title: Allelic subtypic determinants of hepatitis B surface antigen (i and t) that are distinct from d/y or w/r.
abstract: A monoclonal antibody (I-18) was raised against an enneapeptide representing amino acids 125 to 133 of the product of the S gene of hepatitis B virus DNA [S(125-133) segment] with a sequence of Thr-Ile-126-Pro-Ala-Gln-Gly-Thr-Ser-Met. Another monoclonal antibody (T-7) was raised against an S(125-133) segment in which Ile-126 was replaced by Thr-126. In a panel of 16 samples of hepatitis B surface antigen (HBsAg) with known S gene sequences, I-18 reacted with 5 with Ile-126. T-7 reacted with 10 HBsAg samples with Thr-126; it did not, however, react with the remaining one of subtype ayw with Thr-126 flanked by Met-125 and Thr-127. The two allelic subtypic determinants, specified by Ile-126 and Thr-126 and distinct from d/y or w/r, were named i and t after isoleucine and threonine, which regulate them. They were expressed in a mutually exclusive fashion in 216 (83%) of 260 HBsAg samples from asymptomatic carriers. They were not detected in 36 (14%) samples; the failure to detect an i or t determinant was particularly common in HBsAg samples of subtype ayw (26 [79%] of 33). A part of the S gene sequence was determined for eight HBsAg samples without a detectable i or t determinant. They had an Ile-126 or Thr-126 residue that was flanked by Thr-127, not the Pro-127 commonly possessed by HBsAg samples displaying an i or t determinant. Expression of the i/t allele, therefore, would require Pro-127. In eight (3%) of the samples, both i and t determinants were detected; the presence of i and t on the selfsame HBsAg particles was verified by sandwiching the particles between I-18 and T-7. A point mutation from thymine to cytosine at nucleotide 377 in the S gene, contributing different second letters to codon 126 (ATT for Ile and ACT for Thr), would have been responsible for the assembly of HBsAg particles with both i and t determinants by means of phenotypic mixing.
authors.affiliation: Immunology Division, Jichi Medical School, Tochigi-ken, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Ohnuma
authors.forename: A
authors.initials: A
authors.lastname: Machida
authors.forename: H
authors.initials: H
authors.lastname: Okamoto
authors.forename: F
authors.initials: F
authors.lastname: Tsuda
authors.forename: M
authors.initials: M
authors.lastname: Sakamoto
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
authors.forename: Y
authors.initials: Y
authors.lastname: Miyakawa
authors.forename: M
authors.initials: M
authors.lastname: Mayumi
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D002353:Carrier State / Q000276:immunology; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D006509:Hepatitis B / Q000235:genetics / Q000276:immunology; D006514:Hepatitis B Surface Antigens / Q000097:blood / Q000145:classification / Q000235:genetics / Q000276:immunology*; D006515:Hepatitis B virus / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000939:Epitopes; D006514:Hepatitis B Surface Antigens; D009842:Oligopeptides