Neutralizing antibodies and the course of HIV-induced disease.

The capacity to neutralize the human immunodeficiency virus (HIV) in vitro was examined in 52 sera obtained from 23 seropositive individuals in addition to 7 negative control sera. Neutralization was measured as the activity of a serum to protect MT-4 cells against the cytopathic effect of HTLV-IIIB. Virus neutralization depended on HIV antibodies. Some sera had HIV neutralizing antibody titers of several thousands. All serum samples had been titrated in two ELISAs based either on disrupted HTLV-IIIB or on a bacterially synthesized polypeptide (ENV-80) of gp41 as a test antigen. The correlation of neutralizing activity of the sera with ELISA titers was low. A correlation of serum neutralizing titers with the stage of the disease could not be observed. However, in a longitudinal study with 6 patients over up to 22 months an increase in neutralizing antibodies seemed to protect against progression of the disease. The implications of these findings for antibody treatment and vaccine development are discussed.