T follicular helper (Tfh) CD4 T cells are located within the germinal centers (GC) of lymph nodes (LN), are a source of residual viral replication during antiretroviral therapy and contribute to the latent reservoir. Broadly neutralizing antibodies (bnAbs) can target HIV-expressing Tfh cells to purge the latent reservoir either alone or as bispecific antibodies that also target CD8 T cells. We tested multiple bnAbs for their ability to detect HIV-infected cells. We also characterized the localization, frequency, and function of CD8 T cells in GCs. In vitro infected CD4 T cells and Tfh from HIV-infected subjects were surface stained with multiple different bnAbs. We analyzed the phenotype, localization and function of CD8 T cells in tonsils and LNs from non-infected and HIV-infected viremic individuals. Polychromatic flow cytometry was used for phenotypic analysis and confocal imaging for spacial localization. In vitro cytolytic activity of sorted CD8 T cell populations was tested in a killing assay using an anti-HIV Env/anti-CD3 bispecific-antibody. CD4bs and glycan V1/2 and V3 directed bnAbs very efficiently stained in vitro infected CD4 T cells and Tfh from HIV-infected subjects. Phenotypic analysis of tonsillar cells revealed a memory population of CD8 T cells expressing a CCR7lowCXCR5high profile compatible with follicular localization, and confocal imaging confirmed the presence of a small population of CD8 T cells within the GC. These GC CD8 T cells were expanded in HIV-infected LNs, and they produced perforin and GzB. GC localized CD8 T cells had the greatest ability to mediate killing of HIV-infected target cells after cross-linking with an anti-HIV Env/anti-CD3 bispecific antibody. BnAbs can detect surface expression of HIV envelope on Tfh in vivo. HIV infection is characterized by accumulation of CD8 T cells within LN follicles. These CD8 T cells are functionally capable of mediating bispecific antibody-mediated killing of HIV-infected CD4 T cells.
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