Neutralizing antibodies have limited effects on the control of establishedHIV-1 infection in vivo

Neutralizing antibodies can protect against challenge with HIV-1 in vivo if present at appropriate concentrations at the time of viral challenge, but any role in the control of established infection is unclear. Here, we show that high serum concentrations of neutralizing monoclonal antibodies, eithe r singly or as a cocktail, have little sustained effect on viral load in es tablished HIV-1 infection in hu-PBL-SCID mice. In some instances, virus rep lication of neutralization-sensitive virus continues even in the presence o f high levels of neutralizing antibody. In most instances, neutralization e scape occurs in a few days, even from a cocktail of three antibodies that r ecognize distinct epitopes. The results imply that humoral immunity is unli kely to play a significant role in the control of established HIV-1 infecti on in humans.