Background
Men who have sex with men (MSM) have been identified as a high-risk group for anal cancer. HPV has been found associated with this neoplasia as it has been in cervical cancer. Concurrent infection with HIV may facilitate or accelerate the pathological consequences of HPV infections. In Mexico, where cervical cancer is a major public health problem, little is known about the prevalence of anal cancer and the role of HPV in the HIV-positive population of MSM. Methods: We analysed 323 anal exudates from HIV-positive MSM, from the HIV Clinic at Instituto Nacional de Ciencias Médicas y Nutrición ‘Salvador Zubirán’, in Mexico City. Extraction and purification of DNA was performed with the Genomics Wizard kit (Promega), HPV detection was performed by PCR using primers MY09/11. All negative samples underwent a PCR for identification of fragment of the β-globin gene to check DNA integrity. Positive samples were subjected to PCR using specific primers for E6 of type 16, and the LCR from type 18. The identification of variants was determined by sequencing the E6 gene and the LCR of 40 samples positive for HPV type 16, using the Big Dye terminator kit and AB Prism 3100. We used INNO-LiPA HPV Genotyping Extra kit (INNOGENETICS), for the identification of 28 different types of HPV using SPF10 primers in these samples. Results: The prevalence of HPV in the anal epithelium of 323 patients was high (86%). 28% were positive for type 16, and 9% for type 18. Among those patients who were type 16+, all except one were co-infected with other HPV types that included 21 different types present in the following order: 11, 51, 52, 66, 68, 74, 18, 45, 35, 26, 44, 70, 53, 54, 82, 31, 33, 56, 58, 59. In addition, in these patients, European variants were the most prevalent, followed by Asian American ones. Conclusions: The prevalence of HPV was high in the anal canal of a group of 323 HIV+ MSM in Mexico City. A group of 40 HPV16-positive patients showed multiple co-infections with other different HPV types. In addition, European variants of type 16 were the most prevalent. This study emphasises the need for an early detection of HPV infections in the anal canal of MSM who are positive for HIV in order to avoid progression to anal neoplasia.
Risks involved in vertical shafts construction for the eastern drainage tunnel in Mexico
