However, researchers at the Pasteur Institute in Paris isolated a previously unknown and genetically distinct retrovirus in patients with AIDS which was later named HIV.

[12] The RNA component is 9749 nucleotides long[13][14] and bears a 5’ cap (Gppp), a 3’ poly(A) tail, and many open reading frames (ORFs).

At the surface of the virion can be found a limited number of the envelope glycoprotein (Env) of HIV, a trimer formed by heterodimers of gp120 and gp41.

Env is responsible for binding to its primary host receptor, CD4, and its co-receptor (mainly CCR5 or CXCR4), leading to viral entry into its target cell.

This is one of the most densely glycosylated molecules known and the density is sufficiently high to prevent the normal maturation process of glycans during biogenesis in the endoplasmic reticulum and Golgi apparatus.

[20] The unusual processing and high density means that almost all broadly neutralising antibodies that have so far been identified (from a subset of patients that have been infected for many months to years) bind to or, are adapted to cope with, these envelope glycans.

[23] These advances in structural biology were made possible due to the development of stable recombinant forms of the viral spike by the introduction of an intersubunit disulphide bond and an isoleucine to proline mutation in gp41.

[citation needed] HIV employs a sophisticated system of differential RNA splicing to obtain nine different gene products from a less than 10kb genome.

[citation needed] An RNA secondary structure determined by SHAPE analysis has shown to contain three stem loops and is located between the HIV protease and reverse transcriptase genes.

This cis regulatory RNA has been shown to be conserved throughout the HIV family and is thought to influence the viral life cycle.

Env serves as a molecular target of a medicine treating individuals with HIV-1 infection, and a source of immunogen to develop AIDS vaccine.