MedicalResearch.com Interview with;
Eduardo L. Franco DrPH, FRSC, FCAHS
James McGill Professor Departments of Oncology and Epidemiology & Biostatistics, Director, Division of Cancer Epidemiology, Minda de Gunzburg Chair, Department of Oncology, Division of Cancer Epidemiology Department of Oncology
McGill University, Montreal, Quebec, Canada
Medical Research: What should clinicians and patients take away from your report?
Dr. Franco: Our findings of oral transmission of human papillomavirus (HPV) infection in men are part of a larger molecular epidemiologic study called ‘HPV Infection and Transmission among Couples through Heterosexual Activity’ (HITCH) cohort study. The focus of the HITCH study is to understand how HPV is transmitted within couples via sexual contact and other behaviors. We measure the presence of this virus using highly-sensitive molecular assays for HPV DNA in the genital surfaces (vagina and penis), oral cavity, and hands. We also take a blood sample to look for the presence of antibodies against HPV. We take multiple samples over a period of two years at pre-scheduled visits. We have previously published results focused exclusively on genital transmission. The present report is the first in the HITCH study to look at what happens in terms of characteristics that place male participants to be at risk of oral HPV infection.
To our knowledge, this is the first study to show a high risk of oral HPV infection among men whose female partners had a genital or oral HPV infection, suggesting that transmission may occur through oral or genital routes. We looked at transmission for 36 individual HPV genotypes, which improved our ability to study risk determinants. Risk was also significantly higher among men who had ever smoked, had a high number of lifetime sex partners, or were in non-monogamous relationships. Our results are largely consistent with previous studies that have found male sex practices and smoking to be the most significant risk factors for oral HPV infection.
We observed increased prevalence of oral HPV infection among men with a genital HPV-positive partner suggesting oral sex and possibly deep kissing as modes of transmission to the oral tract. The fact that we examined this association at the HPV genotype level enhances the credibility that the genital-oral route is truly an efficient form of HPV transmission during sexual activity. Interestingly, we also found that oral HPV prevalence was higher among men who had a concurrent genital HPV infection. While auto-inoculation comes to mind to explain these results, we must also consider that that these men acquired infections at both oral and genital sites from their infected partners. Moreover, increased susceptibility to HPV infection among some individuals could account for this finding.
With such strong results (> 100-fold and >20-fold greater risks if female partner had an oral or genital HPV infection, respectively) for the oral-oral and oro-genital routes it is now clear why condom protection is not as important as we wished it to be in preventing transmission of HPV infection. This is an important message for clinicians and patients. On the bright side is the fact that although oral transmission is highly probable via these sexual practices, on average only 7.2% of HITCH men had an oral HPV infection, which indicates that although HPV is easy to acquire it is also easy for it to be spontaneously cleared from the oral cavity, perhaps via an immune response. The clinically relevant consequence of HPV infection is a precancerous lesion and ultimately cancer. Luckily, these are detectable endpoints at an earlier stage and take many years to develop. There are no clinical guidelines that specify testing exfoliated oral samples for HPV infection , as we did, as part of best practices in oral healthcare. Clinical examination for flat or verrucous lesions continues to be the main focus of clinical examination for oral HPV infection. Counselling may also be helpful, keeping in mind the negative psychological consequences for the couple if the clinical importance of HPV infection is overplayed.
Vaccination against the main types of HPV that cause cancer or benign warty lesions is already available in most countries. HITCH couples were beyond the reach of the successful school-based vaccination that is ongoing in Canada. HPV vaccination is expected to substantially decrease risk of HPV infection by the vaccine-targeted types.