Introduction
Noroviruses (NoVs) are important pathogens causing gastroenteritis in children and young animals. Infection with NoV in children and young animals can cause intestinal lesions and post-infectious diarrhea (Smiley,Chang,Hayes,Vinje, & Saif, 2002; Bridger,Hall, & Brown, 1984; Woode & Bridger, 1978). In humans, NoV is one of the most important etiological agents of gastroenteritis; however, little is known about NoV causing diarrhea in cattle.
NoVs are small non-enveloped, positive-sense single-stranded RNA viruses. According to the diversity of the VP1 amino acid (aa) sequence, NoVs are divided into seven genogroups (GI to GVII). Bovine NoVs (BNoVs) belong to GIII and are further divided into two different genotypes, i.e., genotype 1 (Bo/Jena/1980/DE) and genotype 2 (Bo/newbury2/1976/UK), which were first identified in Germany (Otto et al., 2011) and the UK (Jung,Scheuer,Zhang,Wang, & Saif, 2014). The BNoV genome, which has a size of 7.5–7.7 kb, contains three open reading frames (ORFs). Starting from the 5’ end of the genome, ORF1 encodes a non-structural protein, including an enzyme responsible for transcription, viral genome replication, and accurate initiation of RNA synthesis by RNA-dependent RNA polymerase (RdRp). RdRp prevents the virus from losing its genetic information (Deval,Jin,Chuang, & Kao, 2017; Lee,Chung, & Kim, 2017). ORF2 encodes the major capsid protein VP1 . It is involved in receptor recognition and host specificity (Chen et al., 2004).Viral evasion of antibody neutralization results in frequent variations in theVP1 aa sequences, which are also associated with the emergence of new epidemic strains (Lochridge & Hardy, 2007; Lindesmith et al., 2013). ORF3 encodes the minor capsid protein VP2 , a hypervariable protein that may play a role in maintaining the stability of NoV particles (Lin,Fengling,Lianzhu,Yuxiu, & Yanhua, 2014).
Previous studies have reported the detection of BNoV in many countries including the UK (Woode & Bridger, 1978; Bridger,Hall, & Brown, 1984), Germany (Gunther,Otto, & Heilmann, 1984), the Netherlands (van der Poel et al., 2003; van Der Poel et al., 2000), the USA (Cho et al., 2013; Wise et al., 2004), New Zealand (Wolf et al., 2007), South Korea (Park et al., 2007), Norway (Jor,Myrmel, & Jonassen, 2010), France (Kaplon,Guenau,Asdrubal,Pothier, & Ambert-Balay, 2011), Turkey (Kaplon,Guenau,Asdrubal,Pothier, & Ambert-Balay, 2011), and Tunisia (Hassine-Zaafrane et al., 2012). According to previous reports, BNoV was first detected in Southern China in 2018 (Wang,Yue, & Tang, 2019), and it was detected in central China in 2019 (Shi,Wang,Xu,Zhang, & Lan, 2019).
BNoV has become a threat to the global cattle industry, and it may bring huge economic losses to the cattle industry in China. Although BNoV is prevalent globally, the study of its pathogenicity, epidemiology, and molecular biology is only in the preliminary stage. Up to now, GenBank contained only seven complete BNoV genome sequences; two are GIII.1 strains (GenBank accession numbers: MK159169 and AJ011099) and five are GIII.2 strains (GenBank accession numbers: JX145650, AY126474, AF097917, MN122335.1, and EU794907). In China, only two BNoV genomes have been completely sequenced, i.e., one from southern China and one from central China. There are not enough data to establish the genetic relationship and evolutionary rate of BNoVs in China. At present, the virus has not been successfully isolated, hindering the development of an effective vaccine. We studied the molecular profile of the virus and analyzed its genetic variation, in order to provide a reference for the prevention and control of viral spread in China.
We identified a BNoV strain, named Bo/CH/HB/BD/2019, from Hebei, in northern China, and conducted phylogenetic analysis of the entire genome and the VP1 region. BNoV may be highly prevalent in China, but there are few epidemiological data on the prevalence of the virus. This study lays a foundation for the further exploration of the molecular biological characteristics of BNoV and the prevalence of BNoV in China.