Background Prevention and treatment of anal intraepithelial neoplasia (AIN) in HIV+ men who have sex with men (MSM) is subject of discussion. Knowledge on causative HPV types is crucial in understanding AIN and in vaccination studies. However, data on AIN-specific HPV are limited and whole tissue sections (WTS) often show multiple HPV infections.

In this study, we analysed whether WTS and subsequent laser capture micro-dissection (LCM) with HPV PCR genotyping accurately detects type-specific HPV DNA in individual areas of high grade (HG)AIN.

Methods 31 WTS with HGAIN of 21 HIV+ MSM were analysed by the SPF10 PCR/LiPA25 (version 1) HPV genotyping system. In case of multiple HPV types, PCR was repeated in selected areas of AIN, isolated by LCM.

Results WTS PCR showed a single HPV type in 17 (55%). In the remaining 14 WTS sections with multiple HPV types, PCR was repeated in LCM-isolated dysplastic areas (median: 4 per WTS). In 12 of 14 these samples, the number of HPV types could be reduced to single HPV types within discrete areas of a lesion, resulting in a total of 29 (17+12), in which (components of) HGAIN show a singe HPV type. HPV 16 was found in 14/29 (48%), HPV 18 in 3 and HPV 58 in 3. The remaining HPV types that could be linked to a lesional area were HPV 26, 31, 35, 39, 52, 53, 54, 59, 67, 68/73, 74, 91 and one indeterminate HPV type.

Conclusion WTS PCR and subsequent LCM PCR is accurate in detecting lesion specific HPV types in AIN and it seems that 94% of the AIN-lesions (on macroscopic or microscopic level) are caused by a single HPV type. Apart from HPV 16, the predominant type, a wide range of other HPV types are responsible for HGAIN, which has consequences for vaccination development.