December 15, 2017
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Men with HPV16 at 20-fold increased risk for reinfection after 1 year

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Men infected with HPV16 — the strain responsible for most HPV-related cancers — were 20 times more likely to be reinfected with the same type after 1 year, according to recent data.

Slyvia L. Ranjeva, a PhD student in the department of ecology and evolution at the University of Chicago and the Pritzker School of Medicine, and colleagues said the findings, published in the Proceedings of the National Academy of Science, suggest that infection with HPV16 does not induce protective immunity in men the way other viruses often do. The results also highlight the importance of vaccination before sexual contact to prevent initial infections.

Vaccinating boys before HPV exposure could be a highly effective way to reduce the burden of HPV infection,” Ranjeva said in a press release. “Vaccinating men who have already been infected might also be effective.”

Approximately 40% of women and 45% of men in the United States are infected with HPV, according to the researchers. The high prevalence is attributed to the coexistence of more than 200 different types of HPV, they added. To better understand the prevalence and diversity of HPV, Ranjeva and colleagues examined data on 4,123 unvaccinated men aged 18 to 70 years enrolled in the HIM study, which tracks genital HPV infection and demographic and behavioral traits in unvaccinated men.

Approximately 65% of men in the study contracted HPV, according to the researchers. The mean prevalence of each individual HPV type did not exceed 10%. Although such wide diversity usually occurs when viruses evolve to compete with other viruses, the researchers found no evidence of immune-mediated competition among HPV types.

“Pathogen strains compete by inducing adaptive immune responses that are specific to shared antigens, limiting the growth rates of antigenically similar competitors. The accumulation of specific immunity in the host population to common strains decreases the transmission of those strains and promotes the spread of rarer antigenic variants,” they wrote. “Rather than inducing protective immunity, HPV infection strongly increases the risk of future infection by the same type. Thus, high HPV prevalence results from frequent reinfection or persistent infections within individuals.”

For HPV16, men with a previous infection were 20.4 times more likely to be reinfected after 1 year and 13.5 times more likely to be reinfected after 3 years than men with no previous infection. For other HPV types, this increase in odds ranged from 19.1-fold to 20.5-fold after the first year and 7.4-fold to 20.5-fold after 3 years of initial infection. The increased risk for reinfection was similar among sexually active men and celibate men, suggesting that reinfection is not driven by sexual transmission but rather autoinoculation or reactivation of latent virus, or both, according to the researchers.

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“Our results imply that the HPV vaccine has the potential to lower HPV prevalence far more than previously expected,” they concluded. – by Stephanie Viguers

Disclosures: Ranjeva reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.