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Kirby Institute is pleased to present:
Chan Phetsouphanh - "Novel approaches to the characterization of antigen-specific CD4+ T cells in HIV-1 infection."
Abstract:
Immune reconstitution is typical in chronic HIV-1 infected individuals who are treated with cART. The characteristics of this were monitored in 20 chronically infected subjects recruited through the PrIRIS study. Changes in CD4+ T cell function were characterized in the context of increases in CD4+ T-cell counts and decreases in plasma viral load over the first year of therapy using the CD25/OX40 assay and a range of other phenotypic assays.
The CD25/OX40 assay was used to identify antigen-specific CD4+ T-cells in vitro. In healthy individuals the majority of CMV-specific responses were from the effector memory (Tem) subset, with TT-specific responses arising from the central memory (Tcm) subset. In chronic HIV+ subjects post-therapy, the ratio of the responding memory subsets was inverted, with a greater gag response coming from the Tcm subset at week 48 compared to week 4. As activation decreased, the percentages of responding Tem cells decreased, but long-term Tcm responses were maintained.
A qualitative multiplex single-cell RT-PCR assay was developed to be used downstream of the CD25/OX40 assay. Lineage specific transcription factor profiling, allowed delineation of Th1 (Tbet), Th2 (Gata3), Th17 (Rorc), Tregs (Foxp3) and Tfh (BCL6) cells within an antigen specific population. Results demonstrated >80% of activated Ag-specific single cells expressed only 1 transcription factor. CMV-specific CD4+ T-cells displayed a dominant Th1-like response, and TT-specific cells displayed a Th2-like response. HIV-specific CD4+ T cells displayed a Th1-like response at early time points.
PKC-θ a novel protein kinase plays an important role in T cell development, proliferation, differentiation and chromatin remodelling. In Ag-specific CD4+ T-cells, PKC-θ was bound in intronic regions of genes, where it was highly associated with permissive histone marks and enhancer-like chromatin state. NF-kB (p65) was identified as having common binding sites to PKC-θ. p65 motifs were found mostly within the promoter, 5’UTR and exons of inducible genes. This result highlights the possible involvement of NF-kB and PKC-θ as potential binding partners.
In conclusion, the characterization of virus-specific CD4+ T-cells at the cellular and molecular level are likely to reveal mechanisms for the manipulation of immunological memory development and its maintenance, allowing improved design of immunotherapies and vaccines.
Biography :
Chan is a PhD candidate in the IVPP program under the supervision of Prof. Tony Kelleher. His project involves the characterization of antigen specific CD4+ T-cells in HIV-1 infection.
