HIV-2 (source code)
= HIV-2
{c}
= Human immunodeficiency virus type 2
{synonym}
<HIV-2> is one of the two recognized types of <human immunodeficiency virus>, alongside <HIV-1>. Like <HIV-1>, it is a <Lentivirus> whose infection can lead to <AIDS>. These type names identify related <viruses>; they do not name successive stages of one infection.<Human Immunodeficiency Virus in the NIH HIV Glossary>[definition, two HIV types and advanced disease stage]{ref}<Lentivirus report by the International Committee on Taxonomy of Viruses>[genus classification]{ref}
A landmark 1986 report by <F. Clavel> and colleagues described a distinct human <retrovirus> recovered from two patients with <AIDS> from western Africa. The researchers found biological and morphological similarities to the virus then called LAV/HTLV-III, while some <antigens> differed. The combination made the classification question experimentally meaningful: similar appearance and disease association did not establish that the agents were identical.<Isolation of a new human retrovirus from West African patients with AIDS by F. Clavel and others>[Science 233, 343–346, Abstract: isolation and partial characterization]{ref}
The logic can be illustrated with an abstract identification problem. Suppose two virus preparations share an observed structural feature, while one tested <antigen> differs. The shared observation supplies evidence of similarity; the differing observation supplies a way to distinguish the preparations. Neither one measurement alone establishes all their evolutionary relationships. A scientific classification combines such comparisons with further molecular evidence.
The shared <reverse transcription> strategy explains the placement of <HIV-2> within <Retroviridae>, whereas distinguishing it from <HIV-1> requires information finer than that family-level mechanism. A broad replication category and a type-specific identification answer different biological questions.
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