Neutralization of clade C and clade B viruses in the U87 pseudotype neutralization assay by antibodies to rgp120.

Virus neutralization titers were measured in the U87 pseudotype virus neutralization assay [18], [19]. 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, virus neutralization was considered significant if the neutralization titers were at least 3-fold greater than those observed against the control pseudotype virus, aMLV. The positive control was an HIV+ sera (N16).