Characterization of a novel human calicivirus that may be a naturally occurring recombinant

We identified a Norwalk-like calicivirus (CV) whose genome likely was deriv ed from naturally occurring recombination. This strain (Arg320) was detecte d by the EIA developed against recombinant Mexico virus (rMxV) capsids, but the viral RNA polymerase sequence was closer to Lordsdale virus, in a sepa rate genetic cluster of Norwalk-like viruses. A 3.3 kb cDNA from the RNA po lymerase region to the 3' end of the genome of Arg320 was cloned and sequen ced. The sequence demonstrated that the capsid region of Arg320 shared 95% amino acid identity with MxV, but 68% identity with Lordsdale virus, while the RNA polymerase region shared 95% identity with Lordsdale virus, but 87% identity with MxV. Pair-wise sequence comparisons identified a potential r ecombination site at the polymerase/capsid junction. This is the first exam ple of a naturally occurring recombinant in the CV family. Further studies to search for and characterize other strains may be necessary for understan ding the genetic diversity of the family.