Immunisation with whole purified human immunodeficiency virus type 1 particles elicits enhancing antibodies in rhesus macaques

Six Rhesus macaques were hyperimmunized with either live infectious human i mmunodeficiency virus type 1 (HIV-1) or with beta-propiolactone - or formal in - inactivated HIV-1. The virus used was HIV-1 BX08, a primary virus isol ate grown in human PBMC. Instead of eliciting virus-neutralizing antibodies , this regimen induced antibodies that enhanced HIV-1 infectivity for PBMC by 10 to 90 fold. Enhancement was also seen in a cell-to-cell fusion assay using a Semliki Forest virus replicon to express BX08 gp160 in CD4(+), and CCR5(+) HeLa cell cultures. These observations raise the concern that whole virus particles-based HIV-1 vaccines might elicit enhancing antibodies tha t could play a facilitating role in the transmission and/or evolution of th e disease.