C-Terminal Fragments of gpl20 and Synthetic Peptides from Five HTLV-III Strains: Prevalence of Antibodies to the HTLV-III-MN Isolate in Infected Individuals

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Abstract
The immunoreactivity of HTLV-III-infected individuals and virus-inoculated chimpanzees with gpl20 synthetic peptides of the HTLV-III gpl20 envelope principle neutralizing domain (amino acid 301-324 sequences), derived from the HTLV-III isolates 3B, RF, MN, WMJ2, and SC were determined. Sequential bleeds from an infected lab worker and chimpanzees, both infected with the HTLV-IIIB, were immunoreactive only with the 3B peptide. In contrast, 33 HTLV-III-infected individuals were immunoreactive with the HTLV-IIIMN peptide. Of these 33 individuals, 23 were also immunoreactive with the HTLV-IIISC peptide, and 18 with the HTLV-IIIWMJ2 peptide. The data suggest that HTLV-III strains related to MN are most prevalent among HTLV-III-infected individuals. The binding specificities of goat sera generated against either of these synthetic peptides or the C-terminal fragment of gpl20 (PB-1, amino acid 287-467, derived from the HTLV-III isolates 3B, RF, MN, WMJ2, and SC) were also determined. Four different ELISA formats (peptide sera/peptide antigens, peptide sera/PB-1 antigens, PB-1 sera/PB-1 antigens, and PB-1 sera/peptide antigens) were utilized to determine the cross-reactivity patterns of goat sera with the antigens. Goat sera generated against MN and SC sequences (PB-1 proteins, as well as synthetic peptides) were highly cross reactive. Thus, patient sera cross reactivity to multiple strains of the principal neutralizing domain may reflect the antigenic relatedness of the virus isolates rather than multiple infection events or strains generated during disease progression.