Table 1.

Trends in foamy virus (FV) research.

Exogenous FVs infect a wide range of mammals; the presence of endogenous FVs in the genome of several animal species suggest a possible ancient marine origin of theses retroviruses.

Zoonotic transmission of simian FVs has been reported all over the world and is currently ongoing; Bites are strongly associated with these transmission events; Neither pathogenicity nor human-to-human transmission have yet been reported.

The prototype foamy virus (PFV) integrase was the first retroviral integrase to be crystallized in complex with viral DNA; FV intasome interacts with nucleosomes.

The replication strategy of FVs shares features with orthoretroviruses, hepadnaviruses, and other retroid elements; Molecular biology of FVs has been mostly studied in cell culture systems. Replication in natural or experimental animal models is poorly described and probably diverse.

FVs induce type I interferons (IFNs), are susceptible to them and to type II IFNs, as well as to several restriction factors; with the exception of neutralizing antibodies against cell-free viral particles, adaptive immune responses are currently undescribed.

Foamy virus vectors (FVV) have come of age; Well-characterized replication-deficient vectors are available; FVV are effective in small and large preclinical models of human diseases.

3D structures of four FV proteins are known, namely the protease, RNAse H, integrase, and N-terminal Gag.