A genotypic characterization of enteroviral antigenic variants isolated in eastern Canada.

Antigenic variation within serotypes of enteroviruses can have a significant impact on the effectiveness of routine diagnosis by neutralization assays. The focus of this particular study was to initiate a genetic characterization of echovirus type 9 (E9) antigenic variants and nontypeable strains isolated in Canada from 1991 to 1993. All variant strains were initially identified by the serological parameter of neutralization 'breakthrough' during conventional serotyping using the Lim-Benyesh-Melnick antiserum pools and by assessing neutralization endpoints using micro-neutralization methodology. Both E9 variant and non-variant isolates were further characterized by sequencing amplicons generated from the VP2 capsid protein-coding region of these particular strains. Variants from the provinces of Ontario and New Brunswick were shown to include a number of genotypically distinct strains and all the variant strains were significantly different from non-variant E9 isolates when nucleotide sequences were compared. A similar genetic analysis of two completely non-typeable isolates from Quebec showed that these viruses seemed to belong to a genetic cluster of enteroviruses that included coxsackievirus A16 and enterovirus 71 serotypes. The use of genetic typing by sequence analysis provides a molecular tool for determining the genotypic diversity of variant and non-typeable isolates and their possible relatedness to other enteroviral strains.