Figure 2. . HIV consists of two copies of positive-sense ssRNA, housed in a conical capsid.

HIV genome is composed by at least nine genes, defined gag, pol, env, tat, rev, nef, vif, vpr, vpu, encoding 19 proteins and two LTR regions at their 5′- and 3′-ends. Gag, pol and env codify structural proteins, which are incorporated into the new virions. Env encodes a precursor glycoprotein (gp160), which is cleaved into two parts, defined gp120 and gp41, by a cellular protease. Three molecules of gp120 and three of gp41 form a structure anchoring to the viral envelope. This apparatus allows gp120 to interact with specific receptors on target cells, such as CD4. The Gag (group-specific antigen) gene encodes the information for the synthesis of a 55-kDa polyprotein. This molecule is cut into several proteins after viral budding, including MA, CA, NC, spacer p1, spacer p2 and p6 domain. The pol gene encodes the enzymatic PR, RT and IN. Tat, rev, nef, vif, vpr and vpu represent regulatory genes and express proteins, modulating and regulating viral infectivity and replication and affecting the HIV ability to induce disease in the infected host (see text).

CA: Capsid; IN: Integrase; LTR: Long terminal repeat; MA: Matrix; NC: Nucleocapsid; PR: Proteins protease; RT: Reverse transcriptase.