Secretors of HBGA and Susceptibility to Norovirus and Rotavirus Diarrhea

Viral gastroenteritis

Since the discovery of norovirus in 1972 as a cause of what was contemporarily known as acute infectious non-bacterial gastroenteritis, scientific understanding of the viral gastroenteritides has continued to evolve. It is now recognised that a small number of viruses are the predominant cause of acute gastroenteritis worldwide, in both high-income and low-income settings. Although treatment is still largely restricted to the replacement of fluid and electrolytes, improved diagnostics have allowed attribution of illness, enabling both targeted treatment of individual patients and prioritisation of interventions for populations worldwide. Questions remain regarding specific genetic and immunological factors underlying host susceptibility, and the optimal clinical management of patients who are susceptible to severe or prolonged manifestations of disease. Meanwhile, the worldwide implementation of rotavirus vaccines has led to substantial reductions in morbidity and mortality, and spurred interest in vaccine development to diminish the impact of the most prevalent viruses that are implicated in this syndrome.

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.

Microbiota-induced regulatory T cells associate with FUT2-dependent susceptibility to rotavirus gastroenteritis

The FUT2 α1,2fucosyltransferase contributes to the synthesis of fucosylated glycans used as attachment factors by several pathogens, including noroviruses and rotaviruses, that can induce life-threatening gastroenteritis in young children. FUT2 genetic polymorphisms impairing fucosylation are strongly associated with resistance to dominant strains of both noroviruses and rotaviruses. Interestingly, the wild-type allele associated with viral gastroenteritis susceptibility inversely appears to be protective against several inflammatory or autoimmune diseases for yet unclear reasons, although a FUT2 influence on microbiota composition has been observed. Here, we studied a cohort of young healthy adults and showed that the wild-type FUT2 allele was associated with the presence of anti-RVA antibodies, either neutralizing antibodies or serum IgA, confirming its association with the risk of RVA gastroenteritis. Strikingly, it was also associated with the frequency of gut microbiota-induced regulatory T cells (Tregs), so-called DP8α Tregs, albeit only in individuals who had anti-RVA neutralizing antibodies or high titers of anti-RVA IgAs. DP8α Tregs specifically recognize the human symbiont Faecalibacterium prausnitzii, which strongly supports their induction by this anti-inflammatory bacterium. The proportion of F. prausnitzii in feces was also associated with the FUT2 wild-type allele. These observations link the FUT2 genotype with the risk of RVA gastroenteritis, the microbiota and microbiota-induced DP8α Treg cells, suggesting that the anti-RVA immune response might involve an induction/expansion of these T lymphocytes later providing a balanced immunological state that confers protection against inflammatory diseases.

Histo-blood group antigens and rotavirus vaccine virus shedding in Australian infants

Rotavirus vaccine performance varies between high and low income countries. One possible explanation is inherited histo-blood group antigens (HBGAs) the expression of which differs between populations. HBGAs are polymorphic glycans on mucosal surfaces. Their presence indicates the secretor phenotype, while their absence identifies a non-secretor status. HBGAs can act as rotavirus receptors and might influence live-attenuated rotavirus vaccine virus replication and shedding. Studies in low and middle income countries of the human rotavirus vaccine Rotarix (RV1), suggest HBGA secretor phenotype is important for vaccine immunogenicity. We investigated in a high income country the association between HBGA phenotype (secretor and Lewis) and the bovine-human reassortment vaccine RotaTeq (RV5) vaccine shedding in the stools of infants following each vaccine dose. Eighty-two infants from an Australian birth cohort provided saliva and weekly stool samples after RV5 vaccination doses. Lewis and secretor HBGA phenotyping was identified from saliva samples and confirmed by genotyping. Vaccine virus strains were detected by real-time polymerase chain reaction assays. No significant association between secretor status and vaccine virus shedding was identified. The proportion of infants who shed rotavirus following the first RV5 dose for secretor and non-secretor infants was 57/64 (89%) and 17/18 (94%), respectively, decreasing to 24/64 (33%) and 9/18 (50%) after the second dose and 26/64 (42%) and 8/18 (44%) following the third vaccine dose, respectively. Similarly, no significant differences were observed in vaccine virus shedding by Lewis, or combined Lewis and secretor status, after each vaccine dose. We found HBGAs were not associated with RV5 vaccine virus shedding in Australian infants.