Rotavirus NSP4: a multifunctional viral enterotoxin

Genomic analysis of DS-1-like human rotavirus A strains uncovers genetic relatedness of NSP4 gene with animal strains in Manhiça District, Southern Mozambique

Post rotavirus vaccine introduction in Mozambique (September 2015), we documented a decline in rotavirus-associated diarrhoea and genotypes changes in our diarrhoeal surveillance spanning 2008-2021. This study aimed to perform whole-genome sequencing of rotavirus strains from 2009 to 2012 (pre-vaccine) and 2017-2018 (post-vaccine). Rotavirus strains previously detected by conventional PCR as G2P[4], G2P[6], G3P[4], G8P[4], G8P[6], and G9P[6] from children with moderate-to-severe and less-severe diarrhoea and without diarrhoea (healthy community controls) were sequenced using Illumina MiSeq® platform and analysed using bioinformatics tools. All these G and P-type combinations exhibited DS-1-like constellation in the rest of the genome segments as, I2-R2-C2-M2-A2-N2-T2-E2-H2. Phylogenetic analysis revealed that strains from children with and without diarrhoea clustered together with other Mozambican and global strains. Notably, the NSP4 gene of strains G3P[4] and G8P[4] in children with diarrhoea clustered with animal strains, such as bovine and caprine, with similarity identities ranging from 89.1 to 97.0% nucleotide and 89.5-97.0% amino acids. Our findings revealed genetic similarities among rotavirus strains from children with and without diarrhoea, as well as with animal strains, reinforcing the need of implementing studies with One Health approach in our setting, to elucidate the genetic diversity of this important pathogen.

Effects of Rotavirus NSP4 on the Immune Response and Protection of Rotavirus-Norovirus Recombinant Subunit Vaccines in Different Immune Pathways

Diarrheal disease continues to be a major cause of global morbidity and mortality among children under 5 years of age. To address the current issues associated with oral attenuated rotavirus vaccines, the study of parenteral rotavirus vaccines has promising prospects. In our previous study, we reported that rotavirus nonstructural protein 4 (NSP4) did not increase the IgG antibody titer of co-immune antigen but did have a protective effect against diarrhea via the intramuscular injection method. Here, we explored whether NSP4 can exert adjuvant effects on mucosal immune pathways. In this study, we immunized mice via muscle and nasal routes, gavaged them with the rotavirus Wa strain or the rotavirus SA11 strain, and then tested the protective effects of immune sera against both viruses. The results revealed that the serum-specific VP8* IgG antibody titers of the mice immunized via the nasal route were much lower than those of the mice immunized by intramuscular injection, and the specific IgA antibodies were almost undetectable in the bronchoalveolar lavage fluid (BALF). NSP4 did not increase the titer of specific VP8* antibodies in either immune pathway. Therefore, in the two vaccines (PP-NSP4-VP8* and PP-VP8*+NSP4) used in this study, NSP4 was unable to perform its potential adjuvant role through the mucosal immune pathway. Instead, NSP4 was used as a co-immunized antigen to stimulate the mice to produce specific binding antibodies that play a protective role against diarrhea.

Molecular Characterization of Avian Rotaviruses F and G Detected in Brazilian Poultry Flocks

Avian rotaviruses (RVs) are important etiologic agents of gastroenteritis in birds. In general, avian RVs are understudied; consequently, there is a paucity of information regarding these viruses. Therefore, the characterization of these viral species is highly relevant because more robust information on genetic, epidemiologic, and evolutionary characteristics can clarify the importance of these infections, and inform efficient prevention and control measures. In this study, we describe partial genome characterizations of two avian RV species, RVF and RVG, detected in asymptomatic poultry flocks in Brazil. Complete or partial sequences of at least one of the genomic segments encoding VP1, VP2, VP4, VP6, VP7, NSP1, NSP4, NSP4, or NSP5 of 23 RVF and 3 RVG strains were obtained, and demonstrated that multiple variants of both RVF and RVG circulate among Brazilian poultry. In this study, new and important information regarding the genomic characteristics of RVF and RVG is described. In addition, the circulation of these viruses in the study region and the genetic variability of the strains detected are demonstrated. Thus, the data generated in this work should help in understanding the genetics and ecology of these viruses. Nonetheless, the availability of a greater number of sequences is necessary to advance the understanding of the evolution and zoonotic potential of these viruses.

N-Glycosylation of Rotavirus NSP4 Protein Affects Viral Replication and Pathogenesis

Rotavirus (RV), the most common cause of gastroenteritis in children, carries a high economic and health burden worldwide. RV encodes six structural proteins and six nonstructural proteins (NSPs) that play different roles in viral replication. NSP4, a multifunctional protein involved in various viral replication processes, has two conserved N-glycosylation sites; however, the role of glycans remains elusive. Here, we used recombinant viruses generated by a reverse genetics system to determine the role of NSP4 N-glycosylation during viral replication and pathogenesis. The growth rate of recombinant viruses that lost one glycosylation site was as high as that of the wild-type virus. However, a recombinant virus that lost both glycosylation sites (glycosylation-defective virus) showed attenuated replication in cultured cell lines. Specifically, replications of glycosylation-defective virus in MA104 and HT29 cells were 10- and 100,000-fold lower, respectively, than that of the wild-type, suggesting that N-glycosylation of NSP4 plays a critical role in RV replication. The glycosylation-defective virus showed NSP4 mislocalization, delay of cytosolic Ca²⁺ elevation, and less viroplasm formation in MA104 cells; however, these impairments were not observed in HT29 cells. Further analysis revealed that assembly of glycosylation-defective virus was severely impaired in HT29 cells but not in MA104 cells, suggesting that RV replication mechanism is highly cell type dependent. In vivo mouse experiments also showed that the glycosylation-defective virus was less pathogenic than the wild-type virus. Taken together, the data suggest that N-glycosylation of NSP4 plays a vital role in viral replication and pathogenicity. IMPORTANCE Rotavirus is the main cause of gastroenteritis in young children and infants worldwide, contributing to 128,500 deaths each year. Here, we used a reverse genetics approach to examine the role of NSP4 N-glycosylation. An N-glycosylation-defective virus showed attenuated and cell-type-dependent replication in vitro. In addition, mice infected with the N-glycosylation-defective virus had less severe diarrhea than mice infected with the wild type. These results suggest that N-glycosylation affects viral replication and pathogenesis. Considering the reduced pathogenicity in vivo and the high propagation rate in MA104 cells, this glycosylation-defective virus could be an ideal live attenuated vaccine candidate.

Efficacy of Microencapsulated Probiotic as Adjunct Therapy on Resolution of Diarrhea, Copper-Zinc Homeostasis, Immunoglobulins, and Inflammatory Markers in Serum of Spontaneous Rotavirus-Infected Diarrhoetic Calves

The objective of this study was to assess the efficacy of a microencapsulated probiotic as an adjunct therapy in rotavirus-positive diarrhea of neonatal calves that received supportive treatment or supportive along with microencapsulated probiotic treatment, for 5 days. We examined whether microencapsulated Lactobacillus acidophilus NCDC15 probiotic treatment in rotavirus-infected diarrhoetic calves led to faster resolution of diarrhea, amelioration of zinc-copper imbalance, improved the immunoglobulin A and immunoglobulin G, and decreased the inflammatory markers in serum. Calves with rotavirus-positive diarrhea < 4-week age and fecal scores ≥ 2 were randomly assigned into two groups. The supportive along with microencapsulated probiotic treatment significantly (p < 0.05) increased zinc and immunoglobulin A concentrations and decreased copper, tumor necrosis factor-α, and nitric oxide level in serum on days 3 and 5 from pretreatment values; the immunoglobulin G concentration was elevated (p < 0.05) on day 5. The mean resolution time of abnormal fecal score was 5.3 and 3.3 days in supportive treatment and supportive along with microencapsulated probiotic groups, respectively, in log-rank Mantel-Cox test. The calves in the supportive along with microencapsulated probiotic treatment group had faster resolution of diarrhea than supportive treatment group in Dunn's multiple comparisons test. This study demonstrates that supportive treatment along with microencapsulated probiotic administered to naturally rotavirus-infected diarrhoetic calves at onset of diarrhea led to faster resolution of diarrhea, improved zinc and immunoglobulin levels, and decreased the inflammatory parameters in serum of rotavirus-infected diarrhoetic calves.

Solution of a dynamical memory effect COVID-19 infection system with leaky vaccination efficacy by non-singular kernel fractional derivatives

In this paper, the recent trends of COVID-19 infection spread have been studied to explore the advantages of leaky vaccination dynamics in SEVR (Susceptible Effected Vaccinated Recovered) compartmental model with the help of Caputo-Fabrizio (CF) and Atangana-Baleanu derivative in the Caputo sense (ABC) non-singular kernel fractional derivative operators with memory effect within the model to show possible long-term approaches of the infection along with limited defensive vaccine efficacy that can be designed numerically over the closed interval ranging from 0 to 1. One of the main goals is to provide a stepping information about the usefulness of the aforementioned non-singular kernel fractional approaches for a lenient case as well as a critical case in COVID-19 infection spread. Another is to investigate the effect of death rate on state variables. The estimation of death rate for state variables with suitable vaccine efficacy has a significant role in the stability of state variables in terms of basic reproduction number that is derived using next generation matrix method, and order of the fractional derivative. For non-integral orders the pandemic modeling sense viz, CF and ABC, has been compared thoroughly. Graphical presentations together with numerical results have proposed that the methodology is powerful and accurate which can provide new speculations for COVID-19 dynamical systems.

Enterotoxigenic Escherichia coli Heat-Stable Toxin and Ebola Virus Delta Peptide: Similarities and Differences

Enterotoxigenic Escherichia coli (ETEC) STb toxin exhibits striking structural similarity to Ebola virus (EBOV) delta peptide. Both ETEC and EBOV delta peptide are enterotoxins. Comparison of the structural and functional similarities and differences of these two toxins illuminates features that are important in induction of pathogenesis by a bacterial and viral pathogen.

Ebola virus delta peptide is an enterotoxin

During the 2013-2016 West African (WA) Ebola virus (EBOV) outbreak, severe gastrointestinal symptoms were common in patients and associated with poor outcome. Delta peptide is a conserved product of post-translational processing of the abundant EBOV soluble glycoprotein (sGP). The murine ligated ileal loop model was used to demonstrate that delta peptide is a potent enterotoxin. Dramatic intestinal fluid accumulation follows injection of biologically relevant amounts of delta peptide into ileal loops, along with gross alteration of villous architecture and loss of goblet cells. Transcriptomic analyses show that delta peptide triggers damage response and cell survival pathways and downregulates expression of transporters and exchangers. Induction of diarrhea by delta peptide occurs via cellular damage and regulation of genes that encode proteins involved in fluid secretion. While distinct differences exist between the ileal loop murine model and EBOV infection in humans, these results suggest that delta peptide may contribute to EBOV-induced gastrointestinal pathology.

A Narrative Review on the Unexplored Potential of Colostrum as a Preventative Treatment and Therapy for Diarrhea in Neonatal Dairy Calves

Diarrhea is the leading cause of morbidity and mortality in pre-weaned dairy calves and, as such, represents a significant animal health and welfare concern. Furthermore, digestive disease early in life is associated with several long-term consequences such as reduced growth rate and decreased milk yield during the first lactation, thus generating severe economic losses. The majority of diarrheic cases in young calves are treated with antimicrobials; however, it is necessary to develop alternative treatments, as excessive antimicrobial usage can lead to antimicrobial resistance and can negatively impact the gut microflora of a calf. Bovine colostrum is abundant in immune and bioactive factors that improve immune function and development. This rich and natural combination of immunoglobulins, natural antimicrobial factors, growth factors, anti-inflammatories and nutrients may be an attractive alternative to antimicrobials in the treatment of diarrhea in young dairy calves. There is evidence that supports the use of colostrum as an early treatment for diarrhea in young calves. Future research should investigate its therapeutic and economic effectiveness.

Development and characterization of a plant-derived rotavirus-like particle vaccine

BACKGROUND

Virus-like particles (VLPs) are unable to replicate in the recipient but stimulate the immune system through recognition of repetitive subunits. Parenterally delivered rotavirus-VLP (Ro-VLP) vaccine could have the potential to overcome the weaknesses of licensed oral live-attenuated rotavirus vaccines, namely, low efficacy in low-income and high mortality settings and a potential risk of intussusception.

METHODS

A monovalent Ro-VLP composed of viral protein (VP) 7, VP6 and VP2 of G1 genotype specificity was produced in Nicotiana benthamiana using Agrobacterium tumefaciens infiltration-based transient recombinant expression system. Plants expressing recombinant G1 Ro-VLP were harvested, then the resultant biomass was processed through a series of clarification and purification steps including standard extraction, filtration, ultrafiltration and chromatography. The purified G1 Ro-VLP was subsequently examined for its immunogenicity and toxicological profile using animal models.

RESULTS

G1 Ro-VLP had a purity of ≥90% and was structurally similar to triple-layered rotavirus particles as determined by cryogenic transmission electron microscopy. Two doses of aluminum hydroxide-adjuvanted G1 Ro-VLP (1 μg, 5 μg or 30 μg), administered intramuscularly, elicited a robust homotypic neutralizing antibody response in rats. Also, rabbits administered G1 Ro-VLP (10 μg or 30 μg) four times intramuscularly with aluminum hydroxide adjuvant did not show any significant toxicity.

CONCLUSIONS

Plant-derived Ro-VLP composed of VP7, VP6 and VP2 structural proteins would be a plausible alternative to live-attenuated oral rotavirus vaccines currently distributed worldwide.

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.

Metagenomic characterisation of additional and novel avian viruses from Australian wild ducks

Birds, notably wild ducks, are reservoirs of pathogenic and zoonotic viruses such as influenza viruses and coronaviruses. In the current study, we used metagenomics to detect and characterise avian DNA and RNA viruses from wild Pacific black ducks, Chestnut teals and Grey teals collected at different time points from a single location. We characterised a likely new species of duck aviadenovirus and a novel duck gyrovirus. We also report what, to the best of our knowledge, is the first finding of an avian orthoreovirus from Pacific black ducks and a rotavirus F from Chestnut teals. Other viruses characterised from the samples from these wild ducks belong to the virus families Astroviridae, Caliciviridae and Coronaviridae. Some of the viruses may have potential cross-species transmissibility, while others indicated a wide genetic diversity of duck viruses within a genus. The study also showed evidence of potential transmission of viruses along the East Asian-Australasian Flyway; potentially facilitated by migrating shorebirds. The detection and characterisation of several avian viruses not previously described, and causing asymptomatic but potentially also symptomatic infections suggest the need for more virus surveillance studies for pathogenic and potential zoonotic viruses in wildlife reservoirs.

Splenial Lesions in Benign Convulsions With Gastroenteritis Associated With Rotavirus Infection

OBJECTIVE

To investigate clinical risk factors for acute magnetic resonance imaging (MRI) abnormalities in patients with benign convulsions with mild gastroenteritis or benign infantile epilepsy.

STUDY DESIGN

We investigated clinical and diffusion-weighted imaging findings in 32 patients with benign convulsions with mild gastroenteritis and 22 patients with benign infantile epilepsy who underwent MRI within seven days of seizure onset between 2010 and 2015.

RESULTS

Diffusion-weighted imaging showed signal hyperintensity in the splenium of the corpus callosum in seven patients with benign convulsions with mild gastroenteritis, but no abnormalities in patients with benign infantile epilepsy. Patients with benign convulsions with mild gastroenteritis with splenial lesions showed a higher rate of rotavirus detection from feces (P = 0.006), higher serum level of C-reactive protein (P = 0.04), and shorter interval between seizure onset and MRI (P = 0.002) than patients with benign convulsions with mild gastroenteritis without splenial lesions. Multivariate analysis revealed rotavirus infection as a significant risk factor for splenial lesions on diffusion-weighted imaging in patients with benign convulsions with mild gastroenteritis (P = 0.02).

CONCLUSIONS

Splenial lesions are often seen during acute period in patients with benign convulsions with mild gastroenteritis. Rotavirus infection is a risk factor for splenial lesions in patients with benign convulsions with mild gastroenteritis, suggesting the role of rotavirus to cause edema in the corpus callosum. From our observations, benign convulsions with mild gastroenteritis with a splenial lesion on diffusion-weighted imaging suggests good outcomes, and extensive evaluation of these patients may be unnecessary.

Risk factors for the recurrence of convulsions with mild gastroenteritis in children

PURPOSE

To identify risk factors for the recurrence of convulsions with mild gastroenteritis (CwG)¹ in children.

METHODS

Altogether, 613 children with CwG admitted to Children's Hospital of Shanxi Province from January 2010 to December 2015 were selected, their clinical data were retrospectively analyzed, and patients were followed up for 4-10 years. Risk factors for the recurrence of CwG were analyzed based on the clinical characteristics of the children.

RESULTS

Relapse occurred in 35 patients (6.3 %). Recurrence occurred within 6 months after the first CwG in majority of the patients (80 %), and recurrence occurred once in most patients (91.4 %). Risk factors associated with CwG recurrence were age at first attack of ≤18 months (recurrence rates at ages ≤ and >18 months were 8.7 %, and 3.1 %, respectively; χ2 = 4.856, P = 0.028), and a history of convulsions in first-degree relatives (recurrence rates in first-degree relatives with and without a history of convulsion were 20 % and 6.2 %, respectively; χ2 = 5.501, P = 0.019).

CONCLUSIONS

Children with CwG have a possibility of recurrence. The risk of recurrence within 6 months of onset is high and such patients should be carefully observed. Furthermore, the age of onset of ≤18 months and history of convulsions in first-degree relatives are risks factors for CwG recurrence; therefore, these children should be closely followed up.

Profiling of rotavirus 3'UTR-binding proteins reveals the ATP synthase subunit ATP5B as a host factor that supports late-stage virus replication

Genome replication and virion assembly of segmented RNA viruses are highly coordinated events, tightly regulated by sequence and structural elements in the UTRs of viral RNA. This process is poorly defined and likely requires the participation of host proteins in concert with viral proteins. In this study, we employed a proteomics-based approach, named RNA-protein interaction detection (RaPID), to comprehensively screen for host proteins that bind to a conserved motif within the rotavirus (RV) 3' terminus. Using this assay, we identified ATP5B, a core subunit of the mitochondrial ATP synthase, as having high affinity to the RV 3'UTR consensus sequences. During RV infection, ATP5B bound to the RV 3'UTR and co-localized with viral RNA and viroplasm. Functionally, siRNA-mediated genetic depletion of ATP5B or other ATP synthase subunits such as ATP5A1 and ATP5O reduced the production of infectious viral progeny without significant alteration of intracellular viral RNA levels or RNA translation. Chemical inhibition of ATP synthase diminished RV yield in both conventional cell culture and in human intestinal enteroids, indicating that ATP5B positively regulates late-stage RV maturation in primary intestinal epithelial cells. Collectively, our results shed light on the role of host proteins in RV genome assembly and particle formation and identify ATP5B as a novel pro-RV RNA-binding protein, contributing to our understanding of how host ATP synthases may galvanize virus growth and pathogenesis.

Genome characterization of Turkey Rotavirus G strains from the United States identifies potential recombination events with human Rotavirus B strains

Rotavirus G (RVG) strains have been detected in a variety of avian species, but RVG genomes have been published from only a single pigeon and two chicken strains. Two turkey RVG strains were identified and characterized, one in a hatchery with no reported health issues and the other in a hatchery with high embryo/poult mortality. The two turkey RVG strains shared only an 85.3 % nucleotide sequence identity in the VP7 gene while the other genes possessed high nucleotide identity among them (96.3–99.9 %). Low nucleotide percentage identities (31.6–87.3 %) occurred among the pigeon and chicken RVG strains. Interestingly, potential recombination events were detected between our RVG strains and a human RVB strain, in the VP6 and NSP3 segments. The epidemiology of RVG in avian flocks and the pathogenicity of the two different RVG strains should be further investigated to understand the ecology and impact of RVG in commercial poultry flocks.

Analysis of NSP4 Gene and Its Association with Genotyping of Rotavirus Group A in Stool Samples

Background

Non-structural protein 4 (NSP4) is a critical protein for rotavirus (RV) replication and assembly. This protein has multiple domains and motifs that predispose its function and activity. NSP4 has a sequence divergence in human and animal RVs. Recently, 14 genotypes (E1-E14) of NSP4 have been identified, and E1 and E2 have been shown to be the most common genotypes in human.

Methods

The gene and protein sequence of NSP4 in RV-positive samples were inspected with the aim of NSP4 genotyping and variation analysis in viroporin and other domains. P and G typings of RV samples were carried out by WHO primers using a semi-multiplex PCR method. Non-typeable RV samples were amplified by conserved primers and sequenced.

Results

In viroporin and enterotoxin, conserved sequence was detected, and amino acids substitution with the same biochemical properties was found.

Conclusion

Association of NSP4 genotype with P or G genotyping G1/G9 correlates with E1 genogroups. In electrophoretyping of RV, E2 genotype had a short pattern when compared to E1.

In vitro antiviral activity of Lactobacillus casei and Bifidobacterium adolescentis against rotavirus infection monitored by NSP4 protein production

AIMS

The aim of this study was to determine the antiviral activity of four probiotic metabolites (Lactobacillus and Bifidobacetrium species) against rotavirus in vitro infection monitored by the NSP4 protein production and Ca(2+) release.

METHODS AND RESULTS

The antiviral effect of the metabolites was performed due a comparison between a blocking model and an intracelullar model on MA104 cells, with the response of NSP4 production and Ca(2+) liberation measured by flow cytometry. Significant results were obtained with the metabolites of Lactobacillus casei, and Bifidobacterium adolescentis in the reduction of the protein production (P = 0·04 and P = 0·014) and Ca(2+) liberation (P = 0·094 and P = 0·020) in the intracellular model, which suggests a successful antiviral activity against RV infection.

CONCLUSIONS

This study demonstrates that probiotic metabolites were able to interfere with the final amount of intracellular NSP4 protein and a successful Ca(2+) regulation, which suggests a new approach to the mechanism exerted by probiotics against the rotavirus infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

A novel anti-rotaviral effect exerted by probiotic metabolites monitored by the NSP4 protein during the RV in vitro infection and the effect on the Ca(2+) release is reported; suggesting a reduction on the impact of the infection by decreasing the damage of the cells preventing the electrolyte loss.

Rotavirus NSP486-175 interacts with H9c2(2-1) cells in vitro, elevates intracellular Ca2+ levels and can become cytotoxic: a possible mechanism for extra-intestinal pathogenesis

Rotavirus (RV) is the predominant cause of infantile gastroenteritis with multiple pathogenic factors, among which enterotoxin NSP4 is the most significant factor. NSP4 has been shown to induce elevation of the intracellular calcium concentration, alteration of the cytoskeleton organization, and cytopathic effect among other processes. However, increasing evidence suggests that RVs can escape from the gastrointestinal tract and invade other organs and tissues to cause extra-intestinal diseases. In this study, we investigated whether NSP4 has a pathogenic effect on extra-intestinal cells and examined possible molecular mechanisms in vitro. Our results showed that NSP4_86-175 has important functions in increasing intracellular Ca²⁺ concentration, altering actin cytoskeleton organization and inducing cellular damage in H9c2(2-1) cells. Blockade of the integrin α2 receptor using a specific antibody attenuated the increase of intracellular Ca²⁺ concentration and alleviated the observed cytopathic effects, suggesting that integrin α2 may be a receptor for NSP4_86-175. Collectively, these results indicate that extracellular NSP4_86-175 can induce elevation of the intracellular Ca²⁺ concentration, cause cytotoxic changes, and disrupt the actin cytoskeleton in H9c2(2-1) cells, which may constitute a possible mechanism for RV extra-intestinal pathogenesis.

Designing, Construction and Expression of a Recombinant Fusion Protein Comprising the Hepatitis E Virus ORF2 and Rotavirus NSP4 in the Baculovirus Expression System

Background

The hepatitis E virus (HEV) accounts for hepatitis E infection with relatively high mortality rate in pregnant women that can lead to fulminant hepatitis. The baculovirus expression system (BES) has the capability to produce high-level recombinant proteins and could be useful for vaccine designing.

Objectives

The aim of this study was designing a recombinant hepatitis E virus ORF2 and Rotavirus NSP4 (ORF2-NSP4) and to evaluating construction these recombinant proteins in the BES.

Methods

The truncated ORF2 gene (112-607) and truncated ORF2-NSP4 were subcloned in pFastBac1 plasmid, separately, followed by digestion and confirmed by digestion and sequencing. Then the products were transformed into Escherichia coli DH5α and retransformed in DH10Bac competent cells. Finally the white colonies containing Bacmid DNA subjected to PCR for confirming transformation. Bacmid DNA containing HEV truncated ORF2 and HEV truncated ORF2-NSP4 genes were transfected into SF9 cells using BES. The expressed proteins in the cell lysate were evaluated by SDS-PAGE and determined by the western blot assay.

Results

The lengths of subcloned genes, truncated ORF2 and truncated ORF2-NSP4 were 1500 and 2000bp, respectively. After retransforming in DH10Bac, the size of PCR products were 300 bp in Bacmid DNA without recombination while it was 4300 and 3800 bp in Bacmid truncated ORF2-NSP4 and Bacmid truncated ORF2 PCR products. The analysis of protein expression by SDS-PAGE and immunoblotting revealed the presence of 56 KDa for truncated ORF2 and 74.5 KDa for truncated ORF2-NSP4 proteins.

Conclusions

The results of the present study showed that the baculovirus expression system (SF9 cells) was able to express truncated ORF2 and truncated ORF2-NSP4 proteins as a potential candidate vaccine.

Benign convulsions in children with mild gastroenteritis

BACKGROUND

Benign convulsions with mild gastroenteritis (CwG) is a clinical condition characterized by convulsions occurring in otherwise healthy children, usually in the absence of fever and in the presence of mild acute gastroenteritis. Until now, CwG had not been fully recognized as an epileptic syndrome, and several aspects of this condition are not clearly defined, especially its pathogenesis.

METHODS

The main aim of this paper is to discuss after the review of the literature what is known about CwG to facilitate its recognition and treatment.

RESULTS

CwG is a benign condition that has several clinical and prognostic similarities with febrile seizures. The disease occurs in infants and in children who are 1 month to 3 years old, during the winter and early spring when rotavirus and norovirus are circulating. In most cases, seizures follow gastrointestinal symptoms. In a minority of patients, the seizures and gastrointestinal symptoms occur before or simultaneously with the development of diarrhoea. Even if convulsions are mostly described as generalized tonic-clonic, the ictal recordings have always demonstrated a focal origin. Electroencephalography, lumbar punctures, and radiological examinations are not useful because they are normal in these patients; and when alterations are present, they disappear in a relatively short time. Only prolonged seizures, which are usually not common, require antiepileptic treatments in the acute phase.

CONCLUSION

Knowledge of CwG characteristics is essential for paediatricians to avoid useless hospitalization, examinations and, above all, drug administration, as the drugs have potential side effects.

Intradermal delivery of DNA encoding HCV NS3 and perforin elicits robust cell-mediated immunity in mice and pigs

Currently, no vaccine is available against hepatitis C virus (HCV), and although DNA vaccines have considerable potential, this has not been realised. Previously, the efficacy of DNA vaccines for human immunodeficiency virus (HIV) and HCV was shown to be enhanced by including the gene for a cytolytic protein, viz. perforin. In this study, we examined the mechanism of cell death by this bicistronic DNA vaccine, which encoded the HCV non-structural protein 3 (NS3) under the control of the CMV promoter and perforin is controlled by the SV40 promoter. Compared with a canonical DNA vaccine and a bicistronic DNA vaccine encoding NS3 and the proapoptotic gene NSP4, the perforin-containing vaccine elicited enhanced cell-mediated immune responses against the NS3 protein in vaccinated mice and pigs, as determined by ELISpot and intracellular cytokine staining, whereas a mouse challenge model suggested that the immunity was CD8(+) T-cell-dependent. The results of the study showed that the inclusion of perforin in the DNA vaccine altered the fate of NS3-positive cells from apoptosis to necrosis, and this resulted in more robust immune responses in mice and pigs, the latter of which represents an accepted large animal model in which to test vaccine efficacy.

Molecular characterisation of the NSP4 gene of group A human rotavirus G2P[4] strains circulating in São Paulo, Brazil, from 1994 and 2006 to 2010

Group A human rotaviruses (HuRVA) are causative agents of acute gastroenteritis. Six viral structural proteins (VPs) and six nonstructural proteins (NSPs) are produced in RV-infected cells. NSP4 is a diarrhoea-inducing viral enterotoxin and NSP4 gene analysis revealed at least 15 (E1-E15) genotypes. This study analysed the NSP4 genetic diversity of HuRVA G2P[4] strains collected in the state of São Paulo (SP) from 1994 and 2006-2010 using reverse transcription-polymerase chain reaction, sequencing and phylogenetic analysis. Forty (97.6%) G2P[4] strains displayed genotype E2; one strain (2.4%) displayed genotype E1. These results are consistent with the proposed linkage between VP4/VP7 (G2P[4]) and the NSP4 (E2) genotype of HuRVA. NSP4 phylogenetic analysis showed distinct clusters, with grouping of most strains by their genotype and collection year, and most strains from SP were clustered together with strains from other Brazilian states. A deduced amino acid sequence alignment for E2 showed many variations in the C-terminal region, including the VP4-binding domain. Considering the ability of NSP4 to generate host immunity, monitoring NSP4 variations, along with those in the VP4 or VP7 protein, is important for evaluating the circulation and pathogenesis of RV. Finally, the presence of one G2P[4]E1 strain reinforces the idea that new genotype combinations emerge through reassortment and independent segregation.

The Diverse Forms of Lactose Intolerance and the Putative Linkage to Several Cancers

Lactase-phlorizin hydrolase (LPH) is a membrane glycoprotein and the only β-galactosidase of the brush border membrane of the intestinal epithelium. Besides active transcription, expression of the active LPH requires different maturation steps of the polypeptide through the secretory pathway, including N- and O-glycosylation, dimerization and proteolytic cleavage steps. The inability to digest lactose due to insufficient lactase activity results in gastrointestinal symptoms known as lactose intolerance. In this review, we will concentrate on the structural and functional features of LPH protein and summarize the cellular and molecular mechanism required for its maturation and trafficking. Then, different types of lactose intolerance are discussed, and the molecular aspects of lactase persistence/non-persistence phenotypes are investigated. Finally, we will review the literature focusing on the lactase persistence/non-persistence populations as a comparative model in order to determine the protective or adverse effects of milk and dairy foods on the incidence of colorectal, ovarian and prostate cancers.

Investigation of Stilbenoids as Potential Therapeutic Agents for Rotavirus Gastroenteritis

Rotavirus (RV) infections cause severe diarrhea in infants and young children worldwide. Vaccines are available but cost prohibitive for many countries and only reduce severe symptoms. Vaccinated infants continue to shed infectious particles, and studies show decreased efficacy of the RV vaccines in tropical and subtropical countries where they are needed most. Continuing surveillance for new RV strains, assessment of vaccine efficacy, and development of cost effective antiviral drugs remain an important aspect of RV studies. This study was to determine the efficacy of antioxidant and anti-inflammatory stilbenoids to inhibit RV replication. Peanut (A. hypogaea) hairy root cultures were induced to produce stilbenoids, which were purified by high performance countercurrent chromatography (HPCCC) and analyzed by HPLC. HT29.f8 cells were infected with RV in the presence stilbenoids. Cell viability counts showed no cytotoxic effects on HT29.f8 cells. Viral infectivity titers were calculated and comparatively assessed to determine the effects of stilbenoid treatments. Two stilbenoids, trans-arachidin-1 and trans-arachidin-3, show a significant decrease in RV infectivity titers. Western blot analyses performed on the infected cell lysates complemented the infectivity titrations and indicated a significant decrease in viral replication. These studies show the therapeutic potential of the stilbenoids against RV replication.

Long-term follow-up in children with benign convulsions associated with gastroenteritis

BACKGROUND

The outcome of benign convulsions associated with gastroenteritis (CwG) has generally been reported as being excellent. However, these data need to be confirmed in studies with longer follow-up evaluations.

AIM

To assess the long-term neurological outcome of a large sample of children presenting with CwG.

METHODS

We reviewed clinical features of 81 subjects presenting with CwG (1994-2010) from three different Italian centers with a follow-up period of at least 3 years.

RESULTS

Follow-up period ranged from 39 months to 15 years (mean 9.8 years). Neurological examination and cognitive level at the last evaluation were normal in all the patients. A mild attention deficit was detected in three cases (3.7%). Fourteen children (17.3%) received chronic anti-epileptic therapy. Interictal EEG abnormalities detected at onset in 20 patients (24.7%) reverted to normal. Transient EEG epileptiform abnormalities were detected in other three cases (3.7%), and a transient photosensitivity in one (1.2%). No recurrence of CwG was observed. Three patients (3.7%) presented with a febrile seizure and two (2.5%) with an unprovoked seizure, but none developed epilepsy.

CONCLUSIONS

The long-term evaluation of children with CwG confirms the excellent prognosis of this condition, with normal psychomotor development and low risk of relapse and of subsequent epilepsy.

CD8+ T lymphocyte response against extrahepatic biliary epithelium is activated by epitopes within NSP4 in experimental biliary atresia

Interferon (IFN)-γ-driven and CD8+ T cell-dependent inflammatory injury to extrahepatic biliary epithelium (EHBE) is likely to be involved in the development of biliary atresia (BA). We previously showed that viral protein NSP4 is the pathogenic immunogen that causes biliary injury in BA. In this study, NSP4 or four synthetic NSP4 (NSP4(157-170), NSP4(144-152), NSP4(93-110), NSP4(24-32)) identified by computer analysis as candidate CD8+ T cell epitopes were injected into neonatal mice. The pathogenic NSP4 epitopes were confirmed by studying extrahepatic bile duct injury, IFN-γ release and CD8+ T cell response against EHBE. The results revealed, at 7 days postinjection, inoculation of glutathione S-transferase (GST)-NSP4 caused EHBE injury and BA in neonatal mice. At 7 or 14 days postinject, inoculation of GST-NSP4, NSP4(144-152), or NSP4(157-170) increased IFN-γ release by CD8+ T cells, elevated the population of hepatic memory CD8+ T cells, and augmented cytotoxicity of CD8+ T cells to rhesus rotavirus (RRV)-infected or naive EHBE cells. Furthermore, depletion of CD8+ T cells in mice abrogated the elevation of GST-NSP4-induced serum IFN-γ. Lastly, parenteral immunization of mouse dams with GST-NSP4, NSP4(144-152), or NSP4(157-170) decreased the incidence of RRV-induced BA in their offspring. Overall, this study reports the CD8+ T cell response against EHBE is activated by epitopes within rotavirus NSP4 in experimental BA. Neonatal passive immunization by maternal vaccination against NSP4(144-152) or NSP4(157-170) is effective in protecting neonates from developing RRV-related BA.

Whole-genome analyses of DS-1-like human G2P[4] and G8P[4] rotavirus strains from Eastern, Western and Southern Africa

Group A rotaviruses (RVAs) with distinct G and P genotype combinations have been reported globally. We report the genome composition and possible origin of seven G8P[4] and five G2P[4] human RVA strains based on the genetic evolution of all 11 genome segments at the nucleotide level. Twelve RVA ELISA positive stool samples collected in the representative countries of Eastern, Southern and West Africa during the 2007-2012 surveillance seasons were subjected to sequencing using the Ion Torrent PGM and Illumina MiSeq platforms. A reference-based assembly was performed using CLC Bio's clc_ref_assemble_long program, and full-genome consensus sequences were obtained. With the exception of the neutralising antigen, VP7, all study strains exhibited the DS-1-like genome constellation (P[4]-I2-R2-C2-M2-A2-N2-T2-E2-H2) and clustered phylogenetically with reference strains having a DS-1-like genetic backbone. Comparison of the nucleotide and amino acid sequences with selected global cognate genome segments revealed nucleotide and amino acid sequence identities of 81.7-100 % and 90.6-100 %, respectively, with NSP4 gene segment showing the most diversity among the strains. Bayesian analyses of all gene sequences to estimate the time of divergence of the lineage indicated that divergence times ranged from 16 to 44 years, except for the NSP4 gene where the lineage seemed to arise in the more distant past at an estimated 203 years ago. However, the long-term effects of changes found within the NSP4 genome segment should be further explored, and thus we recommend continued whole-genome analyses from larger sample sets to determine the evolutionary mechanisms of the DS-1-like strains collected in Africa.

Systemic rotavirus infection

A new paradigm of rotavirus disease is emerging and rotavirus infection is no longer considered to be localized and confined to the GI tract. New evidence indicates that rotavirus infection is systemic. Viral antigen and infectious virus frequently enter the circulation in both children and animal model systems. Clinical case reports of systemic sequelae to rotavirus infection in children continue to accumulate, suggesting involvement in systemic disease syndromes. The use of animal models is providing biological and molecular evidence for infection at peripheral sites. Thus, infection at peripheral sites may account for reports of systemic sequelae to rotavirus infection. The importance of systemic sequelae and the ability of vaccination to prevent such sequelae remains to be determined.

An overview of calf diarrhea - infectious etiology, diagnosis, and intervention

Calf diarrhea is a commonly reported disease in young animals, and still a major cause of productivity and economic loss to cattle producers worldwide. In the report of the 2007 National Animal Health Monitoring System for U.S. dairy, half of the deaths among unweaned calves was attributed to diarrhea. Multiple pathogens are known or postulated to cause or contribute to calf diarrhea development. Other factors including both the environment and management practices influence disease severity or outcomes. The multifactorial nature of calf diarrhea makes this disease hard to control effectively in modern cow-calf operations. The purpose of this review is to provide a better understanding of a) the ecology and pathogenesis of well-known and potential bovine enteric pathogens implicated in calf diarrhea, b) describe diagnostic tests used to detect various enteric pathogens along with their pros and cons, and c) propose improved intervention strategies for treating calf diarrhea.

Mutational analysis of the rotavirus NSP4 enterotoxic domain that binds to caveolin-1

Background

Rotavirus (RV) nonstructural protein 4 (NSP4) is the first described viral enterotoxin, which induces early secretory diarrhea in neonatal rodents. Our previous data show a direct interaction between RV NSP4 and the structural protein of caveolae, caveolin-1 (cav-1), in yeast and mammalian cells. The binding site of cav-1 mapped to the NSP4 amphipathic helix, and led us to examine which helical face was responsible for the interaction.

Methods

A panel of NSP4 mutants were prepared and tested for binding to cav-1 by yeast two hybrid and direct binding assays. The charged residues of the NSP4 amphipathic helix were changed to alanine (NSP4_46-175-ala6); and three residues in the hydrophobic face were altered to charged amino acids (NSP4_46-175-HydroMut). In total, twelve mutants of NSP4 were generated to define the cav-1 binding site. Synthetic peptides corresponding to the hydrophobic and charged faces of NSP4 were examined for structural changes by circular dichroism (CD) and diarrhea induction by a neonatal mouse study.

Results

Mutations of the hydrophilic face (NSP4_46-175-Ala6) bound cav-1 akin to wild type NSP4. In contrast, disruption of the hydrophobic face (NSP4_46-175-HydroMut) failed to bind cav-1. These data suggest NSP4 and cav-1 associate via a hydrophobic interaction. Analyses of mutant synthetic peptides in which the hydrophobic residues in the enterotoxic domain of NSP4 were altered suggested a critical hydrophobic residue. Both NSP4_{HydroMut112-140,} that contains three charged amino acids (aa113, 124, 131) changed from the original hydrophobic residues and NSP4_{AlaAcidic112-140} that contained three alanine residues substituted for negatively charged (aa114, 125, 132) amino acids failed to induce diarrhea. Whereas peptides NSP4wild type _112−140 and NSP4_{AlaBasic112-140} that contained three alanine substituted for positively charged (aa115, 119, 133) amino acids, induced diarrhea.

Conclusions

These data show that the cav-1 binding domain is within the hydrophobic face of the NSP4 amphipathic helix. The integrity of the helical structure is important for both cav-1 binding and diarrhea induction implying a connection between NSP4 functional and binding activities.

Human G9P[8] rotavirus strains circulating in Cameroon, 1999-2000: Genetic relationships with other G9 strains and detection of a new G9 subtype

Group A rotaviruses (RV-A) are the leading cause of viral gastroenteritis in children worldwide and genotype G9P[8] is one of the five most common genotypes detected in humans. In order to gain insight into the degree of genetic variability of G9P[8] strains circulating in Cameroon, stool samples were collected during the 1999-2000 rotavirus season in two different geographic regions in Cameroon (Southwest and Western Regions). By RT-PCR, 15 G9P[8] strains (15/89=16.8%) were identified whose genomic configurations was subsequently determined by complete or partial gene sequencing. In general, all Cameroonian G9 strains clustered into current globally-spread sublineages of the VP7 gene and displayed 86.6-100% nucleotide identity amongst themselves and 81.2-99.5% nucleotide identity with global G9 strains. The full genome classification of all Cameroonian strains was G9-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1 but phylogenetic analysis of each gene revealed that the strains were spread across 4 or more distinct lineages. An unusual strain, RVA/Human-wt/CMR/6788/1999/G9P[8], which shared the genomic constellation of other Cameroonian G9P[8] strains, contained a novel G9 subtype which diverged significantly (18.8% nucleotide and 19% amino acid distance) from previously described G9 strains. Nucleotide and amino acid alignments revealed that the 3' end of this gene is highly divergent from other G9 VP7 genes suggesting that it arose through extensive accumulation of point mutations. The results of this study demonstrate that diverse G9 strains circulated in Cameroon during 1999-2000.

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.

Construction of an artificial recombinant bicistronic plasmid DNA vaccine against porcine rotavirus

The attenuated Salmonella typhimurium χ4550 strain was used to harbour a reconstructed bicistronic DNA vaccine against porcine rotavirus, which carried the rotavirus nonstructural protein 4 (NSP4) and VP7 genes simultaneously. Using a balanced lethal system, the kanamycin resistance gene of expressing eukaryotic plasmids pVAX1 and pVAXD were replaced by the aspartate β-semialdehyde dehydrogenase (asd) gene. The NSP4 cleavage product (259-525) of rotavirus OSU strain and VP7 full-length genes were amplified by reverse transcription polymerase chain reaction and then inserted into the eukaryotic single-expression plasmid, pVAX1-asd, and the eukaryotic dual-expression plasmid, pVAXD-asd, respectively. The recombinant plasmids pVAX1-asd-NSP4, pVAX1-asd-VP7 and pVAXD-asd-NSP4-VP7 were transformed into the attenuated S. typhimurium χ4550 strain by electrotransformation. An indirect immunofluorescence assay of the expressed COS-7 cell suggested that the recombinant S. typhimurium χ4550 strain was constructed successfully. The recombinant S. typhimurium χ4550 strain was orally administered to BALB/c mice. The group immunised with dual- expression plasmids produced a significantly higher level of serum Immunoglobulin G (IgG) and intestinal Immunoglobulin A (IgA) than the group immunised with single-expression plasmids. These results indicated that eukaryotic bicistronic plasmid DNA vaccines could be successfully constructed to enhance humoural, mucosal and cellular immune response against rotavirus infection.

Rotavirus infection of cells in culture induces activation of RhoA and changes in the actin and tubulin cytoskeleton

Rotavirus infection induces an increase in [Ca²⁺]_cyto, which in turn may affect the distribution of the cytoskeleton proteins in the infected cell. Changes in microfilaments, including the formation of stress fibers, were observed starting at 0.5 h.p.i. using fluorescent phalloidin. Western blot analysis indicated that RhoA is activated between 0.5 and 1 h.p.i. Neither the phosphorylation of RhoA nor the formation of stress fibers were observed in cells infected with virions pre-treated with an anti-VP5* non-neutralizing mAb, suggesting that RhoA activation is stimulated by the interaction of the virus with integrins forming the cell receptor complex. In addition, the structure of the tubulin cytoskeleton was also studied. Alterations of the microtubules were evident starting at 3 h.p.i. and by 7 h.p.i. when microtubules were markedly displaced toward the periphery of the cell cytoplasm. Loading of rotavirus-infected cells with either a Ca²⁺ chelator (BAPTA) or transfection with siRNAs to silence NSP4, reversed the changes observed in both the microfilaments and microtubules distribution, but not the appearance of stress fibers. These results indicate that alterations in the distribution of actin microfilaments are initiated early during infection by the activation of RhoA, and that latter changes in the Ca²⁺ homeostasis promoted by NSP4 during infection may be responsible for other alterations in the actin and tubulin cytoskeleton.

Rotaviral enterotoxin nonstructural protein 4 targets mitochondria for activation of apoptosis during infection

Viruses have evolved to encode multifunctional proteins to control the intricate cellular signaling pathways by using very few viral proteins. Rotavirus is known to express six nonstructural and six structural proteins. Among them, NSP4 is the enterotoxin, known to disrupt cellular Ca(2+) homeostasis by translocating to endoplasmic reticulum. In this study, we have observed translocation of NSP4 to mitochondria resulting in dissipation of mitochondrial membrane potential during virus infection and NSP4 overexpression. Furthermore, transfection of the N- and C-terminal truncated NSP4 mutants followed by analyzing NSP4 localization by immunofluorescence microscopy identified the 61-83-amino acid region as the shortest mitochondrial targeting signal. NSP4 exerts its proapoptotic effect by interacting with mitochondrial proteins adenine nucleotide translocator and voltage-dependent anion channel, resulting in dissipation of mitochondrial potential, release of cytochrome c from mitochondria, and caspase activation. During early infection, apoptosis activation by NSP4 was inhibited by the activation of cellular survival pathways (PI3K/AKT), because PI3K inhibitor results in early induction of apoptosis. However, in the presence of both PI3K inhibitor and NSP4 siRNA, apoptosis was delayed suggesting that the early apoptotic signal is initiated by NSP4 expression. This proapoptotic function of NSP4 is balanced by another virus-encoded protein, NSP1, which is implicated in PI3K/AKT activation because overexpression of both NSP4 and NSP1 in cells resulted in reduced apoptosis compared with only NSP4-expressing cells. Overall, this study reports on the mechanism by which enterotoxin NSP4 exerts cytotoxicity and the mechanism by which virus counteracts it at the early stage for efficient infection.

Characterisation of a G9P[8] rotavirus strain identified during a gastroenteritis outbreak in Alice Springs, Australia post Rotarix™ vaccine introduction

A large rotavirus gastroenteritis outbreak occurred in the Alice Springs region of the Northern Territory, Australia from the 12th of March until the 11th of July 2007. The outbreak occurred five months after the introduction of the Rotarix™ vaccine. Electropherotype and sequence analysis demonstrated that a single G9P[8] strain was responsible for the outbreak and that the strain remained highly conserved during the outbreak period. The outbreak strain contained amino acid changes in regions of the VP7 and NSP4 genes, with known biological function, when compared to previously characterised G9P[8] strains from Australia and other international locations. The recent vaccine introduction was unlikely to have influenced genotype selection in this setting. Importantly, Rotarix™ vaccine was highly effective against the G9P[8] outbreak strain.

Elucidation of the Rotavirus NSP4-Caveolin-1 and -Cholesterol Interactions Using Synthetic Peptides

Rotavirus (RV) NSP4, the first described viral enterotoxin, is a multifunctional glycoprotein that contributes to viral pathogenesis, morphogenesis, and replication. NSP4 binds both termini of caveolin-1 and is isolated from caveolae fractions that are rich in anionic phospholipids and cholesterol. These interactions indicate that cholesterol/caveolin-1 plays a role in NSP4 transport to the cell surface, which is essential to its enterotoxic activity. Synthetic peptides were utilized to identify target(s) of intervention by exploring the NSP4-caveolin-1 and -cholesterol interactions. NSP4_112–140 that overlaps the caveolin-1 binding domain and a cholesterol recognition amino acid consensus (CRAC) motif and both termini of caveolin-1 (N-caveolin-1_2–20,  _19–40 and C-caveolin-1_161–180) were synthesized. Direct fluorescence-binding assays were employed to determine binding affinities of the NSP4-caveolin-1 peptides and cholesterol. Intracellular cholesterol alteration revealed a redistribution of NSP4 and disintegration of viroplasms. These data further imply interruption of NSP4_112–140-N-caveolin-1_19–40 and cholesterol interactions may block NSP4 intracellular transport, hence enterotoxicity.

Rotavirus NSP4 is secreted from infected cells as an oligomeric lipoprotein and binds to glycosaminoglycans on the surface of non-infected cells

Background

Nonstructural glycoprotein 4 (NSP4) encoded by rotavirus is the only viral protein currently believed to function as an enterotoxin. NSP4 is synthesized as an intracellular transmembrane glycoprotein and as such is essential for virus assembly. Infection of polarized Caco-2 cells with rotavirus also results in the secretion of glycosylated NSP4 apparently in a soluble form despite retention of its transmembrane domain. We have examined the structure, solubility and cell-binding properties of this secreted form of NSP4 to further understand the biochemical basis for its enterotoxic function. We show here that NSP4 is secreted as discrete detergent-sensitive oligomers in a complex with phospholipids and demonstrate that this secreted form of NSP4 can bind to glycosaminoglycans present on the surface of a range of different cell types.

Methods

NSP4 was purified from the medium of infected cells after ultracentrifugation and ultrafiltration by successive lectin-affinity and ion exchange chromatography. Oligomerisation of NSP4 was examined by density gradient centrifugation and chemical crosslinking and the lipid content was assessed by analytical thin layer chromatography and flame ionization detection. Binding of NSP4 to various cell lines was measured using a flow cytometric-based assay.

Results

Secreted NSP4 formed oligomers that contained phospholipid but dissociated to a dimeric species in the presence of non-ionic detergent. The purified glycoprotein binds to the surface of various non-infected cells of distinct lineage. Binding of NSP4 to HT-29, a cell line of intestinal origin, is saturable and independent of divalent cations. Complementary biochemical approaches reveal that NSP4 binds to sulfated glycosaminoglycans on the plasma membrane.

Conclusion

Our study is the first to analyze an authentic (i.e. non-recombinant) form of NSP4 that is secreted from virus-infected cells. Despite retention of the transmembrane domain, secreted NSP4 remains soluble in an aqueous environment as an oligomeric lipoprotein that can bind to various cell types via an interaction with glycosaminoglycans. This broad cellular tropism exhibited by NSP4 may have implications for the pathophysiology of rotavirus disease.

The rotavirus enterotoxin (NSP4) promotes re-modeling of the intracellular microtubule network

Expression of the rotavirus enterotoxin (NSP4) in transfected monkey kidney cells was found to result in a dramatic re-modeling of the microtubule (MT) network. This important centrosome organized cytoskeletal element was dissolved by expression of NSP4 and re-formed in a ring array at the periphery of the cell, similar to that seen following normal virus infection. Site directed mutagenesis of the N-linked glycosylation sites in NSP4 was employed to show that glycosylation of NSP4 was not required for it to promote changes in the MT network. This result together with experiments using conventional inhibitors indicated that NSP4's ability to cause elevation of intracellular calcium levels was also not necessary to effect the changes in the MT network. Use of the centrosome function inhibitor nocodazole demonstrated that NSP4 based remodeling of the MT network was dominant over the normal organizational role of the centrosome. Finally the remodeling of the MT network was shown not to be linked to cellular apoptosis or necrosis. The potential importance of this newly recognised role for NSP4 in the overall process of intracellular pathogenesis by rotaviruses is discussed.

Detection of a porcine rotavirus strain with VP4, VP7 and NSP4 genes of different animal origins

A new rotavirus strain, sh0902, was detected in diarrheic piglets on a farm in Shanghai, China, and its genotype was characterized as G1P[7]. Analysis of the VP4, VP7 and NSP4 genes demonstrated VP4 homology to bovine and swine rotavirus strains; the nucleotide (nt) and amino acid (aa) identities were 99.7% and 99.5%, respectively. The VP7 gene was highly homologous to that of a giant panda rotavirus strain, with 98.5% similarity at the nt level and 99% similarity at the aa level. The nucleotide sequence of the NSP4 gene displayed high homology to human rotavirus strain R479, with 99.7% identity at the nt level and 99.3% identity at the aa level. This is the first report of an unusual porcine rotavirus strain with VP4, VP7 and NSP4 genes that are highly homologous to bovine, swine, giant panda and human strains isolated at geographically distant sites (South Korea, China and India). Our data indicate that rotaviruses have circulated among humans and animals and undergone genome reassortment.

Rotavirus NSP4: Cell type-dependent transport kinetics to the exofacial plasma membrane and release from intact infected cells

Background

Rotavirus NSP4 localizes to multiple intracellular sites and is multifunctional, contributing to RV morphogenesis, replication and pathogenesis. One function of NSP4 is the induction of early secretory diarrhea by binding surface receptors to initiate signaling events. The aims of this study were to determine the transport kinetics of NSP4 to the exofacial plasma membrane (PM), the subsequent release from intact infected cells, and rebinding to naïve and/or neighboring cells in two cell types.

Methods

Transport kinetics was evaluated using surface-specific biotinylation/streptavidin pull-downs and exofacial exposure of NSP4 was confirmed by antibody binding to intact cells, and fluorescent resonant energy transfer. Transfected cells similarly were monitored to discern NSP4 movement in the absence of infection or other viral proteins. Endoglycosidase H digestions, preparation of CY3- or CY5- labeled F(ab)₂ fragments, confocal imaging, and determination of preferential polarized transport employed standard laboratory techniques. Mock-infected, mock-biotinylated and non-specific antibodies served as controls.

Results

Only full-length (FL), endoglycosidase-sensitive NSP4 was detected on the exofacial surface of two cell types, whereas the corresponding cell lysates showed multiple glycosylated forms. The C-terminus of FL NSP4 was detected on exofacial-membrane surfaces at different times in different cell types prior to its release into culture media. Transport to the PM was rapid and distinct yet FL NSP4 was secreted from both cell types at a time similar to the release of virus. NSP4-containing, clarified media from both cells bound surface molecules of naïve cells, and imaging showed secreted NSP4 from one or more infected cells bound neighboring cell membranes in culture. Preferential sorting to apical or basolateral membranes also was distinct in different polarized cells.

Conclusions

The intracellular transport of NSP4 to the PM, translocation across the PM, exposure of the C-terminus on the cell surface and subsequent secretion occurs via an unusual, complex and likely cell-dependent process. The exofacial exposure of the C-terminus poses several questions and suggests an atypical mechanism by which NSP4 traverses the PM and interacts with membrane lipids. Mechanistic details of the unconventional trafficking of NSP4, interactions with host-cell specific molecules and subsequent release require additional study.

Rotavirus toxin NSP4 induces diarrhea by activation of TMEM16A and inhibition of Na+ absorption

Rotavirus infection is the most frequent cause for severe diarrhea in infants, killing more than 600,000 every year. The nonstructural protein NSP4 acts as a rotavirus enterotoxin, inducing secretory diarrhea without any structural organ damage. Electrolyte transport was assessed in the colonic epithelium from pups and adult mice using Ussing chamber recordings. Western blots and immunocytochemistry was performed in intestinal tissues from wild-type and TMEM16A knockout mice. Ion channel currents were recorded using patch clamp techniques. We show that the synthetic NSP4(114-135) peptide uses multiple pro-secretory pathways to induce diarrhea, by activating the recently identified Ca2+ -activated Cl- channel TMEM16A, and by inhibiting Na+ absorption by the epithelial Na+ channel ENaC and the Na+ /glucose cotransporter SGLT1. Activation of secretion and inhibition of Na+ absorption by NSP4(114-135), respectively, could be potently suppressed by wheat germ agglutinin which probably competes with NSP4(114-135) for binding to an unknown glycolipid receptor. The present paper gives a clue as to mechanisms of rotavirus-induced diarrhea and suggests wheat germ agglutinin as a simple and effective therapy.

An inside job: subversion of the host secretory pathway by intestinal pathogens

PURPOSE OF REVIEW

The cellular secretory pathway, composed of the endoplasmic reticulum, Golgi apparatus, and cellular vesicles, mediates the intracellular trafficking of proteins and lipids. Gastrointestinal pathogens frequently affect the functions of enterocytes, the differentiated cells involved in secretion and absorption of extracellular molecules. Microbial pathogenesis can be enhanced by altering the trafficking of key molecules such as brush border enzymes, soluble immune mediators such as cytokines and chemokines, and MHC Class I molecules, all of which rely on the secretory pathway for their appropriate cellular localization. This review focuses on our current understanding of the distinct mechanisms employed by enteric pathogens to antagonize the secretory pathway.

RECENT FINDINGS

Many pathogens encode individual or multiple proteins to antagonize the secretory pathway, including disrupting the trafficking of vesicles between the endoplasmic reticulum, Golgi, and plasma membrane. This antagonism allows for increased pathogenesis and can assist, directly or indirectly, in microbial replication. Virtually all arms of the secretory pathway are targeted by intestinal pathogens, supporting the pathogenic significance of shutting this pathway down.

SUMMARY

This review summarizes the mechanisms utilized by gut pathogens to disrupt the cellular secretory pathway and addresses potential therapeutic targets to combat these highly prevalent and burdensome microbes.