To clarify the binding characteristics of human norovirus (HuNoV) with histo-blood group antigens (HBGAs)-like substances from Pacific oysters, this study used an Escherichia coli expression system to clone and express HuNoV GI.5 and GII.4 P proteins, and analyzed the binding characteristics of HuNoV P proteins with salivary HBGAs and HBGAs-like substances from Pacific oysters using enzyme-linked immunosorbent assay. The results showed that HuNoV GII.4 exhibited good binding characteristics with blood type A, B, AB, and O salivary HBGAs, while GI.5 HuNoV exhibited weak binding characteristics with blood type B salivary HBGAs but had significant advantage in binding with type O salivary HBGAs. HuNoV GI.5 and GII.4 could be bioaccumulated in the gills, digestive gland, and mantle of Pacific oysters, with the highest bioaccumulation in the digestive gland. Both types of HuNoV were mainly bound to type A and H1 HBGAs-like substances; HuNoV GII.4 had different degrees of binding with type Lea, Leb, Lex, and Ley HBGAs-like substances, while HuNoV GI.5 had weak binding with type Leb HBGAs-like substances but significant advantage in binding with type H1 HBGAs-like substances. In summary, different types of HuNoV have different binding characteristics with HBGAs or HBGAs-like substances. Specifically, HuNoV GII.4 shows broad-spectrum binding characteristics whereas HuNoV GI.5 shows selective binding characteristics.

Alginate oligosaccharides (AOS) are low molecular mass linear polymers containing 2–10 monosaccharides obtained by the degradation of alginate. They have various bioactivities including anti-inflammatory, antibacterial, antioxidant, antitumor, and immunomodulation. Thus, AOS have a wide range of applications in the fields of medicine, food, feed and agriculture. The bioactivity of AOS is closely related to its structure, including mode of degradation, degree of polymerization, ratio of mannuronic acid to guluronic acid, non-reducing end structure, and modification. Directed enzymatic degradation of alginate produces functional AOS with specific monomer composition and polymerization degree. Furthermore, the sources, properties and reaction conditions of enzymes affect the product distribution. In this article, the enzymatic preparation of functional AOS and its influential factors are systematically reviewed, and the structure-function relationship of functional AOS is discussed. It is expected that this review will provide a theoretical reference for the directed preparation and application of AOS.