12th International AIDS Conference Geneva, Switzerland - June 28-July 3, 1998

Int Conf AIDS 1998 Jun 28-Jul 3; 12:17 (abstract no. 11176)

Smith TL, Van Rensburg EJ, Engelbrecht S
University of Stellenbosch, Cape Town, South Africa.

OBJECTIVES: The objective of this study was to examine the neutralization of South African HIV-1 subtypes B, C, and D using sera obtained from HIV-1-infected individuals.

METHODS: Thirty-two sera from 25 patients were tested for their ability to neutralize HIVIIIB and 4 isolates representing subtypes B, C, D and a recombinant gag C/env B. A CEM-SS cell line-based assay was used and the neutralizing titer was defined as the reciprocal of the highest dilution yielding a 50% reduction in p24 antigen using an enzyme immunosorbent assay (EIA). The 35 amino acid V3 region of the isolates and a few of the serum samples used in the neutralization assay were amplified by PCR and directly sequenced.

RESULTS: All the isolates were neutralized better by subtype-specific sera, except for the C isolate, which was neutralized by both subtype B and C sera. The C subtype was neutralized by 18/25 (72%) sera, HIVIIIB by 19/32 (59%) sera, the D isolate by 7/31 (23%) sera, the B/C isolate by 4/25 (16%) sera. Five sera were unable to neutralize any of the isolates. Analysis of the V3 sequences revealed variability between the consensus HIV-1 sequences, the isolates, and the serum samples. This variability could have influenced the outcome of the neutralization assay results.

CONCLUSIONS: The subtype C isolate was better neutralized with the sera tested, than the HIVIIIB laboratory strain. Therefore, vaccine formulation should be broadened to include multiple subtypes, especially C, which is currently the most prevalent worldwide.

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