Oral Abstract Session 01 - Global HIV Vaccine Enterprise

Topic 4: Clinical Vaccine Trials and Trial Site Challenges
P04.13
New HIV Peptide-Based Immunoassay Resolves
Vaccine-Induced Seropositivity in HIV Vaccine (Phase
III) Trial Participants
O. Penezina 1 , D. Clapham 1 , J. Collins 1 , V. Kovalenko 1 , N. Krueger 1 ,
I.R. Rodriguez-Chavez 2 , M.P. Busch 3 , A.E. Levin 1
1 Immunetics, Boston, MA, USA; 2 NIH/NIDCR, Bethesda, MD,
USA; 3 Blood Systems Research Institute, San Francisco, CA,
USA
Background: HIV Vaccine trials bring the significant risk of
vaccine-induced HIV seropositivity(VISP) resulting in negative
personal consequences for vaccinees. The overall rate of VISP
in licensed EIA tests is reported as 41.7%(JAMA 2010;304:275-
283). We have developed and modified the peptide-based HIV
Selectest immunoassay(J.Virol 2006;80:2092-2099), which
discriminates VISP from true HIV infection, in a format suitable
for routine laboratory use, and have evaluated its performance
on samples from three Phase III HIV vaccine trials.
Methods: The HIV Selectest incorporated five synthetic peptides
in a single well microplate ELISA. Serum panels evaluated
comprised well-characterized HIV-positive sera from clades A,B
and C, worldwide panels comprising all major clades, blood
donor controls, and sera from vaccine and placebo recipients in
RV144, Vax003 and Vax004 trials.
Results: 360 serum samples from the RV144 vaccine trial,
including 170 samples from vaccinated subjects at the peak
immune response, 120 pre-immune samples, and 70 subjects
from the placebo group were tested on the HIV Selectest. One
(1) subject(0.6%) among the vaccine recipient group yielded
false-positive results, while 3 placebo recipients (4.3%) and
1 pre-immune serum sample (0.8%) were also false positive
in the HIV Selectest. All false-positive samples demonstrated
broad non-specific cross-reactivity that was not restricted to a
particular HIV-specific peptide.
Similar results were obtained with samples from the VAX003 and
VAX004 vaccine trials. One subject out of 87(1.2%) tested after
the final vaccination(7thvisit) at the peak of the immune response
was detected as false positive. Two additional samples out of
96(2.1%) taken after the 4thvisit were likewise detected as falsepositive,
bringing the average false-positive rate for both groups
to 1.6%.
Blood donors yielded a statistically equivalent false-positive rate
of 1.2%. Detection sensitivity for HIV positive samples was 96%
among 648 serum samples representing different clades.
Conclusion: The HIV Selectest ELISA has demonstrated
significantly better discrimination of VISP than currently licensed
HIV serologic assays.
P04.14
AIDS Vaccine 2012
Posters
A New Method for Integrated Analysis Applied
to Gene Expression and Cytokines Secretion
in Response to LIPO-5 Vaccine in HIV-Negative
Volunteers
R. Thiebaut 1 , B. Liquet 1 , H. Hocini 1 , S. Hue 1 , L. Richert 1 ,
M. Raimbault 1 , K. Lê Cao 1 , Y. Levy 1
1 INSERM U897, Bordeaux, France
Background: We present an integrated analysis of gene
expression and cytokine secretion using a novel statistical
method applied to the ANRS VAC18 trial.
Methods: The statistical approach combines multilevel and
multivariate analyses. The statistical approach is based on a
variance decomposition followed by a sparse Partial Least Square
Discriminant Analysis (sPLS-DA) to select the discriminative
features (genes, cytokines) separating the classes in a supervised
framework, or sPLS to select subsets of correlated features
(genes and cytokines) in an integrative framework.
HIV-LIPO-5 vaccine is a mix of five synthetic HIV-1 peptides
(from Gag, Pol, Nef), each coupled to a palmytoil tail. PBMCs
from 12 HIV-negative volunteers were collected before (W0)
and after vaccination (W14). PBMC were stimulated with either
i) the HIV-LIPO-5 vaccine; or ii) a pool of 15-mer Gag peptides
included in the HIV-LIPO-5 vaccine (Gag+); or iii) a pool of 15-mer
peptides not included in LIPO-5 vaccine (Gag-). Production of 10
cytokines was assessed at day 11 (MILLIPLEX MAP kit, Millipore).
Gene transcription in PBMC was assessed after 6- and 24-hour
stimulations (Illumina Human HT12-v4 chips).
Results: After vaccination, the multilevel discriminant analysis
led to the selection of 290 genes over three components that
gave a good separation of the four groups of stimulation. The first
component that distinguished LIPO5 stimulation from the others
included a cluster of genes belonging to the metallothionein
family (MT1M, MT2A,…) possibly linked to the effect of the
palmytoil tail. The second component separated Gag+ from
other stimulations. The multilevel sPLS showed similar profiles of
correlations between gene expression and cytokine secretion for
TH2 (IL5 and IL13), IL21 and IL1b, TNF and IL6.
Conclusion: This new statistical approach helps in analyzing
complex designs. In VAC18, it revealed the differential responses
to vaccine peptides and the lipid adjuvant. Gene expression
signatures associated with cytokine responses were identified.
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POSTERS