Oral Abstract Session 01 - Global HIV Vaccine Enterprise

Oral Abstract Session 04: Mucosal Immunity
OA04.03
Expanded Memory CD4+ T Cells in the Fetal and the
Infant Gut; a Mucosal Route for Mother-to-Child-
Transmission of HIV-1
M.J. Bunders 1 , C. van der Loos 1 , P.L. Klarenbeek 1 , J. van Hamme 1 ,
J. Wilde 1 , N. de Vries 1 , R.A. van Lier 1 , N. Kootstra 1 , S.T. Pals 1 ,
T.W. Kuijpers 1
1 Academic Medical Centre, Amsterdam, Netherlands
Background: Cord blood-derived CD4+ T cells have a naïve
phenotype and do not express CCR5, the mandatory coreceptor
for transmitted HIV-1 R5 strains in infants. This leaves
the question unanswered: what are the target cells for MTCT of
HIV-1 and where do they reside? We hypothesized that in infant
mucosal tissues, CD4+CCR5+ T cells may be present to facilitate
mucosal transmission of HIV-1.
Methods: Using multicolor immuno-histochemistry, flowcytometry
and next-generation sequencing of the T cell receptor, we analyzed
various human fetal and infant tissues to identify memory CD4+ T
cells as targets for HIV-1.
Results: Here, we demonstrate the previously unrecognized
abundance of memory CD4+CCR5+ T cells in the human fetal and
infant gut mucosa. CD4+ T cells from mesenteric lymph node were
mostly naïve, similar to blood. T helper differentiation profiles
as determined by transcription factors differed by tissue, with
T-bet and ROR_t predominantly expressed by memory T cells in
the gut mucosa. Next-generation sequencing for high-resolution
screening of the T-cell receptor _-chain repertoire of clonal T cells
as a hallmark of memory cells, identified expanded T cell clones
in the gut mucosa (30%) and not in lymph node or cord blood.
The gut mucosal fetal and infant CD4+ T cells were extremely
susceptible to HIV-1 without any prestimulation; pol proviral DNA
levels were similar to infected PHA stimulated adult PBMCs.
Conclusion: In conclusion, we show that extensive adaptive
immunity, with a tissue-depended distribution is present before
birth, resulting in the gut mucosa as the preferential site for
memory CD4+ T cells. These memory CD4+CCR5+T cells provide
a large pool of susceptible cells for ingested HIV-1 at birth and
during breastfeeding, indicating a mucosal route of MTCT of HIV-
1, which can be targeted in future prevention strategies.
Oral Abstract Sessions
OA04.04
Cell Free HIV-1 Virus Can Infect Inner and Outer
Foreskin Polarized Explants
M.P. Lemos 1 , M.L. Perez 1 , J. Sanchez 2 , J. Lama 2 , S. Montano 3 ,
J. McElrath 1
1 Fred Hutchinson Cancer Research Center, Seattle, WA, USA;
2 IMPACTA, Lima, Peru; 3 Naval Medical Research Unit 6, Lima, Peru
Background: In sexually insertive men, HIV is predominantly
transmitted at the penile surface. We report two mayor advances
in the study of HIV infections at the foreskin.
Methods: First, we have developed cryopreservation methods
that allow infection of foreskin tissue explants after thawing
(654 +/- 178.3 pg of p24/gr of tissue) and provide comparable
infection rates to fresh samples( 716.5 +/- 446pg of p24/gr of
tissue). Second, we have developed an ex vivo assay that uses
human foreskin explants to replicate the polarized viral entry.
After 12h of polarized exposure, HIV entering the explant
is amplified for 6 days of culture with activated PBMCs and
measured using p24 ELISA.
Results: Preserving the epithelial barriers, we show that polarized
infections permit the entry and expansion of less virus (68.28 +/-
10.65pg of p24/gr of tissue) than non-polarized infections (650.4
+/- 205.9pg of p24/gr of tissue) where the virus can enter the
CD4 T cell rich epidermal-dermal interface (p=0.04). Using 10000
TCID50 of HIV-1Bal per explants, we can detect infection in 100%
of the non-polarized assays and 69% of the polarized explants.
Lastly, comparing foreskin tissue from 4 donors, we demonstrate
that the inner and outer foreskin are both equally able to support
cell-free HIV infection in polarized assays (inner 77.67 +/- 64.7 vs.
outer 92.82 +/- 66.81pg p24/gr of tissue p=0.369) and in nonpolarized
assays (inner 730.9 +/- 323.7 vs. outer 625 +/ 301.2pg
p24/gr of tissue p=0.41).
Conclusion: We hope that this approach could be used efficiently
as a model to evaluate the efficacy of prevention strategies.
AIDS Vaccine 2012
63
ORAL ABSTRACT SESSIONS