IDENTIFICATION OF A VARIANT A-SPECIFIC NEUTRALIZING EPITOPE ON GLYCOPROTEIN-B (GB) OF HUMAN HERPESVIRUS-6 (HHV-6)

Based on genetic, antigenic, and growth properties, human herpesvirus- 6 (HHV-6) can be classified into two groups, Variant A (HHV-6A) and va riant B (HHV-6B). We have mapped the HHV-6A-specific epitope on glycop rotein B (gB), which was recognized by a monoclonal antibody (MAb), 87 -y-13, with a complement-independent neutralizing activity. Plasmids c arrying various chimeric gB sequences formed between strains U1102(HHV -6A) and HST(HHV-6B) and carrying sequences for a series of carboxy-te rminal deletions of U1102 gB were constructed, By using the plasmids, in vitro transcription and subsequent in vitro translation were carrie d out Immunoprecipitation assay of the translated products with MAb 87 -y-13 revealed that MAb 87-y-13 was able to react only with in vitro t ranslational products containing the sequence between amino acid resid ues 335 and 395 of U1102 gB. Amino acid sequence comparison between HH V-6A and HHV-6B in this region showed that amino acid residues 347, 38 7, and 393-395 were HHV-GA-specific. To determine which amino acid res idue(s) was involved in recognition by MAb 87-y-13 as well as in the n eutralizing activity, point mutations were introduced at those amino a cid positions. Immunoprecipitation assay of the mutagenized gB with po int mutations suggested that the neutralizing MAb 87-y-13 was involved in the recognition of the amino acid Asn at residue 347 of U1102 gB ( HHV-6A), This site may play an important role in viral infection. (C) 1996 Academic Press, Inc.