Molecular characterization of the NSP4 gene of human group A rotavirus samples from the West Central region of Brazil

Genotyping and Molecular Characterization of VP6 and NSP4 Genes of Unusual Rotavirus Group A Isolated from Children with Acute Gastroenteritis

Group A rotavirus (RVA), which causes acute gastroenteritis (AGE) in children worldwide, is categorized mainly based on VP7 (genotype G) and VP4 (genotype P) genes. Genotypes that circulate at <1% are considered unusual. Important genes also include VP6 (genotype I) and NSP4 (genotype E). VP6 establishes the group and affects immunogenicity, while NSP4, as an enterotoxin, is responsible for the clinical symptoms. The aim of this study was to genotype the VP6 and NSP4 genes and molecularly characterize the NSP4 and VP6 genes of unusual RVA. Unusual RVA strains extracted from fecal samples of children ≤16 years with AGE were genotyped in VP6 and NSP4 genes with Sanger sequencing. In a 15-year period (2007-2021), 54.8% (34/62) of unusual RVA were successfully I and E genotyped. Three different I and E genotypes were identified; I2 (73.5%, 25/34) and E2 (35.3%, 12/34) were the most common. E3 genotype was detected from 2017 onwards. The uncommon combination of I2-E3 was found in 26.5% (9/34) of the strains and G3-P[9]-I2-E3 remained the most frequent G-P-I-E combination (20.6%, 7/34). Children infected with RVA E2 strains had a statistically higher frequency of dehydration (50%) than those infected with RVA E3 strains (p = 0.019). Multiple substitutions were detected in NSP4, but their functional effect remains unknown. The result indicates the genetic diversity of RVA strains. Continuous surveillance of the RVA based on the whole genome will provide better knowledge of its evolution.

VP7, VP4, and NSP4 genes of species a rotaviruses isolated from sewage in Nigeria, 2014/2015: partial sequence characterization and biophysical analysis of NSP4 (enterotoxin)

Species A rotavirus are an important cause of childhood gastroenteritis, and the main contributor to its pathogenicity is the enterotoxin (NSP4) protein. Some biophysical properties of partial NSP4 genes of RVAs isolated from sewage in Nigeria during 2014/2015 were investigated. Samples were typed by RT-PCR and Sanger sequencing of partial VP4, VP7 and NSP4 genes. Phylogeny identified lineages within genotypes, predicted glycosylation sites; hydrophobicity profiles and amino acid alignments were employed to determine some biophysical properties of the NSP4 protein. The VP7 sequences of our isolates were the most diversified, the majority of the isolates carried NSP4 genes of the E1 genotype. Genotype specific variations both in hydrophobicity and potential glycosylation were identified, mutations were highest within the H3 hydrophobic domain and VP4 binding domain. The study of RVA NSP4 genes from non-clinical samples revealed that there were structural consistencies with those of reference genes.

Genotyping and sequence characterization of the NSP4 gene of human group A rotavirus strains in Northern Iran

Rotavirus is known to be responsible for remarkable numbers of severe diarrheal episodes and even death in infants and young children. In this study, we aimed to survey genetic diversity and variation analysis of viroporin, which is encoded by the rotavirus NSP4 segment. Thirty-five rotavirus-positive specimens were obtained, and RNA extraction and polymerase chain reaction amplification were performed. After the sequencing process, four specimens were excluded, and the final 31 samples remained for genetic diversity and variation analysis. The predominant single G/P combination was G1P[8] (~78%), followed by G2P[8] (~13%), and equal percentages (3%) of G2P[4], G3P[8], and G-non-typeable-P[8]. Further analyses revealed that variations could be found in the three regions of NSP4, including VP4 binding site (aa 112-146), double-layered particle binding site (aa 161-175), and finally, in the predicted amphipathic alpha-helix. Phylogenic tree analysis demonstrated that the mentioned samples clustered with genotype E1 and E2 reference sequences. As previously reported in the literature, in this study, it was revealed that no apparent correlation exists in the deduced amino acid sequences corresponding to this region between the rotaviruses collected from patients with and without diarrhea.

Non-structural Enterotoxin (NSP4) Gene based Molecular Characterization of Caprine and Ovine Rotavirus A, India

Rotavirus A (RVA) causes viral gastroenteritis in humans and animals, including calves, piglets, and foals. The current study reports the genetic characterization of the full-length enterotoxin gene, NSP4, from caprine and ovine species. Upon characterizing eight full-length NSP4 genes by sequencing, it was found that the four caprine and three ovine RVAs NSP4 genes are of E2 genotype and the sole ovine RVA isolate was found to be of E1 genotype. In the sequence and phyloanalysis of the NSP4 gene the seven E2 genotypes clustered with bovine, human, and caprine isolates from India and Bangladesh, respectively. The E1 genotype of ovine RVA was closer to human RVA isolate from India. The nucleotide per cent identity analysis revealed that all E2 genotype strains of caprine and ovine species ranged from 88.4% to 90.4% and it was found common to both the reference human RVA isolates DS-1 and AU-1. Whereas, the E1 genotype ovine strain clustered with human RVA isolates with 93.1% nucleotide per cent identity. The RVA strains circulating in caprine and ovine populations may share a common origin which is usually found in artiodactyl species because humans share a common dwelling with animals. Future studies are needed to confirm these findings of their relationship with humans and large animals.

Sequence and structural analyses of NSP4 proteins from human group A rotavirus strains detected in Tunisia

BACKGROUND

The NSP4 protein of group A rotavirus (RVA) has been recognized as a viral enterotoxin and plays important roles in viral pathogenesis and morphogenesis. Domains involved in structural and functional interactions have been proposed mainly based on the simian SA11 strain.

METHODS

NSP4 has been classified into 15 different genotypes (E1-E15), and the aim of this study was to analyze the sequences of 46 RVA strains in order to determine the aminoacid (aa) differences between E1 and E2 genotypes. Another aspect was to characterize the structural and physicochemical properties of these strains.

RESULTS

Comparison of deduced aa sequences of the NSP4 protein showed that divergences between NSP4 genotypes E1 and E2 were mostly observed in the VP4-binding, the interspecies variable domain (ISVD) and the double-layered particle (DLP) binding domains. Interestingly, uncommon variations in residues 131 and 138, which are known to be important aa in pathogenesis, were found in one unusual animal derived strain belonging to the E2 genotype. Concerning the structural aspect, no significant differences were noted.

CONCLUSION

The presence of punctual aa variations in the NSP4 genotypes may indicate that NSP4 mutates mainly via accumulation of point mutations.

Characterization of the NSP4 gene of group A human rotavirus G1P[8] strains circulating in Sapporo, Japan from 1987 to 2000

The genetic diversity of the NSP4 gene of rotavirus G1P[8] strains obtained in Sapporo was analyzed, Japan from 1987 to 2000. Sixty-four strains, which were distributed across the whole study period, were included. All G1P[8] NSP4 genes detected in this study belonged to genotype E1, which divided into at least three lineages. The Sapporo rotavirus G1P[8] isolates were found in each lineage. The mean estimated substitution rate was 1.40 × 10(-3) nucleotide substitutions per site per year, which was comparable to that of the G1P[8] VP7 gene. Comparison of the deduced NSP4 amino acid sequences showed genetic diversity at the center of antigenic site II, but not in the enterotoxic domain. This report represents the first investigation of the genetic diversity and evolution of group A rotavirus NSP4 genes in Asia.

Rapid detection of human rotavirus using NSP4 gene specific reverse transcription loop-mediated isothermal amplification assay

The seasonal outbreaks of human rotavirus (RV) infection occur every winter. Most patients are diagnosed clinically by a rapid latex agglutination detection kit or polymerase chain reaction assays for RV from stool samples, but some problems have been reported on the specificity and sensitivity of such rapid detection assays. To ratify these issues, a sensitive, specific, simple, and rapid nucleic acid based diagnostic method is expected to be introduced and the reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed to detect the RV in human stool samples by incubation at 60 °C for 1 h and amplification was confirmed by electrophoretic laddering, restriction enzyme digestion, and hydroxynapthol blue discoloration. The assay established in this study was found to detect only the RVs and no cross-reaction with other viruses, demonstrating its high specificity. By using serial samples dilution as template, the detection limit of LAMP was 10 times more than that of PCR. The results showed the potential clinical feasibility of RT-LAMP as a useful diagnostic tool for the detection of RV with high sensitivity in comparison to conventional RT-PCR.

Mutation distribution in the NSP4 protein in rotaviruses isolated from Mexican children with moderate to severe gastroenteritis

The NSP4 protein is a multifunctional protein that plays a role in the morphogenesis and pathogenesis of the rotavirus. Although NSP4 is considered an enterotoxin, the relationship between gastroenteritis severity and amino acid variations in NSP4 of the human rotavirus remains unclear. In this study, we analyzed the sequence diversity of NSP4 and the severity of gastroenteritis of children with moderate to severe gastroenteritis. The rotavirus-infected children were hospitalized before the rotavirus vaccine program in Mexico. All children had diarrhea within 1-4 days, 44 (88%) were vomiting and 35 (70%) had fevers. The severity analysis showed that 13 (26%) cases had mild gastroenteritis, 23 (46%) moderate gastroenteritis and 14 (28%) severe. NSP4 phylogenetic analysis showed three clusters within the genotype E1. Sequence analysis revealed similar mutations inside each cluster, and an uncommon variation in residue 144 was found in five of the Mexican NSP4 sequences. Most of the amino acid variations were located in the VP4 and VP6 binding site domains, with no relationship to different grades of gastroenteritis. This finding indicates that severe gastroenteritis caused by the rotavirus appears to be related to diverse viral or cellular factors instead of NSP4 activity as a unique pathogenic factor.

Molecular characterization of the NSP4 gene of human group A rotavirus strains circulating in Tunisia from 2006 to 2008

Non-structural protein 4 (NSP4), encoded by group A rotavirus (RVA) genome segment 10, is a multifunctional protein and the first recognized virus-encoded enterotoxin. Recently, a new classification system for RVAs was proposed and a total of 14 NSP4 genotypes (E1-E14) are currently described. The most common NSP4 genotypes in humans are Wa-like E1 and DS-1-like E2. This report represents the first investigation on the genetic diversity of RVA NSP4 genes in Tunisia from 2006 to 2008. In the present study, the NSP4-encoding genes of human RVA strains with different G/P-genotype combinations were analyzed. NSP4 genes of 261 RVA-positive fecal samples were analyzed using a semi-nested reverse transcriptase-polymerase chain reaction and in addition the NSP4 gene of 46 representative RVA strains were sequenced. Phylogenetic analysis of the Tunisian NSP4 nucleotide sequences revealed the presence of two NSP4 genotypes. Genotype E1 was found to be associated with G1P[8], G3P[6], G3P[8], G4P[6] and G4P[8], whereas genotype E2 was associated with G2P[4], G2P[6] and G6P[9] samples. These results support the hypothesis that P[8] carrying RVA strains usually possess the E1 genotype, whereas P[4] carrying RVA strains usually possess the E2 genotype. P[6] carrying strains were found with both E1 and E2. The unusual G6P[9] strains possessed a E2 genotype with a possible animal origin. These results underline the need for further investigations to assess the validity of NSP4 as a suitable target for epidemiologic surveillance of RVA infections and vaccine development.

Genotyping of human rotaviruses circulating among children with diarrhea in Valencia, Venezuela

Rotavirus infection is the most common cause of severe gastroenteritis during childhood worldwide, especially in developing countries. Two rotavirus vaccines are available for childhood immunization programs. Evaluation of the vaccine performance will benefit from knowledge of the epidemiological features of rotavirus infection in regional settings. Limited information on the molecular characteristics of the rotavirus types circulating in Venezuela is available. Eighty seven (89.7%) of the 97 ELISA rotavirus positive stool samples collected from children with diarrhea aged <5 years during 2003 in Valencia (Carabobo State), were G-, P- and NSP4-genotyped by RT-PCR and/or automated sequencing. Four common combinations, G3P[8]/NSP4-E1, G2P[4]/NSP4-E2, G9P[8]/NSP4-E1, and G1P[8]/NSP4-E1 were responsible for 50.6%, 35.6%, 5.7%, and 1.1%, respectively of cases of rotavirus diarrhea, most of them (66%) in children ≤12 months. One uncommon G8P[14]/NSP4-E2 strain was also detected. Temporal fluctuation of genotype distribution occurred, but no differences by age, diarrhea severity score, sex, treatment type or patient medical attention were observed, except for the G3P[8]/NSP4-E1, associated with a more severe dehydration than any other type (P < 0.01). The results confirm the broad diversity among rotavirus strains circulating in Venezuela prior to vaccine implementation, showing the predominance of G3, significant proportion of G2 and moderate circulation of G9 strains. Epidemiological surveillance is needed to detect the emergence of new genotypes that could escape protection induced by vaccination.

Multiple-gene characterization of rotavirus strains: evidence of genetic linkage among the VP7-, VP4-, VP6-, and NSP4-encoding genes

A total of 162 rotavirus strains detected between 1996 and 2006 among individuals with diarrhea in Rio de Janeiro, Brazil, were analyzed by multiple-gene genotyping. Characterization of strains was done by RT-PCR assay for amplification and typing of the VP7-, VP4-, VP6-, and NSP4-encoding genes. Overall, 139 (85.8%) strains belonged to the common group A rotavirus combinations: 67 (41.4%) belonged to genotype G1-P[8]-I1-E1; 18 (11.1%) were G2-P[4]-I2-E2; 11 (6.8%) were G3-P[8]-I1-E1; 12 (7.4%) were G4-P[8]-I1-E1; and 31 (19.1%) were G9-P[8]-I1-E1. Two samples presented mixed genotypes (G1 + G3-P[8]-I1-E1 and G1 + G9-P[9]-I1-E1) and rare combinations, such as G2-P[6]-I2-E2 and G9-P[6]-I2-E2, were detected in six (3.7%) strains. The results suggest a linkage among all four genes. Genotypes G1/G3/G4/G5/G9-P[8] were correlated strongly to I1-E1 genotypes and G2-P[4]/P[6] were correlated to I2-E2 genotypes. Unusual combinations of genes, such as G3-P[9]-I2-E2, G9-P[9]-I1-E2, and G3-P[9]-I3-E3, were observed in 15 (9.3%) strains. The characterization of multiple genes allows a more complete analysis of the rotavirus isolates and provides evidence of natural reassortment of strains.