Prevalence and risk factors for oral HPV in the healthy population
Description
HPV prevalence in oral rinse and HPV-specific antibodies in peripheral blood were investigated in two groups of participants (mean age 23.2 and 55.7 years). Additionally, the risk factors for oral HPV infection and prevalence of HPV-specific antibodies were evaluated.
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In this study, two groups of participants were evaluated. Group I included 388 students of medicine, mean age 23.2 . The exclusion criterion was a history of head and neck or cervical cancer. Students previously vaccinated against HPV provided only an oral rinse sample while from the unvaccinated, a blood sample was also taken. Each participant was assigned a unique ID number to be used for marking the respective oral rinse and blood samples and questionnaire. All participants signed an informed consent. The study was approved by local ethics committee. Group II consisted of 215 subjects with mean age 55.7 enrolled in the scope of previous studies. All of them were unvaccinated as they had been sampled before HPV vaccines were licensed in the European Union. Information about their oral HPV DNA status and seropositivity was also taken from previous studies, with four samples being unavailable for serological analysis. All Group I participants were asked to fill in an anonymized on-line questionnaire to collect data on age, sexual history, education, HPV vaccination status (vaccine type, first dose in relation to the start of sexual life), history of tonsillectomy, tongue or lip piercing, method of birth, and use of tobacco, alcohol, and drugs. Other questions were related to sexual behaviour, i.e. to sexual orientation, age at first sexual intercourse, number of open-mouth kissing partners, number of vaginal and oral sex partners in their lifetime and in the last 12 months, usage of condom during vaginal intercourse, and former and current genital infections. The questionnaire for Group II, which was administered within a previous study, did not fully overlap with the new one. Oral exfoliated cells were obtained after oral rinse by gargling with 10 ml of phosphate buffered saline solution. DNA for HPV detection was extracted using the Puregene Core Kit B (Gentra Qiagen). HPV DNA detection and typing were performed by PCR with primers specific for the L1 region BSGP5+/ 6+bio (broad-spectrum GP5+ primers and 5′-end biotin-labelled GP6+ primers) and by the reverse line blot hybridization (RLB) method. The presence of antibodies against the antigens derived from HPV-specific proteins was tested using an in-house ELISA as has been described previously. L1-based virus-like particles (VLP), mimicking HPV6, 11, 16, 18, 31, 33, 45, 52, and 58 capsids, were prepared using the recombinant baculovirus expression system and served as antigens to detect antibodies to viral capsids. The presence of antibodies to HPV16 E6 and E7 oncoproteins, was tested using the GST capture system, overexpressed in bacteria as fusion proteins with glutathione-S-transferase (GST). The T-test and Fisher's exact test were used for comparison of HPV positive and negative subjects. The significance level was set to 5%. Statistics were calculated in R version 3.3 Core Team using the psych package.