CD8+ T Cell Subsets with Noncytotoxic Anti-HIV Activity

Scott Killian, UC-San Francisco
Biomedical and Clinical Sciences

Background: The ability of CD8+T cells to inhibit HIV replication through cytotoxic and non-cytotoxic mechanisms has been well described [1;2]. However, many features of the effector cell response remain unclear. Subset differences, regulatory effects, and priming efficiency could explain the observed variation in the quality of CD8+T effector cell responses between individuals. We have previously investigated the non-cytotoxic effector properties of several CD8+ T cell subsets. Differential effector activity has been observed to be associated with CD28, HLA-DR, CD11b, andVCAM expression, but not CD38 and CD57 expression [3;4]. Importantly, we and others have observed that IL-2 is required for optimal inhibition of HIV replication by CD8+ cell non-cytotoxic effects [5-7].These observations have heightened our interest in the investigation of IL-2 responsive CD8+ cells and potential CD8+ regulatory cell subsets.

Methods: CD8+ cells were isolated from the PBMC of HIV-1 infected subjects using immunomagnetic beads. These cells were then stained antibodies specific for various surface markers and sorted into phenotypically distinct populations using a FACSDiva. Antiviral activity was assessed upon coculturing the CD8+ cell subsets with acutely infected heterologous CD4+ cells. CD4+ cells, after 3 days of PHA stimulation, were infected with the CXCR4 tropic, chemokine resistant, primary HIV-1 isolate SF33. HIV replication was assessed by measuring the reverse transcriptase (RT) levels present in the cell culture supernatants at days 4 and 7.

Results / Expected Results: Our studies suggest that CD8+ cells with non-cytotoxic activity can be further distinguished by cell surface markers (e. g. CCR7). Our observations also indicate that other subsets of CD8+ cells may have the ability to negate or regulate this anti-HIV activity.

Conclusion: As these studies will better characterize the relationship between phenotype and CD8+ T cell immune responses, the proposed research can potentially be applied to improve future therapeutic and vaccine strategies.