Background Previously we observed elevated HPV seroprevalence in men who had sex with men (MSM) and men who had sex with men and women (MSMW) compared to men who had sex with women (MSW). We hypothesise that the higher seroprevalence is associated with HPV infection at multiple anatomic sites, and the presence of mucosal epithelium infection as opposed to keratinised epithelium infection. We assessed associations between HPV seropositivity and prevalent HPV infection at anal canal and external genitalia in men to test the hypothesis.
Methods Enrolment data for 1663 men, including 1474 MSW, 83 MSM and 106 MSMW, were analysed. HPV L1 VLP-based ELISA was used for serum antibody testing and Linear Array for HPV DNA testing. Associations were estimated for HPV 6 and 16, respectively, using logistic regression. MSM and MSMW were combined to form the group MSM.
Results Overall HPV 6 and 16 seroprevalence was 9.9% and 14.1%. HPV 6 and 16 DNA was present in 2.2% and 2.7% of anal samples, and 6.4% and 7.3% of genital samples. Seroprevalence of HPV 6 and 16 was significantly higher in MSM compared to MSW (32.8 vs 6.9%; 34.4 vs 11.5%). Similarly, HPV 6 and 16 DNA was more frequently detected in anal samples (9.5 vs 1.2%; 9.0 vs 1.8%) and genital samples (7.4 vs 6.2%; 9.0 vs 7.1%) of MSM than MSW. Men with simultaneous anal and genital HPV infection (AOR—9.20 and 6.79) or anal HPV infection alone (AOR—19.93 and 3.19) were significantly more likely to be HPV 6 and 16 seropositive. There was no association of seropositivity with prevalent genital HPV 6 or 16 infection. Strong positive associations were detected in MSW and MSM who were anal HPV 6 positive, regardless of coinfection with genital HPV 6. In contrast, no association was observed among MSW with anal HPV 16, with or without genital coinfection. However, significant associations were observed in MSM with anal HPV 16 (with coinfection—AOR, 10.94, 95% CI, 1.18 to 101.68; without—AOR, 4.96, 95% CI, 1.40 to 17.57).
Conclusion We found type-specific associations of HPV 6 and 16 seropositivity with prevalent anal HPV infection, but not with prevalent genital HPV infection alone. Anal HPV 6 infection was associated with seropositivity in both MSW and MSM, while anal HPV 16 infection was only associated with seropositivity in MSM. Our data suggest that, in men, anal HPV infection may be more efficient than genital HPV infection in inducing immune responses. This may have relevance for protective immunity or the lack thereof, conferred by natural infection.
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