Persistent human papillomavirus (HPV) infections may have minimal changes in viral load, and viral loads between sex partners may be correlated, according to a study published in the Journal of Infectious Diseases.
Affecting an estimated 80% of sexually active individuals at least once in a lifetime, HPV is the most prevalent sexually transmitted infection. Persistent infection with this virus leads to the development of cervical cancer and anogenital warts, as well as other oral and anogenital cancers. It is estimated that approximately 5% of the tumor burden worldwide is attributed to HPV.
Many strategies have been implemented in attempts to prevent and control HPV-related diseases, but much remains unknown about determinants for susceptibility and infectivity. Viral load (the productivity of DNA replication) is believed to play a major role in HPV infectivity. Previous studies have shown that within individuals, viral load predicts HPV persistence and clearance, and within long-term couples, viral loads have been shown to be associated with incidence of new type-specific HPV infections. As most HPV is transmitted in the early stages of a sexual relationship, this Canadian prospective cohort study studied the association between HPV viral loads and HPV concordance in young, recently formed, heterosexual couples who are sexually active.
Data used were from the HPV Infection and Transmission among Couples through Heterosexual Activity (HITCH) cohort study. In total, 492 couples (women aged 18-26 years and men aged 18-45 years) were included. At 0 and 4 months, web-based questionnaires were completed and genital samples were collected. Samples were tested for HPV DNA via polymerase chain reaction, and viral loads of HPV strains 6, 11, 16, 18, 31, 42, and 51 were quantified using type-specific real-time polymerase chain reaction. Using a multilevel, mixed-effects linear/logistic regression model, correlations between viral loads and type-specific HPV prevalence, incidence, and clearance were evaluated.
None of the included participants were HIV-positive or immunosuppressed. The median number of lifetime vaginal sex partners was 5 for both women and men. On average, couples were having vaginal sex for 4 months at the baseline visit (median of 60 encounters). Of the women, 12.0% had received ³1 dose of the HPV vaccine at baseline; 0.4% of the men had done so.
Of the 1040 genital samples provided, 402 tested positive for at least 1 strain of HPV. The viral load difference between HPV types was sex-dependent: male genital samples demonstrated higher viral loads. In individuals with persistent HPV infections, measurements at baseline and at follow-up showed that viral loads were correlated and relatively constant over time (men P <.001; women P =.018). This correlation was stronger in men than in women. Viral loads were also correlated in couples if both partners had an infection with the same strain of HPV, which suggested that increased viral loads increase transmission and/or viral activity in the partner (P =.05).
Researchers also highlighted that in men, high viral load was associated with prevalent and incident type-specific HPV infections in their partner, whereas in women, viral load was associated with prevalence in their partner at the same and subsequent visits. For example, in the case where men did not have HPV, the prevalence of a given HPV strain in women in the same visit was 2.5%, whereas the prevalence increased to 46.7% when men had low HPV viral load, 54.5% for medium viral load, and 75.2% for high viral load. Further, clearance of HPV infection was associated with sexual partner positivity for the infection, regardless of viral load.
Overall, the study authors concluded that, “Future studies are needed to identify determinants for high HPV viral loads, and to determine whether viral loads predict future clinical disease, to advance our understanding of the natural history of HPV infections and provide insights on preventative strategies.”
Wissing MD, Louvanto K, Comète E, et al. Human papillomavirus viral load and transmission in young, recently-formed heterosexual couples [published online May 7, 2019]. doi:10.1093/infdis/jiz238/5486405