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

Int Conf AIDS 1998 Jun 28-Jul 3; 12:16-7 (abstract no. 11172)

Santiago ML, Hafalla JC, Santiago EG, Manalo MA, Martin C, Cajimat MN, De Groot AS
Research Inst. for Tropical Medicine, Muntinlupa City, Manila, Philippines.

OBJECTIVE: To investigate the antigenic and sequence diversity of the V3 loop region in viral isolates in the Philippines.

DESIGN: Antisera from 44 HIV+ individuals in the Philippines were subjected to an enzymeimmunoassay (PEIA) using the MN (KRIHIGGPGRAFYTTK) and consensus E (TSITIGPGRVFYRTG) peptides then correlated with HMA patterns and V3 loop sequences.

RESULTS: Majority of individuals (n = 40.91%) reacted to the peptide in PEIA. This included all subtype B-infected (n = 28) antisera and 4 isolates of subtypes C, D, F and putatively, an E/G recombinant. Only 4 out of 12 subtype-E antisera reacted with the consensus E peptide, while 4 reacted to both peptides, suggestive of a mixed genotype infection. HMA and sequence analyses of multiple cloned PCR products from a single-time point specimen in one patient confirmed a mixed subtype C and E infection. However, HMA analyses in the remaining 3 patients did not support this hypothesis. Majority (51%) of the isolates had the GPGR motif, followed by GPGQ (12%) and GVGR (10%). Based on comparisons with the 1996 LANL V3 loop tabulations, a potentially novel crown motif RRGR was identified in a commercial sex worker. Five potentially unique V3-octamers were also identified, including one subtype B-isolate which had reduced MN reactivity (RIGPGSIF).

CONCLUSION: Philippine HIV-1 isolates show limited antigenic diversity with respect to antibody reactivity to the MN peptide. This complements genetic analyses which show that V3 loop motifs in the Philippines had greater similarity to Western strains of HIV-1.

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