Sapovirus (SaV) is an agent of gastroenteritis for humans and swine, and is divided into five distinct genogroups (GI-GV) based on its capsid gene sequences. Typical methods of SaV detection include electron microscopy (EM), enzyme-linked immunosorbent assay (ELISA), and reverse transcription-polymerase chain reaction (RT-PCR). A novel TaqMan-based real-time RT-PCR assay was developed that is sensitive and has the ability to detect the broad range of genetically diverse human SaV strains. A nucleotide alignment of 10 full-length SaV genome sequences was subjected to similarity plot analysis, which indicated that the most conserved site was the polymerase-capsid junction in open reading frame 1 (ORF1). Based on multiple alignments of the 27 available sequences encoding this junction, we designed sets of primers and TaqMan MGB probes that detect human SaV GI, GII, GIV, and GV sequences in a single tube. The reactivity was confirmed with SaV GI, GII, GIV, and GV control plasmids, and the efficiency ranged from 2.5 x 10(7) to 2.5 x 10(1) copies per tube. Analysis using clinical stool specimens revealed that the present system was capable of detecting SaV GI, GII, GIV, and GV sequences, and no cross-reactivity was observed against other enteric viruses, including norovirus (NoV), rotavirus, astrovirus, and adenovirus. This is the first real-time RT-PCR system that could detect all genogroups of human sapoviruses.

The P[19] genotype belongs to the P[II] genogroup of group A rotaviruses (RVs). However, unlike the other P[II] RVs, which mainly infect humans, P[19] RVs commonly infect animals (pigs), making P[19] unique for the study of RV diversity and host ranges. Through in vitro binding assays and saturation transfer difference (STD) nuclear magnetic resonance (NMR), we found that P[19] could bind mucin cores 2, 4, and 6, as well as type 1 histo-blood group antigens (HBGAs). The common sequences of these glycans serve as minimal binding units, while additional residues, such as the A, B, H, and Lewis epitopes of the type 1 HBGAs, can further define the binding outcomes and therefore likely the host ranges for P[19] RVs. This complex binding property of P[19] is shared with the other three P[II] RVs (P[4], P[6], and P[8]) in that all of them recognized the type 1 HBGA precursor, although P[4] and P[8], but not P[6], also bind to mucin cores. Moreover, while essential for P[4] and P[8] binding, the addition of the Lewis epitope blocked P[6] and P[19] binding to type 1 HBGAs. Chemical-shift NMR of P[19] VP8* identified a ligand binding interface that has shifted away from the known RV P-genotype binding sites but is conserved among all P[II] RVs and two P[I] RVs (P[10] and P[12]), suggesting an evolutionary connection among these human and animal RVs. Taken together, these data are important for hypotheses on potential mechanisms for RV diversity, host ranges, and cross-species transmission.IMPORTANCE In this study, we found that our P[19] strain and other P[II] RVs recognize mucin cores and the type 1 HBGA precursors as the minimal functional units and that additional saccharides adjacent to these units can alter binding outcomes and thereby possibly host ranges. These data may help to explain why some P[II] RVs, such as P[6] and P[19], commonly infect animals but rarely humans, while others, such as the P[4] and P[8] RVs, mainly infect humans and are predominant over other P genotypes. Elucidation of the molecular bases for strain-specific host ranges and cross-species transmission of these human and animal RVs is important to understand RV epidemiology and disease burden, which may impact development of control and prevention strategies against RV gastroenteritis.

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Rotavirus G3P [3] strains have been reported from a variety of species including humans, cats, dogs, monkeys, goats, and cows. Here, we report the characterization of the first human G3P[3] rotavirus from East Asia identified in a 2-year-old child who was treated in a hospital's emergency ward in Taiwan in February 2005. Sequence and phylogenetic analysis demonstrated a close genetic relationship between the VP4, VP6, VP7, and NSP4 genes of Taiwanese G3P[3] strain 04-94s51 and an Italian canine strain isolated a decade ago, suggesting a canine origin for the Taiwanese strain. In contrast, the Taiwanese strain was only moderately related to wellcharacterized canine-origin human G3P[3] strains Ro1845 and HCR3, suggesting a distinct origin for the rotavirus strain from Taiwan.