Characterization of CD4+ T cell subsets and HIV susceptibility in the inner and outer foreskin of Ugandan men

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Abstract
Problem: Biological mechanisms of foreskin HIV acquisition are poorly defined. The inner foreskin is preferentially infected in explant models, so we hypothesized that this site would be enriched for HIV‐susceptible CD4+ T cells and proinflammatory/chemoattractant cytokines.Method of study: A total of 42 HIV‐uninfected Ugandan men without genital symptoms provided foreskin tissues and swabs at the time of elective penile circumcision. The immune phenotype of foreskin‐derived CD4+ T cells and entry of a CCR5‐tropic HIV pseudovirus was characterized, and specific cytokine levels assayed by multiplexed chemiluminescent ELISA.Results: Unexpectedly, outer foreskin CD4+ T cells more frequently expressed CCR5 (median 29.2% vs 22.9%, P = 0.01) and CD69 (median 36.5% vs 15%, P < 0.01), and on a per‐cell basis, HIV entry was higher. However, overall CD4+ T cell density was approximately twofold higher in the inner foreskin, and several highly susceptible T cell subsets were increased at this site, including Th17 cells (20.0% vs 14.1%, P = 0.0021). Specific pro‐inflammatory cytokine levels were also higher on the inner foreskin surface (IL‐17, IL‐8, RANTES and IL‐1β; all P < 0.05).Conclusion: There was marked heterogeneity in CD4+ T cell populations and immune milieu between inner and outer foreskin tissues. Despite higher per‐cell viral entry into CD4+ T cells from the outer foreskin, the higher target cell density and enriched pro‐inflammatory cytokines of the inner foreskin suggest that this may be a preferential site for HIV acquisition.

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