A FUT2 gene common polymorphism determines resistance to rotavirus A of the P[8] genotype

Vaccine Take of RV3-BB Rotavirus Vaccine Observed in Indonesian Infants Regardless of HBGA Status

BACKGROUND

Histo-blood group antigen (HBGA) status may affect vaccine efficacy due to rotavirus strains binding to HBGAs in a P genotype-dependent manner. This study aimed to determine if HBGA status affected vaccine take of the G3P[6] neonatal vaccine RV3-BB.

METHODS

DNA was extracted from stool samples collected in a subset (n = 164) of the RV3-BB phase IIb trial in Indonesian infants. FUT2 and FUT3 genes were amplified and sequenced, with any single-nucleotide polymorphisms analyzed to infer Lewis and secretor status. Measures of positive cumulative vaccine take were defined as serum immune response (immunoglobulin A or serum-neutralizing antibody) and/or stool excretion of RV3-BB virus. Participants were stratified by HBGA status and measures of vaccine take.

RESULTS

In 147 of 164 participants, Lewis and secretor phenotype were determined. Positive vaccine take was recorded for 144 (97.9%) of 147 participants with the combined phenotype determined. Cumulative vaccine take was not significantly associated with secretor status (relative risk, 1.00 [95% CI, .94-1.06]; P = .97) or Lewis phenotype (relative risk, 1.03 [95% CI, .94-1.14]; P = .33), nor was a difference observed when analyzed by each component of vaccine take.

CONCLUSIONS

The RV3-BB vaccine produced positive cumulative vaccine take, irrespective of HBGA status in Indonesian infants.

Genotypes predisposing for celiac disease and autoimmune diabetes and risk of infections in early childhood

OBJECTIVES

Infections in early childhood have been associated with risk of celiac disease (CD) and type 1 diabetes (T1D). We investigated whether this is driven by susceptibility genes for autoimmune disease by comparing infection frequency by genetic susceptibility variants for CD or T1D.

METHODS

We genotyped 373 controls and 384 children who developed CD or T1D in the population-based Norwegian Mother, Father and Child Cohort study (MoBa) study for human leukocyte antigen (HLA)-DQ, FUT2, SH2B3, and PTPN22, and calculated a weighted non-HLA genetic risk score (GRS) for CD and T1D based on over 40 SNPs. Parents reported infections in questionnaires when children were 6 and 18 months old. We used negative binomial regression to estimate incidence rate ratio (IRR) for infections by genotype.

RESULTS

HLA genotypes for CD and T1D or non-HLA GRS for T1D were not associated with infections. The non-HLA GRS for CD was associated with a nonsignificantly lower frequency of infections (aIRR: 0.95, 95% CI: 0.87-1.03 per weighted allele score), and significantly so when restricting to healthy controls (aIRR: 0.89, 0.81-0.99). Participants homozygous for rs601338(A;A) at FUT2, often referred to as nonsecretors, had a nonsignificantly lower risk of infections (aIRR: 0.91, 95% CI: 0.83-1.01). SH2B3 and PTPN22 genotypes were not associated with infections. The association between infections and risk of CD (OR: 1.15 per five infections) was strengthened after adjustment for HLA genotype and non-HLA GRS (OR: 1.24).

CONCLUSIONS

HLA variants and non-HLA GRS conferring susceptibility for CD were not associated with increased risk of infections in early childhood and is unlikely to drive the observed association between infections and risk of CD or T1D in many studies.

Culture of Human Rotaviruses in Relevant Models Shows Differences in Culture-Adapted and Nonculture-Adapted Strains

Rotavirus (RV) is the leading cause of acute gastroenteritis (AGE) in children under 5 years old worldwide, and several studies have demonstrated that histo-blood group antigens (HBGAs) play a role in its infection process. In the present study, human stool filtrates from patients diagnosed with RV diarrhea (genotyped as P[8]) were used to infect differentiated Caco-2 cells (dCaco-2) to determine whether such viral strains of clinical origin had the ability to replicate in cell cultures displaying HBGAs. The cell culture-adapted human RV Wa model strain (P[8] genotype) was used as a control. A time-course analysis of infection was conducted in dCaco-2 at 1, 24, 48, 72, and 96 h. The replication of two selected clinical isolates and Wa was further assayed in MA104, undifferentiated Caco-2 (uCaco-2), HT29, and HT29-M6 cells, as well as in monolayers of differentiated human intestinal enteroids (HIEs). The results showed that the culture-adapted Wa strain replicated more efficiently in MA104 cells than other utilized cell types. In contrast, clinical virus isolates replicated more efficiently in dCaco-2 cells and HIEs. Furthermore, through surface plasmon resonance analysis of the interaction between the RV spike protein (VP8*) and its glycan receptor (the H antigen), the V7 RV clinical isolate showed 45 times better affinity compared to VP8* from the Wa strain. These findings support the hypothesis that the differences in virus tropism between clinical virus isolates and RV Wa could be a consequence of the different HBGA contents on the surface of the cell lines employed. dCaco-2, HT29, and HT29M6 cells and HIEs display HBGAs on their surfaces, whereas MA104 and uCaco-2 cells do not. These results indicate the relevance of using non-cell culture-adapted human RV to investigate the replication of rotavirus in relevant infection models.

Elucidating the conformational dynamics of histo-blood group antigens and their interactions with the rotavirus spike protein through computational lens

In the present study, we investigated the conformational dynamics of histo-blood group antigens (HBGAs) and their interactions with the VP8* domain of four rotavirus genotypes (P[4], P[6], P[19], and P[11]) utilizing all-atom molecular dynamics simulations in explicit water. Our study revealed distinct changes in the dynamic behavior of the same glycan due to linkage variations. We observed that LNFPI HBGA having a terminal β linkage shows two dominant conformations after complexation, whereas only one was obtained for LNFPI with a terminal α linkage. Interestingly, both variants displayed a single dominant structure in the free state. Similarly, LNT and LNnT show a shift in their dihedral linkage profile between their two terminal monosaccharides because of a change in the linkage from β(1-3) to β(1-4). The molecular mechanics generalized Born surface area (MM/GBSA) calculations yielded the highest binding affinity for LNFPI(β)/P[6] (-13.93 kcal/mol) due to the formation of numerous hydrogen bonds between VP8* and HBGAs. LNnT binds more strongly to P[11] (-12.88 kcal/mol) than LNT (-4.41 kcal/mol), suggesting a single change in the glycan linkage might impact its binding profile significantly. We have also identified critical amino acids and monosaccharides (Gal and GlcNAc) that contributed significantly to the protein-ligand binding through the per-residue decomposition of binding free energy. Moreover, we found that the interaction between the same glycan and different protein receptors within the same rotavirus genogroup influenced the micro-level dynamics of the glycan. Overall, our study helps a deeper understanding of the H-type HBGA and rotavirus spike protein interaction.Communicated by Ramaswamy H. Sarma.

Genome-wide association study of chronic sputum production implicates loci involved in mucus production and infection

BACKGROUND

Chronic sputum production impacts on quality of life and is a feature of many respiratory diseases. Identification of the genetic variants associated with chronic sputum production in a disease agnostic sample could improve understanding of its causes and identify new molecular targets for treatment.

METHODS

We conducted a genome-wide association study (GWAS) of chronic sputum production in UK Biobank. Signals meeting genome-wide significance (p<5×10-8) were investigated in additional independent studies, were fine-mapped and putative causal genes identified by gene expression analysis. GWASs of respiratory traits were interrogated to identify whether the signals were driven by existing respiratory disease among the cases and variants were further investigated for wider pleiotropic effects using phenome-wide association studies (PheWASs).

RESULTS

From a GWAS of 9714 cases and 48 471 controls, we identified six novel genome-wide significant signals for chronic sputum production including signals in the human leukocyte antigen (HLA) locus, chromosome 11 mucin locus (containing MUC2, MUC5AC and MUC5B) and FUT2 locus. The four common variant associations were supported by independent studies with a combined sample size of up to 2203 cases and 17 627 controls. The mucin locus signal had previously been reported for association with moderate-to-severe asthma. The HLA signal was fine-mapped to an amino acid change of threonine to arginine (frequency 36.8%) in HLA-DRB1 (HLA-DRB1*03:147). The signal near FUT2 was associated with expression of several genes including FUT2, for which the direction of effect was tissue dependent. Our PheWAS identified a wide range of associations including blood cell traits, liver biomarkers, infections, gastrointestinal and thyroid-associated diseases, and respiratory disease.

CONCLUSIONS

Novel signals at the FUT2 and mucin loci suggest that mucin fucosylation may be a driver of chronic sputum production even in the absence of diagnosed respiratory disease and provide genetic support for this pathway as a target for therapeutic intervention.

Extent of the protection afforded by histo-blood group polymorphism against rotavirus gastroenteritis in metropolitan France and French Guiana

Human rotaviruses attach to histo-blood group antigens glycans and null alleles of the ABO, FUT2 and FUT3 genes seem to confer diminished risk of gastroenteritis. Yet, the true extent of this protection remains poorly quantified. Here, we conducted a prospective study to evaluate the risk of consulting at the hospital in non-vaccinated pediatric patients according to the ABO, FUT2 (secretor) and FUT3 (Lewis) polymorphisms, in Metropolitan France and French Guiana. At both locations, P genotypes were largely dominated by P [8]-3, with P [6] cases exclusively found in French Guiana. The FUT2 null (nonsecretor) and FUT3 null (Lewis negative) phenotypes conferred near full protection against severe gastroenteritis due to P [8]-3 strains (OR 0.03, 95% CI [0.00–0.21] and 0.1, 95% CI [0.01–0.43], respectively in Metropolitan France; OR 0.08, 95% CI [0.01–0.52] and 0.14, 95%CI [0.01–0.99], respectively in French Guiana). Blood group O also appeared protective in Metropolitan France (OR 0.38, 95% CI [0.23–0.62]), but not in French Guiana. The discrepancy between the two locations was explained by a recruitment at the hospital of less severe cases in French Guiana than in Metropolitan France. Considering the frequencies of the null ABO, Secretor and Lewis phenotypes, the data indicate that in a Western European population, 34% (95% CI [29%; 39%]) of infants are genetically protected against rotavirus gastroenteritis of sufficient severity to lead to hospital visit.

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.

The Association between Symptomatic Rotavirus Infection and Histo-Blood Group Antigens in Young Children with Diarrhea in Pretoria, South Africa

OBJECTIVES

Recently, histo-blood group antigens (HBGAs) have been identified as receptors or attachment factors of several viral pathogens. Among rotaviruses, HBGAs interact with the outer viral protein, VP4, which has been identified as a potential susceptibility factor, although the findings are inconsistent throughout populations due to HBGA polymorphisms. We investigated the association between HBGA phenotypes and rotavirus infection in children with acute gastroenteritis in northern Pretoria, South Africa.

METHODS

Paired diarrheal stool and saliva samples were collected from children aged ≤ 59 months (n = 342) with acute moderate to severe diarrhea, attending two health care facilities. Rotaviruses in the stool samples were detected by commercial EIA and the rotavirus strains were characterized by RT-PCR targeting the outer capsid VP7 (G-type) and VP4 (P-type) antigens for genotyping. Saliva-based ELISAs were performed to determine A, B, H, and Lewis antigens for blood group typing.

RESULTS

Blood type O was the most common blood group (62.5%) in this population, followed by groups A (26.0%), B (9.3%), and AB (2.2%). The H1-based secretors were common (82.7%) compared to the non-secretors (17.3%), and the Lewis antigen positive phenotypes (Le^(a+b+)) were predominant (54.5%). Blood type A children were more likely to be infected by rotavirus (38.8%) than any other blood types. P[4] rotaviruses (21/49; 42.9%) infected only secretor individuals, whereas P[6] rotaviruses (3/49; 6.1%) only infected Le^(a-b-), although the numbers were very low. On the contrary, P[8] rotaviruses infected children with a wide range of blood group phenotypes, including Le^(a-b-) and non-secretors.

CONCLUSIONS

Our findings demonstrated that Lewis antigens, or the lack thereof, may serve as susceptibility factors to rotaviral infection by specific VP4 genotypes as observed elsewhere. Potentially, the P[8] strains remain the predominant human VP4 genotype due to their ability to bind to a variety of HBGA phenotypes.

A reverse genetics system for human rotavirus G2P[4]

Rotaviruses (RVs) are an important cause of acute gastroenteritis in young children. Recently, versatile plasmid-based reverse genetics systems were developed for several human RV genotypes; however, these systems have not been developed for all commonly circulating human RV genotypes. In this study, we established a reverse genetics system for G2P[4] human RV strain HN126. Nucleotide sequence analysis, including that of the terminal ends of the viral double-stranded RNA genome, revealed that HN126 possessed a DS-1-like genotype constellation. Eleven plasmids, each encoding 11 gene segments of the RV genome, and expression plasmids encoding vaccinia virus RNA capping enzyme (D1R and D12L), Nelson Bay orthoreovirus FAST, and NSP2 and NSP5 of HN126, were transfected into BHK-T7 cells, and recombinant strain HN126 was generated. Using HN126 or simian RV strain SA11 as backbone viruses, reassortant RVs carrying the outer and intermediate capsid proteins (VP4, VP7 and VP6) of HN126 and/or SA11 (in various combinations) were generated. Viral replication analysis of the single, double and triple reassortant viruses suggested that homologous combination of the VP4 and VP7 proteins contributed to efficient virus infectivity and interaction between other viral or cellular proteins. Further studies of reassortant viruses between simian and other human RV strains will contribute to developing an appropriate model for human RV research, as well as suitable backbone viruses for generation of recombinant vaccine candidates.

Association of histo-blood group antigens and predisposition to gastrointestinal diseases

Infectious gastroenteritis is a common illness afflicting people worldwide. The two most common etiological agents of viral gastroenteritis, rotavirus and norovirus are known to recognize histo-blood group antigens (HBGAs) as attachment receptors. ABO, Lewis, and secretor HBGAs are distributed abundantly on mucosal epithelia, red blood cell membranes, and also secreted in biological fluids, such as saliva, intestinal content, milk, and blood. HBGAs are fucosylated glycans that have been implicated in the attachment of some enteric pathogens such as bacteria, parasites, and viruses. Single nucleotide polymorphisms in the genes encoding ABO (H), fucosyltransferase gene FUT2 (Secretor/Se), FUT3 (Lewis/Le) have been associated with changes in enzyme expression and HBGAs production. The highly polymorphic HBGAs among different populations and races influence genotype-specific susceptibility or resistance to enteric pathogens and its epidemiology, and vaccination seroconversion. Therefore, there is an urgent need to conduct population-based investigations to understand predisposition to enteric infections and gastrointestinal diseases. This review focuses on the relationship between HBGAs and predisposition to common human gastrointestinal illnesses caused by viral, bacterial, and parasitic agents.

Intestinal Norovirus Binding Patterns in Nonsecretor Individuals

Human norovirus (HuNoV) infection is associated with an active FUT2 gene, which characterizes the secretor phenotype. However, nonsecretor individuals are also affected by HuNoV infection although in a lesser proportion. Here, we studied GII.3, GII.4, and GII.17 HuNoV interactions in nonsecretor individuals using virus-like particles (VLPs). Only GII.4 HuNoV specifically interacted with nonsecretor saliva. Competition experiments using histo-blood group antigen (HBGA)-specific monoclonal antibodies (MAbs) demonstrate that GII.4 VLPs recognized the Lewis a (Le^a) antigen. We also analyzed HuNoV VLP interactions on duodenum tissue blocks from healthy nonsecretor 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 an interaction with the Le^a antigen. In 3 individuals, binding was restricted to either GII.4 alone or GII.3 and GII.17. Finally, we performed a VLP binding assay on proximal and distal colon tissue blocks from a nonsecretor patient with Crohn's 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. The binding of GII.4 and GII.17 HuNoV VLPs was linked to Le^a in regenerative mucosae from the proximal and distal colon. Overall, our data clearly showed that Le^a has a pivotal role in the recognition of HuNoV in nonsecretors. We also showed that Le^a is expressed in inflammatory/regenerative tissues and interacts with HuNoV in a nonsecretor individual. The physiological and immunological consequences of such interactions in nonsecretors have yet to be elucidated. IMPORTANCE Human norovirus (HuNoV) is the main etiological agent of viral gastroenteritis in all age classes. HuNoV infection affects mainly secretor individuals where ABO(H) and Lewis histo-blood group antigens (HBGAs) are present in the small intestine. Nonsecretor individuals, who only express Lewis (Le) antigens, are less susceptible to HuNoV infection. Here, we studied the interaction of common HuNoV genotypes (GII.3, GII.4, and GII.17) in nonsecretor individuals using synthetic viral particles. Saliva binding assays showed that only GII.4 interacted with nonsecretor saliva via the Lewis a (Le^a) antigen Surprisingly, the three genotypes interacted with nonsecretor enterocytes via the Le^a antigen on duodenal tissue blocks, which were more relevant for HuNoV/HBGA studies. The Le^a antigen also played a pivotal role in the recognition of GII.4 and GII.17 particles by inflammatory colon tissue from a nonsecretor Crohn's disease patient. The implications of HuNoV binding in nonsecretors remain to be elucidated in physiological and pathological conditions encountered in other intestinal diseases.

Historic and Prehistoric Epidemics: An Overview of Sources Available for the Study of Ancient Pathogens

Since life on earth developed, parasitic microbes have thrived. Increases in host numbers, or the conquest of a new species, provide an opportunity for such a pathogen to enjoy, before host defense systems kick in, a similar upsurge in reproduction. Outbreaks, caused by "endemic" pathogens, and epidemics, caused by "novel" pathogens, have thus been creating chaos and destruction since prehistorical times. To study such (pre)historic epidemics, recent advances in the ancient DNA field, applied to both archeological and historical remains, have helped tremendously to elucidate the evolutionary trajectory of pathogens. These studies have offered new and unexpected insights into the evolution of, for instance, smallpox virus, hepatitis B virus, and the plague-causing bacterium Yersinia pestis. Furthermore, burial patterns and historical publications can help in tracking down ancient pathogens. Another source of information is our genome, where selective sweeps in immune-related genes relate to past pathogen attacks, while multiple viruses have left their genomes behind for us to study. This review will discuss the sources available to investigate (pre)historic diseases, as molecular knowledge of historic and prehistoric pathogens may help us understand the past and the present, and prepare us for future epidemics.

Association of Secretor Status with Enteropathy and Growth among Children in Bangladesh Aged 1-24 Months

Secretor status refers to the ability of an individual to secrete blood group antigens into body fluids and onto the different epithelial surfaces. Concurrent findings have demonstrated an association of the secretor status of children with susceptibility to a plethora of enteropathogens. We aimed to determine a possible association of secretor status of children with childhood enteropathy, an important causal factor for childhood growth failure. Participants of the Malnutrition and Enteric Disease (MAL-ED) birth cohort study from the Bangladesh site were enrolled along with their mothers. Saliva was analyzed for determining blood groups and secretor status of the children and their mothers by using an in-house ELISA. Approximately 59% of children and 65% of mothers were found to be secretor positive. Secretor-positive children were found to have a significantly positive association with alpha-1-antitrypsin (β-coefficient: 0.11, 95% CI: 0.07, 0.21, P < 0.01) and with environmental enteric dysfunction score (β-coefficient: 0.32, 95% CI: 0.29, 0.65, P = 0.05). However, despite a negative effect size, secretor-positive children did not show any statistical significance with length-for-age and weight-for-age z scores (LAZ and WAZ), respectively. Our findings indicate toward the genetic factor of secretor status of children being associated with childhood growth faltering, through increased susceptibility to distinct enteropathogens and the consequent development of enteric inflammation and enteropathy among children. However, these findings are only applicable in Bangladeshi settings and thus need to be validated in several other similar settings, to establish a possible relationship between the secretor status of children with enteropathy and resulting childhood growth failure.

Fucosyltransferase 2: A Genetic Risk Factor for Intestinal Diseases

The fucosyltransferase 2 gene (FUT2) mediates the synthesis of histoblood group antigens (HBGA) that occur in vivo from multiple organs, particularly on the surface of intestinal epithelial cells and body fluids. To date, many studies have demonstrated that the interaction of HBGA with the host microbiota is the cause of pathogenesis of intestinal diseases, making FUT2 non-secretor a risk factor for inflammatory bowel disease (IBD) due to the lack of HBGA. As HBGA also acts as an attachment site for norovirus (NoV) and rotavirus (RV), the non-secretor becomes a protective factor for both viral infections. In addition, the interaction of norovirus and rotavirus with symbiotic bacteria has been found to play an important role in regulating enteroviral infection in IBD. Given the current incomplete understanding of the complex phenomenon and the underlying pathogenesis of intestinal diseases such as IBD, it has recently been hypothesized that the FUT2 gene regulates intestinal bacteria through attachment sites, may help to unravel the role of FUT2 and intestinal flora in the mechanism of intestinal diseases in the future, and provide new ideas for the prevention and treatment of intestinal diseases through more in-depth studies.

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.

Rotaviruses: From Pathogenesis to Disease Control—A Critical Review

Since their first recognition in human cases about four decades ago, rotaviruses have remained the leading cause of acute severe dehydrating diarrhea among infants and young children worldwide. The WHO prequalification of oral rotavirus vaccines (ORV) a decade ago and its introduction in many countries have yielded a significant decline in the global burden of the disease, although not without challenges to achieving global effectiveness. Poised by the unending malady of rotavirus diarrhea and the attributable death cases in developing countries, we provide detailed insights into rotavirus biology, exposure pathways, cellular receptors and pathogenesis, host immune response, epidemiology, and vaccination. Additionally, recent developments on the various host, viral and environmental associated factors impacting ORV performance in low-and middle-income countries (LMIC) are reviewed and their significance assessed. In addition, we review the advances in nonvaccine strategies (probiotics, candidate anti-rotaviral drugs, breastfeeding) to disease prevention and management.

Structural basis of P[II] rotavirus evolution and host ranges under selection of histo-blood group antigens

Group A rotaviruses cause severe gastroenteritis in infants and young children worldwide, with P[II] genogroup rotaviruses (RVs) responsible for >90% of global cases. RVs have diverse host ranges in different human and animal populations determined by host histo-blood group antigen (HBGA) receptor polymorphism, but details governing diversity, host ranges, and species barriers remain elusive. In this study, crystal structures of complexes of the major P[II] genogroup P[4] and P[8] genotype RV VP8* receptor-binding domains together with Lewis epitope-containing LNDFH I glycans in combination with VP8* receptor-glycan ligand affinity measurements based on NMR titration experiments revealed the structural basis for RV genotype-specific switching between ββ and βα HBGA receptor-binding sites that determine RV host ranges. The data support the hypothesis that P[II] RV evolution progressed from animals to humans under the selection of type 1 HBGAs guided by stepwise host synthesis of type 1 ABH and Lewis HBGAs. The results help explain disease burden, species barriers, epidemiology, and limited efficacy of current RV vaccines in developing countries. The structural data has the potential to impact the design of future vaccine strategies against RV gastroenteritis.

Maternal H-antigen secretor status is an early biomarker for potential preterm delivery

OBJECTIVE

Pre-pregnancy or first trimester biomarkers predicting preterm delivery are lacking. The purpose of this study was to determine whether maternal H-antigen (secretor status) is a potential biomarker for preterm delivery.

METHODS

This cohort study examined maternal saliva samples and birth data gathered by the National Children's Study Vanguard pilot phase (2009-2014) and included 300 women who were ≥18 years old and provided birth data and saliva samples. The maternal secretor status phenotype was determined by quantifying H-antigen in saliva using enzyme-linked immunoassay. Mothers were stratified by secretor status and multivariable analysis estimated adjusted associations with preterm delivery.

RESULTS

Maternal lack of H-antigen production was an independent risk factor for preterm delivery after adjusting for known confounders (aOR 4.53; 95% CI: 1.74, 11.81; P = 0.002).

CONCLUSIONS

Maternal H-antigen may be a biomarker identifying women at-risk for preterm delivery. Prospective cohort studies validating these findings are needed.

Secretors of HBGA and Susceptibility to Norovirus and Rotavirus Diarrhea

Histo-blood group antigen contains oligosaccharides that serve as receptors for norovirus (NoV) and rotavirus (RV). The receptors are only present on the surface of intestinal mucosal epithelial cells of secretors; therefore, secretors are susceptible to NoV and RV diarrhea and nonsecretors are resistant. The prevalence of secretors in different countries varies between 50% and 90%. Secretor rates evolved in response to environmental pressures such as infectious diseases.

Rotavirus vaccines performance: dynamic interdependence of host, pathogen and environment

INTRODUCTION

As of January 2021, rotavirus vaccination programs have been implemented in 109 countries and their use has resulted in a positive impact on rotavirus-related diarrheal hospitalizations and mortality in children below 5 years of age. Despite these successes, several countries in Africa and Asia where disease burden is high have not yet implemented rotavirus vaccination at all or at a scale sufficient enough to demonstrate impact. This could be, among other reasons, due to poor vaccine coverage and the modest levels of efficacy and effectiveness of the vaccines in these resource-limited settings.

AREAS COVERED

We review various factors related to the human host (malnutrition, maternally derived antibodies and breastfeeding, genetic factors, blood group, and co-administration with oral polio vaccine), rotavirus pathogen (force of infection, strain diversity and coinfections), and the environment (related to the human microbiome) which reflect complex and interconnected processes leading to diminished vaccine performance in resource-limited settings.

EXPERT OPINION

Addressing the limiting factors for vaccine efficacy is needed but likely to take a long time to be resolved. An immediate solution is to increase the immunization coverage to higher values generating an overall effect of adequate proportion of protected population to reduce the prevalence of rotavirus disease.

Human genomics of the humoral immune response against polyomaviruses

Human polyomaviruses are widespread in humans and can cause severe disease in immunocompromised individuals. To identify human genetic determinants of the humoral immune response against polyomaviruses, we performed genome-wide association studies and meta-analyses of qualitative and quantitative immunoglobulin G responses against BK polyomavirus (BKPyV), JC polyomavirus (JCPyV), Merkel cellpolyomavirus (MCPyV), WU polyomavirus (WUPyV), and human polyomavirus 6 (HPyV6) in 15,660 individuals of European ancestry from three independent studies. We observed significant associations for all tested viruses: JCPyV, HPyV6, and MCPyV associated with human leukocyte antigen class II variation, BKPyV and JCPyV with variants in FUT2, responsible for secretor status, MCPyV with variants in STING1, involved in interferon induction, and WUPyV with a functional variant in MUC1, previously associated with risk for gastric cancer. These results provide insights into the genetic control of a family of very prevalent human viruses, highlighting genes and pathways that play a modulating role in human humoral immunity.

Detection of the weak-secretor rs1047781 (385A>T) single nucleotide polymorphism using an unlabeled probe high-resolution melting-based method

FUT2 encodes galactoside 2-α-l-fucosyltransferase 2 which determines the secretor status of ABO(H) blood group antigens. Secretors have at least one functional FUT2 allele (Se), while nonsecretors or weak secretors are homozygous for nonfunctional (non- or weak secretor) FUT2 alleles (se or Se^w ). The Se^w having the 385A>T missense SNP (rs1047781) is the prevalent nonfunctional allele in East and Southeast Asians. In this study, we developed an unlabeled-probe high-resolution melting (HRM) analysis for genotyping of 385A>T and validated the method by analyzing 72 Japanese whose 385A>T genotypes were confirmed by DNA sequencing. The unlabeled-probe HRM analysis clearly discriminated three genotypes of 385A>T. In addition, the results obtained for the 72 Japanese by this method were fully concordant with previous ones. Estimation of secretor status using this cost-effective method may be useful in East and Southeast Asian populations.

The role of the blood group-related glycosyltransferases FUT2 and B4GALNT2 in susceptibility to infectious disease

The glycosylation profile of the gastrointestinal tract is an important factor mediating host-microbe interactions. Variation in these glycan structures is often mediated by blood group-related glycosyltransferases, and can lead to wide-ranging differences in susceptibility to both infectious- as well as chronic disease. In this review, we focus on the interplay between host glycosylation, the intestinal microbiota and susceptibility to gastrointestinal pathogens based on studies of two exemplary blood group-related glycosyltransferases that are conserved between mice and humans, namely FUT2 and B4GALNT2. We highlight that differences in susceptibility can arise due to both changes in direct interactions, such as bacterial adhesion, as well as indirect effects mediated by the intestinal microbiota. Although a large body of experimental work exists for direct interactions between host and pathogen, determining the more complex and variable mechanisms underlying three-way interactions involving the intestinal microbiota will be the subject of much-needed future research.

Survey and characterization of nonfunctional alleles of FUT2 in a database

The expression of ABO antigens in human saliva is regulated by the FUT2 gene, which encodes a secretor type α(1,2)fucosyltransferase. Secretors express ABO substrates in saliva and non-secretors do not. Secretor status is an object of concern, especially for susceptibility to various infectious diseases. A multitude of single nucleotide polymorphisms (SNPs) and copy number variations (CNVs) have been reported, and they show unique distributions among different populations. In this study, we selected 18 uncharacterized FUT2 alleles listed in the Erythrogene database and obtained genomic DNA having these alleles. We experimentally confirmed the haplotypes, but 10 of 18 alleles disagreed with those in the database, which may be attributed to their low frequency. We then examined the activity of the encoded α(1,2)fucosyltransferase for 13 alleles by flow cytometry of H antigen expression. The impact of each nonsynonymous SNP on the enzyme was also estimated by software. We finally identified two non-secretor alleles (se610and se357,856,863) and one weak secretor allele (se262,357), while in silico analysis predicted that many alleles impair the function. The present results suggest that correct haplotyping and functional assays are desirable for analysis of the FUT2 gene.

High-resolution melting analysis for detection of fusion allele of FUT2

The secretor status of ABH antigens, determined by FUT2 polymorphisms, affects susceptibility to various infectious diseases. In addition to many SNPs responsible for the nonsecretor phenotype, five nonfunctional alleles (se) resulting from copy number variations have been reported. One of the five alleles generated by an unequal crossover between FUT2 and a pseudogene (SEC1), is sefus . This allele may be misidentified as a functional allele if only common inactivating SNPs are genotyped because it contains the 3' region of the functional FUT2. Therefore, accurate detection of sefus is desirable. For this purpose, a high-resolution melting (HRM) analysis is developed for detection of sefus in which a 284bp fragment of SEC1 and sefus but not FUT2, are amplified. This HRM analysis detected sefus reliably. Thus, an initial screening or prescreening for sefus using HRM analysis seems to be useful for association studies of FUT2.

Infection of porcine small intestinal enteroids with human and pig rotavirus A strains reveals contrasting roles for histo-blood group antigens and terminal sialic acids

Rotaviruses (RVs) are a leading cause of acute viral gastroenteritis in young children and livestock worldwide. Growing evidence suggests that host cellular glycans, such as histo-blood group antigens (HBGAs) and sialic acids (SA), are recognized by the RV surface protein VP4. However, a mechanistic understanding of these interactions and their effects on RV infection and pathogenesis is lacking. Here, we established a porcine crypt-derived 3Dintestinalenteroids (PIEs) culture system which contains all intestinal epithelial cells identified in vivo and represents a unique physiologically functional model to study RV-glycan interactions in vitro. PIEs expressing different HBGAs (A+, H+, and A+/H+) were established and isolation, propagation, differentiation and RV infection conditions were optimized. Differentiated PIEs were infected with human RV (HRV) G1P[8] Wa, porcine RV (PRV) G9P[13], PRV Gottfried G4P[6] or PRV OSU G5P[7] virulent and attenuated strains and virus replication was measured by qRT-PCR. Our results indicated that virulent HRV G1P[8] Wa replicated to the highest titers in A⁺ PIEs, while a distinct trend was observed for PRV G9P[13] or G5P[7] with highest titers in H⁺ PIEs. Attenuated Wa and Gottfried strains replicated poorly in PIEs while the replication of attenuated G9P[13] and OSU strains in PIEs was relatively efficient. However, the replication of all 4 attenuate strains was less affected by the PIE HBGA phenotypes. HBGA synthesis inhibitor 2-F-Peracetyl-Fucose (2F) treatment demonstrated that HBGAs are essential for G1P[8] Wa replication; however, they may only serve as a cofactor for PRVs G9P[13] and OSU G5P[7]. Interestingly, contrasting outcomes were observed following sialidase treatment which significantly enhanced G9P[13] replication, but inhibited the growth of G5P[7]. These observations suggest that some additional receptors recognized by G9P[13] become unmasked after removal of terminal SA. Overall, our results confirm that differential HBGAs-RV and SA-RV interactions determine replication efficacy of virulent group A RVs in PIEs. Consequently, targeting individual glycans for development of therapeutics may not yield uniform results for various RV strains.

Cell surface glycans, including histo-blood group antigens (HBGA) and sialic acids (SAs), have been shown to serve as receptors/attachment factors for many pathogens including RVs. However, how those glycans affect RV replication remains largely unknown due the lack of reliable in vitro models. To solve this problem, we established a 3D porcine intestinal enteroid (PIE) model that recapitulates the complex intestinal morphology better than conventional cell lines. By utilizing PIEs expressing different types of HBGAs, we found that several RV strains including Wa G1P[8], OSU G5P[7] and G9P[13] show preference for certain HBGA types. Interestingly, only Wa replication was reduced when HBGAs synthesis was inhibited, while that of OSU and G9P[13] was only marginally affected, which indicates that they may utilize alternative attachment factors for infection. Sialidase treatment strongly inhibited the growth of OSU, while G9P[13] replication was significantly enhanced. These findings suggest that SAs play contrasting roles in the infection of PRV OSU and G9P[13] strains. Overall, our studies demonstrate that PIEs can serve as a model to study pathogen-glycan interactions and suggest that genetically distinct RVs have evolved diverse mechanisms of cell attachment and/or entry.

Association between circulating rotavirus genotypes and histo-blood group antigens in the children hospitalized with acute gastroenteritis in Iran

Rotaviruses are the dominant cause of severe acute gastroenteritis in children under 5 years of age. Previous studies showed that some children are less susceptible to rotavirus gastroenteritis. It has been shown that this resistance depends on the rotavirus genotype and also human histo-blood group antigens (HBGAs), which works as a receptor for rotavirus surface protein (VP4). The present study aimed to evaluate the human genetic susceptibility to rotavirus gastroenteritis in Iran and to obtain a comparative analysis between rotavirus gastroenteritis and secretor or Lewis status in case and control groups in the Iranian population. The study was performed on fecal specimens from 108 children with acute rotavirus gastroenteritis from 2015 to 2017. A total of 50 fecal specimens from children with acute gastroenteritis of unknown etiology were also used as a control group. After the genotyping of positive rotavirus cases and human HBGAs by Sanger sequencing, the phylogenetic tree analysis showed that all rotavirus strains from Iran belonged to P[II]. The most common genotype was P[8] (n = 102; 94.4%), while the remaining belonged to P[4] (n = 3; 2.8%) and P[6] (n = 3; 2.8%) genotypes. The P[8] genotype was found to be associated with secretor and Lewis positive status (p < .05).

Specific Norovirus Interaction with Lewis x and Lewis a on Human Intestinal Inflammatory Mucosa during Refractory Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), are progressive diseases affecting millions of people each year. Flare-ups during IBD result in severe mucosal alterations of the small intestine (in CD) and in the colon and rectum (in CD and UC).

Inflammatory bowel disease (IBD), which includes Crohn’s disease (CD) and ulcerative colitis (UC), is related to immunological and microbial factors, with the possible implication of enteric viruses. We characterized the interaction between human noroviruses (HuNoVs) and blood group antigens in refractory CD and UC using HuNoV virus-like particles (VLPs) and histological tissues. Immunohistochemistry was conducted on inflammatory tissue samples from the small intestine, colon, and rectum in 15 CD and 9 UC patients. Analysis of the regenerative mucosa of the colon and rectum revealed strong expression of sialylated Lewis a (sLe^a) and Lewis x (sLe^x) antigens and HuNoV VLP binding in the absence of ABO antigen expression in both UC and CD. Competition experiments using sialidase, lectins, and monoclonal antibodies demonstrated that HuNoV attachment mostly involved Le^a and, to a lesser extent, Le^x moieties on regenerative mucosa in both UC and CD. Further studies will be required to understand the implications of specific HuNoV binding to regenerative mucosa in refractory IBD.

IMPORTANCE Inflammatory bowel diseases (IBD), including Crohn’s disease (CD) and ulcerative colitis (UC), are progressive diseases affecting millions of people each year. Flare-ups during IBD result in severe mucosal alterations of the small intestine (in CD) and in the colon and rectum (in CD and UC). Immunohistochemical analysis of CD and UC samples showed strong expression of known tumoral markers sialyl Lewis a (CA19.9) and sialyl Lewis x (CD15s) antigens on colonic and rectal regenerative mucosa, concurrent with strong human norovirus (HuNov) VLP GII.4 affinity. Sialidase treatment and competition experiments using histo-blood group antigen (HBGA)-specific monoclonal antibodies and lectins clearly demonstrated the implication of the Lewis a moiety and, to a lesser extent, the Lewis x moiety in HuNov recognition in regenerative mucosa of CD and UC tissues. Further studies are required to explore the possible implications of enteric viruses in the impairment of epithelial repair and dysregulation of inflammatory pathways during severe IBD.

Can the FUT2 Non-secretor Phenotype Associated With Gut Microbiota Increase the Children Susceptibility for Type 1 Diabetes? A Mini Review

The global toll of type 1 diabetes (T1D) has steadily increased over the last decades. It is now widely acknowledged that T1D pathophysiology is more complex than expected. Indeed, a multifaceted interplay between genetic, metabolic, inflammatory and environmental factors exists that leads to heterogeneous clinical manifestations across individuals. Children with non-secretor phenotype and those affected by T1D share low abundance of bifidobacteria, low content of short-chain fatty acids, intestinal phosphatase alkaline and a high incidence of inflammatory bowel diseases. In this context, host-gut microbiota dyad may represent a relevant contributor to T1D development and progression due to its crucial role in shaping host immunity and susceptibility to autoimmune conditions. The FUT2 gene is responsible for the composition and functional properties of glycans in mucosal tissues and bodily secretions, including human milk. FUT2 polymorphisms may profoundly influence gut microbiota composition and host susceptibility to viral infections and chronic inflammatory disease. In this minireview, the possible interplay between mothers' phenotype, host FUT2 genetic background and gut microbiota composition will be discussed in perspective of the T1D onset. The study of FUT2-gut microbiota interaction may add a new piece on the puzzling T1D etiology and unveil novel targets of intervention to contrast T1D development and progression. Dietary interventions, including the intake of α-(1, 2)-fucosyl oligosaccharides in formula milk and the use of specific prebiotics and probiotics, could be hypothesized.

Genetic susceptibility to rotavirus infection in Chinese children: a population-based case-control study

Rotaviruses (RVs) are the leading cause of acute gastroenteritis in children, while histo-blood group antigens (HBGAs) are believed to be host attachment and susceptibility factors of RVs. A large case-control study nested in a population-based diarrhea surveillance targeting children <5 y of age was performed in rural Hebei province, north China. Saliva and serum samples were collected from all participants to determine HBGA phenotyping, FUT2 mutations, and RV IgG antibody titers. A logistic model was employed to assess the association between host HBGA secretor status and risk of RV infection. Among 235 RV cases and 680 non-diarrhea controls studied, 82.4% of participants were IgG positive by an average age of 77 months. Out of the 235 RV cases, 216 (91.9%) were secretors, whereas the secretor rate was 76.3% in the non-diarrhea controls, resulted in an adjusted OR of 3.0 (95%CI: 1.9-4.7, P < .0001) between the two groups. Our population-based case-control study indicated a strong association between host HBGA secretor status and risk of RV infection in Chinese children. The high prevalence of Lewis-positive secretor status strongly suggests that Chinese children may be genetically susceptible to current co-circulating RV strains, and thus, a universal childhood immunization program against RV disease should be successful in China.

The landscape of host genetic factors involved in immune response to common viral infections

BACKGROUND

Humans and viruses have co-evolved for millennia resulting in a complex host genetic architecture. Understanding the genetic mechanisms of immune response to viral infection provides insight into disease etiology and therapeutic opportunities.

METHODS

We conducted a comprehensive study including genome-wide and transcriptome-wide association analyses to identify genetic loci associated with immunoglobulin G antibody response to 28 antigens for 16 viruses using serological data from 7924 European ancestry participants in the UK Biobank cohort.

RESULTS

Signals in human leukocyte antigen (HLA) class II region dominated the landscape of viral antibody response, with 40 independent loci and 14 independent classical alleles, 7 of which exhibited pleiotropic effects across viral families. We identified specific amino acid (AA) residues that are associated with seroreactivity, the strongest associations presented in a range of AA positions within DRβ1 at positions 11, 13, 71, and 74 for Epstein-Barr virus (EBV), Varicella zoster virus (VZV), human herpesvirus 7, (HHV7), and Merkel cell polyomavirus (MCV). Genome-wide association analyses discovered 7 novel genetic loci outside the HLA associated with viral antibody response (P < 5.0 × 10-8), including FUT2 (19q13.33) for human polyomavirus BK (BKV), STING1 (5q31.2) for MCV, and CXCR5 (11q23.3) and TBKBP1 (17q21.32) for HHV7. Transcriptome-wide association analyses identified 114 genes associated with response to viral infection, 12 outside of the HLA region, including ECSCR: P = 5.0 × 10-15 (MCV), NTN5: P = 1.1 × 10-9 (BKV), and P2RY13: P = 1.1 × 10-8 EBV nuclear antigen. We also demonstrated pleiotropy between viral response genes and complex diseases, from autoimmune disorders to cancer to neurodegenerative and psychiatric conditions.

CONCLUSIONS

Our study confirms the importance of the HLA region in host response to viral infection and elucidates novel genetic determinants beyond the HLA that contribute to host-virus interaction.

FUT2, Secretor Status and FUT3 Polymorphisms of Children with Acute Diarrhea Infected with Rotavirus and Norovirus in Brazil

Host susceptibility according to human histo-blood group antigens (HBGAs) is widely known for norovirus infection, but is less described for rotavirus. Due to the variable HBGA polymorphism among populations, we aimed to evaluate the association between HBGA phenotypes (ABH, Lewis and secretor status) and susceptibility to rotavirus and norovirus symptomatic infection, and the polymorphisms of FUT2 and FUT3, of children from southeastern Brazil. Paired fecal-buccal specimens from 272 children with acute diarrhea were used to determine rotavirus/norovirus genotypes and HBGAs phenotypes/genotypes, respectively. Altogether, 100 (36.8%) children were infected with rotavirus and norovirus. The rotavirus P[8] genotype predominates (85.7%). Most of the noroviruses (93.8%) belonged to genogroup II (GII). GII.4 Sydney represented 76% (35/46) amongst five other genotypes. Rotavirus and noroviruses infected predominantly children with secretor status (97% and 98.5%, respectively). However, fewer rotavirus-infected children were Lewis-negative (8.6%) than the norovirus-infected ones (18.5%). FUT3 single nucleotide polymorphisms (SNP) occurred mostly at the T59G > G508A > T202C > C314T positions. Our results reinforce the current knowledge that secretors are more susceptible to infection by both rotavirus and norovirus than non-secretors. The high rate for Lewis negative (17.1%) and the combination of SNPs, beyond the secretor status, may reflect the highly mixed population in Brazil.

The landscape of host genetic factors involved in immune response to common viral infections

INTRODUCTION

Humans and viruses have co-evolved for millennia resulting in a complex host genetic architecture. Understanding the genetic mechanisms of immune response to viral infection provides insight into disease etiology and therapeutic opportunities.

METHODS

We conducted a comprehensive study including genome-wide and transcriptome-wide association analyses to identify genetic loci associated with immunoglobulin G antibody response to 28 antigens for 16 viruses using serological data from 7924 European ancestry participants in the UK Biobank cohort.

RESULTS

Signals in human leukocyte antigen (HLA) class II region dominated the landscape of viral antibody response, with 40 independent loci and 14 independent classical alleles, 7 of which exhibited pleiotropic effects across viral families. We identified specific amino acid (AA) residues that are associated with seroreactivity, the strongest associations presented in a range of AA positions within DRβ1 at positions 11, 13, 71, and 74 for Epstein-Barr Virus (EBV), Varicella Zoster Virus (VZV), Human Herpes virus 7, (HHV7) and Merkel cell polyomavirus (MCV). Genome-wide association analyses discovered 7 novel genetic loci outside the HLA associated with viral antibody response (P<5.×10-8), including FUT2 (19q13.33) for human polyomavirus BK (BKV), STING1 (5q31.2) for MCV, as well as CXCR5 (11q23.3) and TBKBP1 (17q21.32) for HHV7. Transcriptome-wide association analyses identified 114 genes associated with response to viral infection, 12 outside of the HLA region, including ECSCR: P=5.0×10-15 (MCV), NTN5: P=1.1×10-9 (BKV), and P2RY13: P=1.1×10-8 EBV nuclear antigen. We also demonstrated pleiotropy between viral response genes and complex diseases; from autoimmune disorders to cancer to neurodegenerative and psychiatric conditions.

CONCLUSIONS

Our study confirms the importance of the HLA region in host response to viral infection and elucidates novel genetic determinants beyond the HLA that contribute to host-virus interaction.

Host-Range Shift Between Emerging P[8]-4 Rotavirus and Common P[8] and P[4] Strains

In Tunisia, we observed that rotavirus P[8]-3 and P[4] strains in young children with gastroenteritis associate with secretor histo-blood group phenotype. In contrast, the emerging P[8]-4 strain, representing 10% of cases, was exclusively found in nonsecretor patients. Unlike VP8* from P[8]-3 and P[4] strains, the P[8]-4 VP8* protein attached to glycans from saliva samples regardless of the donor's secretor status. Interestingly, a high frequency of FUT2 enzyme deficiency (nonsecretor phenotype) was observed in the population. This may allow cocirculation of P[8]-3 and P[8]-4 strains in secretor and nonsecretor children, respectively.

FUT2 polymorphism in Latin American populations

BACKGROUND

The secretor type α(1,2)fucosyltransferase gene (FUT2) is known to be rich in population-specific polymorphisms. However, genetic variations of FUT2 have not been well examined in Latin American populations in which nonsecretors are rare.

METHODS

Conventional polymerase chain reactions and direct sequencing were performed to detect single nucleotide polymorphisms (SNPs) and copy number variations (CNVs) of FUT2 in Mexicans including Americans of Mexican ancestry, Puerto Ricans, Caribbeans, and Colombians. FUT2 alleles were determined by cloning into plasmids or PHASE software. The impact of uncharacterized missense SNPs on the enzyme activity were examined by transient transfection assays and estimated by several software programs.

RESULTS

Three alleles, Se357, Se, and se428, were common, and the frequency of nonsecretors was relatively low in the studied populations. We also encountered several alleles specific to Africans, Europeans, and South and East Asians including a South Asian-specific sedel. In contrast to the in silico prediction, a transient expression study suggested that both of two missense SNPs, 235G > A and 304G > A, did not impair the enzyme activity.

CONCLUSIONS

The allelic polymorphism of FUT2 suggests that the modern Latin American populations were formed via genetic admixture among Native Americans and populations whose ancestors migrated from other continents. In this study, we have observed a discrepancy between in silico and functional analyses for FUT2 for the first time. Therefore, experimental functional analysis is required for evaluation of SNPs of FUT2.

Identification of Milk and Cheese Intake Biomarkers in Healthy Adults Reveals High Interindividual Variability of Lewis System-Related Oligosaccharides

BACKGROUND

The use of biomarkers of food intake (BFIs) in blood and urine has shown great promise for assessing dietary intake and complementing traditional dietary assessment tools whose use is prone to misreporting.

OBJECTIVE

Untargeted LC-MS metabolomics was applied to identify candidate BFIs for assessing the intake of milk and cheese and to explore the metabolic response to the ingestion of these foods.

METHODS

A randomized controlled crossover study was conducted in healthy adults [5 women, 6 men; age: 23.6 ± 5.0 y; BMI (kg/m2): 22.1 ± 1.7].  After a single isocaloric intake of milk (600 mL), cheese (100 g), or soy-based drink (600 mL), serum and urine samples were collected postprandially up to 6 h and after fasting after 24 h. Untargeted metabolomics was conducted using LC-MS. Discriminant metabolites were selected in serum by multivariate statistical analysis, and their mass distribution and postprandial kinetics were compared.

RESULTS

Serum metabolites discriminant for cheese intake had a significantly lower mass distribution than metabolites characterizing milk intake (P = 4.1 × 10-4). Candidate BFIs for milk or cheese included saccharides, a hydroxy acid, amino acids, amino acid derivatives, and dipeptides. Two serum oligosaccharides, blood group H disaccharide (BGH) and Lewis A trisaccharide (LeA), specifically reflected milk intake but with high interindividual variability. The 2 oligosaccharides showed related but opposing trends: subjects showing an increase in either oligosaccharide did not show any increase in the other oligosaccharide. This result was confirmed in urine.

CONCLUSIONS

New candidate BFIs for milk or cheese could be identified in healthy adults, most of which were related to protein metabolism. The increase in serum of LeA and BGH after cow-milk intake in adults calls for further investigations considering the beneficial health effects on newborns of such oligosaccharides in maternal milk. The trial is registered at clinicaltrials.gov as NCT02705560.

Structural Basis of Glycan Recognition in Globally Predominant Human P[8] Rotavirus

Rotavirus (RV) causes acute gastroenteritis in infants and children worldwide. Recent studies showed that glycans such as histo-blood group antigens (HBGAs) function as cell attachment factors affecting RV host susceptibility and prevalence. P[8] is the predominant RV genotype in humans, but the structural basis of how P[8] RVs interact with glycan ligands remains elusive. In this study, we characterized the interactions between P[8] VP8*s and glycans which showed that VP8*, the RV glycan binding domain, recognized both mucin core 2 and H type 1 antigens according to the ELISA-based oligosaccharide binding assays. Importantly, we determined the structural basis of P[8] RV-glycans interaction from the crystal structures of a Rotateq P[8] VP8* in complex with core 2 and H type 1 glycans at 1.8 Å and 2.3 Å, respectively, revealing a common binding pocket and similar binding mode. Structural and sequence analysis demonstrated that the glycan binding site is conserved among RVs in the P[II] genogroup, while genotype-specific amino acid variations determined different glycan binding preference. Our data elucidated the detailed structural basis of the interactions between human P[8] RVs and different host glycan factors, shedding light on RV infection, epidemiology, and development of anti-viral agents.

Molecular basis of P[II] major human rotavirus VP8* domain recognition of histo-blood group antigens

Initial cell attachment of rotavirus (RV) to specific cell surface glycan receptors, which is the essential first step in RV infection, is mediated by the VP8* domain of the spike protein VP4. Recently, human histo-blood group antigens (HBGAs) have been identified as receptors or attachment factors for human RV strains. RV strains in the P[4] and P[8] genotypes of the P[II] genogroup share common recognition of the Lewis b (Le^b) and H type 1 antigens, however, the molecular basis of receptor recognition by the major human P[8] RVs remains unknown due to lack of experimental structural information. Here, we used nuclear magnetic resonance (NMR) spectroscopy-based titration experiments and NMR-derived high ambiguity driven docking (HADDOCK) methods to elucidate the molecular basis for P[8] VP8* recognition of the Le^b (LNDFH I) and type 1 HBGAs. We also used X-ray crystallography to determine the molecular details underlying P[6] recognition of H type 1 HBGAs. Unlike P[6]/P[19] VP8*s that recognize H type 1 HBGAs in a binding surface composed of an α-helix and a β-sheet, referred as the “βα binding site”, the P[8] and P[4] VP8*s bind Le^b HBGAs in a previously undescribed pocket formed by the edges of two β-sheets, referred to as the “ββ binding site”. Importantly, the P[8] and P[4] VP8*s retain binding capability to non-Le^b type 1 HBGAs using the βα binding site. The presence of two distinct binding sites for Le^b and non-Le^b HBGA glycans in the P[8] and P[4] VP8* domains suggests host-pathogen co-evolution under structural and functional adaptation of RV pathogens to host glycan polymorphisms. Assessment and understanding of the precise impact of this co-evolutionary process in determining RV host ranges and cross-species RV transmission should facilitate improved RV vaccine development and prediction of future RV strain emergence and epidemics.

Rotaviruses (RV)s are the main cause of severe diarrhea in humans and animals. Significant advances in understanding RV diversity, evolution and epidemiology have been made after discovering that RVs recognize histo-blood group antigens (HBGAs) as host cell receptors or attachment factors. While different RV strains are known to have distinct binding preferences for HBGA receptor ligands, their molecular basis in controlling strain-specific host ranges remains unclear. In this study, we used solution nuclear magnetic resonance spectroscopy and X-ray crystallography to determine the molecular-level details for interactions of the human P[8] and P[6] RV VP8* domains with their HBGA receptors ligands. The distinct binding patterns observed between these major human RVs and their respective glycan ligands provide insight into the evolutionary relationships between different P[II] genotypes that ultimately determine host ranges, disease burden, zoonosis and epidemiology, which may impact future strategies for development of vaccines to protect against RV infections.

The Impact of Human Genetic Polymorphisms on Rotavirus Susceptibility, Epidemiology, and Vaccine Take

Innate resistance to viral infections can be attributed to mutations in genes involved in the immune response, or to the receptor/ligand. A remarkable example of the latter is the recently described Mendelian trait resistance to clinically important and globally predominating genotypes of rotavirus, the most common agent of severe dehydrating gastroenteritis in children worldwide. This resistance appears to be rotavirus genotype-dependent and is mainly mediated by histo-blood group antigens (HBGAs), which function as a receptor or attachment factors on gut epithelial surfaces. HBGA synthesis is mediated by fucosyltransferases and glycosyltransferases under the genetic control of the FUT2 (secretor), FUT3 (Lewis), and ABO (H) genes on chromosome 19. Significant genotypic and phenotypic diversity of HBGA expression exists between different human populations. This genetic diversity has an effect on genotype-specific susceptibility, molecular epidemiology, and vaccine take. Here, we will discuss studies on genetic susceptibility to rotavirus infection and place them in the context of population susceptibility, rotavirus epidemiology, vaccine take, and public health impact.

Human Neonatal Rotavirus Vaccine (RV3-BB) Produces Vaccine Take Irrespective of Histo-Blood Group Antigen Status

BACKGROUND

VP4 [P] genotype binding specificities of rotaviruses and differential expression of histo-blood group antigens (HBGAs) between populations may contribute to reduced efficacy against severe rotavirus disease. P[6]-based rotavirus vaccines could broaden protection in such settings, particularly in Africa, where the Lewis-negative phenotype and P[6] rotavirus strains are common.

METHODS

The association between HBGA status and G3P[6] rotavirus vaccine (RV3-BB) take was investigated in a phase 2A study of RV3-BB vaccine involving 46 individuals in Dunedin, New Zealand, during 2012-2014. FUT2 and FUT3 genotypes were determined from DNA extracted from stool specimens, and frequencies of positive cumulative vaccine take, defined as an RV3-BB serum immune response (either immunoglobulin A or serum neutralizing antibody) and/or stool excretion of the vaccine strain, stratified by HBGA status were determined.

RESULTS

RV3-BB produced positive cumulative vaccine take in 29 of 32 individuals (91%) who expressed a functional FUT2 enzyme (the secretor group), 13 of 13 (100%) who were FUT2 null (the nonsecretor group), and 1 of 1 with reduced FUT2 activity (i.e., a weak secretor); in 37 of 40 individuals (93%) who expressed a functional FUT3 enzyme (the Lewis-positive group) and 3 of 3 who were FUT3 null (the Lewis-negative group); and in 25 of 28 Lewis-positive secretors (89%), 12 of 12 Lewis-positive nonsecretors (100%), 2 of 2 Lewis-negative secretors, and 1 of 1 Lewis-negative weak secretor.

CONCLUSIONS

RV3-BB produced positive cumulative vaccine take irrespective of HBGA status. RV3-BB has the potential to provide an improved level of protection in settings where P[6] rotavirus disease is endemic, irrespective of the HBGA profile of the population.

Fucosyltransferase Gene Polymorphisms and Lewisb-Negative Status Are Frequent in Swedish Newborns, With Implications for Infectious Disease Susceptibility and Personalized Medicine

BACKGROUND

Single-nucleotide polymorphisms (SNPs) in the fucosyltransferase genes FUT2 and FUT3 have been associated with susceptibility to various infectious and inflammatory disorders. FUT variations influence the expression of human histo-blood group antigens (HBGAs) (H-type 1 and Lewis), which are highly expressed in the gut and play an important role in microbial attachment, metabolism, colonization, and shaping of the microbiome. In particular, FUT polymorphisms confer susceptibility to specific rotavirus and norovirus genotypes, which has important global health implications.

METHODS

We designed a genotyping method using a nested polymerase chain reaction approach to determine the frequency of SNPs in FUT2 and FUT3, thereby inferring the prevalence of Lewisb-positive, Lewisb-negative, secretor, and nonsecretor phenotypes in 520 Swedish newborns.

RESULTS

There was an increased frequency of homozygotes for the minor allele for 1 SNP in FUT2 and 4 SNPs in FUT3. Overall, 37.3% of newborns were found to have Lewis b negative phenotypes (Le (a+b-) or Le (a-b-). Using our new, sensitive genotyping method, we were able to genetically define the Le (a-b-) individuals based on their secretor status and found that the frequency of Lewis b negative newborns in our cohort was 28%.

CONCLUSIONS

Given the high frequency of fucosyltransferase polymorphisms observed in our newborn cohort and the implications for disease susceptibility, FUT genotyping might play a future role in personalized health care, including recommendations for disease screening, therapy, and vaccination.

Pathology of Rotavirus-driven Multiple Organ Failure in a 16-month-old Boy

Autopsy investigation of a fatal case of rotavirus severe acute gastroenteritis and multiple organ failure in a 16-month boy with previous intrauterine growth retardation showed colocalization of nonstructural and structural rotavirus proteins within viroplasms in nephrons. This case brings new insights into extraintestinal rotavirus infection and new clues to its abilities to bind to human histo-blood group antigens.

Rotavirus Vaccine Take in Infants Is Associated With Secretor Status

Rotaviruses bind to enterocytes in a genotype-specific manner via histo-blood group antigens (HBGAs), which are also detectable in saliva. We evaluated antirotavirus immunoglobulin A seroconversion ('vaccine take") among 166 Ghanaian infants after 2-3 doses of G1P[8] rotavirus vaccine during a vaccine trial, by HBGA status from saliva collected at age 4.1 years. Only secretor status was associated with seroconversion: 41% seroconversion for secretors vs 13% for nonsecretors; relative risk, 3.2 (95% confidence interval, 1.2-8.1; P = .016). Neither Lewis antigen nor salivary antigen blood type was associated with seroconversion. Likelihood of "take" for any particular rotavirus vaccine may differ across populations based on HBGAs.

Maternal hepatitis B or C status and the long-term risk of gastrointestinal morbidity for offspring: A population-based cohort study

BACKGROUND

More than 360 million people have chronic hepatitis B or C (HBV/HCV) infection worldwide, many of which are women at childbearing age. While the risk of perinatal HBV/HCV has been well established, the long-term implications on offspring health, have been less studied. We aimed to evaluate the association between maternal HBV/HCV carrier status and long-term gastrointestinal (GI) morbidities in offspring.

AIMS & METHODS

A population-based cohort analysis compared the risk for long-term childhood GI morbidities in children born to HBV/HCV carrier mothers vs the risk in those who were born to noncarriers. Childhood GI morbidities were predefined based on ICD-9 codes, as recorded in hospital medical files. Children with congenital malformations and multiple gestations were excluded from the analysis. A Kaplan-Meier survival curve was constructed to compare the cumulative GI morbidities over time, and a Cox proportional hazards model was used to control for confounders.

RESULTS

During the study period (1991-2014), 242 342 newborns met the inclusion criteria: 771 (0.3%) were born to HBV/HCV mothers and 241 571 (99.7%) were not. The median follow-up was 10.51 years (0-18 years). Offspring to HBV/HCV mothers had a higher incidence of GI diseases (9.3% vs 5.4%, OR = 1.82; 95% CI 1.43-2.32; Kaplan-Meier log-rank = 0.001). The increased risk remained significant in the Cox proportional hazards models, which adjusted for gestational age, mode of delivery and pregnancy complications (adjusted HR = 2.26, 95% CI: 1.79-2.85; P < .001).

CONCLUSION

Maternal HBV or HCV carrier status is an independent risk factor for long-term the GI morbidity of offspring.

Maternal Human Milk Oligosaccharide Profile Modulates the Impact of an Intervention with Iron and Galacto-Oligosaccharides in Kenyan Infants

There is little data on human milk oligosaccharide (HMO) composition in Sub-Saharan Africa. Iron fortificants adversely affect the infant gut microbiota, while co-provision of prebiotic galacto-oligosaccharides (GOS) mitigates most of the adverse effects. Whether variations in maternal HMO profile can influence the infant response to iron and/or GOS fortificants is unknown. The aim of this study was to determine HMO profiles and the secretor/non-secretor phenotype of lactating Kenyan mothers and investigate their effects on the maternal and infant gut microbiota, and on the infant response to a fortification intervention with 5 mg iron (2.5 mg as sodium iron ethylenediaminetetraacetate and 2.5 mg as ferrous fumarate) and 7.5 g GOS. We studied mother–infant pairs (n = 80) participating in a 4-month intervention trial in which the infants (aged 6.5–9.5 months) received daily a micronutrient powder without iron, with iron or with iron and GOS. We assessed: (1) maternal secretor status and HMO composition; (2) effects of secretor status on the maternal and infant gut microbiota in a cross-sectional analysis at baseline of the intervention trial; and (3) interactions between secretor status and intervention groups during the intervention trial on the infant gut microbiota, gut inflammation, iron status, growth and infectious morbidity. Secretor prevalence was 72% and HMOs differed between secretors and non-secretors and over time of lactation. Secretor status did not predict the baseline composition of the maternal and infant gut microbiota. There was a secretor-status-by-intervention-group interaction on Bifidobacterium (p = 0.021), Z-scores for length-for-age (p = 0.022) and weight-for-age (p = 0.018), and soluble transferrin receptor (p = 0.041). In the no iron group, longitudinal prevalence of diarrhea was higher among infants of non-secretors (23.8%) than of secretors (10.4%) (p = 0.001). In conclusion, HMO profile may modulate the infant gut microbiota response to fortificant iron; compared to infants of secretor mothers, infants of non-secretor mothers may be more vulnerable to the adverse effect of iron but also benefit more from the co-provision of GOS.

Nonsecretor Histo-blood Group Antigen Phenotype Is Associated With Reduced Risk of Clinical Rotavirus Vaccine Failure in Malawian Infants

BACKGROUND

Histo-blood group antigen (HBGA) Lewis/secretor phenotypes predict genotype-specific susceptibility to rotavirus gastroenteritis (RVGE). We tested the hypothesis that nonsecretor/Lewis-negative phenotype leads to reduced vaccine take and lower clinical protection following vaccination with G1P[8] rotavirus vaccine (RV1) in Malawian infants.

METHODS

A cohort study recruited infants receiving RV1 at age 6 and 10 weeks. HBGA phenotype was determined by salivary enzyme-linked immunosorbent assay (ELISA). RV1 vaccine virus shedding was detected by quantitative real-time polymerase chain reaction (qRT-PCR) in stool collected on alternate days for 10 days post-immunization. Plasma rotavirus-specific immunoglobulin A was determined by ELISA pre- and post-immunization. In a case-control study, HBGA phenotype distribution was compared between RV1-vaccinated infants with RVGE and 1:1 age-matched community controls. Rotavirus genotype was determined by RT-PCR.

RESULTS

In 202 cohort participants, neither overall vaccine virus fecal shedding nor seroconversion differed by HBGA phenotype. In 238 case-control infants, nonsecretor phenotype was less common in infants with clinical vaccine failure (odds ratio [OR], 0.39; 95% confidence interval [CI], 0.20-0.75). Nonsecretor phenotype was less common in infants with P[8] RVGE (OR, 0.12; 95% CI, 0.03-0.50) and P[4] RVGE (OR, 0.17; 95% CI, 0.04-0.75). Lewis-negative phenotype was more common in infants with P[6] RVGE (OR, 3.2; 95% CI, 1.4-7.2).

CONCLUSIONS

Nonsecretor phenotype was associated with reduced risk of rotavirus vaccine failure. There was no significant association between HBGA phenotype and vaccine take. These data refute the hypothesis that high prevalence of nonsecretor/Lewis-negative phenotypes contributes to lower rotavirus vaccine effectiveness in Malawi.

Human VP8* mAbs neutralize rotavirus selectively in human intestinal epithelial cells

We previously generated 32 rotavirus-specific (RV-specific) recombinant monoclonal antibodies (mAbs) derived from B cells isolated from human intestinal resections. Twenty-four of these mAbs were specific for the VP8* fragment of RV VP4, and most (20 of 24) were non-neutralizing when tested in the conventional MA104 cell-based assay. We reexamined the ability of these mAbs to neutralize RVs in human intestinal epithelial cells including ileal enteroids and HT-29 cells. Most (18 of 20) of the "non-neutralizing" VP8* mAbs efficiently neutralized human RV in HT-29 cells or enteroids. Serum RV neutralization titers in adults and infants were significantly higher in HT-29 than MA104 cells and adsorption of these sera with recombinant VP8* lowered the neutralization titers in HT-29 but not MA104 cells. VP8* mAbs also protected suckling mice from diarrhea in an in vivo challenge model. X-ray crystallographic analysis of one VP8* mAb (mAb9) in complex with human RV VP8* revealed that the mAb interaction site was distinct from the human histo-blood group antigen binding site. Since MA104 cells are the most commonly used cell line to detect anti-RV neutralization activity, these findings suggest that prior vaccine and other studies of human RV neutralization responses may have underestimated the contribution of VP8* antibodies to the overall neutralization titer.

Histo-blood group antigens and rotavirus vaccine shedding in Nicaraguan infants

ABO, Lewis and secretor histo-blood group antigens (HBGA) are susceptibility factors for rotavirus in a P-genotype dependent manner and can influence IgA seroconversion rates following rotavirus vaccination. To investigate the association between HBGA phenotypes and rotavirus vaccine shedding fecal samples (n = 304) from a total of 141 infants vaccinated with Rotarix (n = 71) and RotaTeq (n = 70) were prospectively sampled in three time frames (≤3, 4–7 and ≥8 days) after first vaccination dose. Rotavirus was detected with qPCR and genotypes determined by G/P multiplex PCR and/or sequencing. HBGAs were determined by hemagglutination and saliva based ELISA. Low shedding rates were observed, with slightly more children vaccinated with RotaTeq (19%) than Rotarix (11%) shedding rotavirus at ≥4 days post vaccination (DPV). At ≥4 DPV no infant of Lewis A (n = 6) or nonsecretor (n = 9) phenotype in the Rotarix cohort shed rotavirus; the same observation was made for Lewis A infants (n = 7) in the RotaTeq cohort. Putative in-vivo gene reassortment among RotaTeq strains occurred, yielding mainly G1P[8] strains. The bovine derived P[5] genotype included in RotaTeq was able to replicate and be shed at long time frames (>13 DPV). The results of this study are consistent with that HBGA phenotype influences vaccine strain shedding as similarly observed for natural infections. Due to the low overall shedding rates observed, additional studies are however warranted.