Molecular epidemiology of norovirus GII.15 in Qingdao City

Abstract

Objective To analyze the molecular epidemiology of norovirus (NoV) genotype GⅡ.15 in Qingdao City. Methods One thousand four hundred and twelve stool samples were collected from suspected NoV infected patients and detected by real-time polymerase chain reaction (PCR). Open reading frame (ORF)1-ORF2 and VP1 gene were amplified by reverse transcription (RT)-PCR and sequenced for genotyping, evolutionary analysis and homology modeling. Results Seven cases of GⅡ.15 type were detected including four sporadic cases and one outbreak.The VP1 gene was highly homologous and had little variation compared with early strain J23/US/1999. The differences of amino acids between strains in Qingdao City were mainly asparagine/asparticacid(N/D)300 and proline/serine(P/S)302.Homology modeling suggested that VP1 of GⅡ.15 strain was composed of S domain and P domain (P1 subdomain included 224-276 and 431-555, P2 subdomain included 277-430). S domain contained eight anti-parallel β-sandwiches and two α-helixes, and P1 subdomain contained one α-helix and seven β-strands, and the P2 subdomain folded into a compact barrel-like structure consisting of six β-strands.Argnine (R)-glycine (G)-valine (V)-motif (289-291) and three specific loci including glutarnine (Q)313, asparagine (N)349 and Q389 were located in the P2 subdomain, with NGR-motif (265-267) located at 22nd upstream of RGV-motif.Site I (SNR-alanine(A)- histidine(H)357-361), Site Ⅱ (D388) and Site Ⅲ (G454, G455) were the main characteristic sites of histo-blood group antigens (HBGA) binding interface, which may be similar to the binding pattern of GⅡ.4 type VA387 and HBGA. Conclusion Although GⅡ.15 type NoV evolves very slowly, it may still have the risk to become an epidemic strain, which needs to be monitored and further studied. Key words: Norovirus GⅡ.15; Epidemiology, molecular