Measuring the contribution of γδ T cells to the persistent HIV reservoir.

Objective: To study the contribution of gamma delta T cells to the persistent HIV reservoir. Design: Fifteen HIV-seropositive individuals on suppressive ART were included. We performed parallel quantitative viral outgrowth assays (QVOA) of resting CD4(+)T (rCD4) cells in the presence or absence of gamma delta T cells. Methods: Resting alpha beta+CD4(+)T cells were magnetically isolated from PBMCs using two different custom cocktails, only one kit contained antibodies to deplete gamma delta T cells, resulting in two populations: rCD4 cells and rCD4 cells depleted of gamma delta cells. Frequency of infection was analyzed by QVOA and DNA measurements. Results: Recovery of replication-competent HIV from cultures of rCD4 cells was similar in 11 individuals despite the presence of gamma delta T cells. In four donors, HIV recovery was lower when gamma delta T cells were present. Expression of the cytotoxic marker CD16(+)on V delta 2 cells was the only variable associated with the lower HIV recovery. Our results highlight the potency of those responses since a mean of 10 000 gamma delta T cells were present within 2.5 million rCD4 cells. However, despite the low frequency of gamma delta T cells, the presence of cytotoxic V delta 2 cells correlated with lower HIV recovery from cultures of rCD4 cells. Conclusion: Results of this study show that quantification of the contribution of gamma delta T cells to the reservoir is challenging because of their low numbers compared with conventional rCD4 cells and highlights the potent antiviral function of gamma delta T cells and the impact of their presence on the frequency of latent HIV infection.