Prevalence, clinical significance, and strain specificity of neutralizing antibody to the human immunodeficiency virus.

A semiautomated microtiter assay has been developed to quantitate neutralizing antibody to the human immunodeficiency virus. This assay has been found to be highly specific. Forty-four sera that were negative by enzyme-linked immunosorbent assay (ELISA) were tested under code: 42 were negative (less than 1:2), and 2 had titers of 1:2. By contrast, of 178 sera positive by western blot, 92.7% had detectable neutralizing antibody, and 12.5% had titers greater than or equal to 1:128. Neutralizing antibody titers correlated poorly with clinical diagnosis and T4/T8 ratios. Different isolates differed quantitatively in their sensitivity to neutralization by antibodies obtained from different patients; however, all strains tested so far have been neutralizable by all the sera tested. Neutralizing antibody titers correlated weakly, if at all, with direct or competition ELISA titers.