A SINGLE AMINO-ACID SUBSTITUTION IN THE CAPSID PROTEIN VP1 OF COXSACKIEVIRUS B3 (CVB3) ALTERS PLAQUE PHENOTYPE IN VERO CELLS BUT NOT CARDIOVIRULENCE IN A MOUSE MODEL

We previously described a large plaque attenuant (p14V-1) derived from a cardiovirulent Coxsackievirus B3 (CVB3) and showed that there were no major determinants of either attenuation or plaque phenotype in the 5' nontranslated region (5'NTR). Part of the region encoding the last 124 amino acids of VP3 and the first 106 amino acids of VP1 of the at tenuant was then sequenced and compared to the wild-type. Three nucleo tide changes were found in the VP1 coding region: a silent single base change at nucleotide position 2467 (C to U) and a double-base change at position 2690-1 (AA to GT), which leads to a change from lysine to serine at amino acid position 80. This mutation maps to the begining o f B-C loop of the three-dimensional structure of VP1 of CVB3, where a distinct surface projection is formed. Two infectious chimeric cDNA cl ones were constructed, based on a cardiovirulent cDNA construct. In on e construct, the 5'NTR and the VP3-VP1 region were from p14V-1 and in the other, only the VP3-VP1 region was from this attenuant. Both chime ric viruses produced large plaques on Vero cell monolayers, similar to p14V-1 but larger than the prototypic cardiovirulent virus. In vivo e xperiments showed that both chimeric viruses induced myocarditis in a murine model, similar to wild-type virus. We conclude that mutation se rine-80 in capsid protein VP1 of p14V-1 is a determinant of the large plaque phenotype but is not responsible for attenuation.