[Genetic variability of type 3 echoviruses]. / Variabilité génétique des échovirus de type 3.

The aim of the present work was to assess the genetic and antigenic variability in the VP1 region of type 3 echviruses (E-3), an enterovirus serotype associated to meningitis, neuro-muscular diseases and type 1 diabetes in human. Forty-six VP1 sequences of E-3, among which 9 were isolated in tunisian infants, were included. Phylogenetic analyses and nucleotidic divergence rates were studied in the complete VP1 region and in a 290-nucleotides fragment in the 5' part of the P1. Aminoacid sequences were deduced in the aim to identify genotype-specific antigenetic determinants. E-3 sequences divided into two genogroups, I and II; the genetic variability within the E-3 serotype reached 29.1%. Genogroup I included sequences with a relatively high genetic diversity among each other, some of them grouped in one genotype with at most 15.1% divergence rate. The sequences included in Genogroup II have a maximum of 13.8% divergence corresponding probably to only one genotype. The two genogroups have a concomitant circulation and a wide geographical and temporal distribution. Aminoacid substitutions that may be specific to genogroups, genotypes and special variant were noted. This work provides a first tentative of classification of E-3 into genogroups and genotypes and reports new E-3 sequences from North Africa. It contributes to a better understanding of the molecular epidemiology of human enteroviruses, and of Echoviruses type 3 in particular, a serotype that remains insufficiently studied in the international literature.