Capsid diversity in small round-structured viruses: molecular characterization of an antigenically distinct human enteric calicivirus.
Studies of antigenic variation between small round-structured viruses (SRSVs) using immune electron microscopy have revealed 3 antigenic types currently circulating in the UK represented by the strains SRSV/Bri/93/UK, SRSV/Sot/91/UK and SRSV/Mel/89/UK. Mel/89/UK RNA was isolated from a 1989 school outbreak of gastroenteritis. The 3'-terminal 3435 nucleotides (excluding the poly(A) tail) were determined by RT-PCR and cDNA sequencing, completing our molecular characterization of antigenically diverse SRSVs. Coding regions for the calicivirus RNA polymerase and capsid protein were found together with a 3' open reading frame of unknown function. The polymerase region was most highly conserved between Mel/89/UK and the other two SRSVs while the 3' open reading frame exhibited extreme variation. Phylogenetic analysis of SRSV capsids showed that Mel/89/UK differed significantly from Bri/93/UK and Sot/91/UK (62 and 39% identity, respectively) and was distinct from 6 other non-UK SRSVs that had been previously characterized. This was consistent with the designation of Mel/89/UK as a novel antigenic variant. Comparison of the capsid amino acid sequences of the 3 UK strains together with the antigenically distinct SRSV/Nor/68/US revealed a hypervariable region that could be surface-exposed and contain the SRSV antigenic determinants.
Department of Molecular Microbiology, University Medical School, Southampton General Hospital, UK.
S M
SM
Green
P R
PR
Lambden
E O
EO
Caul
C R
CR
Ashley
I N
IN
Clarke
D000595:Amino Acid Sequence; D000956:Antigens, Viral / Q000235:genetics* / Q000276:immunology; D001483:Base Sequence; D002213:Capsid / Q000235:genetics* / Q000276:immunology; D004279:DNA, Viral; D005759:Gastroenteritis / Q000821:virology; D014644:Genetic Variation; D016679:Genome, Viral; D006801:Humans; D007422:Intestines / Q000821:virology; D008969:Molecular Sequence Data; D009663:Norwalk virus / Q000235:genetics* / Q000276:immunology / Q000648:ultrastructure; D016366:Open Reading Frames; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid
D000956:Antigens, Viral; D004279:DNA, Viral