English: Schematic description of the mechanism of the four classes of currently available antiviral drugs against HIV: fusion inhibitors ( interfere with the binding, fusion or entry of an HIV virion), reverse-transcriptase inhibitors (interfere with the translation of viral RNA into DNA), integrase inhibitors (block the viral enzyme integrase, that inserts the viral genome into the DNA of the host cell), protease inhibitors (block proteolytic cleavage of protein precursors that are necessary for the production of infectious viral particles)