Genus Spumavirus
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Type Species |
Chimpanzee foamy virus |
(CFV) |
Distinguishing Features
Virions exhibit a distinctive morphology with prominent surface spikes and a central uncondensed core. Capsid assembly occurs in the cytoplasm prior to budding into the endoplasmatic reticulum or from the plasma membrane. Capsid budding requires the presence of Env Protein. No cleavage of Gag protein precursors into MA, CA, NC subunits is detectable in infectious virions. Protein Mr are: Gag precursor ± 74 
103; N-terminal Gag cleavage product ± 70 103; Pol precursor ± 127 103; RT ± 80 103; IN ± 40 103; Env precursor ± 130 103; SU ± 80 103; TM ± 48 103; Tas/Bel-1 ± 35 103; Bet (Bel-1/Bel-2 fusion protein) ± 60 103; Env-Bet fusion protein ± 170 103. The genome is about 11.6 kb in size; its organization is illustrated in Figure 8. There are two proteins (designated tas/bel-1, and bet) that are produced in cells in addition to gag, pol, and env. Tas is a DNA binding protein with transactivating function. The functions of the other accessory protein is unknown. The tRNA primer is tRNAlys1,2. The LTR of primate foamy viruses is about 1770 nts long, of which the U3 region is about 1400 nts, the R region about 200 nts and the U5 region is some 150 nts in length. In bovine and feline viruses it is 950 -1000 nts. Spumaviruses make use of two start sites of transcription, R in the LTR and an internal promoter (IP) located upstream of the accessory reading frames in the env gene. The activity of both promoters is Tas dependent. The additional major criteria distinguishing spumaviruses from the other genera of the family Retroviridae are the expression of the Pol protein from a spliced subgenomic mRNA and the presence of large amounts of reverse trancribed DNA in the virion.
Viruses have a widespread distribution and exogenous viruses are found in many mammals. No natural human infections are known. Human infections have been documented as a result of rare zoonotic transmissions from non-human primates. A distantly related endogenous virus has been reported. Many isolates cause characteristic “foamy” cytopathology in cell culture. No diseases have been associated with spumavirus infections. No oncogene-containing member of the genus has been found.
List of Species Demarcation Criteria in the Genus
The list of species demarcation criteria is:
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Differences in genome and gene product sequences, |
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Differences in natural host range. |
List of Species in the Genus
Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:
Species in the Genus
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Bovine foamy virus |
[U94514] |
(BFV) |
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Chimpanzee foamy virus |
[U04327] |
(CFV) |
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Chimpanzee foamy virus human isolate (formerly Human foamy virus, HFV) |
[Y07725] |
(CFV/Hu) |
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Feline foamy virus |
[Y08851] |
(FFV) |
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Simian foamy virus 1 |
[X54482] |
(SFV-1) |
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Simian foamy virus 3 |
[M74895] |
(SFV-3) |
List of Unassigned Viruses in the Family
None reported.
Phylogenetic Relationships within the Family
See Fig. 9.
Similarity with Other Taxa
None reported.
Derivation of Names
Lenti: from Latin lentus, “slow”.
Retro: from Latin retro, “backwards”, refers to the activity of reverse transcriptase and the transfer of genetic information from RNA to DNA.
Spuma: from Latin spuma, “foam”.
