Age-dependent diarrhea induced by a rotaviral nonstructural glycoprotein

Live Attenuated Human Rotavirus Vaccine, Rotarix™

Rotavirus infections are the leading cause of severe gastroenteritis in young children worldwide. Recently two new rotavirus vaccines have entered the world market. This review provides a summary of the rationale, development, and evaluation of one of these vaccines, Rotarix. Rotarix is a live oral rotavirus vaccine developed from a single protective human strain following multiple passages in tissue culture to attenuate the strain. The vaccine is administered as two oral doses at approximately 2 and 4 months of age. Large safety and efficacy trials have shown the vaccine is safe, not associated with intussusception, and effective against the most common circulating human serotypes. Efficacy against severe rotavirus gastroenteritis and hospitalization have ranged from 85 to 100 percent.

Bestrophin-1 enables Ca2+-activated Cl- conductance in epithelia

Epithelial cells express calcium-activated Cl(-) channels of unknown molecular identity. These Cl(-) channels play a central role in diseases such as secretory diarrhea, polycystic kidney disease, and cystic fibrosis. The family of bestrophins has been suggested to form calcium-activated Cl(-) channels. Here, we demonstrate molecular and functional expression of bestrophin-1 (BEST1) in mouse and human airways, colon, and kidney. Endogenous calcium-activated whole cell Cl(-) currents coincide with endogenous expression of the Vmd2 gene product BEST1 in murine and human epithelial cells, whereas calcium-activated Cl(-) currents are absent in epithelial tissues lacking BEST1 expression. Blocking expression of BEST1 with short interfering RNA or applying an anti-BEST1 antibody to a patch pipette suppressed ATP-induced whole cell Cl(-) currents. Calcium-dependent Cl(-) currents were activated by ATP in HEK293 cells expressing BEST1. Thus, BEST1 may form the Ca2+-activated Cl(-) current, or it may be a component of a Cl(-) channel complex in epithelial tissues.

Cytobiological consequences of calcium-signaling alterations induced by human viral proteins

Since calcium-signaling regulates specific and fundamental cellular processes, it represents the ideal target of viral proteins, in order for the virus to control cellular functions and favour its persistence, multiplication and spread. A detailed analysis of reports focused on the impact of viral proteins on calcium-signaling has shown that virus-related elevations of cytosolic calcium levels allow increased viral protein expression (HIV-1, HSV-1/2), viral replication (HBx, enterovirus 2B, HTLV-1 p12(I), HHV-8, EBV), viral maturation (rotavirus), viral release (enterovirus 2B) and cell immortalization (EBV). Interestingly, virus-induced decreased cytosolic calcium levels have been found to be associated with inhibition of immune cells functions (HIV-1 Tat, HHV-8 K15, EBV LMP2A). Finally, several viral proteins are able to modulate intracellular calcium-signaling to control cell viability (HIV-1 Tat, HTLV-1 p13(II), HCV core, HBx, enterovirus 2B, HHV-8 K7). These data point out calcium-signaling as a key cellular target for viral infection and should stimulate further studies exploring new calcium-related therapeutic strategies.

Rotavirus NSP4 induces a novel vesicular compartment regulated by calcium and associated with viroplasms

Rotavirus is a major cause of infantile viral gastroenteritis. Rotavirus nonstructural protein 4 (NSP4) has pleiotropic properties and functions in viral morphogenesis as well as pathogenesis. Recent reports show that the inhibition of NSP4 expression by small interfering RNAs leads to alteration of the production and distribution of other viral proteins and mRNA synthesis, suggesting that NSP4 also affects virus replication by unknown mechanisms. This report describes studies aimed at correlating the localization of intracellular NSP4 in cells with its functions. To be able to follow the localization of NSP4, we fused the C terminus of full-length NSP4 with the enhanced green fluorescent protein (EGFP) and expressed this fusion protein inducibly in a HEK 293-based cell line to avoid possible cytotoxicity. NSP4-EGFP was initially localized in the endoplasmic reticulum (ER) as documented by Endo H-sensitive glycosylation and colocalization with ER marker proteins. Only a small fraction of NSP4-EGFP colocalized with the ER-Golgi intermediate compartment (ERGIC) marker ERGIC-53. NSP4-EGFP did not enter the Golgi apparatus, in agreement with the Endo H sensitivity and a previous report that secretion of an NSP4 cleavage product generated in rotavirus-infected cells is not inhibited by brefeldin A. A significant population of expressed NSP4-EGFP was distributed in novel vesicular structures throughout the cytoplasm, not colocalizing with ER, ERGIC, Golgi, endosomal, or lysosomal markers, thus diverging from known biosynthetic pathways. The appearance of vesicular NSP4-EGFP was dependent on intracellular calcium levels, and vesicular NSP4-EGFP colocalized with the autophagosomal marker LC3. In rotavirus-infected cells, NSP4 colocalized with LC3 in cap-like structures associated with viroplasms, the site of nascent viral RNA replication, suggesting a possible new mechanism for the involvement of NSP4 in virus replication.

Role of nitric oxide during rotavirus infection

The pathophysiological mechanisms behind rotavirus-induced diarrhoea still remain incomplete. Current views suggest that the non-structural protein 4 (NSP4) of rotavirus and the enteric nervous system (ENS) participate in water secretion and diarrhoea. In the present work the role of nitric oxide (NO) in rotavirus infection and disease has been studied in vitro, mice and humans. Incubation of human intestinal epithelial cells (HT-29) with purified NSP4 but not with infectious virus produced NO2/NO3 accumulation in the incubation media. The NSP4-induced release of NO metabolites occurred within the first minutes after the addition of the toxin. Mice infected with murine rotavirus (strain EDIM) accumulated NO2/NO3 in the urine at the onset for diarrhoea. Following rotavirus infection, inducible nitric oxide synthetase (iNOS) mRNA was upregulated in ileum, but not in duodenum or jejunum of newborn pups within 5 days post-infection. A prospective clinical study including 46 children with acute rotavirus infection and age-matched controls concluded that rotavirus infection stimulates NO production during the course of the disease (P < 0.001). These observations identify NO as an important mediator of host responses during rotavirus infection.

Rotavirus vaccines: current prospects and future challenges

Rotavirus is the most common cause of severe diarrhoea in children worldwide and diarrhoeal deaths in children in developing countries. Accelerated development and introduction of rotavirus vaccines into global immunisation programmes has been a high priority for many international agencies, including WHO and the Global Alliance for Vaccines and Immunizations. Vaccines have been developed that could prevent the enormous morbidity and mortality from rotavirus and their effect should be measurable within 2-3 years. Two live oral rotavirus vaccines have been licensed in many countries; one is derived from an attenuated human strain of rotavirus and the other combines five bovine-human reassortant strains. Each vaccine has proven highly effective in preventing severe rotavirus diarrhoea in children and safe from the possible complication of intussusception. In developed countries, these vaccines could substantially reduce the number and associated costs of child hospitalisations and clinical visits for acute diarrhoea. In developing countries, they could reduce deaths from diarrhoea and improve child survival through programmes for childhood immunisations and diarrhoeal disease control. Although many scientific, programmatic, and financial challenges face the global use of rotavirus vaccines, these vaccines-and new candidates in the pipeline-hold promise to make an immediate and measurable effect to improve child health and survival from this common burden affecting all children.

Rotavirus viremia and extraintestinal viral infection in the neonatal rat model

Rotaviruses infect mature, differentiated enterocytes of the small intestine and, by an unknown mechanism, escape the gastrointestinal tract and cause viremia. The neonatal rat model of rotavirus infection was used to determine the kinetics of viremia, spread, and pathology of rotavirus in extraintestinal organs. Five-day-old rat pups were inoculated intragastrically with an animal (RRV) or human (HAL1166) rotavirus or phosphate-buffered saline. Blood was collected from a subset of rat pups, and following perfusion to remove residual blood, organs were removed and homogenized to analyze rotavirus-specific antigen by enzyme-linked immunosorbent assay and infectious rotavirus by fluorescent focus assay or fixed in formalin for histology and immunohistochemistry. Viremia was detected following rotavirus infection with RRV and HAL1166. The RRV 50% antigenemia dose was 1.8 x 10(3) PFU, and the 50% diarrhea dose was 7.7 x 10(5) PFU, indicating that infection and viremia occurred in the absence of diarrhea and that detecting rotavirus antigen in the blood was a more sensitive measure of infection than diarrhea. Rotavirus antigens and infectious virus were detected in multiple organs (stomach, intestines, liver, lungs, spleen, kidneys, pancreas, thymus, and bladder). Histopathological changes due to rotavirus infection included acute inflammation of the portal tract and bile duct, microsteatosis, necrosis, and inflammatory cell infiltrates in the parenchymas of the liver and lungs. Colocalization of structural and nonstructural proteins with histopathology in the liver and lungs indicated that the histological changes observed were due to rotavirus infection and replication. Replicating rotavirus was also detected in macrophages in the lungs and blood vessels, indicating a possible mechanism of rotavirus dissemination. Extraintestinal infectious rotavirus, but not diarrhea, was observed in the presence of passively or actively acquired rotavirus-specific antibody. These findings alter the previously accepted concept of rotavirus pathogenesis to include not only gastroenteritis but also viremia, and they indicate that rotavirus could cause a broad array of systemic diseases in a number of different organs.

Isolation and characterization of a new simian rotavirus, YK-1

Background

To effectively analyze the requirements for protection to rotavirus infection, a reliable animal model that reasonably mimics infection and disease in humans is needed. A requirement for an effective animal model is the availability of appropriate rotavirus stocks for challenge.

Results

A new simian rotavirus, designated YK-1, was isolated from a 2-year-old immunodeficient pigtailed macaque with chronic diarrhea. YK-1 was distinguishable by electropherotype from the other simian rotavirus strains, SA11 and RRV. One variant of YK-1, clone 311, which was isolated after adaptation and plaque purification in cell cultures, displayed an unusual RNA electropherotype with an abnormally migrating gene 11 segment. Sequence analysis demonstrated a genetic rearrangement that involved a partial duplication of the gene 11 ORF encoding NSP5. YK-1 was identified as a Group A rotavirus belonging to subgroup 1. To further characterize the YK-1 strain, the genes encoding VP4, VP7, and NSP4 were sequenced. Analysis of VP4 and VP7 gene fragments suggests that this strain is a G3P[3] rotavirus and is closely related to the simian rotavirus strain RRV. Serotype analysis also identified YK-1 as a G3 rotavirus. The NSP4 genotype of YK-1 is C, the same genotype as RRV.

Conclusion

This newly isolated rotavirus, YK-1, is being used to establish a nonhuman primate model for studying the infectivity, immunity, and pathogenesis of rotavirus and for evaluating candidate rotavirus vaccines.

The nisin-controlled gene expression system: Construction, application and improvements

Lactic acid bacteria are widely used in industrial fermentation. The potential use of these bacteria as homologous and heterologous protein expression hosts has been investigated extensively. The NIsin-Controlled gene Expression system (the NICE system) is an efficient and promising gene expression system based on the autoregulation mechanism of nisin biosynthesis in the Lactococcus lactis. In the NICE system, the membrane-located histidine kinase NisK senses the inducing signal nisin and autophosphorylates, then transfers phosphorous group to intracellular response regulator protein NisR which activates nisA promoter to express the downstream gene(s). The NICE system allows regulated overproduction of a variety of interest proteins by several Gram-positive bacteria, especially L. lactis. The essential elements for system construction, its application for expression of some biotechnologically important proteins and further improvements of this system are discussed.

Full genomic analysis of human rotavirus strain B4106 and lapine rotavirus strain 30/96 provides evidence for interspecies transmission

The Belgian rotavirus strain B4106, isolated from a child with gastroenteritis, was previously found to have VP7 (G3), VP4 (P[14]), and NSP4 (A genotype) genes closely related to those of lapine rotaviruses, suggesting a possible lapine origin or natural reassortment of strain B4106. To investigate the origin of this unusual strain, the gene sequences encoding VP1, VP2, VP3, VP6, NSP1, NSP2, NSP3, and NSP5/6 were also determined. To allow comparison to a lapine strain, the 11 double-stranded RNA segments of a European G3P[14] rabbit rotavirus strain 30/96 were also determined. The complete genome similarity between strains B4106 and 30/96 was 93.4% at the nucleotide level and 96.9% at the amino acid level. All 11 genome segments of strain B4106 were closely related to those of lapine rotaviruses and clustered with the lapine strains in phylogenetic analyses. In addition, sequence analyses of the NSP5 gene of strain B4106 revealed that the altered electrophoretic mobility of NSP5, resulting in a super-short pattern, was due to a gene rearrangement (head-to-tail partial duplication, combined with two short insertions and a deletion). Altogether, these findings confirm that a rotavirus strain with an entirely lapine genome complement was able to infect and cause severe disease in a human child.

Rotavirus vaccine: early introduction in Latin America-risks and benefits

Rotavirus infection is the cause of severe gastroenteritis of young children worldwide, leading to an estimate of 600,000 deaths a year. Efforts to develop an effective and safe vaccine resulted in licensing in 1998 of a live oral vaccine (RotaShield) that was withdrawn less than 1 year later when reports of cases of intussusception were linked to its application. This led to development of new rotavirus vaccine candidates that are currently in late phase III clinical trials. One of these vaccines, GlaxoSmithKline's Rotarix, was licensed in July 2004 to be used in Mexico. This review describes the general background for rotavirus vaccine development, the different vaccine candidates that have been tested or are currently being evaluated, the association of rotavirus vaccination with the bowel blockage known as intussuception, and discusses the benefits and risks of the fast-track introduction of Rotarix in Latin America, and particularly in Mexico.

Generation and immunogenicity of a recombinant replication-incompetent adenovirus expressing human rotavirus NSP4 protein

AIM: To investigate the efficacy of passive protection induced by the recombinant adeno-virus bearing human rotavirus NSP4 gene and to explore the clues for novel rotavirus vaccine development.

METHODS: Human rotavirus NSP4 protein was expressed in a recombinant adenovirus. AdEasy system was recruited to facilitate the preparation and the NSP4 gene was inserted into the early 1 region of the vector by homologous recombination in E.coli. The expression of NSP4 was confirmed by Western blotting. The resultant recombinant adenovirus rvAdEasyNSP4 was induced to mice by intranasal (i.n.) immunization. Specific IgG and IgA antibodies were detected in the murine serum. Murine pups born to the rvAdEasyNSP4 immunized dams were challenged with simian rotavirus SA11 strain orally 4 d after birth, and the induced diarrhea was graded.

RESULTS: The recombinant adenovirus rvAdEasyNSP4 showed typical morphology under electron microscope. The transcription of NSP4 specific mRNA by rvAdEasyNSP4 was confirmed with RT-PCR in infected 293 cells, and the expression of the NSP4 protein was verified by Western blotting. After immunization for three times, the positive rates of serum IgG antibody were 28.5%, 85.7% and 100%, respectively, while after the first immunization, the titer of serum IgG reached 1:1 000. After immunization, the positive rate of IgA antibody reached the level of 71.4%. Moderate protection was achieved after simian rotavirus SA11 strain challenged in murine pups.

CONCLUSION: NSP4 protein of human rotavirus strain can be expressed by a recombinant adenovirus vector and trigger effective immune response in mice, laying a solid foundation for the development of novel rotavirus genetic engineering vaccine.

Low-barrier hydrogen bond between phosphate and the amide group in phosphopeptide

As the conversion between the monoionic (1) and diionic (2) form of the phosphate occurs, the phosphorylated peptides or proteins can not only cause the formation of a hydrogen bond between the phosphate group and the amide group but also change the strength of the hydrogen bond to form low-barrier hydrogen bonds (LBHBs). This reversible protonation of the phosphate group, which changes both the electrostatic properties of the phosphate group and the strength of the hydrogen bond, provides a possible mechanism in regulating protein function.

Molecular analysis of VP4, VP7, and NSP4 genes of P[6]G2 rotavirus genotype strains recovered from neonates admitted to hospital in Belém, Brazil

This investigation describes the molecular characterization of P[6]G2 rotavirus strains from hospitalized neonates with community-acquired diarrhea (CAD), nosocomial diarrhea (ND), and asymptomatic nosocomial infection (ANI) in Belém, Brazil. Twenty-six rotavirus strains with P[6]G2 genotype were sequenced to genes coding for VP4, VP7, and NSP4 proteins. Phylogenetic analysis of the VP4 gene, including prototype strains RV3, ST3, M37, and U1205, showed that local P[6]G2 strains clustered forming a distinct lineage (bootstrap of 99%). Brazilian P[6]G2 strains had the highest homology (ranging from 96.0%-98.3%) with the African strain GR1107, G4P[6]. Phylogenetic tree for VP7 gene was constructed including old and new G2 African strains SA3958GR/97, SA356PT/96, SA514GR/87, SA4476PT/97, BF3676/99, GH1803/99, and representative strains of G1, G3, G4, G5, G8, and G9 genotypes. The Brazilian P[6]G2 samples fell into a distinct group (bootstrap value of 97%) and showed homology rates ranging from 92.1% to 93.5% with P[6]G2 African strains BF3676/99, GH1803/99, and SA3958GR/97. Nucleotide sequence analysis of the NSP4 gene, including human prototype strains S2, KUN, DS-1, RV5, RV3 and ST3, and animal prototype OSU, showed that all neonatal isolates fell into genotype A and clustered with a bootstrap value of 100%, with in-group similarities ranging from 99.3% to 100%. In this study no significant differences in nucleotide sequences of the VP4, VP7, and NSP4 genes could be observed when comparing diarrheic (CAD and ND) and non-diarrheic (ANI) babies. Monitoring of rotavirus strains in hospital environments is of particular importance, since it is claimed currently that an efficacious rotavirus vaccine, when available for routine use, will determine an impact on hospital-acquired rotavirus disease.

The rotavirus enterotoxin NSP4 directly interacts with the caveolar structural protein caveolin-1

Rotavirus nonstructural protein 4 (NSP4) is known to function as an intracellular receptor at the endoplasmic reticulum (ER) critical to viral morphogenesis and is the first characterized viral enterotoxin. Exogenously added NSP4 induces diarrhea in rodent pups and stimulates secretory chloride currents across intestinal segments as measured in Ussing chambers. Circular dichroism studies further reveal that intact NSP4 and the enterotoxic peptide (NSP4(114-135)) that is located within the extended, C-terminal amphipathic helix preferentially interact with caveola-like model membranes. We now show colocalization of NSP4 and caveolin-1 in NSP4-transfected and rotavirus-infected mammalian cells in reticular structures surrounding the nucleus (likely ER), in the cytosol, and at the cell periphery by laser scanning confocal microscopy. A direct interaction between NSP4 residues 112 to 140 and caveolin-1 was determined by the Pro-Quest yeast two-hybrid system with full-length NSP4 and seven overlapping deletion mutants as bait, caveolin-1 as prey, and vice versa. Coimmunoprecipitation of NSP4-caveolin-1 complexes from rotavirus-infected mammalian cells demonstrated that the interaction occurs during viral infection. Finally, binding of caveolin-1 from mammalian cell lysates to Sepharose-bound, NSP4-specific synthetic peptides confirmed the yeast two-hybrid data and further delineated the binding domain to amino acids 114 to 135. We propose that the association of NSP4 and caveolin-1 contributes to NSP4 intracellular trafficking from the ER to the cell surface and speculate that exogenously added NSP4 stimulates signaling molecules located in caveola microdomains.

The Rotavirus Vaccine Saga

Rotavirus is the single most common cause of acute, dehydrating gastroenteritis worldwide. This is a highly contagious and highly democratic disease. The attack rate in infants and young children is similar regardless of sanitation, socioeconomics or geography. Rotavirus vaccine development began in the early 1980s using a "Jennerian" approach based on rotaviruses that normally infect animals. Although these vaccines were found to be generally safe, protection from disease was inconsistent. The second generation of vaccines was based on the same animal viruses configured to carry the relevant coat proteins of human rotaviruses. An attenuated human rotavirus vaccine has also been developed. After close to 20 years of laboratory and clinical studies, safe and effective rotavirus vaccines are approaching regulatory approval.

N- and C-terminal cooperation in rotavirus enterotoxin: novel mechanism of modulation of the properties of a multifunctional protein by a structurally and functionally overlapping conformational domain

Rotavirus NSP4 is a multifunctional endoplasmic reticulum (ER)-resident nonstructural protein with the N terminus anchored in the ER and about 131 amino acids (aa) of the C-terminal tail (CT) oriented in the cytoplasm. Previous studies showed a peptide spanning aa 114 to 135 to induce diarrhea in newborn mouse pups with the 50% diarrheal dose approximately 100-fold higher than that for the full-length protein, suggesting a role for other regions in the protein in potentiating its diarrhea-inducing ability. In this report, employing a large number of methods and deletion and amino acid substitution mutants, we provide evidence for the cooperation between the extreme C terminus and a putative amphipathic alpha-helix located between aa 73 and 85 (AAH73-85) at the N terminus of DeltaN72, a mutant that lacked the N-terminal 72 aa of nonstructural protein 4 (NSP4) from Hg18 and SA11. Cooperation between the two termini appears to generate a unique conformational state, specifically recognized by thioflavin T, that promoted efficient multimerization of the oligomer into high-molecular-mass soluble complexes and dramatically enhanced resistance against trypsin digestion, enterotoxin activity of the diarrhea-inducing region (DIR), and double-layered particle-binding activity of the protein. Mutations in either the C terminus, AAH73-85, or the DIR resulted in severely compromised biological functions, suggesting that the properties of NSP4 are subject to modulation by a single and/or overlapping highly sensitive conformational domain that appears to encompass the entire CT. Our results provide for the first time, in the absence of a three-dimensional structure, a unique conformation-dependent mechanism for understanding the NSP4-mediated pleiotropic properties including virus virulence and morphogenesis.

Rotavirus types in Europe and their significance for vaccination

The degree of diversity of cocirculating human rotavirus wild-type strains is high. This article reviews the occurrence and frequency of rotavirus types in European children younger than 5 years of age during the past 10-15 years. To enable greater understanding of the overall epidemiologic situation, rotavirus types found in animals in Europe are described. In addition, rotavirus types occurring in children outside Europe are considered. Taken together, these data provide an essential background to the development of rotavirus vaccines. The different concepts of immunization with the 2 main rotavirus candidate vaccines are briefly discussed, and their potential impact on the epidemiology of cocirculating rotavirus wild-type viruses is considered. A case is made for comprehensive surveillance of cocirculating human rotavirus types in Europe after the implementation of rotavirus vaccination.

Genetic variation ofNSP1 andNSP4 genes among serotype G9 rotaviruses causing hospitalization of children in Melbourne, Australia, 1997–2002

Serotype G9 rotaviruses have emerged as one of the leading causes of gastroenteritis in children worldwide. We examined 29 representative G9 rotavirus isolates from a 6-year collection (1997-2002) and determined the level of variation in genes encoding non-structural proteins, NSP1 and NSP4. Northern hybridization analysis with a whole genome probe derived from the prototype G9 strain, F45, revealed that the NSP1 gene (gene 5) of two isolates (R1 and R14) did not exhibit significant homology. Complementary DNA probes of R1 and R14 genes 5 were used in Northern blot hybridization and indicated the presence of at least two gene 5 alleles among Melbourne G9 rotaviruses. Nucleotide sequence analysis revealed that isolates carrying the R14 gene 5 shared 94-98% sequence identities with one another, while sequence identity to R1 was 78%. Surprisingly, R1 displayed 96% nucleotide identity with the prototype serotype G1 strain, Wa. The detection of different alleles of NSP1 genes prompted us to investigate the level of variation in another non-structural protein, NSP4, a multifunctional protein and the first viral-encoded enterotoxin. Phylogenetic analysis indicated that while all isolates clustered into one group containing the Wa NSP4 allele (genotype 1), isolate R1 was most closely related to Wa. This study reveals new information about the diversity of non-structural proteins of G9 rotaviruses.

Clinical and epidemiological aspects of rotavirus infection

Rotavirus is a major worldwide cause of infant morbidity and mortality, and disease burden in the US is substantial. Vaccination is the only practical way to gain control over rotavirus disease. Prevention through the universal use of improved live oral vaccines is on the horizon.

Evaluation of serum antibody responses against the rotavirus nonstructural protein NSP4 in children after rhesus rotavirus tetravalent vaccination or natural infection

The immune response elicited by the rotavirus nonstructural protein NSP4 and its potential role in protection against rotavirus disease are not well understood. We investigated the serological response to NSP4 and its correlation with disease protection in sera from 110 children suffering acute diarrhea, associated or not with rotavirus, and from 26 children who were recipients of the rhesus rotavirus tetravalent (RRV-TV) vaccine. We used, as antigens in an enzyme-linked immunosorbent assay (ELISA), affinity-purified recombinant NSP4 (residues 85 to 175) from strains SA11, Wa, and RRV (genotypes A, B, and C, respectively) fused to glutathione S-transferase. Seroconversion to NSP4 was observed in 54% (42/78) of the children who suffered from natural rotavirus infection and in 8% (2/26) of the RRV-TV vaccine recipients. Our findings indicate that NSP4 evokes significantly (P < 0.05) higher seroconversion rates after natural infection than after RRV-TV vaccination. The serum antibody levels to NSP4 were modest (titers of < or = 200) in most of the infected and vaccinated children. A heterotypic NSP4 response was detected in 48% of the naturally rotavirus-infected children with a detectable response to NSP4. Following natural infection or RRV-TV vaccination, NSP4 was significantly less immunogenic than the VP6 protein when these responses were independently measured by ELISA. A significant (P < 0.05) proportion of children who did not develop diarrhea associated with rotavirus had antibodies to NSP4 in acute-phase serum, suggesting that serum antibodies against NSP4 might correlate with protection from rotavirus diarrhea. In addition, previous exposures to rotavirus did not affect the NSP4 seroconversion rate.

Molecular characterization of the rotavirus NSP4 enterotoxin homologue from group B rotavirus

The RNA segment (Gene 10) from a human group B rotavirus which encodes the homologue of the rotavirus enterotoxin (NSP4) has been cloned and sequenced. The gene is of the same length (751 nucleotides) as its better-characterized group A rotavirus counterpart but shows minimal homology (approximately 10%) to it at the primary sequence level. Despite this low level of sequence homology, secondary structure predictions for the group B protein (ADRV-NSP4) showed a close similarity of structural features with the group A protein. Full-length ADRV-NSP4 was expressed in Escherichia coli with an amino terminal 6xHis tag that was used to purify it to homogeneity. The cytotoxicity of the purified protein was examined in a rapid dye-uptake assay that assesses membrane permeability and was found to be comparable to its group A counterpart.

Mucosal immunization with a ricin toxin B subunit-rotavirus NSP4 fusion protein stimulates a Th1 lymphocyte response

The castor-oil plant Ricinus communis A-B dimeric toxin B subunit (RTB) was genetically linked at its N-terminus with a 90 amino acid peptide from simian rotavirus SA-11 non-structural protein NSP4(90) and produced in Escherichia coli BL21 cells. Biologically active recombinant NSP4(90)-RTB fusion protein was shown to bind glycoprotein asialofetuin receptor molecules in an in vitro enzyme-linked immunosorbent assay (ELISA). Oral inoculation of the purified NSP4(90)-RTB ligand-antigen fusion protein delivered the chimeric protein to intestinal epidermal cells for mucosal immunization against rotavirus infection. Mice fed the NSP4(90)-RTB fusion protein generated higher humoral and intestinal antibody titers than mice inoculated with NSP4(90) alone. Titers of serum IgG2a antibodies were significantly higher than IgG1 titers suggesting a dominant Th1 lymphocyte immune response. ELISA measurement of cytokines secreted from splenocyte isolated from immunized mice confirmed NSP4(90)-RTB fusion protein stimulates a strong Th1 cell-mediated immune response. The experimental results demonstrate that the ricin toxin B subunit N-terminus can be used as a site for delivery of virus antigens to the gut associated lymphoid tissues for RTB-mediated immune stimulation of antiviral mucosal immune responses.

A rapid and accurate assay for assessing the cytotoxicity of viral proteins

A fluorescence-based assay is presented for measuring the cytoxicity of viral proteins added exogenously to cells. The assay is based on the use of two fluorescent dyes, calcein-AM and ethidium homodimer (EtD-1) to specifically stain living and dead cells respectively and employs fluorescence activated cells sorting (FACS) to achieve a rapid and accurate measurement of the cytotoxic capacity of a potential viral toxin. The assay has been developed using the group B homologue (ADRV-NSP4) of the NSP4 enterotoxin encoded by Group A rotaviruses but should be applicable to assaying any viral protein exhibiting cytotoxic activity.

Comparison of NSP4 protein between group A and B human rotaviruses: detection of novel diarrhea-causing sequences in group B NSP4

The human group B rotavirus is a causative agent of severe adult diarrhea. In this study, we analyzed the NSP4 structure of a group B rotavirus strain, CAL-1, and determined whether enterotoxin activity was present in CAL-1 NSP4. CAL-1 NSP4 was comprised of 219 amino acids which was longer than group A and C rotavirus NSP4, and the primary structures of their sequences differed considerably. However, CAL-1 NSP4 had an enterotoxin-like sequence (residues 106-127) that was only 27% identical to the enterotoxin region of NSP4 of KUN (a group A rotavirus strain) at residues 114-135. Interestingly, both of the synthetic peptides, one (residues 99-128) containing the enterotoxin-like sequence and the other (residues 191-219) containing 29 C-terminal amino acids of CAL-1 NSP4, induced diarrhea in 5.5-day-old mice, but not in 17.5-day-old mice, when administered parenterally. Thus, rotavirus "enterotoxin" sequences could be considerably divergent.

Catalytic Phosphoryl Interactions of Topoisomerase IB

The reversible nucleophilic substitution reaction catalyzed by the vaccinia virus type IB topoisomerase has been investigated by measuring the equilibrium and rate effects of stereospecific sulfur substitution at the two nonbridging oxygen atoms of the attacked phosphodiester group. An energetic analysis of the combined effects of sulfur substitution and site-directed mutagenesis of active site residues of the enzyme has identified enzyme interactions with each oxygen in the ground state and transition state. We use these findings in combination with previous structural and 5'-bridging sulfur substitution results to deduce the web of enzymatic interactions with the nonbridging oxygens as well as the 5'-hydroxyl leaving group. A key finding is the central role of Arg130, which forms electrostatic interactions with both nonbridging oxygens and the 5'-leaving group.

In vitro anti-rotavirus activity of some medicinal plants used in Brazil against diarrhea

Acute diarrhea, especially in children, is a very common disease with worldwide distribution and with a significant public health impact. Rotaviruses have been recognized as the major agents of diarrhea in infants and young children in developed as well as developing countries. In Brazil, diarrhea is one of the principal causes of death, mainly in the infant population. To fight diarrhea, traditional Brazilian medicine uses a great variety of plants. In this work, 12 medicinal plant species were screened for simian (SA-11) and human (HCR3) rotaviruses inhibition in vitro. At non-cytotoxic concentrations, the extracts from Artocarpus integrifolia L. (Moraceae) bark (480 microg/ml) and Spondias lutea L. (Anacardiaceae) leaves (160 microg/ml) had antiviral activity against both viruses. They showed inhibition of 99.2% and 97%, respectively, for human rotavirus, and 96.4% and 96.2% for simian rotavirus. The extracts from Myristica fragrans Houtt (Myristicaceae) seeds (160 microg/ml) and Spongias lutea bark (40 microg/ml) inhibited human rotavirus (90% and 82.2% inhibition, respectively), whereas the extracts from Anacardium occidentale L. (Anacardiaceae) leaves (4 microg/ml) and Psidium guajava L. (Myrtaceae) leaves (8 microg/ml) showed activity only against simian rotavirus (82.2% and 93.8% inhibition, respectively). Our results indicate that the extracts of Artocarpus integrifolia, Myristica fragrans and Spongias lutea can be useful in the treatment of human diarrhea if the etiologic agent is a rotavirus.

Replication and packaging of Norwalk virus RNA in cultured mammalian cells

Human noroviruses, the most common cause of nonbacterial gastroenteritis, are characterized by high infectivity rate, low infectious dose, and unusually high stability outside the host. However, human norovirus research is hindered by the lack of a cell culture system and a small animal model of infection. Norwalk virus (NV) is the prototype strain of human noroviruses. We report here replication of NV viral RNA and its packaging into virus particles in mammalian cells by intracellular expression of native forms of NV viral RNA devoid of extraneous nucleotide sequences derived from the expression vector by the use of replication-deficient vaccinia virus MVA encoding the bacteriophage T7 RNA polymerase (MVA/T7). Expressed genomic RNA was found to replicate; NV subgenomic RNA was transcribed from genomic RNA by use of NV nonstructural proteins expressed from genomic RNA and was subsequently translated into NV capsid protein VP1. Viral genomic RNA was packaged into virus particles generated in mammalian cells. The cesium chloride (CsCl) density gradient profile of virus particles containing genomic RNA was similar to that of NV purified from stool. These observations indicate that the NV cDNA constructed here is a biologically infectious clone, and that mammalian cells have the ability to replicate NV genomic RNA. This work establishes a mammalian cell-based system for analysis of human norovirus replication and, thus, makes it feasible to investigate antiviral agents in mammalian cells.

A uniform mechanism correlating dangling-end stabilization and stacking geometry

The geometry of the dangling base in 105 published structures (from X-ray/NMR) containing single-stranded overhangs has been analyzed and correlated to the thermodynamic stabilization found (UV) for the corresponding dangling base/closing basepair combination in short oligonucleotides. The study considers most combinations of closing basepairs, sequence and dangling base residue type, attached in both the 3'- and 5'-ends of both DNA and RNA. Linear regression analysis showed a straightforward correlation (R = 0.873) between the degree of screening for the hydrogen bonds of the closing basepair provided by the dangling base and the resulting thermodynamic stabilization in both DNA and RNA series with dangling ends either at the 3'- or at the 5'-terminus. Regression analysis of only the datasets from RNA gives an improved correlation, R = 0.934, showing that dangling ends on RNA are more ordered than the dangling ends on DNA, R = 0.376. This study highlights the gain in the free energy of stabilization owing to the favorable stacking between the dangling nucleobase and the neighboring basepair and the resulting strengthening of the hydrogen bond of the closing basepair. By acting as a hydrophobic cap on the terminal of the DNA or RNA duplex, the dangling-end residue restricts the bulk water access to the terminal basepair, thereby providing it with a microenvironment devoid of water, which consequently enhances its thermodynamic stability, making it energetically comparable to the corresponding internal basepair. Thus, one single structural model consisting of the interplay of the above electrostatic interactions can be used to explain the molecular basis of the observed thermodynamic effects for dangling-end attachment to the 3'- and 5'-ends of both DNA and RNA duplexes, which is a key step toward accurate dangling-end effect prediction.

Species-specific but not genotype-specific primary and secondary isotype-specific NSP4 antibody responses in gnotobiotic calves and piglets infected with homologous host bovine (NSP4[A]) or porcine (NSP4[B]) rotavirus

Using recombinant baculoviruses expressing rotavirus NSP4 [A], [B], [C], and [D] genotypes of bovine, porcine, human, simian, or murine origin, we analyzed serum antibody responses to NSP4s in gnotobiotic calves and piglets infected by the oral/alimentary or intraamniotic route with bovine (NSP4[A]) (Wyatt, R.G., Mebus, C.A., Yolken, R.H., Kalica, A.R., James, H.D., Jr., Kapikian, A.Z., Chanock, R.M., 1979. Rotaviral immunity in gnotobiotic calves: heterologous resistance to human virus induced by bovine virus. Science 203(4380), 548-550) or porcine (NSP4[B]) (Hoshino, Y., Saif, L.J., Sereno, M.M., Chanock, R.M., Kapikian, A.Z., 1988. Infection immunity of piglets to either VP3 or VP7 outer capsid protein confers resistance to challenge with a virulent rotavirus bearing the corresponding antigen. J. Virol. 62(3), 744-748) rotaviruses. Following primary infection and challenge with virulent rotaviruses, the animals developed higher or significantly higher antibody titers to homologous host homotypic NSP4s than to heterologous host homotypic or heterologous host heterotypic NSP4s, indicating that antibody responses were species specific rather than genotype specific. Antibody responses to NSP4s corresponded closely with the phylogenetic relationships of NSP4s within a species-specific region of amino acids (aa) 131-141. In contrast, NSP4 genotypes determined by amino acid full-length sequence identity predicted poorly their "serotypes". In piglets, antibodies to NSP4 induced by previous oral infection failed to confer protection against challenge from a porcine rotavirus bearing serotypically different VP4 and VP7 but essentially identical NSP4 to the porcine rotavirus in primary infection. Thus, in an approach to immunization with a live oral rotavirus vaccine, the NSP4 protein does not appear to play an important role in protection against rotavirus disease and infection.

SU proteins from virulent and avirulent EIAV demonstrate distinct biological properties

Biologic activity of equine infectious anemia virus (EIAV) surface (SU) glycoprotein was assayed in a mouse model. Recombinant SU from virulent EIAV17 (SU17), administered intraperitoneally to mouse pups, induced dose-dependent diarrheal responses similar to those reported for SIV SU (Virology 277 (2000) 250). SU17 caused fluid accumulation without histological lesions in mouse intestinal loops, induced chloride secretory currents in Ussing chambers and increased inositol 1,4,5 triphosphate (IP3) levels in HT29 cells. An SU17 peptide, SU17(299-330), provoked a dose-dependent diarrheal response akin to enterotoxic peptides from SIV. In contrast, SU from an avirulent EIAV strain failed to induce a dose response in mouse pups and produced lower levels of activity than SU17 in Ussing chambers and IP3 assays. These results demonstrate that a mouse pup model is useful to monitor EIAV SU biologic activity, showing clear differences between the activities of SU derived from virulent and avirulent viruses, and may provide a useful screen of EIAV virulence.

A porcine G9 rotavirus strain shares neutralization and VP7 phylogenetic sequence lineage 3 characteristics with contemporary human G9 rotavirus strains

Of five globally important VP7 (G) serotypes (G1-4 and 9) of group A rotaviruses (the single most important etiologic agents of infantile diarrhea worldwide), G9 continues to attract considerable attention because of its unique natural history. Serotype G9 rotavirus was isolated from a child with diarrhea first in the United States in 1983 and subsequently in Japan in 1985. Curiously, soon after their detection, G9 rotaviruses were not detected for about a decade in both countries and then reemerged in both countries in the mid-1990s. Unexpectedly, however, such reemerged G9 strains were distinct genetically and molecularly from those isolated in the 1980s. Thus, the origin of the reemerged G9 viruses remains an enigma. Sequence analysis has demonstrated that the G9 rotavirus VP7 gene belongs to one of at least three phylogenetic lineages: lineage 1 (strains isolated in the 1980s in the United States and Japan), lineage 2 (strains first isolated in 1986 and exclusively in India thus far), and lineage 3 (strains that emerged/reemerged in the mid-1990s). Currently, lineage 3 G9 viruses are the most frequently detected G9 strains globally. We characterized a porcine rotavirus (A2 strain) isolated in the United States that was known to belong to the P[7] genotype but had not been serotyped by neutralization. The A2 strain was found to bear serotype G9 and P9 specificities as well as NSP4 [B] and subgroup I characteristics. By VP7-specific neutralization, the porcine G9 strain was more closely related to lineage 3 viruses than to lineage 1 or 2 viruses. Furthermore, by sequence analysis, the A2 VP7 was shown to belong to lineage 3 G9. These findings raise intriguing questions regarding possible explanations for the emergence of variations among the G9 strains.

Clinical characteristics of rotaviruses disease

Rotaviruses are the major causes of viral gastroenteritis in infant and the young children. There are a wide spectrum of clinical signs and symptoms of rotavirosis. Rotavirus infection is fecal-oral infection. Rotaviruses prove with Latex agglutination test and electron microscopy. In a four year period 943 stool samples out of 527 hospitalized patients had been analyzed. A presence of rotavirus is proved with a LA and EM tests at 170 (32,2%) patients age 0-7 years, in their stool samples. Analyzing age groups of these patients, it was found that the rotaviruses infection the most frequently occurred at age group from 7-24 months. From 170 positive patients, 122 or 71,8% were in this age group. At all patients was found diarrhea, vomiting in a 90,5% cases. Mild fever had 65,5% patients, signs of a respiratory infection appeared at 60,7% patients, abdominal pain at 13,3% patients. Severe dehydration had 49,9% patients and metabolic acidosis had 79,2% cases. Macroscopically blood in stool had 6,4% patients, slime in a stool 46,0% patients was found, and aholic stool had 8,4% patients. In all hospitalized patients disease lasted in average 12,6 days, and the hospitalization in average 10,2 days. None of the patient had any kind of complication, all of them very successfully cured. These results confirm that rotaviruses are important health problem among infant and the young children in Bosnia and Herzegovina.

Silencing the morphogenesis of rotavirus

The morphogenesis of rotaviruses follows a unique pathway in which immature double-layered particles (DLPs) assembled in the cytoplasm bud across the membrane of the endoplasmic reticulum (ER), acquiring during this process a transient lipid membrane which is modified with the ER resident viral glycoproteins NSP4 and VP7; these enveloped particles also contain VP4. As the particles move towards the interior of the ER cisternae, the transient lipid membrane and the nonstructural protein NSP4 are lost, while the virus surface proteins VP4 and VP7 rearrange to form the outermost virus protein layer, yielding mature infectious triple-layered particles (TLPs). In this work, we have characterized the role of NSP4 and VP7 in rotavirus morphogenesis by silencing the expression of both glycoproteins through RNA interference. Silencing the expression of either NSP4 or VP7 reduced the yield of viral progeny by 75 to 80%, although the underlying mechanism of this reduction was different in each case. Blocking the synthesis of NSP4 affected the intracellular accumulation and the cellular distribution of several viral proteins, and little or no virus particles (neither DLPs nor TLPs) were assembled. VP7 silencing, in contrast, did not affect the expression or distribution of other viral proteins, but in its absence, enveloped particles accumulated within the lumen of the ER, and no mature infectious virus was produced. Altogether, these results indicate that during a viral infection, NSP4 serves as a receptor for DLPs on the ER membrane and drives the budding of these particles into the ER lumen, while VP7 is required for removing the lipid envelope during the final step of virus morphogenesis.

Humoral immune response to rotavirus NSP4 enterotoxin in Spanish children

The rotavirus non-structural protein 4 (NSP4) has been shown to play a crucial role in rotavirus-induced diarrhea, acting as a viral enterotoxin. It has also been demonstrated that antibody to NSP4 can reduce the severity of rotavirus-induced diarrhea in newborn mice. Two recombinant baculoviruses, expressing the NSP4 protein from the SA11 and Wa rotavirus strains, genotypes A and B, respectively, were used to produce and purify these glycoproteins, which were applied as antigen in an enzyme-linked immunosorbent assay (ELISA) to test the specific antibody response to NSP4 in human sera. Serum samples from 30 children convalescing from a rotavirus infection, from 54 healthy children under 5-years-old, and from 49 adults were tested to determine the presence of antibodies to the viral enterotoxin and to rotavirus structural proteins. Seventy percent of the sera from rotavirus-infected children showed an IgG antibody response to either one or both NSP4 proteins used in this study, although the response was weak. However, IgG antibodies towards either one or both NSP4 proteins were only detected in 26% of the non-convalescent healthy children and in only 18% of the adults. No serum IgA antibodies towards NSP4 were found in this study. IgG antibody recognition of the NSP4 protein from the SA11 and Wa rotavirus strains was not always heterotypic.

Rotavirus serotype G9P[8] and acute gastroenteritis outbreak in children, Northern Australia

Amino acid substitutions on the VP7 and NSP4 proteins were identified in regions known to influence function and may have contributed to the emergence and increased dominance of the outbreak strains.

During 2001, an outbreak of severe acute gastroenteritis swept through Central and northern Australia and caused serious disruption to health services. We tracked and characterized the rotavirus strain implicated in the outbreak. Comparison of the electropherotypes of outbreak samples suggested that one G9P[8] strain was likely responsible for the outbreak. Samples were obtained from geographically distinct regions of Australia where the epidemic had occurred. The outbreak strains showed identical nucleotide sequences in genes encoding three rotavirus proteins, VP7, VP8, and NSP4, but they were distinct from G9P[8] strains isolated in previous years. Several of the amino acid substitutions on the VP7 and NSP4 proteins were identified in regions known to influence function and may have contributed to the emergence and increased dominance of the outbreak strains. Rotavirus serotype surveillance should continue with methods capable of identifying new and emerging types.

Interaction(s) of rotavirus non-structural protein 4 (NSP4) C-terminal peptides with model membranes

Rotavirus is the major cause of dehydrating gastroenteritis in children and young animals. NSP4 (non-structural protein 4), a rotaviral non-structural glycoprotein and a peptide NSP4(114-135) (DKLTTREIEQVELLKRIYDKLT), corresponding to NSP4 amino acids 114-135, induce diarrhoeal disease in a neonatal mouse model and interact with model membranes that mimic caveolae. Correlation of the mechanisms of diarrhoea induction and membrane interactions by NSP4 protein and peptide remain unclear. Several additional NSP4 peptides were synthesized and their interactions with membranes studied by (i) CD, (ii) a filtration-binding assay and (iii) a fluorescent molecule leakage assay. Model membranes that varied in lipid compositions and radius of curvature were utilized to determine the compositional and structural requirements for optimal interaction with the peptides of NSP4. Similar to the intact protein and NSP4(114-135), peptides overlapping residues 114-135 had significantly higher affinities to membranes rich in negatively charged lipids, rich in cholesterol and with a high radius of curvature. In the leakage assay, small and large unilamellar vesicles loaded with the fluorophore/quencher pair 8-aminonaphthalene-1,3,6-trisulphonic acid disodium salt/p -xylene-bis-pyridinium bromide were incubated with the NSP4 peptides and monitored for membrane disruption by lipid reorganization or by pore formation. At a peptide concentration of 15 microM, none of the NSP4 peptides caused leakage. These results confirm that NSP4 interacts with caveolae-like membranes and the alpha-helical region of NSP4(114-135) comprises a membrane interaction domain that does not induce membrane disruption at physiological concentrations.

Single-chain variable fragment (scFv) antibodies against rotavirus NSP4 enterotoxin generated by phage display

The rotavirus non-structural NSP4 protein causes membrane destabilization as well as an increase in intracellular calcium levels in eukaryotic cells and induces diarrhea in young mice, acting as a viral enterotoxin. In this study the phage display technique was used to generate a panel of single-chain variable fragment (scFv) antibodies specific for the NSP4 protein of the human rotavirus strain Wa from a human semi-synthetic scFv library. After several rounds of panning and selection on NSP4 adsorbed to polystyrene tubes, individual scFv were isolated and characterised by fingerprinting and by sequencing the VH and VL genes. The isolated scFv antibodies specifically recognize NSP4 in enzyme immunoassay and in Western blot. Four truncated forms of the NSP4 protein were constructed which allowed us to map the binding region of the selected scFv antibodies to the C-terminal portion of NSP4. The isolated scFv antibodies constitute valuable tools to analyse the mechanisms of NSP4 functions.

Rotavirus enterotoxin NSP4 binds to the extracellular matrix proteins laminin-beta3 and fibronectin

Rotavirus is the most important cause of viral gastroenteritis and dehydrating diarrhea in young children. Rotavirus nonstructural protein 4 (NSP4) is an enterotoxin that was identified as an important agent in symptomatic rotavirus infection. To identify cellular proteins that interact with NSP4, a two-hybrid technique with Saccharomyces cerevisiae was used. NSP4 cDNA, derived from the human rotavirus strain Wa, was cloned into the yeast shuttle vector pGBKT7. An intestinal cDNA library derived from Caco-2 cells cloned into the yeast shuttle vector pGAD10 was screened for proteins that interact with NSP4. Protein interactions were confirmed in vivo by coimmunoprecipitation and immunohistochemical colocalization. After two-hybrid library screening, we repeatedly isolated cDNAs encoding the extracellular matrix (ECM) protein laminin-beta3 (amino acids [aa] 274 to 878) and a cDNA encoding the ECM protein fibronectin (aa 1755 to 1884). Using deletion mutants of NSP4, we mapped the region of interaction with the ECM proteins between aa 87 and 145. Deletion analysis of laminin-beta3 indicated that the region comprising aa 726 to 875 of laminin-beta3 interacts with NSP4. Interaction of NSP4 with either laminin-beta3 or fibronectin was confirmed by coimmunoprecipitation. NSP4 was present in infected enterocytes and in the basement membrane (BM) of infected neonatal mice and colocalized with laminin-beta3, indicating a physiological interaction. In conclusion, two-hybrid screening with NSP4 yielded two potential target proteins, laminin-beta3 and fibronectin, interacting with the enterotoxin NSP4. The release of NSP4 from the basal side of infected epithelial cells and the subsequent binding to ECM proteins localized at the BM may signify a new mechanism by which rotavirus disease is established.

Acute effects of parainfluenza virus on epithelial electrolyte transport

Parainfluenza viruses are important causes of respiratory disease in both children and adults. In particular, they are the major cause of the serious childhood illness croup (laryngotracheobronchitis). The infections produced by parainfluenza viruses are associated with the accumulation of ions and fluid in the respiratory tract. It is not known, however, whether this accumulation is because of a direct effect of the viruses on ion and fluid transport by the respiratory epithelium. Here we show that a model parainfluenza virus (the Sendai virus), in concentrations observed during respiratory infections, activates Cl- secretion and inhibits Na+ absorption across the tracheal epithelium. It does so by binding to a neuraminidase-insensitive glycolipid, possibly asialo-GM1, triggering the release of ATP, which then acts in an autocrine fashion on apical P2Y receptors to produce the observed changes in ion transport. These findings indicate that fluid accumulation in the respiratory tract associated with parainfluenza virus infection is attributable, at least in part, to direct effects of the virus on ion transport by the respiratory epithelium.

Vaccines for rotavirus gastroenteritis universally needed for infants

Rotavirus causes severe and often lifethreatening illness. Universal application of a safe and protective vaccine is justified in both developed and developing nations. Two vaccine candidates, one monovalent (Rotarix) and one multivalent (Rotateq), appear to meet these requirements and are likely to be licensed in the United States in the next 2 or 3 years. Both vaccines exhibited similar safety characteristics. There is little doubt that Rotateq and Rotarix will be shown to be effective for routine protection of infants. Unfortunately, despite numerous clinical trials, the most common serotype (PlaGa) commonly has been encountered as a natural challenge. Therefore, it is not known whether either vaccine possesses advantages in different epidemiological situations. Continuing the analogy with influenza virus, it may be that optimum protection against different serotypes requires a vaccine that is precisely homologous in antigen composition. If so, Rotateq would provide protection against the most common serotype PlaG1 because in includes both Pla and G1 rotavirus reassortants. Further, it would be expected to provide superior protection against G2, G3, and G4 wild-type virus because it contains reassortants of those specificities. In the case of a natural challenge with a serotype that was not G1, G2, G3, or G4, a Rotateq preparation containing a WC3 reassortant expressing the new G serotype could be formulated readily. The monotypic Rotarix may provide ideal protection against the PlaG1 rotavirus because it is composed solely of the PlaG1 strain. It may also provide cross-protection against other rotavirus serotypes adequate to protect against severe and life-threatening disease. In such a case, its monotypic composition may also provide significant economic savings in manufacturing. The resolution of these questions may have to await extensive post-licensure experience with each vaccine. In the future, possible application of rotavirus vaccine for other situations also should be explored, including use in older children to limit nosocomial infection, use in geriatric populations, use in the immunocompromised host, and possibly use in parents and other adults in contact with infants with rotavirus. Both Rotarix and Rotateq likely are to be launched at prices beyond those affordable in the poorest and neediest less-developed countries. It is essential that there be vigorous pursuit of new technologies to manufacture these products at drastically reduced cost if their true lifesaving potential is to be achieved.

Characterization of G10P[11] rotaviruses causing acute gastroenteritis in neonates and infants in Vellore, India

Rotavirus G10P[11] strains, which are commonly found in cattle, have frequently been associated with asymptomatic neonatal infections in India. We report the finding of G10P[11] strains associated with severe disease in neonates in Vellore, southern India. Rotavirus strains from 43 fecal samples collected from neonates with or without gastrointestinal symptoms between 1999 and 2000 were genotyped by reverse transcription-PCR. Forty-one neonates (95%) were infected with G10P[11] rotavirus strains, and 63% of the infections were in children who had gastrointestinal symptoms, including acute watery diarrhea. G10P[11] strains were also seen infecting older children with dehydrating gastroenteritis in Vellore. Characterization of the genes encoding VP7, VP4, VP6, and NSP4 of these strains revealed high sequence homology with the corresponding genes of the asymptomatic neonatal strain I321, which in turn is very closely related to bovine G10P[11] strains circulating in India. No significant differences were seen in the sequences obtained from strains infecting symptomatic neonates or children and asymptomatic neonates.