Oral Abstract Session 01 - Global HIV Vaccine Enterprise

Topic 11: T Cell Immunity
P11.25
Increased Mucosal CD4+ T-Cell Activation Following
Vaccination with an Adenoviral Vector in Rhesus
Macaques
I. Bukh 1 , R. Calcedo 1 , S. Roy 1 , D.G. Carnathan 1 , R. Grant 1 ,
S.J. Ratcliffe 1 , J.M. Wilson 1 , M.R. Betts 1
1 University of Pennsylvania, Philadelphia, PA, USA
Background: The possibility that vaccination with Adenoviral
vectors increased mucosal T-cell activation remains a central
hypothesis to explain the potential enhancement of HIV
acquisition within the STEP trial. Modeling this within rhesus
macaques is complicated because human Adenoviruses,
including Adenovirus type 5 (HAd5), do not productively infect
macaques. We created a vector based upon a naturally occurring
rhesus macaque Adenovirus (SAdV7) to test whether vaccination
with a species-specific Adenoviral vector enhances mucosal
T-cell activation within the natural host.
Methods: Twelve rhesus macaques were vaccinated 3x
intramuscularly with SAdV7 vector. Five HAd5-vaccinated
animals were included as controls. PBMC and rectal biopsies
were obtained at baseline, multiple times post-prime and post-
17 week boost (8x/animal), and post-31 week second boost (1x/
animal). We assessed rectal mucosal lamina propria and blood
for frequency changes of Ad-specific T-cell responses and T-cell
activation levels by measuring IFNg, TNFa, IL2, CD25, Ki67, CD69,
and HLA-DR.
Results: Naturally acquired pre-existing SAdV7-specific CD4+
T-cells were identified in 10/13 macaques within blood and/
or rectal mucosa. Following intramuscular SAdV7 vaccination,
rectal SAdV7-specific CD4+ T-cell responses increased above
baseline in 9/9 animals 2-5 weeks post-prime, and subsequently
contracted. Five weeks post-prime, 10/12 animals had rectal
SAdV7-specific CD4+ T-cell responses ranging from 0.1-16.84%.
As expected, SAdV7-specific CD4+ T-cells expressed CD69 and
other activation markers (but not Ki67). Heightened expression
of CD25, CD69, and HLA-DR was observed on total rectal memory
CD4+ T-cells in SAdV7-vaccinated animals, and maintained 15
weeks after the prime. Interestingly, upregulation of activation
markers in rectal mucosa also occurred in HAd5-vaccinated
animals. No change in activation was observed in the blood
throughout the entire study.
Conclusion: These results indicate that peripheral vaccination
with an Adenovirus vector can increase the activation of mucosal
CD4+ T-cells providing an experimental model to further evaluate
the role of host-vector interactions on increased HIV acquisition.
P11.26
AIDS Vaccine 2012
Posters
Different Abilities of CTL Specific for Two HLA-
A*24:02-Restricted Overlapping Optimal Epitopes to
Select Same HIV-1 Escape Mutant Virus
X. Sun 1 , M. Fujiwara 1 , N. Kuse 1 , S. Oka 2 , M. Takiguchi 1
1 Center for AIDS Research, Kumamoto University, Kumamoto,
Japan; 2 AIDS Clinical Center, National Center for Global Health
and Medicine, Tokyo, Japan
Background: Cytotoxic T lymphocytes (CTLs) are thought to
exert immunologic selection pressure of escape mutation.
Previous reports have showen that some overlapping peptide
epitopes were presented by same HLA molecules. However, the
abilities and properties of those CTLs to selection of same escape
mutation are not well studied.
Methods: CTL clones were established by stimulation of PBMC
with a synthetic peptide (Nef138-8: RYPLTFGW or Nef138-10:
RYPLTFGWCF) by limiting dilution method. Cytotoxic activity
toward peptide-loaded cells was performed by 51Cr releasing
assay. CTL suppression ability was tested by HIV-1 replication
assay toward primary CD4+ cell. In vitro selection of escape
mutation was performed by competitive HIV-1 replication assay.
The frequency of tetramer positive cells in PBMC of HLA-A*24:02+
patients was detected by flow cytometry analysis.
Results: Both 8-mer and 10-mer epitopes specific CTLs were
established from PBMC of the patients. The ability of Nef138-
10-specific CTLs to suppression HIV-1 replication in vitro was
much higher than that of Nef138-8-specific CTLs. In addition,
at the early stage of infection, Nef138-10-specific CTLs was
predominantly elicited in the patients more than the latter ones.
Cross-reactive Nef138-8-specific CTLs recognizing both WT and
2F epitopes were detected in some patients. Moreover, in vitro
competitive HIV-1 assay showed that both CTLs can select escape
mutants, though the ability of Nef138-10-specific CTLs was
stronger than that of Nef138-8-specific ones.
Conclusion: The present study demonstrated that Nef138-10specific
CTLs play a major role in the selection of the escape
mutation, and that Nef138-8-specific CTLs also have ability to
select it. We showed selection of the same escape mutants by
CTL specific for same HLA-restricted overlapping epitopes.
229
POSTERS