Neutralization of clade C and B viruses in the TZM-bl neutralization assay by antibodies to rgp120.

Virus neutralization titers were measured by the TZM-bl neutralization assay [28]. Virus designations include the country of origin as follows: BR, Brazil; CN, China; IN, India; MW, Malawi; SA, South Africa; ZA, South Africa; ZM, Zambia; ZW, Zimbabwe. ND, indicates not done. The neutralizing antibody titer (IC50) is defined as the reciprocal of the plasma dilution that produces a 50% inhibition in target cell infection. A dash indicates no significant neutralization. For this assay, neutralization titers were considered significant if they were 3-fold greater than the titers obtained for each virus pseudotype with normal guinea pig serum (NGPS). The positive control was the 4E10 broadly neutralizing monoclonal antibody.