<P> HIV can infect dendritic cells (DCs) by this CD4 - CCR5 route, but another route using mannose - specific C - type lectin receptors such as DC - SIGN can also be used . DCs are one of the first cells encountered by the virus during sexual transmission . They are currently thought to play an important role by transmitting HIV to T - cells when the virus is captured in the mucosa by DCs . The presence of FEZ - 1, which occurs naturally in neurons, is believed to prevent the infection of cells by HIV . </P> <P> HIV - 1 entry, as well as entry of many other retroviruses, has long been believed to occur exclusively at the plasma membrane . More recently, however, productive infection by pH - independent, clathrin - dependent endocytosis of HIV - 1 has also been reported and was recently suggested to constitute the only route of productive entry . </P> <P> Shortly after the viral capsid enters the cell, an enzyme called reverse transcriptase liberates the single - stranded (+) RNA genome from the attached viral proteins and copies it into a complementary DNA (cDNA) molecule . The process of reverse transcription is extremely error - prone, and the resulting mutations may cause drug resistance or allow the virus to evade the body's immune system . The reverse transcriptase also has ribonuclease activity that degrades the viral RNA during the synthesis of cDNA, as well as DNA - dependent DNA polymerase activity that creates a sense DNA from the antisense cDNA . Together, the cDNA and its complement form a double - stranded viral DNA that is then transported into the cell nucleus . The integration of the viral DNA into the host cell's genome is carried out by another viral enzyme called integrase . </P> <P> This integrated viral DNA may then lie dormant, in the latent stage of HIV infection . To actively produce the virus, certain cellular transcription factors need to be present, the most important of which is NF - κB (NF kappa B), which is upregulated when T - cells become activated . This means that those cells most likely to be killed by HIV are those currently fighting infection . </P>

Based on the large number of hiv replicates produced it is common to find