Molecular determinants for virulence in coxsackievirus B1 infection.

Studies demonstrated that a strain derived from an infectious clone of coxsackievirus B1 (CVB1N) (N. Iizuka, H. Yonekawa, and A. Nomoto, J. Virol. 65:4867-4873, 1991) was 3 to 4 log10 less virulent than the myotropic Tucson strain of CVB1 (CVB1T) following intraperitoneal inoculation of newborn mice. Replacement of nucleotides (nt) 69 to 804 from the 5' untranslated region (5' UTR) and 1A coding region of CVB1N or nt 117 to 161 from the 5' UTR with the corresponding part from CVB1T restored greater than 90% of the virulence. Sequencing of the 5' UTR of CVB1T demonstrated areas with a greater similarity to particular echoviruses than to CVB1N, suggesting that recombination events might have occurred, perhaps influencing the virulence phenotype.