Clinical, Immunologic, and Virologic Observations Related to Human Immunodeficiency Virus (HIV) Type 1 Infection in a Volunteer in an HIV-1 Vaccine Clinical Trial

A vaccine breakthrough occurred in a phase 1 clinical trial of a human immunodeficiency virus (HIV) type 1 candidate subunit vaccine. The vaccine antigen, gp120<inf>SF2</inf>, is a fully glycosylated protein produced in mammalian cells from the HIV<inf>SF2</inf> isolate. After 4 immunizations, the subject developed neutralizing antibodies and lymphoproliferative responses to the gp120 protein. About 18 weeks after the last immunization, the subject became HIV infected. During the acute phase of infection, there was high virus burden, a decline in CD4+ T lymphocytes, increases in rgp120<inf>SF2</inf>-binding antibodies and HIV<inf>SF2</inf>-and HIV<inf>MN</inf>-neutralizing antibodies, and transient lyrnphoproliferative responses to HIV-1 envelope and core proteins. The nucleotide sequence of the V3 loop from 2 virus isolations displayed close similarity to the V3 sequence of the vaccine antigen. Thus, the immunologic responses induced by the vaccine in this subject did not protect him from HIV-1 infection.