Molecular strategy for 'serotyping' of human enteroviruses

To explore further the phylogenetic relationships between human enteroviruses and to develop new diagnostic approaches, we designed a pair of generic primers in order to study a 1452 bp genomic fragment (relative to the poliovirus Mahoney genome), including the 3' end of the VP1-coding region, the 2A- and 2B-coding regions, and the 5' moiety of the 2C-coding region. Fifty-nine of the 64 prototype strains and 45 field isolates of various origins, involving 21 serotypes and 6 strains untypable by standard immunological techniques, were successfully amplified with these primers. By determining the nucleotide sequence of the genomic fragment encoding the C-terminal third of the VP1 capsid protein we developed a molecular typing method based on RT-PCR and sequencing. If field isolate sequences were compared to human enterovirus VP1 sequences available in databases, nucleotide identity score was, in each case, highest with the homotypic prototype (74.8 to 89.4%). Phylogenetic trees were generated from alignments of partial VP1 sequences with several phylogeny algorithms. In all cases, the new classification of enteroviruses into five identified species was confirmed and strains of the same serotype were always monophyletic. Analysis of the results confirmed that the 3' third of the VP1-coding sequence contains serotype-specific information and can be used as the basis of an effective and rapid molecular typing method. Furthermore, the amplification of such a long genomic fragment, including non-structural regions, is straightforward and could be used to investigate genome variability and to identify recombination breakpoints or specific attributes of pathogenicity.