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The emergence of the novel GII.17 Kawasaki 2014 norovirus variant raising the interest of the public, has replaced GII.4 as the predominant cause of noroviruses outbreaks in East Asia during 2014–2015. Antigenic variation of the capsid protein is considered as one of the key mechanisms of norovirus evolution. In this study, we screened a panel of GII.17 mutants. First, we produced norovirus P proteins using cell-free protein synthesis (CFPS) system, comparing the results to pure proteins expressed in a cell-based system. Next, we determined the binding capability of specific monoclonal antibody (mAb) 2D11 using a unique set of wild-type GII.17 strains. Results of the EIA involving a panel of mutant cell-free proteins indicated that Q298 was the key residue within loop 1. These data highlighted the essential residues in the linear antibody binding characteristics of novel GII.17. Furthermore, it supported the CFPS as a promising tool for rapidly screening mutants via the scalable expression of norovirus P proteins. [ABSTRACT FROM AUTHOR]

Human noroviruses (HuNoVs) have been found as the leading cause of acute gastroenteritis outbreaks in all age groups and are significantly correlated with the consumption of shellfish. In this study, the contamination of HuNoVs in shellfish was estimated through a systematic review and meta-analysis. Studies on the contamination of HuNoVs in shellfish were searched from PubMed, Web of Science, Embase, and Cochrane Library from January 2000 to August 2021. A total of 75 studies were included, and the pooled HuNoVs prevalence in shellfish was 29% (95% CI: 23–35) worldwide. As revealed by the results of the subgroup meta-analysis, the prevalence of dominant genogroup was variable, and 4% (95% CI: 3–6), 13% (95% CI: 10–17), with 7% (95% CI: 4–11) of the samples, respectively, contaminated by GI alone, GII alone, and GI&GII. The HuNoVs prevalence of shellfish in Europe, America, and Asia was 33% (95% CI: 24–43), 24% (95% CI: 7–47), and 27% (95% CI: 18–35), respectively, while only 10% (95% CI: 5–17) in Africa. Furthermore, the prevalence of HuNoVs in shellfish was the highest in spring (35%, 95% CI: 23–49) and winter (35%, 95% CI: 22–50), and the lowest in summer (11%, 95% CI: 5–18). Oysters, clams, and mussels had comparable HuNoVs prevalence of 28% (95% CI: 20–37), 27% (95% CI: 16–39) and 24% (95% CI: 17–32), respectively. The prevalence of HuNoVs in shellfish from harvest areas and markets was 30% (95% CI: 23–38) and 30% (95% CI: 19–41), respectively. The results of this study suggest a substantial burden of HuNoVs in shellfish worldwide, with GII.4 (92.86%) and GII.2 (46.43%) as the predominant genotypes. This study provides information regarding the contamination of HuNoVs in shellfish worldwide, which will contribute to the development of appropriate control measures to prevent shellfish-related HuNoVs gastroenteritis. • The pooled prevalence of human noroviruses in shellfish was found as 29% (95% CI: 23–35) worldwide. • GII.4 (92.86%, 26/28) was found as the most common genotype in shellfish. • Significant differences were found in the seasonal and geographical prevalence of human noroviruses in shellfish. [ABSTRACT FROM AUTHOR]

Oysters and mussels are important vectors for norovirus (NoV). An efficient pretreatment method for NoV detection in oysters based on ISO 15216-2:2019 was established in our previous work, but its effectiveness for other types of shellfish remains unknown. Therefore, this study systematically compared the differences between the standard and modified ISO methods in detecting NoV for oysters and mussels. Using the standard ISO method, the recovery rates of NoV in oysters (2.10 ± 0.80 %) and mussels (2.39 ± 0.56 %) were comparable (p > 0.05, unpaired t -test). In contrast, the virus recovery rates in oysters (19.83 ± 3.64 %) and mussels (46.96 ± 3.55 %) were both significantly improved by the modified method. Also, a significant difference was found between the virus recovery rates in two shellfish (p < 0.05, unpaired t -test), resulting in a 2.09-fold difference in their virus concentrations. Additionally, the limits of detection at 95 % probability of the modified ISO method for oysters and mussels could both reach 3.33 × 103 copies/g of digestive glands. Finally, the modified ISO method has been successfully applied in commercial oysters (14/27, 51.85 %) and mussels (15/23, 65.22 %), and the results indicated a significant difference in NoV recovery rates between two shellfish (p < 0.05, one-way analysis of variance). In summary, the modified ISO method showed higher virus recovery rates than the standard ISO method, which would be used as an essential tool for NoV detection in oysters and mussels. • We developed a new method that improves viral detection in oysters and mussels. • Our method provided a higher virus recovery rate than the standard ISO method. • There were significant differences in virus recovery between oysters and mussels using the new method. [ABSTRACT FROM AUTHOR]