WHAT IS HIV-1?
HIV-1 is one of the most rapidly mutating viruses ever encountered. Thus there are many different strains of HIV-1. These strains are all similar, however. All are a specific type of RNA virus (a virus containing RNA as opposed to DNA) known as a retrovirus. To enter a cell, viruses must recognize (bind to) certain proteins encoded by host genes and displayed on the cell surface. These proteins normally act as receptors for other host molecules, but a virus can also make use of them. A virus will bind to these receptors, employing them as entryways into a cell. Once inside a cell, retroviruses insert their genes into a host’s chromosomes. A retrovirus’ genetic material replicates in an unusual way: when a virus enters a cell, a viral enzyme (reverse transcriptase) transcribes viral RNA into duplex DNA. The cell’s machinery then replicates and transcribes this DNA as if it were its own. Retroviruses thereby ensure that viral genes-which can direct the synthesis of an endless supply of v
