Prof. Dr. Lutz Gissmann - Head of the division "genome modifications and carcinogenesis" at the German Cancer Reseach Center (DKFZ) Heidelberg, Ge
The natural history of HPV infections as well as immunizations of animals with the respective papillomaviruses clearly reveal the involvement of the immune system in controlling papillomavirus infections and the diseases associated therewith. For instance, it has been demonstrated that antibodies protect against infection. On the other hand, specific T cells are active in elimination of HPV-positive lesions.
Human papillomaviruses are not particularly immunogenic during the natural course of infection, most likely since the virus is confined to immunologically hidden sites but also as it has acquired the ability to actively suppress the immune system. This is in remarkable contrast to the immune response induced by immunization with virus-like particles when the virus is exposed to and interacts directly with the antigen presenting cells. There is mounting knowledge about the mechanisms of these interactions.
There are two vaccines on the market (Gardasil and Cervarix) both of which contain virus-like particles (VLP) of HPV 16 and 18 that are able to induce neutralizing antibodies. Both products have excellent safety features and provide almost complete protection against infection by these HPV types and against the precursors of cervical cancer associated therewith. For Cervarix it was demonstrated that protection is broader than expected, i.e. is directed also against non-vaccine HPV types, e.g. HPV 31 and 45. In a direct comparison Cervarix also proved to be of higher immunogenicity. Future studies need to address the question whether this feature translates into better and longer protection.