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Functional Profile of HIV-specific T Cells in Rectal Mucosa
J Critchfield1, D Lemongello1, D Young1, M Morris1, M Schreiber1, B Autret1, J Garcia1, D Asmuth1, R Pollard1,1, R Pollard1,1, Barbara Shacklett*1,1, and Barbara Shacklett*1,1
1Univ of California, Davis, US
Background: The gastrointestinal mucosa is an important
site of HIV replication and CD4+ T-cell depletion. Previous studies
have demonstrated that mucosal CD8+ T cells differ from their
counterparts in blood in terms of memory/effector phenotype and expression of perforin. However, detailed comparisons of the functions
and fine specificity of T cells from these 2 compartments have not been
reported. Here, we assessed HIV-specific T cells for antigenic breadth and the
production of 5 effector molecules—interferon-gamma
(IFN-g), tumor necrosis factor-alpha (TNF-a), interleukin-2
(IL-2), macrophage inhibitory protein-1beta (MIP-1b), and
CD107.
Methods: Blood and rectal biopsy tissue were obtained from 19 HIV+
individuals (10 off and 9 on HAART) and 3 healthy controls. Effector
functions were assessed by intracellular cytokine staining using 10-color flow cytometry. Data were analyzed using Boolean gating;
statistical analysis was performed using SPICE and SAS software. Positive
responses were defined as >0.05% of CD8+ T cells after
subtracting controls. For epitope mapping, cells were
expanded and challenged in an IFN-g ELISpot
with pooled peptides corresponding to HIV-1 clade B
consensus Gag, Env, and Nef.
Positive responses were defined as >50 spot-forming cells (SFC)/106
after subtracting background.
Results: Mucosal CD8+
T cells displayed a complex pattern of functions. In both rectum and peripheral
blood mononuclear cells (PBMC), 3 functional categories dominated the
Gag-specific CD8+ T-cell response:
4-function (CD107/IFN-g/MIP-1b/TNF-a); 3-function (CD107/IFN-g/MIP-1b);
dual function (CD107/MIP-1b), and single function (MIP-1b). While the magnitude of
Gag-specific cytokine responses was generally greater in rectum, the breakdown
of responses into functional categories was similar in both compartments (p >0.05). In patients not on HAART,
the breadth of Gag-specific responses was significantly greater in rectal
mucosa as compared to PBMC (p = 0.01).
Conclusions: Mucosal CD8+ T cells are capable of broad and
complex HIV-specific cytokine responses, dominated by secretion of MIP-1b and degranulation. These polyfunctional
cells likely play a major role in immune surveillance of gut mucosa.
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