V3 serotyping of HIV-1 infection: Correlation with genotyping and limitations

HIV-I V3 serotyping is a classification of immunodeficiency viruses based o n antibody binding to V3 peptides that allows obtaining information on circ ulating subtypes that could be important for population-based epidemiologic studies, Recently, several laboratories have developed V3 enzyme-immunoass ays (EIAs) using V3 peptides of subtypes A to E. In the present study, the utility of including additional peptides of subtypes F to H to the EIA was evaluated on a panel of 203 well-characterized serum samples from patients with diverse geographic origins (22 countries) and known HIV-1 genotype (79 A, 61 B, 21 C, 7 D, 7 E, 21 F, 6 G, 1 H). The results indicate a high pred ictive value (ppv) for serotypes B (greater than or equal to 0.86), D (1) a nd E (0.88), and confirm the difficulty of predicting genotype A or C based on serotype A or C. Results also indicate that inclusion of the F peptide in the V3 EIAs may be useful (ppv = 0.61), but introduction of peptides G a nd H failed to demonstrate significant sensitivity or specificity for these subtypes. Correlation between serotyping and aminoacid sequences of the V3 region from 103 samples allowed the identification of key amino-acids that appear essential for subtype-specific seroreactivity.