Human endogenous retroviruses in immunity and cancer

The ultimate form of parasitism and evasion of host immunity is for the virus genome to enter the germline of the host. Retroviruses have invaded the host germline on the grandest scale, and this is evident in the extraordinary abundance of endogenous retroelements in the genome of all vertebrate species that have been examined. Recent studies suggests that such viral endogenisation events continue to shape host immunity and other physiological systems over long evolutionary times and through diverse mechanisms. Some acquire novel function that provides a host fitness advantage, a process known as exaptation. However, this evolutionary adaptability is also exploited by cancer cells in a process termed onco-exaptation. Evidence for both will be presented.