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To determine the antibody reactivity against a V3 sequence based on local HIV-1 strains in Ethiopia, 635 serum samples derived in 1988 and 1993 were analyzed by peptide enzyme immunoassays. V3 peptides were produced according to the Ethiopian subtype C V3 consensus sequence (RKSIRIGPGQTFYAT), the HIV-1MN and HIV-1IIIB strains (subtype B), and the consensus sequences of subtypes A, D, and E. Initial analyses showed that Ethiopian anti-V3 positive sera cross-reacted between subtype A and subtype C peptides, and displayed much lower reactivities to the other peptides. Using inhibition experiments, it was found that the reactivities in the Ethiopian samples were specific for subtype C. A strong reactivity to the Ethiopian V3 consensus sequence was found in the majority of the Ethiopian samples (59%), independent of geographical origin or year of sampling. In Swedish HIV-1-positive sera, the high reactivities were restricted to the subtype B HIV-1MN peptide. A low prevalence (10%) of strong reactivity to the HIV-1MN V3 peptide was found among the Ethiopian samples. Using substitution peptide analogs it was found that a lack of cross-reactivity between subtype B and C peptides was dependent on the Arg-322 to Gln-322 substitution. The present data show that a similar antibody recognition pattern was present in sera sampled during 1993 as in sera sampled during 1988, suggesting that subtype C of HIV-1 has remained the dominant subtype in Ethiopia.

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