ELISpot assay and intracellular cytokine staining. ADVAX was safe and well-tolerated, with no vaccine-related
serious adverse events. Local and systemic reactogenicity events were reported by 64% and 42% of vaccine recipients,
respectively. The majority of events were mild. The IFNc ELISpot response rates to any HIV antigen were 0/9 (0%) in the placebo
group, 3/12 (25%) in the low-dosage group, 4/12 (33%) in the mid-dosage group, and 2/12 (17%) in the high-dosage group.
Overall, responses were generally transient and occurred to each gene product, although volunteers responded to single
antigens only. Binding antibodies to gp120 were not detected in any volunteers, and HIV seroconversion did not occur.
Conclusions/Significance: ADVAX delivered intramuscularly is safe, well-tolerated, and elicits modest but transient cellular
Trial Registration: Clinicaltrials.gov NCT00249106
Citation: Vasan S, Schlesinger SJ, Huang Y, Hurley A, Lombardo A, et al. (2010) Phase 1 Safety and Immunogenicity Evaluation of ADVAX, a Multigenic, DNA-
Based Clade C/B’ HIV-1 Candidate Vaccine. PLoS ONE 5(1): e8617. doi:10.1371/journal.pone.0008617
Editor: Sean Emery, University of New South Wales, Australia
Received June 22, 2009; Accepted November 11, 2009; Published January 25, 2010
Copyright: ? 2010 Vasan et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: Funding for this study was provided by the International AIDS Vaccine Initiative (IAVI) and its donors, including the generous support of the American
people through the United States for International Development (USAID). IAVI played a direct role in study design, data collection and analysis, decision to
publish, and preparation of this manuscript. Support was also provided by the Rockefeller University and University of Rochester Clinical and Translational Science
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: email@example.com
¤a Current address: AIDS Institute, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong SAR, People’s Republic of China
¤b Current address: Pfizer Inc, New York, New York, United States of America
¤c Current address: Novartis Pharmaceuticals, Basel, Switzerland
¤d Current address: Sanofi Pasteur, Swiftwater, Pennsylvania, United States of America
With an estimated 33 million people living with HIV/AIDS
globally, and roughly 2.5 million new infections in 2007 alone, the
need for an efficacious vaccine to prevent or attenuate HIV-1
infection remains paramount . In the People’s Republic of
China, an estimated 700,000 people are living with HIV/AIDS, in
an epidemic spread both through sexual transmission and injection
PLoS ONE | www.plosone.org1January 2010 | Volume 5 | Issue 1 | e8617
drug use. The prevalence of HIV infection among injection drug
users in Yunnan province, which borders Myanmar, Laos, and
Vietnam in the ‘‘golden triangle’’ region, has increased dramat-
ically in the last ten years, to over 40% in several prefectures .
In a separate study, the annual incidence rate of new HIV
infections among intravenous drug users in Guangxi province was
found to be 3.1% .
The Aaron Diamond AIDS Research Center has pursued the
development of a multigenic vaccine regimen based on the
predominant clade C/B’ circulating recombinant form of HIV-1
from Yunnan, China, CRF 007 . After codon-optimization and
certain safety mutations, matched sequences from the env, gag, pol,
nef, and tat genes were inserted into both a naked DNA plasmid
backbone (ADVAX) and a modified vaccinia ankara (MVA) viral
vector (ADMVA) as described by Y. Huang et al. and Z. Chen et
al., respectively [5,6]. These vectors were initially chosen based on
reports of improved cellular immunogenicity of DNA- and MVA-
based vaccines when used in a prime-boost combination in
humans with a variety of antigens [7–9] and on their ability to
control viremia after multiple routes of simian human immuno-
deficiency virus (SHIV) challenge in rhesus macaques [10,11].
The Phase I trial described in this report was designed to assess
the safety, tolerability and humoral and cellular immunogenicty of
ADVAX as a stand-alone HIV-1 vaccine candidate. A parallel
Phase I study of the ADMVA vaccine alone was conducted
separately, as reported in the accompanying manuscript.
The study was conducted at the Rockefeller University Hospital
in New York City, USA, and the University of Rochester Medical
Center in Rochester, New York, USA. The protocol for this trial
and supporting CONSORT checklist are available as supporting
information: see Checklist S1 and Protocol S1. This trial is
registered at clinicaltrials.gov, registry number NCT00249106,
Healthy men and women aged 18–60 years were eligible for
participation if they were not at high risk for HIV-1, as defined by
having none of the following activities in the six months prior to
enrollment: unprotected vaginal or anal sex with a known HIV-1-
infected person or casual partner, injection drug use, acquisition of
a sexually transmitted disease, or sex work for money or drugs.
Participants agreed to safe sexual practices and effective
contraception to avoid pregnancy throughout the duration of the
18-month study. Participants had to demonstrate a clear
understanding of the possibility of HIV-1 seropositivity due to
vaccine-induced antibodies in the event of a humoral immune
response to encoded HIV-1 antigens. Exclusion criteria included
chronic medical conditions, clinically significant abnormal labo-
ratory parameters, infection with Hepatitis B or C virus, or recent
receipt of a vaccine or blood transfusion.
This study was approved by the Institutional Review Boards of
the Rockefeller University Hospital and the University of
Rochester Medical Center. Individual participants in this study
provided written informed consent after appropriate review,
discussion and counseling by the clinical study team. The trial
was monitored by the International AIDS Vaccine Initiative
(IAVI). The study was conducted in compliance with International
Conference on Harmonization - Good Clinical Practice (ICH-
The ADVAX vaccine is a 1:1 mixture of two DNA plasmids
derived from the pVax vector (InvitrogenTM) containing clade C/
B’, codon-optimized HIV-1 gene sequences. The first plasmid
expresses Env under the PCMV promoter and Gag under the
human elongation factor 1a (PhEF1a) promoter, while the
second expresses Pol under the PCMV promoter and a Nef-Tat
fusion under the PhEF1a promoter as previously described .
ADVAX cGMP manufacturing, quality control testing and real-
time stability studies were conducted at Vical Inc. (San Diego,
This study was randomized, dose-escalating, and double blind
with respect to active vaccine or placebo. Safety and tolerability of
ADVAX or placebo in each dosage group were evaluated by an
independent Data Safety Monitoring Board at least 14 days after
the 12thvolunteer had received the second injection, and prior to
initiation of enrollment of the next dosage group. The study design
is summarized in Table 1. The 0.2 mg low dose was chosen based
on safety considerations, to minimize the initial exposure of this
novel investigational vaccine. The maximum dose of 4.0 mg was
chosen based primarily on manufacturing constraints, as this was
the maximum amount of ADVAX that could be concentrated into
a 1.0 mL intramuscular injection volume.
The primary objective was to evaluate the safety and tolerability
of three intramuscular injections with ADVAX at three different
dosage levels in healthy HIV-uninfected adults. The secondary
objective was to evaluate the humoral and cellular immunogenic-
ity of ADVAX versus placebo at each dosage.
Primary endpoints were designed to evaluate the safety of
ADVAX in human volunteers. Local reactogenicity (including
pain, tenderness, erythema, edema, skin damage, induration, and
formation of crust, scab or scar) and systemic reactogenicity
(including fever, chills, headache, nausea, vomiting, malaise,
myalgia, arthralgia, and rash) were assessed by telephone three
days following vaccination and by history and physical examina-
tion two weeks after vaccination. Subjects were monitored for
adverse events, general health and clinical laboratory parameters
at each study visit.
Secondary endpoints were designed to evaluate the cellular and
humoral immunogenicity of ADVAX. Blood for cellular immu-
nogenicity analyses was collected at pre-vaccination baseline, two
weeks after each vaccination, and at weeks 28, 36, 52, and 78 to
follow longer term responses. Serum for humoral immunogenicity
Table 1. Study Design.
Low0.2 mg 12:30, 1, 318
Middle1.0 mg12:3 0, 1, 318
High4.0 mg12:30, 1, 318
ADVAX HIV Vaccine Trial
PLoS ONE | www.plosone.org2January 2010 | Volume 5 | Issue 1 | e8617
analyses was collected at pre-vaccination baseline, four weeks after
each vaccination, and at weeks 28, 36, 52, and 78 to follow longer
term responses. Cellular immunogenicity was assessed by IFNc
ELISpot on frozen peripheral blood mononuclear cells (PBMCs)
at the IAVI Core laboratory at the Imperial College, London, as
previously described . Peptides for stimulation were synthe-
sized by Anaspec (Freemont, CA) and pooled at the IAVI Core
laboratory. Peptide pools consisted of 15mers overlapping by 11
amino acids matched to the Clade C/B’ sequences encoded in the
vaccine, and spanned all gene inserts.
For each pool, the ELISpot value was defined as the mean
replicate (maximum 4) count minus the mean background count.
Four criteria had to be fulfilled for an ELISpot value to be
considered a positive response: 1) for each peptide pool, a single
value had to be .99% of all pre-vaccination and placebo values
for that pool, and .38 Spot Forming/106Cells (SFC) count; 2) the
mean count had to be .4 times the mean background SFC count;
3) the mean background had to be ,55 SFC/106PBMCs; and 4)
the coefficient of variation had to be #70% across the replicate
ELISpot-positive samples were tested for
phenotype, cytokine secretion, and antigen-specific proliferation
using polychromatic flow cytometry. Cryopreserved PBMCs were
thawed rapidly at 37uC and rested overnight, then washed and
resuspended in RPMI media with 10% v/v FCS. 8.76105cells
were co-incubated with 30 mg peptide pools or 20 mg SEB
(Sigma-Aldrich,St. Louis, MO),
Dickinson, Franklin Lakes, NJ), Brefeldin A (Sigma-Aldrich, St.
Louis, MO) and BD Golgistop (Becton Dickinson, Franklin
Lakes, NJ) for 6 hours at 37uC, then at 4uC for no longer than
Staining and flow cytometry.
PBS by centrifugation, stained with 100 mL VIVID for 20
minutes, and then washed twice in FACSwash buffer (2%
bovine serum albumin with 0.15% sodium azide). Cells were
then surface stained with anti-CD4 QD605, anti-CD8 pacific
orange (Invitrogen, Carlsbad, CA), anti-CD27 FITC (Beckton
Dickinson, Franklin Lakes, NJ), and anti-CD45RO (Beckman
Coulter, Fullerton, CA) for 20 minutes at room temperature,
washed twice in PBS, then fixed and permeabilized by incubating
in BD Cytofix Cytoperm solution for 20 minutes at 4uC. Cells
were washed twice in BD Cytofix Cytoperm wash buffer and then
Carlsbad, CA), anti-IFN-c PE Cy7, anti-MIP-1b PE, anti-TNF-
a A700 and anti-IL-2 APC (Beckton Dickinson, Franklin Lakes,
NJ). Cells were acquired on a custom-built BD LSR II cytometer.
At least 500,000 events were collected. Data were analyzed using
Roederer, Vaccine Research Center) software.
gp120 (NIH AIDS Reagent Program) were assessed by ELISA at
pre-vaccination baseline and two weeks after each vaccination, as
described by Huang et al. . In parallel, anti-gp160, anti-p24,
or anti-gp36 Group M/O antibodies were assessed using the
Genetic SystemsTMHIV-1| HIV-2 PLUS O EIA Kit (Bio-Rad
Laboratories, Hercules, CA), at the New York State Department
of Health. Those samples that were positive were further evaluated
by the Genetic SystemsTMHIV-1 Western Blot Kit (Bio-Rad
Laboratories, Hercules, CA) and for viral load quantification using
the Roche Amplicor HIV-1 Monitor v1.5 RNA-PCR Kit (Roche
Diagnostic Systems, Indianapolis, IN) to differentiate a response to
vaccine from de novo HIV infection. Results were monitored by an
independent physician to maintain blinding of the clinical study
Plates were washed twice in
Binding antibodies to Clade C
Each of the three dosage groups consisted of 15 volunteers
randomized in a 4:1 ratio of vaccine to placebo (Table 1). The
small sample size was chosen for an exploratory dose-escalation
study of this novel product while investigating safety and
tolerability of the vaccine. Based on a 10% event rate in the
placebo group (n=9), there was at least 80% power to detect a
significantly greater event rate of 58% or more in the active group
(n=36) at level a=0.05 using Fisher’s exact one-sided test.
Randomization and Blinding
The randomization schedule was prepared by the statisticians at
the Data Coordinating Center at the EMMES Corporation, Inc.
The randomization list was sent to Fisher Clinical Services for
labeling and packaging of study vaccine and placebo in a double
blinded fashion. Study site staff and volunteers remained blinded
with respect to the allocation of placebo or vaccine, but not dosage
Data from all participants, including those lost to follow up and
those not completing the vaccination series, were included in the
analyses. The rate of local and systemic reactogenicity events was
used to assess the differences between dosage groups. Fisher’s exact
test was used for 262 tables, and the Cochran-Armitage trend test
was used to investigate trends in event rates with increasing
As shown in Figure 1, 71 volunteers were screened for this
study, of whom 45 were enrolled. The majority of the 26 screen
failures were due to medical abnormalities: 7 due to chronic
medical conditions, and 7 due to abnormalities on screening
laboratories or urinalysis. Eight volunteers withdrew consent after
completing the screening process. Of the remaining four screen
failures, three were assessed by the study team as being unable to
comply with the protocol, and one completed screening after the
trial was fully enrolled. The average interval from date of
screening to enrollment was 16 days, ranging from 3–35 days.
All three vaccinations of either ADVAX or placebo were
administered to all but one volunteer, who missed the final
vaccine due to relocation. Two participants in total did not
complete the trial for reasons unrelated to the vaccine or the study.
One participant was lost to follow up due to relocation after
receiving only two of the three scheduled vaccinations. The second
participant, who had a prior history of depression, committed
suicide seven weeks after completing her vaccination series, for
reasons unrelated to vaccination.
The low dosage group of volunteers was enrolled from
December 2003 through January 2004, and followed until July
2005. The mid dosage group was enrolled from March 2004
through April 2004, and followed until September 2005. The high
dosage group was enrolled from May 2004 through June 2004,
and followed until November 2005. Baseline demographic and
clinical characteristics for all trial participants are listed in Table 2.
Vaccine Reactogenicity and Adverse Events
The percentage of volunteers experiencing local and systemic
reactogenicity in each dosage group is presented in Figure 2. The
ADVAX HIV Vaccine Trial
PLoS ONE | www.plosone.org3January 2010 | Volume 5 | Issue 1 | e8617
most frequently reported local reactogenicity event in all dosage
groups was pain and/or tenderness at the injection site, followed
by mild erythema/skin discoloration. The most frequently
reported systemic symptom was headache, followed by subjective
fever. These local and systemic events were mostly mild and
usually resolved prior to the subsequent visit (within 3–14 days).
The proportion of volunteers experiencing moderate or severe
local reactions increased significantly with increasing dosage (0%,
8% and 50% in the low, mid and high dose groups, respectively:
two-tailed Cochran-Armitage trend test, p=0.004), whereas dose
had no significant effect on systemic symptoms (p=0.738).
Only one volunteer experienced a serious adverse event, judged
not related to vaccination (suicide in a volunteer with a history of
depression). Of the 177 non-serious adverse events, 136 (77%) were
mild and 164 (93%) were not related or unlikely related to vaccine.
Noneofthe volunteersdiscontinued thestudydueto adverse events.
There werenodifferences inclinical laboratoryparametersbetween
study groups or trends within any study group over time (data not
shown). None of the volunteers developed anti-double-stranded
DNA antibodies at any timepoint throughout the study.
IFNc ELISpot results are summarized in Table 3. The IFNc
ELISpot responses occurred in 3/12 (25%), 4/12 (33%), and 2/12
(17%) volunteers in the low, mid and high dosage groups,
respectively. There were no positive responses to any peptide pool
among the placebo recipients. All but one response occurred only
after the 2ndor 3rdvaccination.
Polyfunctional cytokine-specific responses in the range of 0.4–
0.96% were detected for only one ELISpot-positive donor, a
subject in the low dosage group at week 28, 16 weeks after the last
vaccination. These responses occurred in both CD3+CD4+ T cells
and CD3+CD8+ T cells and showed background subtracted
IFNc, MIP-1b and TNF-a responses to one polymerase pool in
the range of 0.4–0.96%, corresponding with a high ELISpot
response to the same pool. The remaining intracellular cytokine
Figure 1. Clinical Trial Participant Flow Diagram.
ADVAX HIV Vaccine Trial
PLoS ONE | www.plosone.org4January 2010 | Volume 5 | Issue 1 | e8617
assay responses from ELISpot-positive volunteers were below the
limit of detection of the flow cytometry assay.
None of the volunteers developed binding antibodies to Clade C
gp120 following vaccination. Similarly, none of the volunteers
tested positive on clinical HIV-1 ELISA or Western Blot at any
time throughout the study.
This study was the first clinical trial of ADVAX in humans.
Three vaccinations with ADVAX were well-tolerated at all
three dosage levels, with minimal local and systemic reactoge-
Cellular immunogenicity, as measured by IFNc ELISpot assays,
was generally modest,sporadic,and transient,with no apparent dose
response, which is in contrast to the stronger responses observed in
small animals . Responses occurred after the second or third
vaccination in all but one volunteer who formed a transient response
to Gag after the first vaccination. This relatively modest response is
concurrent with other stand-alone intramuscular DNA vaccines,
which have proven weakly immunogenic in humans [14–16].
Given that DNA vaccines provide synergistic priming of the
cellular immune response when boosted by viral vaccines, the
IFNc ELISpot assay does not adequately measure the ability to
prime the immune system. The magnitude of the ELISpot
response also does not necessarily correlate with a protective
immune response either in non-human primates  or in the
recent STEP trial of an adenoviral-based vaccine [18,19]. In our
hands we have seen that the 16 hour detection platform of the
ELISpot is more sensitive for IFNc detection than the 6 hour
detection platform of the flow cytometry assay, which may account
for the paucity of detectable responses on intracellular cytokine
staining. The mechanism of priming by DNA vaccines remains to
be elucidated. Because the correlates of protection to HIV remain
unknown, the relevance of the IFNc ELISPOT and other assays
ultimately remains unknown.
One volunteer in the low dosage group formed a particularly
robust response to polymerase after the third vaccination, which
was of high magnitude and sustained for at least nine months
following vaccination. This was the same volunteer who formed
polyfunctional antigen-specific T cell responses after vaccination.
After unblinding, it was noted that this volunteer was a
homosexual male who had a history of sexual relations with a
long-term HIV-infected partner several years prior to enrolling in
the trial. This volunteer remains HIV uninfected, and qualified for
enrollment into the trial with a negative HIV ELISA, no bands on
HIV western blot, and undetectable viral load. One explanation is
that the robust response to polymerase after vaccination with
ADVAX may reflect a ‘‘boosting’’ effect by ADVAX after
‘‘priming’’ with exposure to HIV in the past, as described
previously . It is also possible that this response is a non-
specific cross reaction to both polymerase peptide pools. However,
this finding may have implications for assessment of responses to
Table 2. Baseline Demographics.
Range 23–5522–46 22–4918–5218–55
Hispanic or Latino01012
Native American or
Native Hawaiian or
Other Pacific Islander
Figure 2. Local and Systemic Reactogenicity by Dosage Group.
Panels A and B depict the percentage of volunteers experiencing local
or systemic reactogenicity, respectively, by severity and dosage group.
Total responses and (percentage of responses) are depicted above each
bar. The proportion of volunteers experiencing moderate or severe local
reactogenicity increased with increasing dosage (two-tailed Cochran-
Armitage trend test, p=0.0040). A similar comparison of systemic
reactogenicity was not statistically significant (p=0.738).
ADVAX HIV Vaccine Trial
PLoS ONE | www.plosone.org5January 2010 | Volume 5 | Issue 1 | e8617
HIV vaccines in high-risk, uninfected populations who may have
prior immunologic exposure to HIV not detected by conventional
screening assays. Further immunologic characterization of this
volunteer pre- and post-vaccination is ongoing.
The fact that no antibody responses were detected is
disappointing, but consistent with the performance of other
stand-alone DNA vaccines delivered to date . Other Clade
C based HIV-1 vaccine candidates have been tested in DNA
prime, Viral vector boost combinations [9,21,22]. To test the
priming ability of ADVAX, two clinical trials are now being
conducted in the United Kingdom and in India, respectively,
where 2 or 3 doses of 4 mg of ADVAX, either administered by
Biojector H 2000 or regular intramuscular needle injection, are
given as prime followed by a recombinant multigenic MVA
expressing HIV-1 Clade C env, gag, RT, rev, tat and nef genes
. Attempts to improve the immunogenicity of DNA vaccines
alone are also underway through improvements in DNA vaccine
delivery or use of adjuvants [13,24]. ADVAX is currently in a
Phase I clinical trial to assess safety and immunogenicity when
delivered by in vivo electroporation with the Tri GridTMDelivery
Found at: doi:10.1371/journal.pone.0008617.s001 (0.19 MB
Found at: doi:10.1371/journal.pone.0008617.s002 (3.74 MB
The authors wish to thank the Clinical and Translational Science Awards
at the Rockefeller University and the University of Rochester Medical
Center and their associated staff for assistance in conducting this clinical
trial; the New York City Department of Public Health Laboratories; V-Bio,
Inc, and Monogram, Inc. for assistance with immunomonitoring assays;
Christine Hogan, M.D., Edward Charles, M.D., and Lucio Verani for
monitoring HIV-1 status; members of our Data and Safety Monitoring
Board; and most importantly, our dedicated clinical trial volunteers.
Conceived and designed the experiments: SV SJS YH AH AL ZC ST PA
MB RB ES MM JG PF DDH. Performed the experiments: SV SJS YH AH
CB MB LC DPD YS LS DKG JG MCK. Analyzed the data: SV SJS YH
AL ZC ST PA MB RB LC CS LD MH CS JC DKG JG PF DDH.
Contributed reagents/materials/analysis tools: SV YH ZC MB RB ES YS
DDH. Wrote the paper: SV AH AL CS LD CS JC MCK DDH.
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Table 3. IFNc ELISpot Results.
ADVAX dosage groups0.2 mg1.0 mg4.0 mg
Positive volunteers3/12 (25%)4/12 (33%)2/12 (17%)
SFC - median2408568
SFC - range88–181054–11066–73
Response Timing–median (week) 146 14
Response Timing–range (week)1–52 6–5214
Table 3 summarizes the IFNc ELISpot response rate and magnitude in spot
forming cells per million PBMCs (SFC) among volunteers receiving ADVAX by
dose group. There were no positive responses in placebo recipients. The timing
of IFNc ELISpot responses and distribution of antigens eliciting these responses
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risk, HIV-negative volunteers who subsequently acquire HIV infection. Vaccine
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