Purpose: This study aims to investigate if the HBGA-expressing bacteria have any protective role on NoV before causing infection.
Methods: Twelve bacteria strains were included belonging to Enterobacter cloacae, Enterobacter aerogenes, Escherichia coli, Clostridium difficile, Bifidobacterium adolescentis, Bifidobacterium longum, and Campylobacter jejuni. The HBGA expression of the bacteria as well as the binding of human NoV virus like particles (VLPs, GI.1 and GII.4 strains) to the bacteria were identified by flow cytometry using the corresponding antibodies. NoV VLPs pre-incubated with HBGA expressing or non-HBGA expressing bacteria were heated and detected by both porcine gastric mucin-binding assay and direct ELISA.
Results: The NoV-binding abilities of the bacteria correlated well with their HBGA expression profiles. Two HBGA expressing E. coli (LMG8223, and self-isolated strain 861, both GI.1 and GII.4 binders) and one non-HBGA expressing E.coli (ATCC 8739, neither GI.1 or GII.4 binder) were selected for the heat treatment test with NoV VLPs. As a result, compared with the same cell numbers of non-HBGA expressing E. coli, the presence of HBGA-expressing E. coli could always maintain higher mucin-binding ability (higher OD values of mucin-binding assay) as well as antigen integrity (higher OD values of direct ELISA) for NoV VLPs of both GI.1 and GII.4 after heat-treatment at 95°C for 2 min.
Significance: These results indicate that HBGA-expressing bacteria may protect NoVs during the food processing treatments and possibly in the human gastrointestinal tract before causing infection, which has to be further investigated in the future.