= Orthoretrovirinae
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<Orthoretrovirinae> is the subfamily of <Retroviridae> containing <Lentivirus> and several other retroviral genera. It includes <human immunodeficiency virus> and <feline immunodeficiency virus>. The family placement describes a replication strategy; it does not imply one host range or one disease outcome for all members.<Orthoretrovirinae report by the International Committee on Taxonomy of Viruses>[Subfamily classification and Distinguishing features]{ref}
A typical <virion> packages two copies of its <RNA> <genome>. After entry and release of the viral core into a host <cell>, <reverse transcription> produces <DNA> that can become an integrated <provirus>. Proteolytic processing of a viral <polyprotein> also releases functional components during maturation.<Orthoretrovirinae report by the International Committee on Taxonomy of Viruses>[Distinguishing features, RNA copies, reverse-transcription timing and protease processing]{ref}<Retroviridae report by the International Committee on Taxonomy of Viruses>[Table 1, replication and integration]{ref}
An invented counting example clarifies the two-copy description. If each packaged <RNA> molecule has 10,000 <nucleotides>, the pair contains 20,000 RNA nucleotides in total. The length of one genome copy is still 10,000 nucleotides. A corresponding 10,000-base-pair double-stranded <DNA> molecule contains 20,000 DNA nucleotides, but its length is conventionally reported in base pairs. Copy count, nucleotide count and base-pair length answer different questions.
The subfamily's genera are distinguished in part by <phylogenetic analysis> of conserved reverse-transcriptase regions. A shared <enzyme> mechanism can coexist with differences in accessory <proteins>, host distribution and cellular targets. Observing the shared mechanism therefore provides a classification clue while leaving those other biological properties to be determined.<Orthoretrovirinae report by the International Committee on Taxonomy of Viruses>[Genus demarcation criteria and differences among members]{ref}
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