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.
PIP: 635 serum samples derived in 1988 and 1993 were analyzed by peptide enzyme immunoassays in order to determine the antibody reactivity against a V3 sequence based on local HIV-1 strains in Ethiopia. V3 peptides were produced according to the Ethiopian subtype C V3 consensus sequence (RKSIRIGPGQTFYAT), the HIV-1-MN and HIV-1-IIIB 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. Antibody reactivity to Ethiopian consensus V3 peptide was found in 96% of the Ethiopian patients. A strong reactivity to the Ethiopian V3 consensus sequence was found in 59% of the Ethiopian samples, independent of geographical origin or year of sampling (1988, 54%; 1993, 60%). In 38% of the 30 Swedish HIV-1-MN positive sera, the high reactivities were restricted to the subtype B HIV-1-MN peptide. As a control, 440 of the sera were screened against the other 5 subtypes, and the number of reactions were as follows: subtype A consensus 302 (69%), B HIV-1-IIIB strain 72 (16%), D consensus 88 (42%), D of HIV-1-ELI strain 50 (11%), and E consensus 116 (26%). A low prevalence (10%) of strong reactivity to the HIV-1MN V3 peptide was found among the Ethiopian samples. The significant ( 50% decrease in optical density value) inhibition of antibody reactivity to the Ethiopian consensus V3 peptide and to the HIV-1-MN V3 peptide, respectively, showed a high specificity of the peptides. Substitution peptide analogs demonstrated that a lack of cross-reactivity between subtype B and C peptides was dependent on the Arg-322 to Gln-322 substitution. 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.