Oral-genital human papillomavirus infection in Polish couples: frequent detection of HPV 42

In the last decades, there has been an increase in data concerning the incidence of HPV infections in humans. The most significant premise from these data is that HPV is the most important risk factor for the development of cervical cancer [1, 2]. According to GLOBOCAN reports, 15% of all tumors diagnosed in 2012 were causally related to the carcinogenic viral infections. Among all viral-associated cancers, the infection with HPV predominates (640,000 cases) and the vast majority of all HPV related tumors (530000) concerns cervical cancer (CC) developed by females [3, 4]. Beside other, rare, ano-genital locations (vulva, anus, vagina and penis), HPV may also inhabit the throat, leading to the development of oropharyngeal cancer (OPC) [2–4]. There are several factors that may facilitate this transmission, like early sexual initiation, the large number of sexual partners during the lifetime or the increased frequency of oro-genital intercourse. More than 90% of HPV infections are transient, being cleared by active immune response within 8 months [5, 6]. On the contrary, for the development of high-grade cervical intraepithelial neoplasia (CIN) and cervical cancer, viral persistence is essential but it may take more than two decades before the development of the abnormal lesions is observed [7].

HPV is small (50–55 nm in diameter) double stranded virus that exhibits tropism to epithelial cells (skin and mucosa). The virus genome length is around 8 kb and is divided into three regions: E (Early), L (Late) and LCR (Long Control Region). In general, HPVs constitute the heterogeneous group of viruses. So far, more than 200 mucosal and cutaneous subtypes were identified [8]. They are classified typically as high risk types (HR) - responsible for neoplastic transformation and low risk types (LR) - causing the benign hyperplastic lesions. The panel of HR HPVs includes among others types: 16, 18, 26, 31, 33, 34, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 70, 73 and 82, while the panel of types: 6, 11, 40, 42, 43, 44, 54, 61, 72 and 81 is considered as LR HPVs [1, 8–10].

The worldwide distribution of given genotypes varies among different localizations [1, 5, 11]. This also translates into the frequency of cancers caused by the viruses, i.e. HPV 16 and 18 are responsible for around 71% of cervical cancers, which occur mostly in less developed countries and for approximately 85% of head and neck cancers, which prevail in more developed countries [4, 12]. In Poland, as a result of numerous screening programs and social campaigns, the number of cervical cancer have decreased, but parallel to the global phenomenon, we observe the increase of oropharyngeal cancers [13]. Although currently three types of vaccinations (2-, 4- and 9-valent) are approved to be used preventively for Polish teenage girls and boys, our population should be treated as unvaccinated, as their long-term effectiveness will be observed when the vaccinated persons reach the age of the greatest incidence of cancer. Moreover, this vaccination is voluntary and payable as it was not included into Polish national immunization program. This condition has an undeniable effect on the low overall number of the vaccinated people.

HPV genotyping is essential for preventing cervical cancer and may also be useful for simultaneous screening of HPV in the oropharynx, as tumors of this region of head and neck seems to be most frequently associated with infection of these viruses. Therefore, in this study, we took an attempt to track the distribution of HPV genotypes in the genital and oral swabs of females with current or previous cervical pathology (each with ascertained HPV genital infection) and their partners, to determine which HPV types dominate in Polish, unvaccinated population and to find whether this distribution is similar in couples in both anatomical sites. Such report will enrich the knowledge concerning the distribution of HPV genotypes in female patients suffering from genital pathology and their asymptomatic partners.

HPV infection contributes to the cancer development in the mucosa of two distinctly distant anatomical sites: genital tract and upper aerodigestive tract. It is an indispensable factor of cervical cancer development but it may also affect other parts of female and male genitals. In the last decade, HPV detection rates have been increasing in the oropharyngeal cancers [3, 4]. This virus is sexually transmitted and its worldwide prevalence in both locations is common [2]. Contemporary, 60% of oropharyngeal tumors are associated with oral HPV infection - likely acquired from genital HPV infection during oral sexual behavior, leaving behind smoking - historically strongly associated risk factor [14].

The genotyping allows to establish the profile of particular HPVs in clinically involved tissues in different populations. It is often difficult to compare the results of HPV genotyping derived from different studies, as diverse methodology is used and various materials are analyzed. This may translate into false negative results [1, 11]. Additionally, the awareness, that during the lifetime man can be infected by HPV even several times and in most cases the infection is efficiently eliminated by the immune system but can somehow recur, is not conducive in obtaining unambiguous results [7]. Nevertheless, it is of great significance to widely analyze the distribution of particular HPVs in more local populations in order to create appropriate screening programs as well as to adjust novel vaccination combinations. Therefore, for our study we have selected only women with current or previous cervical pathology, in which we have further determined their current HPV genotype in the genital tract. To obtain complete information, regarding current virus types distribution throughout the body, additional samples from women and their partners have been taken. Almost all genotypes detectable by the applied test have been found. The most frequently detected genotypes were: HPV 16/31/42/39/54 in women genital swabs and HPV 66/42/16/31/53 in male foreskin as well as HPV 6/39/42/35/16 in female oropharynx and HPV 39/6/42/40/33 in male oropharyngeal area. The results of HPV genotyping in genital swabs generally fit into data observed by other researchers, but with slight difference – the low risk type, i.e. HPV 42 was present among most commonly detected types in each type of swab, in both sexes. Similar results were obtained by Fischer et al., who performed HPV testing on 615 Bavarian female patients with abnormal cytology – the three most commonly detected HPVs were the same: 16, 31 and 42. The remaining types in both studies were also detected but with different frequency [15]. Likely, compatible results were obtained by del Prete et al. who also found the prevalence of the same three HPV genotypes in women’s cervical/vaginal swabs, with HPV 42 as the most frequent [16]. The authors analyzed also male’s urethral swabs, indicating HPV 6, 42, 16 and 31 as most frequent, what is in line with our findings, with one exception - in our study HPV 66 but not HPV 6 was detected most frequently. Surprisingly, in both sexes HPV 18 did not prevail as it was expected [1, 3, 4]. The presence of HPV 42 among most common types detected in each sort of the swabs is striking and suggests that this type may be more prevalent in Polish population. The differences in type-specific prevalence of HPV in various worldwide locations is already shown by Munoz et al. [8]. Another interesting observation applies to HPV in relation to the health condition of the analyzed female cohort. Namely, 71/197 had a previous history of cervical cancer and in this group, HPV 16 and HPV 42 were detected more often than in women diagnosed with dysplasia. It is not surprising for HPV 16, which is the most prevalent high risk type worldwide, however for HPV 42 considered so far as low risk type this is rather intriguing [4, 8, 17]. The explanation could come from the study of Guimera et al., who proved association between single LR-HPV infection and anogenital carcinoma development. She found that HPV 42 and 70 are associated with squamous type of malignancy, showing diffuse p16 staining, typical for high-risk HPV-related tumors. At the same time, she indicated that infection with other low risk types, namely HPV 6/11 did not induce p16 overexpression. Moreover, the E7 sequence of HPV 42 and 70 contain pRB-binding motif and therefore both types could act in a similar way to HR HPV [18].

The genotypes in the individual couples overlapped partially: the concordant types were detected in 33/114 of couples in genital swabs and in 9/11 of couples in oropharyngeal swabs. In these groups, 22/33 and 6/9 couples, respectively, declared a stable relationship lasting at least a year. In the remaining couples we cannot be certain if the virus was transmitted between partners of a given pair. However, our result - 28.9% is concordant with the available data showing, that 13 to 63.2% of couples share the same HPV type in the genital area [19]. Nevertheless, our study shows that the concordant types were detected in couples more frequent in the oropharynx than in genitals, what might suggest a preferential inhabitation of this anatomical region by HPVs.

It should be highlighted, that neither male nor female participants had pathology in the oropharynx during laryngological examination. Similarly, none of the men reported any complaints from the penile. However, beside low risk types, the detected genotypes encompassed also high risk types, potentially causing cancer, therefore there is a constant need for these persons to perform regular check-ups. Especially in cases of oropharyngeal swabs, the positive HPV status is particularly disturbing in the light of recent results from Rosenthal et al., who found that normal, healthy controls lack HPV infection in their oral rinses [20]. The special attention should also be paid by men, while penile cancer, although rare, is a very aggressive malignancy and is associated with HPV infection in approximately 40% of cases [21].

To conclude, our results shed lights on the distribution of HPV genotypes in Polish couples, in which female partner suffered from previously diagnosed cervical cancer or from cervical intraepithelial neoplasia grade I or II. We have pointed out the common infection with HPV 42 in women but also in their partners, in two anatomical sites: in the genital area as well as in the oropharynx. Importantly, HPV 42 was detected as the single infectious agent more often in females with previously diagnosed cervical cancer than in those with CIN I or II. Despite this, we cannot infer that HPV 42 should be reconsidered as high risk type in the general Polish population. Our findings should be verified on a larger group of Polish participants, including healthy controls, followed regularly in 6 months intervals, in oral as well as genital areas.