Molecular analysis of the capsid coding region of a virulent encephalomyocarditis virus isolate after serial cell passages and assessment of its virulence.

EMCV has been recognized as a worldwide-shared pathogen in many host species with natural differences of virulence among strains. Differences of virulence were also demonstrated experimentally after serial passages of particular EMCV strains in cell culture. In order to evaluate the genetic variability of the CCR of an highly virulent Belgian EMCV isolate after 210 passages in cell culture, this region has been molecularly characterised by RT-PCR and sequencing. The analyses enlightened the stability of the isolate as only 3 mutations appeared within the CCR and this was observed between passage 200 and 210. One of the mutations is adjacent to the amino acid described as the differentiation amino acid between diabetogenic and non-diabetogenic variants of EMCV. An experimental inoculation of pigs with the passage 210 of the virus enlightened its attenuation and the challenged pigs were protected against the wild-type virus. Results confirm the ability of EMCV to become attenuated after passages in cell culture.