The Impact of Semen Exposure on the Immune and Microbial Environments of the Female Genital Tract

Abstract

Background: Semen induces an immune response at the female genital tract (FGT) to promote conception. It is also the primary vector for HIV transmission to women during condomless sex. Since genital inflammation and immune activation increase HIV susceptibility in women, semen-induced alterations at the FGT may have implications for HIV risk. Here we investigated the impact of semen exposure, as measured by self-reported condom use and Y-chromosome DNA (YcDNA) detection, on biomarkers of female genital inflammation associated with HIV acquisition. Methods: Stored genital specimens were collected biannually (mean 5 visits) from 153 HIV-negative women participating in the CAPRISA 008 tenofovir gel open-label extension trial. YcDNA was detected in cervicovaginal lavage (CVL) pellets by RT-PCR and served as a biomarker of semen exposure within 15 days of genital sampling. Protein concentrations were measured in CVL supernatants by multiplexed ELISA, and the frequency of activated CD4+CCR5+ HIV targets was assessed on cytobrush-derived specimens by flow cytometry. Common sexually transmitted infections (STIs) and bacterial vaginosis (BV)-associated bacteria were measured by PCR. Multivariable linear mixed models were used to assess the relationship between YcDNA detection and biomarkers of inflammation over time. Results: YcDNA was detected at least once in 69% (106/153) of women during the trial (median 2, range 1–5 visits), and was associated with marital status, cohabitation, the frequency of vaginal sex, and Nugent Score. YcDNA detection but not self-reported condom use was associated with elevated concentrations of several cytokines: IL-12p70, IL-10, IFN-γ, IL-13, IP-10, MIG, IL-7, PDGF-BB, SCF, VEGF, β-NGF, and biomarkers of epithelial barrier integrity: MMP-2 and TIMP-4; and with reduced concentrations of IL-18 and MIF. YcDNA detection was not associated with alterations in immune cell frequencies but was related to increased detection of P. bivia (OR = 1.970; CI 1.309–2.965; P = 0.001) at the FGT. Conclusion: YcDNA detection but not self-reported condom use was associated with alterations in cervicovaginal cytokines, BV-associated bacteria, and matrix metalloproteinases, and may have implications for HIV susceptibility in women. This study highlights the discrepancies related to self-reported condom use and the need for routine screening for biomarkers of semen exposure in studies of mucosal immunity to HIV and other STIs.

Transient association between semen exposure and biomarkers of genital inflammation in South African women at risk of HIV infection

“…We enrolled 152 HIV‐negative women between 20 and 44 years of age from KwaZulu‐Natal who participated in the CAPRISA 008 study [23‐25]. Women participated in the CAPRISA 008 study over two years, between November 2012 and October 2014, and were followed up for an average of 22 months [23,25].…”

“…Women participated in the CAPRISA 008 study over two years, between November 2012 and October 2014, and were followed up for an average of 22 months [23,25]. Demographic data were assessed at baseline, and vaginal specimens (including cervicovaginal lavage (CVL), cytobrushes and vulvovaginal swabs) were collected at enrolment and biannually at months 6, 12, 18, 24 and study exit (average 5 ± 1 visit; 651 genital specimens) as previously reported [24‐27]. Semen biomarkers were measured in vaginal specimens collected at each of the multiple study visits per participant.…”

“…Data were acquired on an LSRII flow cytometer (BD Immunocytometry Systems, San Jose, CA, USA) and analysed with FlowJo™ Software version 9.9 (Tree Star, Inc., US). The gating strategy was previously published [24].…”

Recent Semen Exposure Impacts the Cytokine Response and Bacterial Vaginosis in Women

“…Given the impact that unprotected sexual intercourse has on the vaginal immune response and microbiome, an objective assessment of semen exposure is needed to accurately interpret mucosal immunity and BV data from vaginal fluids of women enrolled in HIV prevention trials. Measurement of semen exposure using biomarkers has been identified as a robust method to reduce the reliance on self-reported sexual activity in studies investigating immunological factors in the FGT, risk of infection or probability of pregnancy (22)(23)(24)(25)(26). Two semen biomarkers; prostate-specific antigen (PSA) and the Ychromosome DNA, have been used to indicate the presence of semen within the FGT (27,28).…”

Semen: A modulator of female genital tract inflammation and a vector for HIV‐1 transmission

“…Several factors in semen may also inhibit the activity of extracellular H 2 O 2 produced by Lactobacilli species and thus promote the growth of BV‐associated microbes 195 . We have demonstrated that recent semen exposure is associated with increased detection of BVAB‐2, Prevotella bivia , and G. vaginalis and reduced detection of Lactobacillus jensenii in vaginal specimens (Jewanraj et al, 2021; accepted) 165 . Increases in other gut‐associated microbes have also been observed in the FGT after protected sexual intercourse, suggesting that these alterations in the vaginal microbiota may also be associated with mechanical contamination rather than just semen itself 185,187 .…”