Fig. 1

Schematic structure of mature and immature HIV-1 particles with lipid bilayer envelope, Env, Gag and Gag-Pol (with their respective domains) and RNA as labelled. HIV-1 is an enveloped retrovirus with a diameter of 120–140 nm. It is comprised of ~ 2400 Gag polyprotein molecules, which assemble into non-infectious immature virus. Viral enzymes are packaged into the virus as part of the Gag-Pol polyproteins at ~ 1:20 ratio. During assembly and budding 7–10 copies of trimeric fusion glycoprotein Env are incorporated into the lipid viral envelope, along with many host and viral accessory proteins such as Vpr, Vif and Vpu (not shown). Following maturation, the individual domains of Gag (matrix (MA), capsid (CA), nucelocapsid (NC) and p6), Pol [protease (PR), reverse transcriptase (RT) and integrase (IN)] are released and together with Env and RNA undergo reorganisation forming a mature fully infectious virus particle