Human sera from varicella-zoster virus (VZV) infections cross-react with human T cell leukaemia virus type 1 (HTLV-1): common epitopes in VZV gene 22 protein and HTLV-1 p19 gag protein.

Twenty-nine of 100 sera from patients recently infected with varicella-zoster virus (VZV) were found to cross-react with human T cell leukaemia virus type 1 (HTLV-1) antigen in the particle agglutination (PA) assay using HTLV-1 antigen-coated gelatin particles. Anti-VZV IgM antibodies were shown to be responsible for this cross-reactivity. Western blot analysis revealed that PA-positive anti-VZV sera reacted with the HTLV-1 gag p19 protein in HTLV-1-infected cells and recombinant p19 protein produced in Escherichia coli. By using a truncated p19, the cross-reactive region was located to the C-terminal 17 amino acids of p19. One oligopeptide derived from the C terminus, PQIPPPYVEPT (amino acids 115 to 125), was capable of inhibiting PA, suggesting that this peptide carries the cross-reactive epitope. A homologous sequence was found in the VZV gene 22 protein by database analysis, and the oligopeptide TNIPPPLALLR (amino acids 1330 to 1340) had the ability to inhibit PA. These findings suggest that some IgM antibodies against the VZV gene 22 protein produced in the early phase of VZV infection are cross-reactive with the HTLV-1 gag p19 protein because they recognize an antigenic determinant containing an IPPP tetrapeptide.