Spumaviruses

Spumaviruses are a genus of retroviruses within the family Retroviridae. They are also known as foamy viruses due to the characteristic vacuolated, foamy appearance of infected cells observed under a microscope. Unlike many other retroviruses, spumaviruses do not appear to cause overt disease in their natural hosts, although they can establish persistent, lifelong infections.

Spumaviruses have a wide host range, infecting a variety of mammals including primates, cats, cattle, horses, and rodents. Human spumaviruses are referred to as human foamy virus (HFV) or simian foamy virus (SFV) when isolated from non-human primates. Transmission typically occurs through close contact, such as bites or mucous membrane exposure.

The genome of spumaviruses is similar to other retroviruses, containing gag, pol, and env genes. A unique feature is the presence of accessory genes, notably bel-1, which are involved in viral replication and pathogenesis. Spumaviruses replicate in the cytoplasm and do not typically integrate into the host cell's genome in the same manner as other retroviruses. Their replication cycle is relatively slow, and they are often detected through serological assays. While not known to cause disease in their natural hosts, spumaviruses are of interest to researchers for understanding retroviral biology and potential zoonotic transmission.