Norwalk virus infection associates with secretor status genotyped from sera

ABO histo-blood group type and secretor status are two genetically determined factors that contribute to resistance and susceptibility to Norwalk virus (NV). Archived serum samples but not saliva samples are available from NV and many other norovirus challenge studies and outbreaks. A person's ABO phenotype is easily determined from their archived sera, but the individual's secretor phenotype cannot easily be ascertained without saliva. We now report that a person's secretor genotype can also be determined from the archived serum samples. Of the 51 volunteers who participated in a NV challenge study, all eight non-secretors were resistant to NV infection, all of the 42 NV-infected volunteers were secretor positive, and a single uninfected secretor was histo-blood group type B. In agreement with a previous report, secretor status was most predictive of risk of NV infection. The methods described in this report should rapidly improve our knowledge of the associations between carbohydrate antigen expression and susceptibility to different strains of the non-cultivatable noroviruses by enabling retrospective studies from previously collected volunteer challenge and outbreak sera.