Classification of sapoviruses based on comparison of phylogenetic trees for structural and non-structural proteins

Sapoviruses (SaVs) compose the Sapovirus genus in the Caliciviridae family. In the genome of SaVs, the junction of coding regions for the non-structural proteins (NSs) and the major structural protein (viral protein 1: VP1) is known as the recombination hotspot. SaVs have been divided into genogroups GI-GXIX based on the phylogenetic relationship of amino acid sequences for VP1. Here, phylogenetic analyses were conducted for NSs and VP1 of 326 SaV strains retrieved from the International Nucleotide Sequence Database. Shared clusters were identified between the phylogenetic trees, and genogroups of SaVs were classified into 10 shared cluster groups, which may represent the monophyletic recombining groups of SaVs. All of human GI, GII, GIV, and GV strains were classified into the same shared cluster group. Continuous surveillance may be warranted for monitoring emergence of intra-genogroup and inter-genogroup recombinants in human SaVs.