The cardiovirulent phenotype of coxsackievirus B3 is determined at a single site in the genomic 5' nontranslated region

Abstract

We report the construction of chimeric coxsackievirus B3 (CVB3) strains in which sequences of an infectious cDNA copy of a noncardiovirulent CVB3 genome were replaced by the homologous sequences from a cardiovirulent CVB3 genome to identify which of 10 predicted genetic sites determine cardiovirulence. Cardiovirulent phenotype expression was consistently linked to nucleotide 234 (U in cardiovirulent CVB3 and C in avirulent CVB3) in the 5 nontranslated region. Reconstructions of the parental noncardiovirulent CVB3 genome from chimeras restored the noncardiovirulent phenotype when tested in mice. Inoculation of severe combined immunodeficient (scid) mice with the noncardiovirulent CVB3 strain resulted in massive cardiomyocyte necrosis in all animals. Sequence analysis of viral genomes isolated from twelve scid mouse hearts showed that only nucleotide position 234 was different (a C3U transition) from that in the input parental noncardiovirulent CVB3 genome. Higher-order RNA structures predicted by two different algorithms did not demonstrate an obvious local effect caused by the C3U change at nucleotide 234. Initial studies of parental and chimeric CVB3 replication in primary cultures of fetal murine heart fibroblasts and in adult murine cardiac myocytes demonstrated that viral RNA transcriptional efficiency is approximately 10-fold lower for noncardiovirulent CVB3 than for cardiovirulent CVB3. CVB3 did not shut off protein synthesis in murine cardiac fibroblasts, nor were levels of viral protein synthesis significantly different as a function of viral phenotype. Taken together, these data support a significant role for determination of the CVB3 cardiovirulence phenotype by nucleotide 234 in the 5 nontranslated region, possibly via a transcriptional mechanism.

Glutathione peroxidase protects mice from viral‐induced myocarditis

“…These data demonstrate that, in a host deficient in GPX-1 activity, an avirulent virus undergoes a phenotypic change to virulence due to point mutations in the genome. Single mutations in various sites in the CVB3 genome have been shown to be associated with cardiovirulence (26,27). Our previous work demonstrating similar point mutations in Se-defi-cient mice suggests that the mutations may be driven by oxidative damage.…”

Host nutritional status: the neglected virulence factor

“…Sequencing of the viral genomic RNA obtained from infected Se-adequate and Se-deficient mice confirmed that a viral genome change had occurred ( Table 1). Out of the ten nucleotide positions that were reported to co-vary with cardiovirulence in CVB3 strains [12], six reverted to the virulent genotype in those virions that replicated in Se-deficient mice [1]. No nucleotide changes were found in viral genomes isolated from Se-adequate control mice.…”

Viral Quasispecies Evolution

“…An amino acid substitution in encephalomyocarditis virus (EMCV) can render the virus diabetogenic (42). Cardiovirulence of coxsackievirus B3 can be determined by a single site at the 5= untranslated region (UTR) (815). (For additional studies on coxsackievirus B pathogenesis and evolution and the relevance of quasispecies for enteroviruses in general, see several chapters of references 232 and 812).…”