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The dynamics of a Chinese porcine G9P[23] rotavirus production in MA-104 cells and intestines of 3-day-old piglets

Year: 2018

Type: article

Abstract: Rotavirus A (RVA) G9 genotype is recognized as an emerging genotype which is spreading worldwide, however, our knowledge on pathogenicity of this virus is limited.In this study, porcine RVA strain HN03 was successfully isolated on MA-104 cells, and the isolate was propagated continuously for 7 passages after a virus cloning at passage 3. The virus titers from 4 to 10 passages ranged from 10 7.1 to 10 8.1 TCID 50 /ml.The growth curve of HN03 strain in cell culture was determined, and the virus production dynamics was confirmed by immunoperoxidase monolayer assay (IPMA).Sequence and phylogenetic analyses based on full-length VP7 and partial VP4 genes indicated that HN03 strain belongs to genotype G9P [23].In addition, the sixth passage of strain HN03 in cell culture was subjected to 3-day-old piglets.All infected piglets developed severe watery diarrhea within 24 hr post-inoculation (hpi), but recovered from disease after 72 hpi.RVA antigen could be detected by IHC in the cytoplasm of villous enterocytes as early as 2 hr after appearance of clinical symptoms and virus antigen load kept increasing in the next 30 hr.The dynamics of RVA HN03 strain proliferation on cells and in pigs extended our understanding of rotavirus pathogenicity. KEY WORDS: G9 genotype, G9P[23], pathogenicity, porcine rotavirusRotaviruses (RVs) belong to the family Reoviridae, and they have a genome of 11 segments of double-stranded RNA encoding 6 structural proteins (VP1-VP4, VP6, and VP7) and five non-structural proteins (NSP1-NSP5/6) [7,11].RVs are classified into 8 major groups (RVA-RVH) based on the antigenic and genetic characteristics of the inner capsid protein VP6 [16].RVA, RVB, RVC, RVE, and RVH have been detected in pigs [7,31].RVA is considered the main cause of severe diarrhea in young children and piglets worldwide [15,18].Based on molecular characterization of VP7 and VP4, RVA strains are further classified into different G and P types [17].To date, at least 27 G genotypes and 38 P genotypes have been identified, several of them being detected from both humans and animals [6,8].Among porcine rotaviruses, the main G genotypes detected in pigs are G3, G4, G5, G9 and G11, whereas genotypes G1, G2, G6, G8, G10, G12 and G26 have been identified occasionally [5,33].Recently, RAV G9 genotype is recognized as an emerging genotype which is spreading worldwide, including mainland China, Taiwan, Korea, Japan, Thailand, Belgium, Italy, U.S. A., and Brazil [1, 13,19,24,26,27,29,32].The rapidly increasing prevalence of this virus raises questions regarding its origin, epidemiological and pathogenicity importance.Until recently, there are only few studies on pathogenicity of porcine G9 rotavirus [12, 25,34].In the present study, we obtained a porcine RVA strain, named as HN03, which was isolated from one porcine rotavirus positive intestinal sample collected from a piglet with diarrhea in Henan Province, China.The isolation, molecular characterization, and an evaluation of pathogenicity in piglets of this virus were described in this study.Immunochemistry straining was applied to different parts of small intestine at different time points after infection to understand the progression of virus infection.

Source: Journal of Veterinary Medical Science

DOI: 10.1292/jvms.17-0657