Human antibodies that neutralize primary human immunodeficiency virus type 1 in vitro do not provide protection in an in vivo model.

Recently, conflicting data have been published about the ability of antibodies which efficiently neutralize T cell-adapted human immunodeficiency virus type 1 (HIV-1) strains to neutralize primary HIV-1 strains in vitro and in vivo. Here we present data indicating that such antibodies fail to neutralize primary HIV-1 strains in vivo. To this end, a newly developed chimeric human-to-mouse model was used, in which several aspects of primary HIV-1 infection are mimicked. Poly- and monoclonal antibodies protected the grafted human cells, in a dose-dependent way, from infection with T cell-adapted HIV-1 in this system. A human monoclonal antibody specific for the CD4 binding domain that efficiently neutralizes HIV-1 IIIB in vitro did not protect the human graft from HIV-1 IIIB infection. None of the antibodies provided protection in the in vivo model against infection with primary HIV-1 strains, although they were able to neutralize these same strains in vitro.