Unexpected replication pathways of foamy viruses.

Foamy viruses make up a distinct subgroup of retroviruses. They are widely distributed among nonhuman primates, felines, and bovines. In their natural hosts and in cases of rare zoonotic transmissions to humans foamy viruses cause persistent and apparently benign infections. While foamy viruses are not of medical importance in causing human or animal diseases, they may become valuable tools for somatic gene transfer in the future. However, a better understanding of the molecular biology of this virus group is a prerequisite for the development of foamy virus vectors. In this respect, recent research has revealed major differences between the foamy virus and the general retroviral replication strategies and some similarities to hepadnaviruses.