An infectious cDNA copy of the genome of a non-cardiovirulent coxsackievirus B3 strain: its complete sequence analysis and comparison to the genomes of cardiovirulent coxsackieviruses

The genome of the non-cardiovirulent coxsackievirus B3 (CVB3) strain CVB3/0 was cloned and sequenced to aid in the elucidation of the viral genetic basis for the CVB3 cardiovirulent phenotype. Reverse-transcribed sub-genomic complementary DNA (cDNA) fragments were enzymatically amplified using generic oligonucleotide primers and were assembled as a complete infectious genomic copy (pCVB3-0) downstream of the T7 RNA polymerase promoter. Positive-strand viral RNA transcribed from pCVB3-0 using T7 RNA polymerase and transfected into HeLa cells produced infectious virus (CVB3/0c). No differences in phenotype were observed comparing growth of CVB3/0c to the parental CVB3/0 in HeLa single-step growth curves, virus yields, or plaque size. When inoculated into C3H/HeJ mice. CVB3/0c achieved cardiac titers equivalent to the parental CVB3/0 and like the parental virus, demonstrated a non-cardiovirulent phenotype. The nucleotide sequence of the cloned CVB3/0 genome was determined and compared to the genomes of infectious cDNA clones of cardiovirulent CVB3 strains. Two consistent differences among nucleotides in non-translated regions and 8 amino acid differences relative to two well-characterized infectious cDNA copies of genomes from cardiovirulent CVB3 strains were identified.