Oral Abstract Session 01 - Global HIV Vaccine Enterprise

POSTERS
Posters
Topic 11: T Cell Immunity
P11.47 LB
Understanding The Precursor Frequencies of HIV-1
Specific CD4+ T Cells In Seronegative Donors
S.L. Campion 1 , T. Brodie 2 , A. Rossetti 2 , N. Goonetilleke 1 ,
F. Sallusto 2 , A. McMichael 1
1 University Of Oxford, Oxford, United Kingdom (Great Britain);
2 IRB, Bellinzona, Switzerland
Background: HIV-1 specific T cell responses are detectable
amongst a proportion of HIV-1 exposed, seronegative
individuals. Previous studies from our group have demonstrated
these responses are predominately mediated by CD4+ T cells
and can be mapped and titrated at the peptide level. Curiously,
approximately 1 in 4 HIV-1 un-exposed seronegative donors
also have demonstrable HIV-1 specific T cell responses. This
observation raises a number of questions regarding the ontogeny
of pre-existing HIV-1 specific T cells and their potential role in the
acquisition of HIV-1
Methods: A highly sensitive T cell library method was used
to screen the naïve, central and effector memory CD4+ T cell
subsets from 10 healthy, HIV-1 seronegative, leukapharesis
donors. 192 cell lines per subset were screened against pools
of overlapping 18mer peptides, spanning the entire HIV-1
proteome and proliferative responses quantified using tritiated
thymidine incorporation.
Results: HIV-1 specific CD4+ T cell response were detectable
within the CD4+ T cell memory compartments of all 10 subjects
tested, albeit at low frequency. HIV-1 specific CD4+ T cell
responses spanned the entire HIV-1 proteome and were typically
of low avidity. There was considerable variability between donors
both in the proteins recognized and precursor frequencies of
HIV-1 specific T cell responses. However, across all subsets tested
CD4+ T cells specific for HIV-1 envelope appeared to exist at
the highest precursor frequency, with Pol seemingly the least
frequently targeted.
Conclusion: We show HIV-1 specific CD4+ T cells to be
detectable within the memory compartment of all 10 donors
tested. In the absence of known prior exposure to HIV-1 these
observations are indicative of low level cross reactivity within
the immune system. The use of the T cell library technique to
interrogate the naïve and memory precursor frequencies of
HIV-1 specific T cells should prove beneficial in the design of
novel therapeutic vaccines.
240
AIDS Vaccine 2012
P11.48 LB
IL-7 Abrogates Memory T Regulatory Cell Functions
By Modulation of CD39/ATP Axis In Vitro And In Vivo
In HIV Infected And Non-Infected Patients
M. Younas 1 , S. Hue 1 , M. Surenaud 1 , C. Lacabaratz 1 , A. Guiguin 1 ,
A. Wiedman 1 , S. Becq 2 , T. Croughs 2 , J. Lelievre 1 , Y. Levy 1
1 Faculté de médecine, Université Paris-Est, Créteil, Créteil,
France; 2 Cytheris, France
Background: IL-7 cytokine regulate the expansion and
maturation of T cells. The good safety profile of IL-7 raises the
opportunity of its use as a vaccine adjuvant. However, its role
on the regulation of T cell responses has not been explored.
We investigated the effects of IL-7 on regulatory T cell (Treg)
functions invitro and invivo.
Methods: Treg and CD8+ T cells were isolated from healthy
donors (n=10) (HD) and chronically HAART treated HIV+ pt
enrolled in a phase I/II IL-7 INSPIRE study (n=6X) (Levy et al,
CID, in press). Treg subpopulations (naïve CD45RA+FoxP3++CD
45RA+CD25++CD127+/-, memory (mTreg) Foxp3highCD45RA-
CD25highCD127low, FoxP3++CD45RA-CD25++CD127+/-) were
cultured with IL-7 (10 ng/ml). Phenotype (CD39, Bcl-2, Stat5P,
purinergic receptor P2X7R), suppression of the proliferation of
autologous antiCD3 activated CD8+ T cells (CFSE stained) and
cytokine profile (IL-17 production) of Treg were analyzed.
Results: In HD, IL-7 induces expression of STAT5 and BCL-2 on all
Treg populations. IL-7 reduces the suppressive effects of mTreg
on CD8+ proliferation (% CFSE low w/wo IL7 was 15% and 40%,
respectively, n=4, P=0.01). This effect was associated with a downmodulation
of CD39 enzyme (MFI 65 vs 90 w/wo IL7, P=0.01)
and an increase of P2X7R expression. IL-7 effect was reproduced
using anti-CD39 blocking antibody and PPAD (inhibitor of P2X7R).
IL-7 incubated Treg switched to a Th17 phenotype as assessed
by the increase of Th17 production and RORgC expression. IL-7
treated patients exhibited a decrease of the frequency of Treg/
CD39+ and an increase of RORgC mRNA in PBMCs as compared
to pre-IL-7 therapy.
Conclusion: IL-7 relieves the suppressive effect of mTreg
through a modulation of the CD39/ATP axis. By increasing P2X7R
expression, IL-7 increases the susceptibility of these cells to ATP,
a trigger of Th17 differentiation. An effect also observed in IL-7
treated patients. These results suggest that IL-7 could be used as
adjuvant to reinforce T cell responses.