Intestinal colonization with Escherichia fergusonii enhances infectivity of GII.12 human norovirus in gnotobiotic pigs

The role of gut microbiota [especially, histo-blood group antigen (HBGA)-expressing bacteria] in influencing human norovirus (HuNoV) infections is unclear. We investigated if infectivity of GII.12 HuNoV in gnotobiotic (Gn) pigs is altered by intestinal colonization with Escherichia fergusonii known to express HBGA A and H on their cell surface. Fifteen piglets were randomly grouped: (1) E. fergusonii + HuNoV (n = 6), (2) HuNoV alone (n = 6), and (3) Mock-inoculated (n = 3). Pigs (8-11-day-old) were inoculated orally with GII.12 HuNoV strain HS206 (9.5 log10 genomic equivalents/pig) or mock. For 2 days prior to viral inoculation, pigs were inoculated orally with E. fergusonii [8 log10 colony forming units/pig/day]. Daily fecal consistency, fecal viral RNA or E. fergusonii shedding, and histopathology (at euthanasia) were evaluated. Unlike the reduced infectivity of GII.4 HuNoV observed previously in Gn pigs colonized with Enterobacter cloacae known to express HBGA A, B, and H on the surface, E. fergusonii + HuNoV pigs exhibited significantly higher cumulative fecal HuNoV RNA shedding at PIDs 6-14 and 1-21 compared with HuNoV alone pigs. Mean days of fecal HuNoV RNA shedding were also significantly greater in E. fergusonii + HuNoV pigs (11.8 ± 1.6 days) compared with HuNoV alone pigs (7.0 ± 1.0 days). By immunofluorescent staining, HuNoV antigen-positive bacteria were detected on the surface of the intestinal epithelium, possibly enhancing attachment of HuNoV to enterocytes, suggesting a potential mechanism by which intestinal colonization with E. fergusonii promoted infectivity of GII.12 HuNoV in Gn pigs.

Histo-blood group antigen profile of Australian Aboriginal children and seropositivity following oral rotavirus vaccination

BACKGROUND

Histo-blood group antigens (HBGAs) may influence immune responses to rotavirus vaccination.

METHODS

HBGA phenotyping was determined by detection of antigens A, B, H and Lewis a and b in saliva using enzyme-linked immunosorbent assay. Secretor status was confirmed by lectin antigen assay if A, B and H antigens were negative or borderline (OD ± 0.1 of threshold of detection). PCR-RFLP analysis was used to identify the FUT2 'G428A' mutation in a subset. Rotavirus seropositivity was defined as serum anti-rotavirus IgA ≥ 20 AU/mL.

RESULTS

Of 156 children, 119 (76 %) were secretors, 129 (83 %) were Lewis antigen positive, and 105 (67 %) were rotavirus IgA seropositive. Eighty-seven of 119 (73 %) secretors were rotavirus seropositive, versus 4/9 (44 %) weak secretors and 13/27 (48 %) non-secretors.

CONCLUSIONS

Most Australian Aboriginal children were secretor and Lewis antigen positive. Non-secretor children were less likely to be seropositive to rotavirus antibodies following vaccination, but this phenotype was less common. HBGA status is unlikely to fully explain underperformance of rotavirus vaccines among Australian Aboriginal children.

Structural and functional characterization of bovine G1P[5] rotavirus VP8* protein

The widely used rotavirus (RV) vaccine, Rotateq, contained reassortment strains of human and bovine G1/2/3/4P[5] RVs. The functional and structural features of bovine G1P[5] VP8* were investigated. Bovine G1P[5] VP8* was identified to interact with sialic acids and sialic acid-containing glycans. In addition, P[5] VP8* recognized α-Gal histo-blood group antigens (HBGAs). Bovine G1P[5] VP8* did not hemagglutinate the tested red blood cells. The crystal structure of P[5] VP8* was determined at 1.7 Å. Structural superimposition revealed that P[5] VP8* was most close to human P[8] VP8*, while much further to VP8*s of porcine P[7] and rhesus P[3]. Sequence alignment showed that amino acids of the putative glycan binding site in P[5] VP8* were different to those in P[3]/P[7] VP8*s, indicating that P[5] VP8* may interact with glycans using different mechanism. This study provided more understanding of P[5] RV infection and the interactions of RV VP8* and glycans.

Relationship Between Rotavirus P[6] Infection in Korean Neonates and Histo-Blood Group Antigen: a Single-Center Study

Background

Rotaviruses are a major cause of pediatric gastroenteritis. The rotavirus P[6] genotype is the most prevalent genotype isolated from Korean neonates but has rarely been reported in other countries. Histo-blood group antigen (HBGA) is known to play an important role in rotavirus infection. We investigated the relationship between rotavirus genotype and HBGA-Lewis blood type in Korean children and explored the reasons for the predominance of rotavirus P[6] strain in Korean neonates.

Methods

Blood and stool samples were collected from 16 rotavirus-infected patients. Rotavirus G (VP7) and P (VP4) genotyping was performed using reverse transcription-PCR and sequencing. Lewis antigen phenotypes (Le^a/Le^b) were tested, and HBGA-Lewis genotype was determined by sequencing the secretor (FUT2) and Lewis (FUT3) genes. Deduced amino acid sequences and three-dimensional structures of the VP8* portion of the rotavirus VP4 protein were analyzed.

Results

All P[6] rotaviruses were isolated from neonates under one month of age, who were negative or weakly positive for the Le^b antigen. However, 10 of the 11 non-P[6] rotaviruses were isolated from older children who were Le^b antigen-positive. The VP8* amino acid sequences differed among P[6], P[4], and P[8] genotypes. Korean P[6] strains showed a unique VP8* sequence with amino acid substitutions, including Y169 > L169, which differed from the sequences of P[6] strains from other countries.

Conclusions

The predominance of the rotavirus P[6] genotype in Korean neonates may be related to the interaction between HBGA-Lewis antigen and the VP8* portion of the VP4 protein, and this information will be helpful in future neonatal vaccine development.

ELISA-Based Methods to Detect and Quantify Norovirus Virus-Like Particle Attachment to Histo-Blood Group Antigens

Histo-blood group antigen (HBGA) recognition by norovirus (NoV) has been studied using various techniques. Enzyme-linked immunosorbent assays (ELISAs) using virus-like particles (VLPs) have enabled us to visualize the last step of HBGAs-NoV binding with a total reaction time of approximately 8 h. Herein, we describe two ELISA-based methods to detect and quantify NoV VLP attachment to HBGAs: saliva-VLP binding assay and carbohydrate-VLP binding assay.

Phylogenetic and biological characterizations of a GI.3 norovirus

Noroviruses (NoVs) are a major cause of acute non-bacterial gastroenteritis worldwide. In this study, we report the isolation, near-complete genome sequencing, and expression and biological characterization of the major capsid protein (VP1) of a GI.3 NoV isolated from a child presenting acute gastroenteritis. The genome of the GI.3 NoV is 7746 bp in length, not including the poly-adenylation tail. Phylogenetic analysis based on the complete VP1 nucleotide sequences indicates that GI.3 NoVs could be divided into four clusters, with 4.6%, 5.3%, 6.6%, 1.9% intracluster variations in nucleotide and 4.8%, 3.8%, 6.1%, 1.7% intracluster variations in amino acid sequences, respectively. A Bayesian evolutionary analysis showed that GI.3 NoVs evolved at 2.44 × 10^-3, 2.78 × 10^-3, and 3.04 × 10^-3 nucleotide substitutions/site/year using a strict clock model, an uncorrelated log-normal model (UCLN), and an uncorrelated exponential derivation model (UCED), respectively. VP1 protein expression using a recombinant baculovirus expression system leads to the successful assembly of virus-like particles (VLPs). In vitro VLP-Histo-blood group antigen (HBGA) binding assay indicates that GI.3 NoV VLPs strongly bind to blood type A salivary HBGAs, moderately bind to blood type O salivary HBGAs, and weakly bind or do not bind to blood type B and AB salivary HBGAs. In vitro VLP-HBGA binding blockade assay indicated that the binding of GI.3 NoV VLPs to blood type A salivary HBGAs could only be blocked by anti-GI.3 NoV VLPs serum but not non-GI.3 NoV genotype-specific hyperimmune sera (GI.2, GI.7, GII.4, GII.6, GII.7, and GII.17). The detailed characterization of GI.3 NoV in this study provides evidence that GI.3 NoV undergoes rapid evolution and exhibits no cross-blocking effects, suggesting that GI.3 NoV may potentially be utilized in the development of multivalent NoV vaccines.

Presence and Distribution of Histo-Blood Group Antigens in Pacific Oysters and the Effects of Exposure to Noroviruses GI.3 and GII.4 on Their Expression

Noroviruses (NoVs) are one of the most important foodborne viral pathogens worldwide. Oysters are common carriers of NoVs and are responsible for their transmission. NoVs recognize human histo-blood group antigens (HBGAs) as receptors. Recent studies indicate that HBGA-like molecules also exist in oyster tissues and that they may play a key role in the binding of NoVs. However, the mechanism by which different genotypes of NoV accumulate in different oyster tissues is unknown. In this study, the presence and distribution of different types of HBGA-like molecules were evaluated in 240 oysters collected from the Shandong Peninsula of People's Republic of China for 1 year. The HBGA-like molecules were detected at various rates and expressed at different levels in different tissues. Immunohistochemistry confirmed the diversity of HBGA-like molecules in four oyster tissues. Eight types of HBGA-like molecules (types A, B, H1, Lewis x, Lewis y, Lewis a, Lewis b, and precursor) were assessed in different tissues. Of these, the type A HBGA-like molecule was consistently expressed in the gills, digestive tissue, and mantle, while types H1 and Lewis b HBGA-like molecules were expressed in the digestive tissues. The expression of HBGA-like molecules in response to the NoV challenge was investigated. The levels of types A, H1, and Lewis x increased significantly in specific oyster tissues after exposure to genogroup II, genotype 4 (GII.4) or genogroup I, genotype 3 (GI.3) NoV. The real-time reverse transcription PCR assays indicated that GI.3 NoV mainly accumulated in the digestive tissues of oysters, whereas GII.4 NoV accumulated in the gills, mantle, and digestive tissues. These results provide new insights into the mechanism of NoV bioaccumulation in oysters and suggest that NoV accumulation in oysters may be related to the expression of HBGA-like molecules.

Bacterial histo-blood group antigens contributing to genotype-dependent removal of human noroviruses with a microfiltration membrane

We demonstrated the genotype-dependent removal of human norovirus particles with a microfiltration (MF) membrane in the presence of bacteria bearing histo-blood group antigens (HBGAs). Three genotypes (GII.3, GII.4, and GII.6) of norovirus-like particles (NoVLPs) were mixed with three bacterial strains (Enterobacter sp. SENG-6, Escherichia coli O86:K61:B7, and Staphylococcus epidermidis), respectively, and the mixture was filtered with an MF membrane having a nominal pore size of 0.45 μm. All NoVLP genotypes were rejected by the MF membrane in the presence of Enterobacter sp. SENG-6, which excreted HBGAs as extracellular polymeric substances (EPS). This MF membrane removal of NoVLPs was not significant when EPS was removed from cells of Enterobacter sp. SENG-6. GII.6 NoVLP was not rejected with the MF membrane in the presence of E. coli O86:K61:B7, but the removal of EPS of E. coli O86:K61:B7 increased the removal efficiency due to the interaction of NoVLPs with the exposed B-antigen in lipopolysaccharide (LPS) of E. coli O86:K61:B7. No MF membrane removal of all three genotypes was observed when S. epidermidis, an HBGA-negative strain, was mixed with NoVLPs. These results demonstrate that the location of HBGAs on bacterial cells is an important factor in determining the genotype-dependent removal efficiency of norovirus particles with the MF membrane. The presence of HBGAs in mixed liquor suspended solids from a membrane bioreactor (MBR) pilot plant was confirmed by immune-transmission electron microscopy, which implies that bacterial HBGAs can contribute to the genotype-dependent removal of human noroviruses with MBR using MF membrane.

The expanding roles of the Sd(a)/Cad carbohydrate antigen and its cognate glycosyltransferase B4GALNT2

BACKGROUND

The histo-blood group antigens are carbohydrate structures present in tissues and body fluids, which contribute to the definition of the individual immunophenotype. One of these, the Sd(a) antigen, is expressed on the surface of erythrocytes and in secretions of the vast majority of the Caucasians and other ethnic groups.

SCOPE OF REVIEW

We describe the multiple and unsuspected aspects of the biology of the Sd(a) antigen and its biosynthetic enzyme β1,4-N-acetylgalactosaminyltransferase 2 (B4GALNT2) in various physiological and pathological settings.

MAJOR CONCLUSIONS

The immunodominant sugar of the Sd(a) antigen is a β1,4-linked N-acetylgalactosamine (GalNAc). Its cognate glycosyltransferase B4GALNT2 displays a restricted pattern of tissue expression, is regulated by unknown mechanisms - including promoter methylation, and encodes at least two different proteins, one of which with an unconventionally long cytoplasmic portion. In different settings, the Sd(a) antigen plays multiple and unsuspected roles. 1) In colon cancer, its dramatic down-regulation plays a potential role in the overexpression of sialyl Lewis antigens, increasing metastasis formation. 2) It is involved in the lytic function of murine cytotoxic T lymphocytes. 3) It prevents the development of muscular dystrophy in various dystrophic murine models, when overexpressed in muscular fibers. 4) It regulates the circulating half-life of the von Willebrand factor (vWf), determining the onset of a bleeding disorder in a murine model.

GENERAL SIGNIFICANCE

The expression of the Sd(a) antigen has a wide impact on the physiology and the pathology of different biological systems.