Neutralization of HIV-1 in vitro is a good measure of the antiviral activity of a given antibody preparation. There is a good correlation between neutralization in vitro and protection: antibody concentrations that neutralize all the challenge virus in an in vitro assay can provide sterilizing immunity in vivo. Preexisting neutralizing antibody concentrations at insufficient levels to provide sterilizing immunity may decrease pathogenicity by reducing the viral inoculum and clearing infected cells, thereby allowing more time for the cellular immune response to mature. Once HIV-1 infection is established, however, even high levels of neutralizing antibody have no or only very limited effects on an infection.

The search for an efficient vaccine merely continues. At the moment, there is no bright spot to report.