Humoral immune response to rotavirus NSP4 enterotoxin in Spanish children

Serological Humoral Immunity Following Natural Infection of Children with High Burden Gastrointestinal Viruses

Acute gastroenteritis (AGE) is a major cause of morbidity and mortality worldwide, resulting in an estimated 440,571 deaths of children under age 5 annually. Rotavirus, norovirus, and sapovirus are leading causes of childhood AGE. A successful rotavirus vaccine has reduced rotavirus hospitalizations by more than 50%. Using rotavirus as a guide, elucidating the determinants, breath, and duration of serological antibody immunity to AGE viruses, as well as host genetic factors that define susceptibility is essential for informing development of future vaccines and improving current vaccine candidates. Here, we summarize the current knowledge of disease burden and serological antibody immunity following natural infection to inform further vaccine development for these three high-burden viruses.

Sero-epidemiological study of the rotavirus VP8* protein from different P genotypes in Valencia, Spain

The aims of the present work were to determine the prevalence and titer of serum antibodies against several rotavirus VP8* proteins from different P genotypes in children and adults in Valencia, Spain; and to determine the role of the secretor status (FUT2_G428A polymorphism) in the antibody response. The VP8* protein from the P[4], P[6], P[8], P[9], P[11], P[14] and P[25] genotypes were produced in E. coli. These proteins were tested with 88 serum samples from children (n = 41, 3.5 years old in average) and from adults (n = 47, 58 years old in average) by ELISA. A subset of 55 samples were genotyped for the FUT2_G428A polymorphism and the antibody titers compared. The same subset of samples was also analysed by ELISA using whole rotavirus Wa particles (G1P[8]) as antigen. Ninety-three per cent of the samples were positive for at least one of the VP8* antigens. Differences in the IgG seroprevalence were found between children and adults for the P[4], P[8] and P[11] genotypes. Similarly, significant differences were found between adults and children in their antibody titers against the P[4], P[8], and P[11] VP8* genotypes, having the children higher antibody titers than adults. Interestingly, positive samples against rare genotypes such as P[11] (only in children), P[14] and P[25] were found. While no statistical differences in the antibody titers between secretors and non-secretors were found for any of the tested P genotypes studied, a higher statistic significant prevalence for the P[25] genotype was found in secretors compared to non-secretors. Significant differences in the antibody titers between secretors and non-secretors were found when the whole viral particles from the Wa rotavirus strain (G1P[8]) were used as the antigen.

Relevance of secretor status genotype and microbiota composition in susceptibility to rotavirus and norovirus infections in humans

Host genetic factors, such as histo-blood group antigens (HBGAs), are associated with susceptibility to norovirus (NoV) and rotavirus (RV) infections. Recent advances point to the gut microbiome as a key player necessary for a viral pathogen to cause infection. In vitro NoV attachment to host cells and resulting infections have been linked to interactions with certain bacterial types in the gut microbiota. We investigated the relationship between host genotype, gut microbiota, and viral infections. Saliva and fecal samples from 35 adult volunteers were analysed for secretor status genotype, the gut microbiota composition by 16S rRNA gene sequencing, and salivary IgA titers to NoV and RV. Higher levels of IgA against NoV and RV were related to secretor-positive status. No significant differences were found between the FUT2 genotype groups, although the multivariate analysis showed a significant impact of host genotype on specific viral susceptibilities in the microbiome composition. A specific link was found between the abundance of certain bacterial groups, such as Faecalibacterium and Ruminococcus spp., and lower IgA titers against NoV and RV. As a conclusion, we can state that there is a link between host genetics, gut microbiota, and susceptibility to viral infections in humans.

Impact of rotavirus vaccine introduction on rotavirus-associated seizures and a related possible mechanism

To determine whether clinical features of rotavirus-associated seizures have been altered by rotavirus vaccination, we compared clinical and laboratory data of 2 groups of patients with rotavirus-associated seizures: pre- and post-vaccine introduction groups. The seizure characteristics differed significantly between the groups, with a lower incidence of fever at seizure onset, longer interval between the onset of gastroenteritis and seizures, and more frequent seizures in the postintroduction group. These characteristics may suggest that seizure susceptibility was increased in the postintroduction group. Based on the lower serum Cl(-) (102.1 ± 4.1 vs 98.2 ± 3.2 mg/dL; P < .01) and Ca(2+) levels (9.2 ± 0.4 vs 9.0 ± 0.3 mg/dL; P = .12) in the postintroduction group, we propose that a change in the subjects' susceptibility to the rotavirus enterotoxin may have played a role in increasing the seizure susceptibility in this group. Our results suggest that a rotavirus vaccination program may modulate the manifestations of rotavirus-associated seizures.

Anti-NSP4 antibody can block rotavirus-induced diarrhea in mice

BACKGROUND

Rotavirus infection is the most common cause of infectious diarrhea and gastroenteritis among children worldwide. The viral proteins (VP), especially VP4- and VP7-induced neutralizing antibodies, were considered to be critical in protective immunity to rotavirus disease. However, whether the antibody to rotavirus nonstructural protein 4 (NSP4) protects against rotavirus-induced diarrhea directly is not completely clear, especially for the protective time course.

MATERIALS AND METHODS

To obtain direct evidence, 12-day-old ICR mice were treated with NSP4 and entire rotavirus to induce diarrhea.

RESULTS

Both NSP4 and rotavirus-treated mice developed diarrhea, which was accompanied by histological changes in the small intestine compared to age-matched control mice. Anti-NSP4 antibody demonstrated protection against both entire rotavirus-induced diarrhea and NSP4-induced diarrhea. The histological changes in the small intestinal were reversible. These data show that early intervention with anti-NSP4 antibody can prevent rotavirus-induced diarrhea in mice; late intervention with anti-NSP4 antibody could halt diarrhea progression in mice.

CONCLUSIONS

Our findings demonstrate for the first time that administration of anti-NSP4 antibody is effective both prior to and during the time course of rotavirus infection. These observations extend our knowledge of rotavirus infection and its therapeutic options.

Design of a multiplex nested PCR for genotyping of the NSP4 from group A rotavirus

A novel PCR method was developed to discriminate amongst genotypes A-C of the rotavirus non-structural protein 4 (NSP4). Genotype-specific primers were designed that correctly identified the NSP4 genotype when evaluated as a multiplex PCR with cell culture adapted rotavirus strains. Rotavirus strains B223 SGIG6P6[1], NCDV SGIG6P6[1] and SA11 SGIG3P5B[2] were used as control for NSP4 genotype A; A34 SGIG5P14[23], Gottfried SGIIG4P2B[6] and Wa SGIIG1P1A[8] for NSP4 genotype B; RRV SGIG3P5B[3] for NSP4 genotype C. Subsequently, the same set of specific primers was used to genotype a set of 77 Swedish clinical samples. The results showed that all human clinical samples analyzed belong to the NSP4 genotype B and the VP6 subgroup II.