Detection and titration of neutralizing antibodies to HIV using an inhibition of the cytopathic effect of the virus on MT4 cells.

An assay for determining neutralizing antibodies in sera from individuals infected with HIV was developed. This assay is based on an inhibition of the cytopathic effect observed after HIV superinfection of the HTLV-1-positive cell-line MT4. Only about 10% of asymptomatic seropositive donors exhibit a high titre over 1/500 up to 1/2000 while in 60% of sera, neutralizing antibodies were not detected. The assay reported here can also be used for the comparison of the biological properties of the different strains of HIV.