Background Biomarkers of HIV exposure could help identify subpopulations at highest risk of HIV acquisition, to focus public health interventions and prevention strategies.This study assessed Y-chromosome single tandem repeat (YSTR) mixtures as biomarkers of receptive anal intercourse without condoms (RAIWC) among men who have sex with men (MSM). We also evaluated the feasibility of self-administered rectal swabs for detection of HIV virions to assess exposures.
Methods Thirty 18-to-50-year-old sexually active, HIV-seronegative MSM were enrolled in New York City. Participants answered daily sexual behavior questions via a mobile phone for 60 days, and were randomized to collecting self-administered rectal swabs daily or after every receptive anal intercourse (RAI) event. Blood collections, rapid HIV diagnostics, and counselling were performed at beginning and end of the study. YSTR mixtures were assessed in DNA from blood and 233 swabs from 20 participants reporting at least one RAIWC event. HIV exposure was measured by virion PCR in 171 swabs linked to reports of RAIWC.
Results As markers of partner’s DNA, YSTR mixtures were found in 41/138 (29.7%) of self-collected swabs linked to mobile reports of RAI. 15/83 (18%) swabs collected after reporting abstinence, insertive sex or RAIWC had YSTR mixtures. No participant became HIV infected during the study, yet exposure to HIV was detected in six rectal swabs corresponding to two different participants. For one participant on pre-exposure prophylaxis (PrEP), rectal HIV virions were found after RAIWC with two different HIV positive partners not on antiretroviral therapy. For the second participant, rectal HIV exposures were identified after RAIWC with two different partners disclosing HIV negative status.
Conclusion YSTR mixtures in self-collected rectal swabs demonstrated 82% specificity but only 30% sensitivity to assess RAIWC. Detection of HIV exposure in self-collected swabs from two uninfected participant indicates it was possible to measure rectal HIV exposures in MSM.
Disclosure No significant relationships.
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