RESULTS:
1 - 3 of 3 for "Zhaojun Duan"
An improved reverse genetics system for rotavirus vaccine strain LLR using five plasmid vectors
Species A rotaviruses (RVs) which belong to the family Sedoreoviridae and contain a genome of 11 segmented dsRNA segments are a leading cause of severe acute gastroenteritis in infants and children younger than 5 years of age. We previously developed a strategy to recover rotavirus vaccine strain LLR from 11 cloned plasmids. Here we report an improved reverse genetics system for LLR by combining two or three transcriptional cassettes in a single plasmid which substantially enhances rescue efficiency from 66.7% (8/12) to 91.7 % (11/12). Furthermore the recombinant LLR stably expressing NLuc was rescued based on the five-plasmid reverse genetics system. Improvements to the rotavirus reverse genetics system will enhance its applicability for studies of rotavirus biology and clinical use.
Diverse novel astroviruses identified in wild Himalayan marmots
With advances in viral surveillance and next-generation sequencing highly diverse novel astroviruses (AstVs) and different animal hosts had been discovered in recent years. However the existence of AstVs in marmots had yet to be shown. Here we identified two highly divergent strains of AstVs (tentatively named Qinghai Himalayanmarmot AstVs HHMAstV1 and HHMAstV2) by viral metagenomic analysis in liver tissues isolated from wild Marmota himalayana in China. Overall 12 of 99 (12.1 %) M . himalayana faecal samples were positive for the presence of genetically diverse AstVs while only HHMAstV1 and HHMAstV2 were identified in 300 liver samples. The complete genomic sequences of HHMAstV1 and HHMAstV2 were 6681 and 6610 nt in length respectively with the typical genomic organization of AstVs. Analysis of the complete ORF 2 sequence showed that these novel AstVs are most closely related to the rabbit AstV mamastrovirus 23 (with 31.0 and 48.0 % shared amino acid identity respectively). Phylogenetic analysis of the amino acid sequences of ORF1a ORF1b and ORF2 indicated that HHMAstV1 and HHMAstV2 form two distinct clusters among the mamastroviruses and may share a common ancestor with the rabbit-specific mamastrovirus 23. These results suggest that HHMAstV1 and HHMAstV2 are two novel species of the genus Mamastrovirus in the Astroviridae. The remarkable diversity of these novel AstVs will contribute to a greater understanding of the evolution and ecology of AstVs although additional studies will be needed to understand the clinical significance of these novel AstVs in marmots as well as in humans.
Characterization of the new GII.17 norovirus variant that emerged recently as the predominant strain in China
Human noroviruses are the most important viral pathogens causing epidemic acute gastroenteritis in which the GII.4 viruses have been predominant worldwide for the past decades. During 2014–2015 winter season a new GII.17 variant emerged as the predominant virus in China surpassing the GII.4 virus in causing significantly increased acute gastroenteritis outbreaks. Genome sequences of the new GII.17 variant was determined and compared with other GII.17 noroviruses revealing residue substitutions at specific locations including the histo-blood group antigen-binding site and the putative antigenic epitopes. Further study of GII.17 outbreaks focusing on host susceptibility showed that the new GII.17 variant infected secretor individuals of A B O and Lewis types. Accordingly the P particles of the new GII.17 variant bound secretor saliva samples of A B O and Lewis types with significantly higher binding signals than those of the P particles of the previous GII.17 variants. In addition human sera collected from the outbreaks exhibited stronger blockade against the binding of the new GII.17 P particles to saliva samples than those against the binding between the P particles of previous GII.17 variants and saliva samples. Taken together our data strongly suggested that the new GII.17 variant gained new histo-blood group antigen-binding ability and antigenic features which may contribute to its predominance in causing human norovirus epidemics.