Molecular epidemiology of HPV and Chlamydia trachomatis pathogenic agents in a large cohort of women from a North-East Italian area: prevalence and distribution of HPV genotypes in the setting of co-infection with Chlamydia trachomatis

Background: Human papillomavirus (HPV) and Chlamydia trachomatis (CT) are two of the most common and widespread sexually transmitted infections (STIs) in worldwide. Recently, a central role of high risk HPV (HR-HPV) genotypes associated to CT as a co-risk factor has been established in the development of cervical cancer (CC). Therefore, to investigate a pathogen as CT, potentially implicated as oncogenic factor for its tendency to cause chronic and persistent infections, together with HPV co-infection, could have a great importance for the public health. Epidemiological data on CT chronic infection and CT/HPV co-infection prevalence are not yet well defined in Italy. The aim of this study was to investigate CT/HPV co-infection in women from a Northern-East Italian area by analyzing the HPV prevalence and genotypes distribution in women at risk for CT chronic infection. Methods: A retrospective study (2009-2014) was conducted on a large cohort of 7135 cervical swabs. 6214 at risk for CT and 921 from women at risk for HPV infection were tested by Real Time PCR. CT genotyping was realized by ompA gene sequencing. A quantitative Real time-PCR was then performed to assess the expression of the CT Hsp60–encoding gene (Ct604 portion), linked to a persistent status of infection. CT/HPV co-infection and prevalence of single or multiple genotypes was investigated using Luminex technology. Results: the overall prevalence of the investigated pathogens resulted to be of 39% for HPV and 4% for CT, respectively. A CT/HPV co-infection was diagnosed in the 58% of the samples from women of which 68% with chronic infection. In women ≤ 25y, CT infection reached a peak of 14%(p< 0.0001), in co-infection with HPV, 68%, with a prevalence of chronic infection in this group of 72%. Of note, a CT infection was associated to HPV multiple genotypes in 78% (p< 0.0221), of these women. By analyzing the HPV genotypes distribution, a single infection was highly detected (60%) in women infected with HPV only, while multiple infections resulted prevalent (68%), in CT/HPV co-infected women. The CT serotype F was confirmed to be the most frequent serovar found in women samples, independently from HPV infection. Of interest, the levels of CT Hsp60 expression in HPV co-infected women were confirmed significantly lower compared to women infected with CT only. Conclusions: Our large study, adds new findings regarding the epidemiology of HPV and CT distribution in women from this geographic area, confirming a high prevalence of multiple HPV infections associated with concomitant chronic disease by CT, especially in young women. Of remarkable interest, in these co-infection specific HPV genotypes were recovered, suggesting that the expression of CT Hsp60, interfering on immunologic pathways, might influence engraftment of HPV particulars genotypes. In comparison to the National data, our study highlights both the high frequency of CT chronic infection and CT/HPV co-infection with multiple HPV infections in young women. This suggests that an early prophylactic HPV vaccination and a screening program for CT/HPV co-infection could play a significant role in STIs prevention and possible development of CC.