Functional studies on the IBD susceptibility gene IL23R implicate reduced receptor function in the protective genetic variant R381Q

Genome-wide association studies (GWAS) in several populations have demonstrated significant association of the IL23R gene with IBD (Crohn's disease (CD) and ulcerative colitis (UC)) and psoriasis, suggesting that perturbation of the IL-23 signaling pathway is relevant to the pathophysiology of these diseases. One particular variant, R381Q (rs11209026), confers strong protection against development of CD. We investigated the effects of this variant in primary T cells from healthy donors carrying IL23R(R381) and IL23R(Q381) haplotypes. Using a proprietary anti-IL23R antibody, ELISA, flow cytometry, phosphoflow and real-time RT-PCR methods, we examined IL23R expression and STAT3 phosphorylation and activation in response to IL-23. IL23R(Q381) was associated with reduced STAT3 phosphorylation upon stimulation with IL-23 and decreased number of IL-23 responsive T-cells. We also observed slightly reduced levels of proinflammatory cytokine secretion in IL23R(Q381) positive donors. Our study shows conclusively that IL23R(Q381) is a loss-of-function allele, further strengthening the implication from GWAS results that the IL-23 pathway is pathogenic in human disease. This data provides an explanation for the protective role of R381Q in CD and may lead to the development of improved therapeutics for autoimmune disorders like CD.

Lung gene expression in a rhesus allergic asthma model correlates with physiologic parameters of disease and exhibits common and distinct pathways with human asthma and a mouse asthma model

Experimental nonhuman primate models of asthma exhibit multiple features that are characteristic of an eosinophilic/T helper 2 (Th2)-high asthma subtype, characterized by the increased expression of Th2 cytokines and responsive genes, in humans. Here, we determine the molecular pathways that are present in a house dust mite-induced rhesus asthma model by analyzing the genomewide lung gene expression profile of the rhesus model and comparing it with that of human Th2-high asthma. We find that a prespecified human Th2 inflammation gene set from human Th2-high asthma is also present in rhesus asthma and that the expression of the genes comprising this gene set is positively correlated in human and rhesus asthma. In addition, as in human Th2-high asthma, the Th2 gene set correlates with physiologic markers of allergic inflammation and disease in rhesus asthma. Comparison of lung gene expression profiles from human Th2-high asthma, the rhesus asthma model, and a common mouse asthma model indicates that genes associated with Th2 inflammation are shared by all three species. However, some pathophysiologic aspects of human asthma (ie, subepithelial fibrosis, angiogenesis, neural biology, and immune host defense biology) are better represented in the gene expression profile of the rhesus model than in the mouse model. Further study of the rhesus asthma model may yield novel insights into the pathogenesis of human Th2-high asthma.

Gene expression patterns of Th2 inflammation and intercellular communication in asthmatic airways

Asthma is canonically thought of as a disorder of excessive Th2-driven inflammation in the airway, although recent studies have described heterogeneity with respect to asthma pathophysiology. We have previously described distinct phenotypes of asthma based on the presence or absence of a three-gene "Th2 signature" in bronchial epithelium, which differ in terms of eosinophilic inflammation, mucin composition, subepithelial fibrosis, and corticosteroid responsiveness. In the present analysis, we sought to describe Th2 inflammation in human asthmatic airways quantitatively with respect to known mediators of inflammation and intercellular communication. Using whole-genome microarray and quantitative real-time PCR analysis of endobronchial biopsies from 27 mild-to-moderate asthmatics and 13 healthy controls with associated clinical and demographic data, we found that asthmatic Th2 inflammation is expressed over a variable continuum, correlating significantly with local and systemic measures of allergy and eosinophilia. We evaluated a composite metric describing 79 coexpressed genes associated with Th2 inflammation against the biological space comprising cytokines, chemokines, and growth factors, identifying distinctive patterns of inflammatory mediators as well as Wnt, TGF-β, and platelet-derived growth factor family members. This integrated description of the factors regulating inflammation, cell migration, and tissue remodeling in asthmatic airways has important consequences for the pathophysiological and clinical impacts of emerging asthma therapeutics targeting Th2 inflammation.

Characterization of intestinal gene expression profiles in Crohn's disease by genome-wide microarray analysis

BACKGROUND

Genome-wide microarray expression analysis creates a comprehensive picture of gene expression at the cellular level. The aim of this study was to investigate differential intestinal gene expression in patients with Crohn's disease (CD) and controls with subanalysis of confirmed CD susceptibility genes, associated pathways, and cell lineage.

METHODS

In all, 172 biopsies from 53 CD and 31 control subjects were studied. Paired endoscopic biopsies were taken at ileocolonoscopy from five specific anatomical locations including the terminal ileum (TI) for RNA extraction and histology. The 41,058 expression sequence tags were analyzed using the Agilent platform.

RESULTS

Analysis of all CD biopsies versus controls showed 259 sequences were upregulated and 87 sequences were downregulated. Upregulated genes in CD included SAA1 (fold change [FC] +7.5, P = 1.47 × 10(-41)) and REGL (FC +7.3, P = 2.3 × 10(-16)), whereas cellular detoxification genes including-SLC14A2 (FC-2.49, P = 0.00002) were downregulated. In the CD TI biopsies diubiquitin (FC+11.3, P < 1 × 10(-45)), MMP3 (FC+7.4, P = 1.3 × 10(-11)), and IRTA1 (FC-11.4, P = 4.7 × 10(-12)) were differentially expressed compared to controls. In the colon SAA1 (FC+6.3, P = 5.3 × 10(-8)) was upregulated and thymic stromal lymphopoietin (TSLP) (FC-2.3, P = 2.7 × 10(-6)) was downregulated comparing noninflamed CD and control biopsies, and the colonic inflammatory CD signature was characterized by downregulation of the organic solute carriers-SLC38A4, SLC26A2, and OST alpha. Of CD susceptibility genes identified by genome-wide association scan IL-23A, JAK2, and STAT3 were upregulated in the CD group, confirming the dysregulation of Th17 signaling.

CONCLUSIONS

These data characterize the dysregulation of a series of specific inflammatory pathways highlighting potential pathogenic mechanisms as well as areas for translation to therapeutic targets.

Association of IFIH1 and other autoimmunity risk alleles with selective IgA deficiency

To understand the genetic predisposition to selective immunoglobulin A deficiency (IgAD), we performed a genome-wide association study in 430 affected individuals (cases) from Sweden and Iceland and 1,090 ethnically matched controls, and we performed replication studies in two independent European cohorts. In addition to the known association of HLA with IgAD, we identified association with a nonsynonymous variant in IFIH1 (rs1990760G>A, P = 7.3 x 10(-10)) which was previously associated with type 1 diabetes and systemic lupus erythematosus. Variants in CLEC16A, another known autoimmunity locus, showed suggestive evidence for association (rs6498142C>G, P = 1.8 x 10(-7)), and 29 additional loci were identified with P < 5 x 10(-5). A survey in IgAD of 118 validated non-HLA autoimmunity loci indicated a significant enrichment for association with autoimmunity loci as compared to non-autoimmunity loci (P = 9.0 x 10(-4)) or random SNPs across the genome (P < 0.0001). These findings support the hypothesis that autoimmune mechanisms may contribute to the pathogenesis of IgAD.

Deconvolution of blood microarray data identifies cellular activation patterns in systemic lupus erythematosus

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease with a complex spectrum of cellular and molecular characteristics including several dramatic changes in the populations of peripheral leukocytes. These changes include general leukopenia, activation of B and T cells, and maturation of granulocytes. The manifestation of SLE in peripheral blood is central to the disease but is incompletely understood. A technique for rigorously characterizing changes in mixed populations of cells, microarray expression deconvolution, has been applied to several areas of biology but not to SLE or to blood. Here we demonstrate that microarray expression deconvolution accurately quantifies the constituents of real blood samples and mixtures of immune-derived cell lines. We characterize a broad spectrum of peripheral leukocyte cell types and states in SLE to uncover novel patterns including: specific activation of NK and T helper lymphocytes, relationships of these patterns to each other, and correlations to clinical variables and measures. The expansion and activation of monocytes, NK cells, and T helper cells in SLE at least partly underlie this disease's prominent interferon signature. These and other patterns of leukocyte dynamics uncovered here correlate with disease severity and treatment, suggest potential new treatments, and extend our understanding of lupus pathology as a complex autoimmune disease involving many arms of the immune system.

Gene signatures reflect the marked heterogeneity of tissue-resident macrophages

Tissue-resident macrophages play an important role in defense against pathogens and perform key functions in organ homeostasis, innate and adaptive immunity. Tissue macrophages originate from blood monocytes that infiltrate virtually every organ in the body. Macrophages in different tissues share many characteristics, including their ability to migrate, phagocytose particles, metabolize lipids and present antigens. Morphologically they are quite heterogeneous, and some distinct functions have been reported. The gene expression profile of macrophages is reflective of both their shared and distinct biological functions. Here, we show that macrophages from murine spleen, liver and peritoneum display dramatically different expression profiles. Clusters of genes were found to represent unique biological functions related to adhesion, antigen presentation, phagocytosis, lipid metabolism and signal transduction. Some gene families, such as integrins, are differentially expressed among the macrophages resident in different tissues, suggesting that the tissue of residence influences their biological function.

Genome-wide association study for Crohn's disease in the Quebec Founder Population identifies multiple validated disease loci

Genome-wide association (GWA) studies offer a powerful unbiased method for the identification of multiple susceptibility genes for complex diseases. Here we report the results of a GWA study for Crohn's disease (CD) using family trios from the Quebec Founder Population (QFP). Haplotype-based association analyses identified multiple regions associated with the disease that met the criteria for genome-wide significance, with many containing a gene whose function appears relevant to CD. A proportion of these were replicated in two independent German Caucasian samples, including the established CD loci NOD2 and IBD5. The recently described IL23R locus was also identified and replicated. For this region, multiple individuals with all major haplotypes in the QFP were sequenced and extensive fine mapping performed to identify risk and protective alleles. Several additional loci, including a region on 3p21 containing several plausible candidate genes, a region near JAKMIP1 on 4p16.1, and two larger regions on chromosome 17 were replicated. Together with previously published loci, the spectrum of CD genes identified to date involves biochemical networks that affect epithelial defense mechanisms, innate and adaptive immune response, and the repair or remodeling of tissue.

Immune response in silico (IRIS): immune-specific genes identified from a compendium of microarray expression data

Immune cell-specific expression is one indication of the importance of a gene's role in the immune response. We have compiled a compendium of microarray expression data for virtually all human genes from six key immune cell types and their activated and differentiated states. Immune Response In Silico (IRIS) is a collection of genes that have been selected for specific expression in immune cells. The expression pattern of IRIS genes recapitulates the phylogeny of immune cells in terms of the lineages of their differentiation. Gene Ontology assignments for IRIS genes reveal significant involvement in inflammation and immunity. Genes encoding CD antigens, cytokines, integrins and many other gene families playing key roles in the immune response are highly represented. IRIS also includes proteins of unknown function and expressed sequence tags that may not represent genes. The predicted cellular localization of IRIS proteins is evenly distributed between cell surface and intracellular compartments, indicating that immune specificity is important at many points in the signaling pathways of the immune response. IRIS provides a resource for further investigation into the function of the immune system and immune diseases.

The secreted protein discovery initiative (SPDI), a large-scale effort to identify novel human secreted and transmembrane proteins: a bioinformatics assessment

A large-scale effort, termed the Secreted Protein Discovery Initiative (SPDI), was undertaken to identify novel secreted and transmembrane proteins. In the first of several approaches, a biological signal sequence trap in yeast cells was utilized to identify cDNA clones encoding putative secreted proteins. A second strategy utilized various algorithms that recognize features such as the hydrophobic properties of signal sequences to identify putative proteins encoded by expressed sequence tags (ESTs) from human cDNA libraries. A third approach surveyed ESTs for protein sequence similarity to a set of known receptors and their ligands with the BLAST algorithm. Finally, both signal-sequence prediction algorithms and BLAST were used to identify single exons of potential genes from within human genomic sequence. The isolation of full-length cDNA clones for each of these candidate genes resulted in the identification of >1000 novel proteins. A total of 256 of these cDNAs are still novel, including variants and novel genes, per the most recent GenBank release version. The success of this large-scale effort was assessed by a bioinformatics analysis of the proteins through predictions of protein domains, subcellular localizations, and possible functional roles. The SPDI collection should facilitate efforts to better understand intercellular communication, may lead to new understandings of human diseases, and provides potential opportunities for the development of therapeutics.

Hypertrophy, hyperplasia, and infectious virus in gut-associated lymphoid tissue of mice after oral inoculation with simian-human or bovine-human reassortant rotaviruses

Oral inoculation of infants with a vaccine that contains simian-human reassortant rotaviruses has been found to be a rare cause of intussusception. Because intussusception can be associated with enlargement of gut-associated lymphoid tissue, we studied the capacity of simian-human and bovine-human reassortant rotaviruses to cause lymphoid hypertrophy and hyperplasia of Peyer's patches (PP) of adult BALB/c mice. Neither hypertrophy nor hyperplasia was detected in PP after oral inoculation with simian-human or bovine-human reassortant rotaviruses. However, infectious virus was detected in PP and mesenteric lymph nodes after oral inoculation with simian, but not bovine, reassortant rotaviruses. Implications of these findings on the pathogenesis of intussusception are discussed.

Molecular characterization of serotype G9 rotavirus strains from a global collection

Between 1992 and 1998, serotype G9 human rotavirus (RV) strains have been detected in 10 countries, including Thailand, India, Brazil, Bangladesh, Malawi, Italy, France, the United States, the United Kingdom, and Australia, suggesting the possible emergence of the fifth common serotype worldwide. Unlike the previously characterized reference G9 strains (i.e., WI61 and F45), the recent G9 isolates had a variety of gene combinations, raising questions concerning their origin and evolution. To identify the progenitor strain and examine the on-going evolution of the recent G9 strains, we characterized by genetic and antigenic analyses 16 isolates obtained from children with diarrhea in India, Bangladesh, the United States, and Malawi. Specifically, we sequenced their VP7 and NSP4 genes and compared the nucleotide (nt) and deduced amino acid sequences with the reference G9 strains. To identify reassortment, we examined the products of five gene segments; VP4, VP7, and NSP4 genotypes (genes 4, 9, and 10); subgroups (gene 6); electropherotypes (gene 11); and the genogroup profiles of all of the recent G9 isolates. Sequence analysis of the VP7 gene indicated that the recent U.S. P[6],G9 strains were closely related to the Malawian G9 strains (>99% nt identity) but distinct from G9 strains of India ( approximately 97% nt identity), Bangladesh ( approximately 98% nt identity), and the reference strains ( approximately 97% nt identity). Phylogenetic analysis identified a single cluster for the U.S. P[6],G9 strains that may have common progenitors with Malawian P[6],G9 strains whereas separate lineages were defined for the Indian, Bangladeshi, and reference G9 strains. Northern hybridization results indicated that all 11 gene segments of the Malawian P[6],G9 strains hybridized with a probe derived from a U.S. strain of the same genotype and may have the same progenitor, different from the Indian G9 strains, whereas the Bangladesh strains may have evolved from the U.S. G9 progenitors. Overall, our findings suggest that much greater diversity among the newly identified G9 strains has been generated by reassortment between gene segments than through the accumulation of mutations in a single gene.

Genetic and antigenic characterization of a serotype P[6]G9 human rotavirus strain isolated in the United States

During an epidemiologic survey of rotavirus infections established to monitor the prevalent G serotypes circulating in the United States, human P[6]G9, subgroup I rotavirus strains causing symptomatic infections were identified as the fourth most common serotype. In this report we describe the molecular and antigenic characterization of one of these P[6]G9 isolates (US1205). Neutralization and sequencing studies have demonstrated that both outer capsid proteins, VP7 and VP4, of US1205 are closely related to but genetically and antigenically distinguishable from those of standard G9 strains (e.g., F45, WI61) and standard P2A[6] strains (e. g., ST3, M37). Thus the complete antigenic type of US1205 is P2A[6]G9, subgroup I. Sequence analysis of the VP6 and NSP4 genes of US1205 indicates that strain US1205 possessed VP6 subgroup I and NSP4A genotype specificities. Finally, Northern hybridization studies suggest that the P[6]G9 strains are closely related to members of the DS-1 genogroup except for their P[6] VP4 gene, which has been commonly identified in strains of both major human genogroups, and their G9 VP7 gene, which may have been derived by reassortment with a Wa genogroup strain. Examination of historic collections and prospective surveillance of strains will be needed to determine whether this strain has been present for some time or if it is emerging to compete with the other common serotypes of rotavirus.

The rotavirus vaccine

A rotavirus vaccine was recently licensed by the Food and Drug Administration and is likely to be recommended for use in all infants by both the Advisory Committee on Immunization Practices and the American Academy of Pediatrics. If used as recommended, the vaccine is likely to prevent much of the 500,000 physician visits, 50,000 hospitalizations, and 20 to 40 deaths caused by rotavirus infections every year in the United States. An understanding of the biology, immunology, and pathogenesis of rotavirus infection will help to explain the strengths and limitations of the rotavirus vaccine.

Identification of two lineages (WA-like and F45-like) within the major rotavirus genotype P[8]

The fourth gene of a porcine (S8) and eight human rotavirus isolates possessing the major human VP4 specificity (P1A serotype and/or P[8] genotype) were partially sequenced and compared to other available P[8] sequences from rotaviruses types G1, G3, G5 and G9 specificities which had been originally recovered from children with diarrhea in Japan, Brazil and the USA. Brazilian rotavirus S8 represented the single known porcine rotavirus with this P specificity. Phylogenetic analysis revealed two lineages or subgenotypes within P[8] strains: the F45-like P subgenotype comprised most of the strains, including all the human G5 isolates analyzed, whereas the Wa- or S8-like subgenotype consisted of only a human isolate obtained in the same geographic region as S8 and an American strain with atypical RNA profile besides the prototypes Wa and S8 viruses. A conserved basic amino acid residue at position 131 in VP4 seemed characteristic of the F45-like P[8] subgenotype.

Relationship among serotype G3P5A rotavirus strains isolated from different host species

The relationship among G3P5A rotavirus strains was analysed by restriction endonuclease assay of the VP4, VP6 and VP7 encoding genes, neutralization assay and phylogenetic analysis. The restriction patterns of the capsid encoding genes were species specific allowing the differentiation among the strains of different origin. The VP7 profiles differentiated human from animal strains more efficiently. The phylogenetic analysis of the VP4 gene demonstrated that HCR3A and K9 are closer related to each other than to other P5A strains. The same occurs to strains Ro1845 and Cat 97. The CU-1 virus appears to be an ancestor of the P5A strains by neutralization and phylogenetic analysis. The results placed the RRV strain definitely in a separate VP4 serotype and genotype from that of P5A strains. Restriction endonuclease assay of the capsid encoding genes seems to be a useful tool to identify the host species of rotavirus strains belonging to the same serotype and/or genotype.

Relative importance of rotavirus-specific effector and memory B cells in protection against challenge

Adult BALB/c mice were orally inoculated with murine (strain EDIM), simian (strain RRV), or bovine (strain WC3) rotavirus. Six or 16 weeks after inoculation, mice were challenged with EDIM. At the time of challenge and in the days immediately following challenge, production of rotavirus-specific immunoglobulin A (IgA), IgG, and IgM by small intestinal lamina propria lymphocytes (LPL) was determined by fragment culture, and quantities of virus-specific antibodies at the intestinal mucosal surface were determined by intestinal lavage. Mice immunized with EDIM were completely protected against EDIM challenge both 6 and 16 weeks after immunization. Protection was associated with production of high levels of IgA by LPL and detection of virus-specific IgA at the intestinal mucosal surface. In addition, animals immunized and later challenged with EDIM did not develop a boost in antibody responses, suggesting that they were also not reinfected. We also found that in mice immunized with nonmurine rotaviruses, (i) quantities of virus-specific IgA generated following challenge were greater 16 weeks than 6 weeks after immunization, (ii) immunization enhanced the magnitude but did not hasten the onset of production of high quantities of virus-specific IgA by LPL after challenge, and (iii) immunization induced partial protection against challenge; however, protection was not associated with either production of virus-specific antibodies by LPL or detection of virus-specific antibodies at the intestinal mucosal surface.

Immunologic correlates of protection against rotavirus challenge after intramuscular immunization of mice

The capacity of intramuscular (i.m.) inoculation of mice with homologous or heterologous host rotaviruses to induce protection from challenge was evaluated. i.m. inoculation with live, wild-type rotavirus (murine strain EDIM) induced complete protection from viral shedding after challenge for at least 6 weeks after inoculation; protection was correlated with production of virus-specific immunoglobulin A (IgA) by lamina propria (LP) lymphocytes. i.m. inoculation with inactivated EDIM, cell culture-adapted EDIM, or simian strain RRV was associated with partial protection, characterized by reduced viral shedding after challenge. Partial protection after challenge was not associated with production of virus-specific IgA by LP lymphocytes. The mechanisms by which i.m. inoculation induces virus-specific humoral immune responses in the small intestinal LP were examined.

The development of multivalent bovine rotavirus (strain WC3) reassortant vaccine for infants

Laboratory and clinical studies have been directed toward development of a vaccine against rotavirus gastroenteritis in infants. First, bovine rotavirus strain WC3, which did not induce neutralizing antibodies to predominant human rotavirus (HRV) serotypes, was determined to be safe and immunogenic; however, it was not protective in all efficacy trials. HRVs adapted to cell culture retained some virulence for infants, but when further attenuated by cold adaptation, they were poorly immunogenic. Reassortant rotaviruses were designed to express HRV surface proteins VP7 (G) or VP4 (P) while retaining a bovine WC3 genome background. Reassortants containing either HRV surface protein and as few as four bovine rotavirus genes were safe in infants. A monovalent WC3 reassortant of serotype G1 specificity was 64%-100% protective in placebo-controlled trials. A quadrivalent WC3 reassortant vaccine with components of HRV G1, G2, G3, and P[8] specificity induced 67% protection against all rotavirus disease in a multicenter efficacy trial.

WC3 reassortant vaccines in children

Bovine rotavirus strain WC3 (P7[5], G6) administered at the 12th passage level was well tolerated clinically in infants and efficiently induced serum virus neutralizing antibody (VNA) with bovine rotavirus G6 specificity. The protective efficacy of WC3 vaccine against all rotavirus disease was inconsistent, varying in four separate trials from 76% to 0%; some selective protection against severe disease was seen in all trials. WC3 reassortants containing the gene for an individual human rotavirus VP7 (G) or VP4 (P) surface antigen were also well tolerated, but preferentially induced VNA to the WC3 parent. Efficacy trials of human G1 VP7 reassortant WI79-9 (P7[5], G1) consistently led to > 60% protection against all rotavirus disease. A quadrivalent WC3 reassortant vaccine was developed to contain four separate monovalent reassortants expressing human rotaviruses surface proteins G1, G2, G3, and P1A [8] respectively. In a multicenter trial including 439 infants, this vaccine induced 67.1% protection against all rotavirus disease (defined as positive for rotavirus antigen by ELISA only [p = < 0.001]) and 72.6% protection when the standard for rotavirus diagnosis was a positive test of stool for both rotavirus antigen by ELISA and rotavirus RNA by electropherotype analysis (p = < 0.001). In this trial, episodes of the most severe rotavirus disease (clinical severity score > 16.0 eight cases) occurred only in placebo recipients.

Dachsous encodes a member of the cadherin superfamily that controls imaginal disc morphogenesis in Drosophila

Mutations in the dachsous gene of Drosophila lead to striking defects in the morphogenesis of the thorax, legs, and wings. The dachsous gene has been cloned and shown to encode a huge transmembrane protein that is a member of the cadherin superfamily, similar to the fat gene reported previously. Both the Dachsous and Fat proteins contain large tandem arrays of cadherin domains--27 and 34, respectively--as compared with 4 cadherin domains in classic vertebrate cadherins. In addition, Dachsous and Fat each has a cytoplasmic domain with sequence similarity to the cytoplasmic beta-catenin-binding domain of classic vertebrate cadherins. The dachsous gene is expressed in the ectoderm of embryos, whereas its expression in larvae is restricted to imaginal discs and specific regions of the brain. The phenotypes of, and genetic interactions between dachsous and fat are consistent with a model in which cell proliferation and morphogenesis of imaginal structures depends on the coupled equilibria between homo- and heterophilic interactions of the Dachsous and Fat cadherin proteins.

Evaluation of the protective efficacy of a serotype 1 bovine-human rotavirus reassortant vaccine in infants

The objective of this study was to evaluate the efficacy of a live, attenuated bovine (strain WC3) x human (strain WI79, serotype G1) rotavirus reassortant (WI79-9) virus vaccine for prevention of symptomatic rotavirus gastroenteritis in infants. The study was a prospective, randomized, double-blind, placebo-controlled trial, conducted over a single rotavirus season in 325 infants who were 2 to 8 months old at enrollment. Subjects were randomized to receive either placebo or WI79-9 virus vaccine at 10(7.3) plaque-forming units in three oral doses each separated by 2 months. Subjects were followed for 7 days after each dose for occurrence of adverse events and during the subsequent winter for development of rotavirus gastroenteritis. Administration of WI79-9 virus vaccine was well-tolerated, and the rates of low grade fever after each dose were no higher in vaccine recipients (8 to 21%) than in placebo recipients (14 to 19%). The protective efficacy of the WI79-9 vaccine during a subsequent epidemic of predominantly serotype G1 rotavirus was 87.0% (95% confidence limits, 62.6 to 95.5%) against relatively severe rotavirus gastroenteritis (rotavirus gastroenteritis with a clinical severity score of > 8) and was 64.1% (95% confidence limits 35.9 to 79.9%) against all symptomatic rotavirus episodes. The WI79-9 vaccine was safe and effective in prevention of homotypic human rotavirus infection in infants. Further studies of reassortant vaccines based on the bovine WC3 rotavirus should be performed.

Enhancement of rotavirus immunogenicity by microencapsulation

It was determined whether microencapsulation of rotavirus enhanced virus-specific immunity in mice. Combinations of several water-soluble anionic polymers and amines were tested for their capacity to form microcapsules which were stable in the presence of simulated gastric acid. Using the combinations of sodium alginate and spermine hydrochloride or sodium chondroitin sulfate and spermine hydrochloride we found that microcapsules (1) captured infectious rotavirus, (2) penetrated into the persisted in gut-associated lymphoid tissue (GALT) after oral inoculation, (3) delivered rotavirus antigen to GALT at levels greater than those detected after oral inoculation with free virus, and (4) enhanced the virus-specific humoral immune response after oral or parenteral immunization.

Comparative analysis of VP8* sequences from rotaviruses possessing M37-like VP4 recovered from children with and without diarrhoea

Rotavirus strains belonging to G types 1 to 4 and having a P3 genotype (M37-like VP4) were recovered from children with symptomatic and asymptomatic infections. Partial sequences of their VP4 genes were determined in an attempt to characterize these strains further. The genomic regions encoding VP8*, the connecting and putative fusion peptides and three other regions in VP5* were sequenced. The deduced amino acid sequences were compared with rotavirus strains belonging to different P genotypes that had been previously reported. High degrees of identity were found between the VP8* fragment of all human P3 strains (92.7 to 99.7%) suggesting that they belong to the same genotype, regardless of differences in their virulence. Furthermore, based on comparative sequence analysis, we did not identify any amino acid(s) that differ appreciably between symptomatic and asymptomatic strains and could therefore be associated with virulence. The results suggest that the P3 genotype, although frequently associated with asymptomatic infections, may not be the single determining factor in attenuation of symptoms.

VP4 genotyping of human rotavirus in the United States

The VP4 (P) and VP7 (G) types of 171 rotavirus isolates obtained from children with diarrhea in the United States were characterized by PCR typing assays. Strains P1G1 predominated (71%); this was followed by strains P1G3 (20%) and P2G2 and P1G4 (2% each). Mixed types were identified in five (3%) specimens. Two (1%) strains bearing the P3 genotype (P3G1 and P3G2) were found in children with severe dehydrating diarrhea, although the P3 genotype has been regarded as a possible marker for virus attenuation.

Amino acid sequence similarity of the VP7 protein of human rotavirus HCR3 to that of canine and feline rotaviruses

The sequence of the VP7 gene of human rotavirus strain HCR3 was determined and its predicted amino acid sequence was compared with that of other rotavirus strains. The VP7 gene is 1062 nucleotides long and contains a single open reading frame of 981 nucleotides capable of encoding a protein of 326 amino acids. The VP7 amino acid sequence similarity of strain HCR3 to those of various human and animal G3 serotypes ranged from 88.7 to 99.4%, and from 60.4 to 88.3% to strains representing each of the other 13 G serotypes. Alignment of four variable regions [VR4, VR5(A), VR7(B) and VR8(C)] of HCR3 with those of G3 strains of different host species showed that HCR3 possesses a sequence almost identical to that of canine rotaviruses and feline rotavirus strain CAT97 in all four regions. A considerable divergence in regions VR4, VR7(B) and VR8(C) was found with strains of human, mouse, monkey, horse and rabbit rotaviruses. This observation together with results of our previous study on VP4 indicated that human rotavirus HCR3 is genetically more closely related to animal rotaviruses than to other human rotaviruses.

Nucleotide sequence of the VP4-encoding gene of an unusual human rotavirus (HCR3)

Human rotavirus strain HCR3 was isolated from the stool of a clinically normal infant and identified as a serotype G3 rotavirus; however, it could not be grouped into any known human VP4 genetic groups by a polymerase chain reaction assay. The fourth gene of strain HCR3, which encodes the outer capsid protein VP4, was sequenced. This gene is 2362 nucleotides in length and contains one open reading frame capable of encoding a protein of 776 amino acids. The VP4 protein of strain HCR3 shared 67.5-73.5% amino acid identity with those of strains KU, RV-5, 1076, and K8, representing four human genetic groups, and relatively high homology (84.7%) with a fifth genetic group represented by strain 69M, whose VP4 shows more similarity to animal than to human strains. Strain HCR3 shared higher VP4 amino acid homology with various animal rotaviruses, ranging from 74.5 to 89.4%. These observations suggest that the VP4 outer capsid protein of strain HCR3 represents a new VP4 genetic group that is more closely related to animal rotaviruses than to human rotaviruses.

Murine rotavirus genes encoding outer capsid proteins VP4 and VP7 are not major determinants of host range restriction and virulence

Simian rotavirus (RRV) and murine rotavirus (EDIM-RW) differ dramatically in the oral inoculum required to cause diarrheal disease in neonatal mouse pups and in their ability to spread and cause disease in uninoculated littermates. A genetic approach was used to explore the molecular basis of these differences. Reassortant viruses were produced in vivo by coinfecting infant mice with RRV and EDIM-RW. Reassortant viruses were isolated by plaque purification of progeny virus obtained from mouse pup intestines on MA104 cells. The plaque-purified reassortants were evaluated for 50% diarrhea dose (DD50) and for the ability to spread and cause diarrhea in uninoculated littermates. The parental RRV strain had a DD50 of 10(5) PFU per animal, while the EDIM-RW parental strain had a DD50 of less than 1 PFU per animal. RRV never spreads from inoculated to uninoculated littermates and causes disease. Twenty-three reassortants were tested. Of great interest were the reassortants D1/5 and C3/2, which derived genes 4 and 7 (encoding VP4 and VP7) from RRV. These viruses had a DD50 similar or identical to that of EDIM-RW and spread efficiently from inoculated mouse pups to uninoculated pups. We conclude that the major outer capsid proteins VP4 and VP7 are not primarily responsible for virulence or host range restriction in the mouse model using a homologous murine rotavirus.

Group A rotaviruses produce extrahepatic biliary obstruction in orally inoculated newborn mice

Extrahepatic biliary atresia is a devastating disease occurring in 1 in 10,000 to 14,000 infants annually in the United States. We have recently described preliminary data suggesting an association of group C rotavirus with biliary atresia in two infants. However, a group C rotavirus animal model of biliary atresia is not presently available. On the other hand, some strains of the better-characterized and much more common group A rotaviruses produce hepatobiliary disease in infant mice. This disease shares many characteristics of the human infection. The present report describes extrahepatic biliary obstruction in immunocompetent BALB/c infant mice infected with a human or animal strain of group A rotavirus. Two-d-old BALB/c mice orally inoculated with hepatobiliary tropic rotavirus were shown to have active virus replication in the biliary tract and liver as early as 48 h postinoculation. At approximately 7 d postinoculation, between one fourth and one half of infant mice, depending on the virus strain, showed signs of inflammation and swelling in the bile ducts. The obstruction was complete in about one half of symptomatic animals. Although there was no obvious atresia as described in human infants, the obstruction was irreversible about 50% of the time, and the resulting fibrosis and bile ductular proliferation in the liver were strikingly similar to those seen in the liver of the human infant with biliary atresia.

Restriction endonuclease analysis of the vp7 genes of human and animal rotaviruses

The vp7 genes of 194 strains of group A rotaviruses representing all known G types were analyzed with three restriction enzymes by direct digestion of amplified cDNA copies or by deduction of the restriction patterns from known sequences. Mammalian rotavirus strains were classified into 28 restriction patterns consisting of combinations of the 6 profiles (s1 to s6) obtained by digestion with Sau96I endonuclease, 9 profiles (h1 to h9) obtained with HaeIII, and 15 profiles (b1 to b15) obtained with BstYI. Digestion with Sau96I and HaeIII identified restriction sites common to all, or almost all, rotavirus strains studied, whereas BstYI was the most discriminating among rotavirus strains. A clear correlation between some restriction patterns or individual profiles and G type and/or host species of origin was found. Several discriminatory restriction sites consisted of type-specific nucleic acid sequences that encoded conserved amino acid residues. Although not directly involved in antigenic diversity, these sites appear to indicate the G type of the isolate. The technique permits rapid comparison of a large number of virus isolates directly from fecal specimens and provides useful markers for investigating the evolution of rotavirus vp7 genes and tracing vaccine virus and interspecies transmission.

Prevalence of serum neutralizing antibody to serotype 9 rotavirus WI61 in children from South America and central Europe

Neutralizing serum antibody to serotype 9 rotavirus WI61 was detected in 41% of 870 Ecuadorian children and 26% of 140 German children. In both areas an age-related prevalence increase was observed. We identified 11 serum samples from Ecuadorian children which neutralized exclusively serotype 9 rotavirus. Thirteen of 71 (18%) German children hospitalized with serologically defined primary rotavirus gastroenteritis showed a seroconversion to serotype 9 rotavirus; however, in 10 of these 13 patients, the infecting serotype could be identified as serotype 1, 3, or 4. Furthermore, all 13 patients showed fourfold increases in titer to at least one further serotype.

Serotypes and electropherotypes of human rotavirus in the USA: 1987-1989

The epidemiology of rotavirus gastroenteritis was investigated for two consecutive seasons (1987-1988 and 1988-1989) in seven locales in the continental USA. The 281 representative fecal samples obtained from children with diarrhea were electropherotyped and serotyped by an enzyme immunoassay with serotype-specific monoclonal antibodies and a new amplification typing technique (polymerase chain reaction typing). Serotype 1 was predominant in both years, particularly in the North and East; serotype 3 was second in frequency and found most often in the South; serotype 2 was detected only occasionally; serotypes 4, 8, and 9 were never found. Rotavirus strains were grouped into five major electropherotypes, each corresponded to a single serotype, and the relative migration of the gene segments 7-9 could be used to distinguish serotype 1 from serotype 3. The amplification typing technique proved to be of great value in typing the 17% of rotavirus-positive specimens untypable by the serologic technique.

Serotype 1 reassortant of bovine rotavirus WC3, strain WI79-9, induces a polytypic antibody response in infants

A reassortant rotavirus, strain W179-9, was constructed bearing gene 9 of serotype 1 rotavirus strain WI79 and all other genes derived from bovine (serotype 6) rotavirus strain WC3. The antigenic phenotype of WI79-9 is bivalent: serotype 1 and serotype 6. WI79-9 administered orally at a dose of 10(7.5) p.f.u. induced no adverse effects in 48 infants of age 2-11 months. Serotype 1- and serotype 6-specific serum neutralizing antibody titres were induced with approximately equal frequency in these infants. Serotype 1-specific antibody responses were inhibited in infants previously seropositive to type 1. The immune response rate was enhanced by administration of a second, 'booster dose'.

Immune protection of infants against rotavirus gastroenteritis by a serotype 1 reassortant of bovine rotavirus WC3

The safety and protective efficacy of a serotype 1 reassortant of bovine rotavirus WC3, disignated strain WI79-9, was evaluated in a double-blind placebo-controlled trial. Rotavirus reassortant WI79-9 contains a gene segment 9 coding for the surface structural protein vp7 of a human serotype 1 rotavirus, with all other gene segments derived from WC3 rotavirus, which had previously been shown to be safe and immunogenic in infants. Infants 2-11 months of age were given two doses of vaccine (10(7.3) plaque-forming units/dose) or of placebo 28 days apart. Adverse reactions to the vaccine were not detected. The incidence of serum plaque reduction neutralization antibody responses to two doses of vaccine was serotype 6, 97%; serotype 3, 68%; and serotype 1, 22%. Active surveillance during the subsequent rotavirus season revealed 8 cases of rotavirus gastroenteritis in 39 placebo control infants and no cases in 38 WI79-9 vaccine recipients (protection = 100%, P = .003). Six cases of rotavirus gastroenteritis were caused by type 1 and two by type 3 virus. Although vaccination with WI79-9 affected only the incidence of rotavirus gastroenteritis, the vaccinated infants exhibited a significantly reduced incidence of total days of diarrhea, fever, and illness associated with gastroenteritis in general.

Polymerase chain reaction amplification and typing of rotavirus nucleic acid from stool specimens

The rotavirus gene segment coding for the major outer capsid glycoprotein vp7 was amplified directly from stool specimens by the polymerase chain reaction (PCR). Double-stranded RNA extracted from stool samples was used as the template for reverse transcription, which was followed immediately and in the same reaction mix with amplification, using the Taq polymerase. Various conditions were examined to optimize the yield of the amplified gene. The concentrations of MgCl2, dimethyl sulfoxide, and template RNA were critical. The choice of primer pairs allowed amplification of the entire segment or specific portions. By using type-specific primers derived from distinct regions on the gene, we devised a PCR typing method in which each human serotype virus produced a characteristic segment size, readily identifiable in agarose gels. The PCR typing method was applied to 10 rotavirus reference strains, including all 6 known human serotypes (serotypes 1, 2, 3, 4, 8, and 9), and to 34 stool specimens previously serotyped by an enzyme immunoassay with monoclonal antibodies. An absolute correlation was found between the molecular and serologic methods. In addition, 14 stool specimens nonserotypable by an enzyme immunoassay with monoclonal antibodies could be typed by the PCR method. Besides the application for rotavirus detection and typing directly from stools, the PCR method provides a rapid and efficient means of obtaining large quantities of cDNA suitable for sequencing, cloning, and other genetic studies, precluding the need for cell culture and virus purification.

Reactogenicity and immunogenicity of rotavirus WC3 vaccine in 5-12 month old infants

Rotavirus is a major cause of acute gastroenteritis in infants worldwide and there is need for an effective vaccine. Rotavirus Wistar calf 3 (WC3) is a strain of bovine origin attenuated by 12 passages in cell culture. A lyophilized candidate vaccine containing 1 x 10(7) PFU of WC3 has been developed. An oral dose was given to 25 French infants 5-12-months old (mean age 8.6 months). No diarrhoea was observed within 2 weeks after vaccination. Unexplained vomiting was reported once and isolated fever greater than 37.8 degrees C was reported 3 times during the first week. One month later, a neutralizing antibody response to serotypes tested was shown in 88% of cases, with heterotypic responses to human serotype 3 (SA11 strain) in 72% and to type 1 (WA strain) in 48%. The percentage of immune response was similar whether the infant had antibody prior to immunization or not, but a booster effect was observed in children who had pre-immunization rotavirus antibodies. Considering these promising results, efficacy trials are in the planning in different parts of the world.

Discrepant rotavirus results in two laboratories using the same enzyme immunoassay

Rotavirus testing was performed on 66 stool samples in two separate laboratories using the same enzyme immunoassay. Sixteen of 46 of the positive results reported by the reference laboratory were negative in the hospital laboratory. In addition, RNA gel electrophoresis had negative results in the 16 discrepant samples. This indicates the need to repeat or confirm positive results.

Protective effect of WC3 vaccine against rotavirus diarrhea in infants during a predominantly serotype 1 rotavirus season

We used a double-blind, placebo-controlled trial to study the efficacy of WC3 rotavirus vaccine administered to 104 infants (ages, three to 12 months) before the rotavirus season. Forty-nine infants received vaccine; 55 received placebo. Rotavirus disease during this season was predominantly caused by a serotype 1 strain. In placebo recipients there were 14 cases of rotavirus diarrhea (attack rate, 25%); 11 were moderate to severe (attack rate, 20%). Vaccinees experienced only three cases of rotavirus disease (attack rate, 6.1%), all mild. When all cases (whether associated with rotavirus or not) of clinically significant diarrhea (CSD) were evaluated, WC3 vaccine provided statistically significant (P less than .01) protection against the total number of episodes of CSD and reduced the number of days of CSD-associated diarrhea, vomiting, fever, or illness. Seventy-one percent of the WC3-vaccinated infants had serum antibody responses to the vaccine. The 14 placebo recipients who experienced natural disease predominantly had antibody responses to serotype 1. Sera taken after the rotavirus season revealed a nearly identical rate (40%) of natural rotavirus infection in the vaccinated and placebo groups.

Rotavirus serotype-specific neutralizing activity in human milk

A plaque reduction neutralization assay was used to determine rotavirus serotype-specific neutralizing activity in human breast milk from 25 mothers of upper socioeconomic background and 20 mothers of a lower socioeconomic status. Levels of neutralizing activity, as well as those of rotavirus-specific antibodies detected by enzyme-linked immunosorbent assay (ELISA), were comparable for each socioeconomic group. Overall, neutralizing activity in human milk was detected in the majority of samples and can be increased many months postpartum. The prevalence of neutralization antibodies (titers, greater than or equal to 1:10) was 77% against Wa (serotype 1), 86% against SA-11 (serotype 3), and 75% against NCDV (bovine) rotavirus. Rotavirus-specific IgA and IgG antibodies detected by ELISA (titers, greater than or equal to 1:10) were present in 35% and 55% of breast milks, respectively. Sequential analysis of repeated breast milk samples from five individual mothers revealed that rotavirus neutralizing activity fluctuated over time, with high activity observed in one mother's milk at 18 months postpartum. Mothers who breast-fed for six months or more tended to have higher milk neutralizing titers against rotavirus.

Rotavirus isolate WI61 representing a presumptive new human serotype

A virus (strain WI61) representing a presumptive new human serotype was isolated from an 18-month-old child with gastroenteritis admitted to Children's Hospital of Philadelphia in February 1983. The WI61 virus was clearly distinguished by cross-neutralization tests from human rotaviruses of serotypes 1, 2, 3, and 4, human 69M, and representative bovine (NCDV), porcine (OSU), and chicken (Ch2) rotaviruses. Antisera generated in guinea pigs hyperimmunized to WI61 virus displayed a partial cross-reactivity with rotaviruses of human serotypes 1, 2, 3, and 4. By means of studies with reassortant rotaviruses, it was presumptively determined that the WI61 virus cross-reactive antigenic determinants are localized on the vp3 surface polypeptide coded by gene segment 4. The characteristic RNA genome electropherotype of WI61 virus was observed in 5 of 59 cases of infant gastroenteritis detected in 1983 and 1984 but has not been observed in a subsequently at Children's Hospital. Serotype WI61-specific neutralizing antibodies were observed in a majority of sera of normal adults and infants of less than 4 or greater than 12 months of age collected in the Philadelphia area. Median antibody titers to WI61 equaled or exceeded those to rotaviruses of serotype 1 or 3. Each of seven samples of commercial cow's milk exhibited neutralizing antibodies to WI61 virus at a titer greater than or equal to that to serotype 1 or 3 or bovine (strain NCDV) rotavirus. However, WI61 rotavirus did not induce disease or a specific serum-neutralizing antibody response when fed to a caesarean-derived colostrum-deprived newborn calf. WI61 rotavirus caused diarrhea in newborn mice with a 50% diarrhea-inducing dose of 10(7.0) PFU.

Gastroenteritis caused by human rotaviruses (serotype three) in a suckling mouse model

The pathogenic potential of human rotaviruses of serotypes 1 through 4 was evaluated in suckling mice. Oral inoculation of three different human rotaviruses of serotype 3 into 5-6 day old CD-1 mice caused disease characterized by diarrhea and dehydration. The mean 50% diarrhea inducing dose (DD50) was 5 X 10(5) pfu. Histopathological examination of small intestines revealed villus epithelial cell vacuolization localized to the distal one-third of the villus. Only Serotype 3 rotaviruses exhibited a rapid phase of viral growth in the intestine between 7 and 12 hours post-inoculation. Larger inocula of rotavirus serotypes 1, 2, and 4 did not cause disease or typical histopathologic changes. However, immunoperoxidase staining for rotavirus antigen was positive in all serotypes tested indicating that infection can occur without apparent disease and is not serotype specific. This convenient in-vivo model can be used to evaluate attenuation of human origin vaccine candidates of serotype 3.

Reassortant rotaviruses containing structural proteins vp3 and vp7 from different parents induce antibodies protective against each parental serotype

Genetic studies of reassortant rotaviruses have demonstrated that gene segments 4 and 9 each segregate with the serotype-specific neutralization phenotype in vitro. Reassortant rotaviruses derived by coinfection of MA-104 cells with the simian strain SA11 and the antigenically distinct bovine strain NCDV were used to determine which viral genes coded for proteins which induced a protective immune response in vivo. In addition, reassortant rotaviruses containing only the gene segment 4 or 9 protein products (vp3 and vp7, respectively) from SA11 or NCDV were used to determine the serotypic specificities of both vp3 and vp7 in several mammalian rotavirus strains. vp3 and vp7 from the murine strain Eb were shown to be indistinguishable from the corresponding proteins from strain SA11. Adult mice orally inoculated with strain Eb developed neutralizing antibodies to both vp3 and vp7. The two naturally occurring bovine rotavirus strains NCDV and UK were shown to contain antigenically similar vp7 but distinct vp3 proteins. Mouse dams orally immunized with a reassortant virus containing only gene 9 from NCDV passively protected their progeny against UK challenge, whereas mouse dams orally immunized with a reassortant virus containing only gene 4 from NCDV did not. Finally, we constructed reassortant viruses that immunized against rotaviruses of two distinct serotypes. SA11 X NCDV reassortants that contained vp3 and vp7 from different parents induced a protective immune response against both parental serotypes. vp3 and vp7 were independently capable of inducing a protective immune response after oral immunization. An understanding of the serotypic specificities of both vp3 and vp7 of human rotavirus isolates will be necessary for the development of successful strategies to protect infants against severe rotavirus infections.

Immune response of infants and children to low-passage bovine rotavirus (strain WC3)

A bovine rotavirus (strain WC3) was isolated from a calf in Pennsylvania and adapted to growth in continuous Cercopithecus cell line CV1. A pool for human vaccine trials was produced at the 12th cell culture passage level. After preliminary testing in adults and older children, a dose of 3 X 10(7) plaque-forming units was given by mouth to 52 infants and children aged 5 months to 6 years. No clinical sequelae were detected, and shedding in feces was detected in only 30% of tested infants. A serum-neutralizing antibody response was induced in 95% of 21 infants aged 5 to 11 months; response rates were slightly reduced in older infants. The antibody response was primarily directed toward bovine rotavirus, but a response to human serotype 3 rotavirus was also observed in approximately 50% of vaccinees. After vaccination with WC3, infants with preexisting antibody to rotaviruses of human serotype 1 or 3 frequently exhibited a booster response to those serotypes. WC3 is a candidate rotaviral vaccine deserving larger trials in children.

Response of adult human volunteers to oral administration of bovine and bovine/human reassortant rotaviruses

Small groups of adult volunteers, in sequence, were inoculated orally with inactivated purified bovine rotavirus of strain NCDV, with live NCDV purified or unpurified and with two different NCDV X human rotavirus reassortant viruses. One of five volunteers given 200 micrograms of ultravioletinactivated NCDV developed a virus-neutralizing (VN) and a binding antibody response detected by enzyme-linked immunosorbent assay (ELISA). Four of 10 volunteers given from 1 X 10(6) to 1 X 10(8) p.f.u. of live NCDV developed VN antibody, but nine of 10 responded when ELISA, HAI and radioimmuno-precipitation tests for serum antibody were also considered. Two different NCDV X human serotype 1 Wa strain virus reassortants, each containing Wa gene segment 9 and the serotype 1 neutralization phenotype, were administered orally in doses up to 10(6) p.f.u. The reassortants were relatively ineffective in eliciting a serum antibody response at the dosage level employed.

Molecular basis of rotavirus virulence: role of gene segment 4

Bovine rotavirus NCDV and simian rotavirus SA-11 exhibited markedly different patterns of gastrointestinal tract disease when inoculated orally into newborn mice. A genetic approach was used to define the molecular basis of these differences. The SA-11 strain of rotavirus was more virulent than the NCDV strain when inoculated orally into newborn mice; the dose of SA-11 required to cause diarrhea in 50% of infant mice was 50-fold less than that required for NCDV. Nineteen reassortant viruses were derived by coinfection of MA-104 cells in vitro with the SA-11 and NCDV strains. The parental origin of reassortant virus double-stranded RNA segments was determined by gene segment migration differences in polyacrylamide gels and hybridization with radioactively labeled parental viral transcripts. The neutralization antigen phenotype of reassortant viruses was determined by plaque reduction neutralization. We found that the dose of SA-11 and NCDV rotavirus required to induce gastroenteritis in newborn mice was determined by gene segment 4. The results suggest that rotavirus virulence may be manipulated by modification or reassortment of gene segment 4.

Rapid inactivation of rotaviruses by exposure to acid buffer or acidic gastric juice

Inactivation rates of three bovine and several primate-origin rotaviruses were determined during exposure to acid buffers at pH 2.0, pH 3.0 or pH 4.0. Each rotavirus was inactivated at pH 2.0 (the acidity most resembling the normal fasting stomach) very rapidly, with half-lives for infectivity determined to be 1 min or less. Each rotavirus was inactivated at a much slower rate at pH 3.0; inactivation at pH 4.0 was minimal. No remarkable differences in acid resistance between different rotavirus strains were detected. Although these determinations were performed at room temperature (23 degrees C), experiments at diverse temperatures indicated an even more rapid rate of viral inactivation by acid at normal body temperature (37 degrees C). Studies of rotavirus exposed to natural human gastric juice at pH 1.8 or pH 2.1 revealed a rate of virus inactivation similar to that observed with glycine buffer of identical pH.