No crucial amino acid changes in the predicted histo blood group antigen-binding sites of norovirus genotype GII.4 capsid between non-secretors and secretors origin might suggest an alternative route of infection or existence of coincidental molecules

Clinical specimens from paediatric acute gastroenteritis patients were examined for evidence of norovirus (NoV) infection as well as their secretor status. Secretors express ABH histo blood group antigens (HBGAs) on the intestinal epithelium and in secretions (saliva, gastric juice, etc.), whilst non-secretors do not. In cases of NoV infection, the detected virus was genotyped according to the nucleic acid sequence of the capsid N-terminal region. The percentages of non-secretors in all infected patients in major genotypes of NoV (GII.2, GII.3, GII.4 and GII.6) varied from 5.7 to 25 %. As two non-secretors were infected with GII.4 NoV clade 2006b, detailed analysis of the main structural protein (capsid protein) was conducted. When the amino acid residues of these specific viruses were compared with four viruses of the same clade obtained from secretors and the outbreak, one virus had two unique amino acids and another had three. However, no common differences were noted between these two viruses. In addition, the predicted HBGA-binding sites (conserved sites) and putative variantspecific epitopes that were recognized by generated human mAbs (that block carbohydrate binding) were also examined. However, no crucial characteristic amino acid changes in the strains from nonsecretors were observed. Nevertheless, these preliminary findings might suggest an alternative route of infection or existence of coincidental molecules.