Scientists had hypothesized that one of the ways in which the first cellular organisms developed was through the mutations that were spread by viruses. This is also how viruses are able to adapt and sometimes jump across species.
The HIV virus is a retrovirus meaning that it carries RNA instead of DNA. Once the RNA is injected into the host cell, the machinery begins to start manufacturing viral proteins and other RNA strands in order to replicate. First, the best way to prevent infection would be to give the cells the correct coding in order to prevent the virus from binding to the surface and passing through the membrane. If the virus was able to pass through the membrane, the next line of defense would be to prevent translation from occurring in order to prevent the viral proteins from assembling and replicating. This means inhibiting enzymes such as RNA polymerase and other protein-assisting enzymes.