Intestinal norovirus binding patterns in non-secretor individuals

Human norovirus (HuNoV) infection is associated with active FUT2 status, which characterizes the secretor phenotype. However, non-secretor individuals are also affected by HuNoV infection although in a lesser proportion. Here, we study GII.3, GII.4 and GII.17 HuNoV interactions in non-secretor individuals using baculovirus-expressed virus-like particles (VLPs). Only GII.4 HuNoV specifically interacted with non-secretor saliva. Competition experiments using HBGA-specific mAbs demonstrate that GII.4 VLPs recognized the Lewis a antigen (Lea). We also analyzed HuNoV VLP interactions on duodenum tissue blocks from healthy non-secretor individuals. VLP binding was observed for the three HuNoV genotypes in 10 of the 13 individuals, and competition experiments demonstrated that VLP recognition was driven by interaction with the Lea antigen. In 3 individuals, binding was restricted to either GII.4 alone or GII.3 and GII.17. One patient did not display VLP binding for any of the three genotypes. Finally, we performed a VLP binding assay on proximal and distal colon tissue blocks from a non-secretor patient with Crohns disease. VLP binding to inflammatory tissues was genotype-specific since GII.4 and GII.17 VLPs were able to interact with regenerative mucosa whereas GII.3 VLP was not. Binding of GII.4 and GII.17 HuNoV VLPs was linked to Lea in regenerative mucosae from the proximal and distal colon. Overall, our data clearly showed that Lea has a pivotal role in the recognition of HuNoV in non-secretors. We also showed that Lea is expressed in inflammatory/regenerative tissues and that it can interact with HuNoV in secretor and non-secretor individuals. The physiological and immunological consequences of such interactions in non-secretors has yet to be elucidated. IMPORTANCEHuman norovirus (HuNoV) is the main etiological agent of viral gastroenteritis in all age classes. HuNoV infection mainly affects secretor individuals, who are characterized by the presence of the ABO(H) and Lewis histo-blood group antigens at the surface of the small intestine. Non-secretor individuals, who only express Lewis antigens (Le), are less susceptible to HuNoV infection. Here we study the interaction of three frequently encountered HuNoV genotypes (GII.3, GII.4 and GII.17) in non-secretor individual using baculovirus-expressed viral particles. Preliminary saliva binding assays showed that only GII.4 interacted with non-secretor saliva via the Lea antigen. Surprisingly, in the binding assays on duodenal tissue blocks, the three genotypes interacted with non-secretor enterocytes via Lea. This suggests that HBGA status in the saliva does not necessarily reflect interactions in the intestines and, secondly, that Lea plays a pivotal role in HuNoV attachment in non-secretors. Similarly, Lea was involved in the recognition of GII.4 and GII.17 HuNoV particles by inflammatory colon tissue from a non-secretor Crohns disease patient. The molecular implications of HuNoV binding in non-secretors remains to be elucidated in physiological and pathological conditions encountered in other intestinal diseases.