Age-dependent rotavirus-enterocyte interactions

Porcine rotavirus C in pigs with gastroenteritis on Thai swine farms, 2011-2016

Swine are economically important food animals, but highly contagious porcine epidemic diarrhea virus (PEDV) and rotavirus can afflict pig herds and contribute significantly to piglet morbidity and mortality. While there have been studies on rotavirus group A (RVA) in Thailand, reports of rotavirus group C (RVC) are limited. Here, we aimed to identify the prevalence of RVC circulating on Thai commercial swine farms. We analyzed 769 feces and intestine mucosal contents of pigs affected with diarrhea between 2011 and 2016 using RT-PCR specific for the PEDV spike (S), rotavirus glycoprotein (G) VP7, and protease-sensitive protein (P) VP4 genes. We found that 6.6% (51/769) of samples tested positive for RVC, of which 11 samples were co-infected with RVA and four samples were co-infected with PEDV. Three samples tested positive for all three viruses. Phylogenetic analysis of the VP7 gene showed that the most frequent RVC genotype was G1, which grouped with the prototypic RVC Cowden strain. While G6 and G9 were also common, G3 was relatively rare. Analysis of the VP4 gene revealed that the most common P type was P[5], followed by P[4], P[7], and P[1]. In all, there were six G/P combinations (G6P[5], G1P[1], G1P[4], G1P[5], G9P[4], and G9P[7]), of which G6P[5] was the most predominant.

Group A rotavirus infection and age-dependent diarrheal disease in rats: a new animal model to study the pathophysiology of rotavirus infection

Group A rotaviruses are major pathogens causing acute gastroenteritis in children and animals. To determine if group A rotavirus replicates and induces disease in rats, antibody-negative Lewis neonatal or adult rats were inoculated orally with tissue culture-adapted human (Wa, WI61, and HAL1166), simian (rhesus rotavirus [RRV] and SA11), bovine (WC3), lapine (ALA), or porcine (OSU) rotavirus strains, wild-type murine (EC(wt)) rotavirus strain, or phosphate-buffered saline (PBS). Rotavirus infection in rats was evaluated by (i) clinical findings, (ii) virus antigen shedding or infectious virus titers in the feces or intestinal contents measured by enzyme-linked immunosorbent assay or fluorescent-focus assay, (iii) histopathological changes in the small intestine, (iv) distribution of rotavirus antigen in small-intestine sections by immunofluorescence, and (v) growth rate. Rotavirus infection of 5-day-old but not > or =21-day-old rats resulted in diarrhea that lasted from 1 to 10 days postinoculation. The severity of disease and spread of infection to naIve littermates differed depending on the virus strain used for inoculation. The duration of virus antigen shedding following infection was considerably prolonged (up to 10 days) in neonatal rats compared to that in 21-day-old rats (1 or 2 days). Based on lack of virus antigen shedding and disease induction, the murine EC(wt) rotavirus was the only strain tested that did not infect rats. Histopathological changes in the small-intestine mucosa of 5-day-old RRV-inoculated rats but not of PBS-inoculated rats was limited to extensive enterocyte vacuolation in the ileum. In RRV-inoculated neonatal rats, rotavirus antigen was detected in the epithelial cells on the upper half of the intestinal villi of the jejunum and ileum. In addition, infection of neonatal rats with RRV but not with PBS resulted in reduced weight gain. Rats infected with group A rotaviruses provide a new animal model with unique features amenable to investigate rotavirus pathogenesis and the molecular mechanisms of intestinal development, including physiological factors that may regulate age-dependent rotavirus-induced diarrhea.

Nutritional status in relation to the efficacy of the rhesus-human reassortant, tetravalent rotavirus vaccine (RRV-TV) in infants from Belém, pará state, Brazil

The rhesus-human reassortant, tetravalent rotavirus vaccine (RRV-TV) was licensed for routine use in the United States of America but it was recently withdrawn from the market because of its possible association with intussusception as an adverse event. The protective efficacy of 3 doses of RRV-TV, in its lower-titer (4 x 10(4) pfu/dose) formulation, was evaluated according to the nutritional status of infants who participated in a phase III trial in Belém, Northern Brazil. A moderate protection conferred by RRV-TV was related to weight-for-age Z-scores (WAZ) greater than -1 only, with rates of 38% (p = 0.04) and 40% (p = 0.04) for all- and- pure rotavirus diarrhoeal cases, respectively. In addition, there was a trend for greater efficacy (43%, p = 0.05) among infants reaching an height-for-age Z-score (HAZ) of > -1. Taking WAZ, HAZ and weight-for-height Z-score (WHZ) indices </= -1 together, there was no significant protection (p > 0.05) if both placebo and vaccine groups are compared. There was no significant difference if rates of mixed and pure rotavirus diarrhoeal cases are compared in relation to HAZ, WAZ and weight-for-height Z-score (WHZ) indices. Although a low number of malnourished infants could be identified in the present study, our data show some evidence that malnutrition may interfere with the efficacy of rotavirus vaccines in developing countries.

Avian-to-mammal transmission of an avian rotavirus: analysis of its pathogenicity in a heterologous mouse model

It has been suggested that group A avian rotaviruses can be transmitted to mammals, but there is no direct evidence that such viruses induce disease in mammals. Suckling mice were orally inoculated with two avian rotaviruses. A pigeon rotavirus, PO-13, was found to induce diarrhea, but a turkey rotavirus, Ty-3, did not. The diarrhea induced by PO-13 was dependent on the age of the mouse. In histopathological examinations, antigens of PO-13 were sporadically detected in absorptive cells in the ileum, and lesions were observed as ballooning degenerations of absorptive cells in a region from the duodenum to the ileum. However, the rotavirus antigen was not detected in the majority of these degenerative cells. These results indicated that PO-13 could infect and induce diarrhea in suckling mice. This is the first evidence of an avian rotavirus being experimentally transmissible to a mammal.

Murine model of rotavirus infection

The murine model of homologous rotavirus infection has been used to study the determinants of protection. The local IgA immune response appears to be the critical factor in generating protective immunity after natural infection. A series of knockout mice were used to evaluate the contribution of T cells and B cells to immunity and resolution from primary infection. Both arms of immune system played a role in the resolution of primary infection but antibody was much more important for prevention of reinfection.

The lesions of rotavirus infection in 1- and 10-day-old gnotobiotic calves

Age-related resistance to rotavirus disease has been described with some rotaviruses. In the present study, we investigated age-related resistance to rotavirus disease by defining extent of intestinal infection, virus replication, and severity of intestinal lesions in groups of three 1- and 10-day-old gnotobiotic calves of mixed breed inoculated orally with a cloned bovine rotavirus of low virulence for calves (strain C3-160) and in two groups of three uninoculated control calves of mixed breed. One-day-old calves inoculated with rotavirus developed diarrhea 26 hours after inoculation, and their feces contained 10(8.5)-10(9.2) TCID50/g feces; inoculated 10-day-old calves did not develop diarrhea, virus excretion commenced on the second or third day after inoculation, and peak concentrations of virus in feces were 10(5.7)-10(7.9) TCID50/g feces. Calves were euthanatized within 8-30 hours after the attainment of peak virus shedding while they were still shedding virus at peak levels. The mean percentage of small intestinal epithelium that was immunostained for rotavirus was three times greater in 1-day-old calves than in 10-day-old calves, and the large intestine was infected more extensively in 1-day-old calves. Immunostaining for rotavirus was maximal in the mid small intestine. Staining of mucin was substantially less in the epithelium of the small intestines and colon of rotavirus-inoculated 1-day-old calves than in age-matched controls. The mean height of villi was reduced to approximately half that of controls in the mid and distal small intestine of rotavirus-inoculated 1-day-old calves and was unchanged in 10-day-old calves. Mean crypt cell production rates were greater than that in controls in both groups of rotavirus-inoculated calves, indicating increased enterocyte loss. Age-related resistance to disease was not due to an inability of rotavirus to infect and replicate in enterocytes with lethal effects but appeared to be associated with a slowing of the pathogenic process, which occurred because insufficient enterocytes became infected and destroyed for lesions to develop.

Reduction of virus shedding by B. bifidum in experimentally induced MRV infection. Statistical application for ELISA

The protective effect of a human strain of Bifidobacterium bifidum (B. bifidum) against murine group A rotavirus (MRV) was examined in the intestines of BALB/c infected mice. In experiments designed to determine whether B. bifidum mediated MRV shedding during diarrheal disease, pregnant dams (and their expected litters) were randomly assigned to the following groups: (1) mice infected with MRV alone; (2) B. bifidum-treated + MRV-infected mice; (3) B. bifidum-treated controls; and (4) saline control animals. An enzyme-linked immunosorbent assay (ELISA) for the detection of group A rotavirus was used to measure virus protein. The sensitivity of the MRV antigen detector ELISA was determined by serially diluting the rotavirus antigen in test samples. Antigen was detected in dilution ranges of 1:256-1:4096 during the acute phase and 1:16-1:512 in the recovery phase of MRV clinical disease, in the samples tested. Treatment with B. bifidum significantly reduced shedding of MRV antigen (P < 0.009) on days 2-10 postinoculation. The reduction in shedding of virus protein corresponded well with delayed onset of acute diarrhea (P < 0.02). Closer examination of tissue cross sections under electron microscopy revealed that the B. bifidum-ingested strain adhered to the epithelium of the small intestine. These results suggest that priming the intestine with B. bifidum is effective against experimental MRV challenge and confirmed the potential usefulness of this detector ELISA for studying the kinetics of group A rotavirus infection in animals and humans.

Murine experimental infection with rotavirus SA-11: clinical and immunohistological characteristics

Six- to eight-day old (lactent) mice were inoculated orally with simian SA-11 rotavirus. During the first hours after infection, the virus was already detected in villous apical enterocytes by immunohistologic reaction of paraffin sections of the duodenum and jejunum but not in the ileum. Late on the first day, some animals developed already diarrhoea and pathologic lesions were observed in the duodenum and jejunum. During the second day most mice developed diarrhoea; tissue lesions were intense and maximal from duodenum to ileum when compared to other days and some colon sections had mild pathological characteristics. At this point, the virus in the ileum was only detected by immunohistologic reaction. During the third day some animals still had diarrhoea but tissue histology was regenerated and no virus could be detected. We conclude that the SA-11 model follows an infection pattern similar to Epizootic Diarrhoea of Infant Mice (EDIM) and propose to study immunological parameters as young susceptible animals mature into adult resistant ones.

Liposome-mediated transfection of intact viral particles reveals that plasma membrane penetration determines permissivity of tissue culture cells to rotavirus

Rotaviruses are an important cause of gastroenteritis in human infants. In vivo, rotavirus displays striking cell tropism with viral replication generally restricted to the villus tip enterocytes of the small intestine. We studied a panel of cell lines that vary significantly in their permissivity to rotavirus infection. L cells and HEp2 cells were relatively resistant to rotavirus infection compared with permissive Ma104 cells and HT29 cells. RNA transcription among the cell lines was proportional to antigen synthesis making a translational or posttranslational block an unlikely source of observed differences in susceptibility. All of the cell lines bound and internalized radiolabeled virus equally well, as measured by escape from surface protease treatment. Analysis of the escape of cell bound virus from neutralizing monoclonal antibody revealed that rotavirus did not immediately enter an eclipse phase in nonpermissive cells, but was internalized in an infectious form for several hours, possibly sequestered within endocytic vacuoles. L cells and HEp2 cells were as permissive as Ma104 and HT29 cells when rotavirus infection was mediated by transfection of single- or double-shelled rotavirus particles with cationic liposomes (Lipofectin). Rotavirus cell tropism in tissue culture cells is determined by the ability of infecting virions to traverse the plasma membrane of the cells into the cytoplasmic compartment.

Molecular basis of age-dependent gastric inactivation of rhesus rotavirus in the mouse

Rotavirus requires specific proteolytic activation by trypsin for efficient replication in tissue culture. To observe the nature of intestinal proteolytic activation of rotavirus in vivo, metabolically labeled rhesus rotavirus (RRV) grown in the presence of trypsin inhibitors was administered to adult and 10-d-old suckling mice by gavage. In the adult stomach, vp4 was cleaved in a manner distinct from in vitro trypsin cleavage. In the suckling stomach, RRV vp4 remains largely uncleaved. The alternative cleavage in the adult stomach was associated with a profound decrease in viral infectivity. vp4 from RRV recovered from the suckling small intestinal lumen was cleaved in a pattern similar or identical to in vitro trypsin-activated virus with bands comigrating with vp5* and vp8*. In contrast, vp4 was not observed in any recognizable form in RRV recovered from adult intestines. Comparison of infectivity of virus recovered from suckling and adult intestines revealed a 10,000-fold decrease in titer in the virus recovered from the adult intestine. In vitro digestions of RRV revealed that pepsin digestion can cleave RRV vp4 and markedly enhance acid-induced loss of rotavirus infectivity. Subsequent digestion with chymotrypsin removes most of the pepsin cleavage products of vp4. Virus injected directly into jejunal loops of adult mice and virus administered orally to adult mice pretreated with antiacid drugs retained infectivity. These studies indicate the development of gastric acid and pepsin secretion may be an important host defense factor in rotavirus gastroenteritis.

A study on delayed hypersensitivity to rotavirus in infancy and childhood

The T-cell responsiveness to rotavirus antigen and phytohaemagglutinin (PHA) together with T-cell total and subsets quantitation was carried out in 50 non-diarrhoeal and six rotavirus diarrhoeal subjects. All individuals in the non-diarrhoeal group responded well to PHA and had normal values for T-cell subsets. The number of positive responders to the rotavirus antigen increased gradually from 0% in the newborns to 92% in older children. The increasing risk of exposure to rotavirus infection is thought to be a chief cause of this age-related variation. All the rotavirus diarrhoeal patients responded well to the rotavirus antigen, indicating a potent test system. The T-cell responses to PHA and the T-cell subsets were significantly low. This could be due to temporary T-cell suppression that may accompany viral infection. Our results are discussed in the context of previous studies.

Identification and partial characterization of a rhesus rotavirus binding glycoprotein on murine enterocytes

In order to assess the possibility that rotavirus binds to a specific cellular receptor on enterocytes, we have used a viral overlay protein blot assay to study viral binding to murine intestinal brush border membranes (BBM). Infectious double-shelled particles of rhesus rotavirus bound specifically to two approximately 300- and 330-kDa glycoproteins from BBM prepared from suckling mice. Significantly less rotavirus binding was observed when adult BBM were examined. Rats have never been shown to harbor natural group A rotavirus infection and correspondingly, rat BBM showed no rotavirus binding activity. In suckling mice, rotavirus was found to bind to villus tip membranes to a much greater extent than to crypt preparations. Rotavirus binding activity was abolished by treatment of membrane preparations with protease. Analysis by glycolytic digestion of BBM with N- and O-glyconases revealed evidence for both N- and O-linked glycosylation of the rotavirus binding protein. Also neuraminidase digestion showed that O-linked sialic acid residues were required for virus binding. Monoclonal antibodies which immunoprecipitate the 300-kDa viral binding glycoprotein react with the apical surface of suckling but not adult enterocytes by Western blot. Baculovirus-expressed vp4, the rotavirus outer capsid spike protein, bound to the 300- and 330-kDa proteins and competed with rotavirus particles for binding sites. The ability of rotavirus to bind via vp4 to large BBM glycoproteins correlates with in vivo rotavirus cell tropism and host range restriction. Specific host cell receptor expression may be important in rotavirus pathogenesis.

Etiology and mechanisms of acute infectious diarrhea in infants in the United States

Infectious diarrhea, caused by a wide variety of viral, bacterial and parasitic pathogens, is a common reason for morbidity and hospitalization for children in the United States. Overall, rotavirus is the most common cause of acute diarrheal disease in infants. Salmonella, Shigella, and Campylobacter are the most frequently isolated bacterial pathogens, and Giardia and Cryptosporidium are the parasites that most commonly produce acute infectious diarrhea. The mechanisms by which these enteropathogens cause diarrhea are highly variable, and include crypt cell proliferation, cellular invasion, elaboration of enterotoxins or cytotoxins, and enteroadhesion. In infants the incidence of diarrheal disease is higher and the severity of the illness is greater than in older children and adults. An increased rate of exposure to enteropathogens, as a result of fecal-oral contamination, may explain some of the increased incidence of diarrhea in infants. However, age-specific differences in host defense mechanisms may also account for the increased susceptibility to and severity of certain enteric infections in infants.

Rotavirus infection detected in neonates from hospitals in urban Bangladesh

A study of neonatal group A rotavirus (RV) infection in 3 hospitals of urban Bangladesh identified 60 infected babies of 100 studied in 2 hospitals. Preliminary evidence based on serotyping and electropherotyping suggest that these RVs differ from community strains.

Memory and distribution of virus-specific cytotoxic T lymphocytes (CTLs) and CTL precursors after rotavirus infection

The gastrointestinal tract is constantly exposed to a variety of potentially invasive bacteria, viruses, and parasites. The first line of defense against these pathogens is the intestinal mucosal surface, which consists of epithelial cells, intraepithelial lymphocytes (IELs), mucus, and secretory immunoglobulins. In addition, the intestine is a rich source of lymphocytes located within Peyer's patches and the lamina propria. Little is known about the function, memory, trafficking, or origin of intestinal T lymphocytes after intestinal infection. We studied the murine cytotoxic T-lymphocyte (CTL) response to the intestinal pathogen rotavirus (simian strain RRV). Adult mice were inoculated orally or via the hind footpad with RRV; virus-specific cytotoxic activities in intestinal and nonintestinal lymphocyte populations were determined by 51Cr release assays. In addition, virus-specific CTL precursor (CTLp) frequencies were determined by limiting-dilution analysis. IELs containing rotavirus-specific cytotoxic activity were detected after oral but not footpad inoculation and expressed alpha/beta but not gamma/delta cell surface protein; virus-specific CTLs did not appear to arise from CTLp among IELs. In addition, the site at which RRV was presented to the immune system determined the site at which RRV-specific CTLp first appeared. Frequencies of rotavirus-specific CTLp detected in Peyer's patches were 25- to 30-fold greater after oral than after footpad inoculation. However, regardless of the route of inoculation, rotavirus-specific CTLp were distributed throughout the lymphoid system 21 days after infection. Implications of these findings for vaccine design are discussed.

Development of an adult mouse model for studies on protection against rotavirus

Although mice have been used as an animal model for studies on rotavirus disease, these studies have been limited by the short time period after birth during which mice are susceptible to rotavirus illness (i.e., approximately 15 days). To overcome this limitation, an adult mouse model was developed in which the endpoint was infection rather than illness. The model developed utilized a strain of mouse rotavirus (EDIM) adapted to grow in culture by multiple passages in MA104 cells. The second cell culture passage of EDIM caused severe diarrhea in neonatal BALB/c mice, and little or no amelioration of disease was observed after nine cell culture passages, even when this preparation was plaque purified. Oral administration of 2 x 10(3) PFU of passage 9 also consistently caused infection of mice 4, 10, 15, 30, 60, 120, and 180 days of age as determined by viral shedding and seroconversion. Reinoculation of these mice with the same virus preparation at 2, 3, or 4 months after the first inoculation produced no evidence of reinfection. In contrast, infection of neonatal mice with the heterotypic WC3 bovine rotavirus did not prevent reinfection with culture-adapted EDIM. Thus, this strain of EDIM caused consistent infection of previously uninoculated neonatal and adult BALB/c mice and produced homotypic but not heterotypic protection against reinfection.

Site of reovirus replication in liver is determined by the type of hepatocellular insult

Reovirus type 1 strain Lang is restricted from replicating in adult murine livers. In noninjured livers, approximately 1% of hepatocytes express reovirus antigen during infection. However, hepatocytes can be induced to express reovirus antigen if challenged with either toxins or trauma. We used selective hepatotoxins or surgical trauma to demonstrate that reovirus antigen localization in liver is determined by the site of hepatocellular insult and the timing of the virus inoculum.

Development of a murine model to study the pathogenesis of rotavirus infection

A murine model to study enteritis induced by bovine (BRV) and murine rotavirus (MRV) has been developed. The course of infection was determined by clinical symptoms of diarrhea and virus isolation as well as histopathological, immunohistochemical, and electron microscopic methods. Both isolates were able to replicate and produce clinical symptoms in neonatal mice. Rotavirus-free neonates were orally inoculated with MRV or BRV and observed over a 192-hr postinoculation (HPI) period. Following infection with 10(4) PFU of virus, diarrhea and maximal intestinal dysfunction, as measured by xylose absorption, did not occur until beyond 20 hr postinfection even though maximal virus production occurred at 10-15 HPI. Immunohistochemically and by electron microscopy we were able to demonstrate viral antigen and virus particles in the enterocytes of villous tips at 5-8 HPI. The appearance of diarrheal symptoms was dependent on the virus dose and the type of virus isolate inoculated. The disease could be induced with doses as low as 1 x 10(2) PFU/mouse of BRV and 1 x 10(1) PFU/mouse of MRV. On the basis of these results, MRV was found to be more virulent than BRV in this model. The model should prove useful for studies designed to assess rotavirus virulence genes and for vaccine protection studies. This work emphasizes the need for early sample collection for critical evaluation of any vaccine or antiviral agent using this model.

Animal model of rotavirus infection in rabbits--protection obtained without shedding of viral antigen

A small animal model was developed in order to investigate the pathogenesis and immunology of rotavirus infections and to study the interaction of different virus strains. Seronegative rabbits of the breed French Lop were used. Two rabbit rotavirus strains, belonging to the same serotype, were used: 82/311 F and R-2, both isolated during diarrhoeal outbreaks in commercial rabbitries. The animals were inoculated orally. The viral shedding and the serological response was monitored by ELISA. Initially six weeks old kits were given four different doses of strain R-2. With doses ranging from 1 x 10(3) to 1 x 10(6) TCID50 all animals seroconverted, but for the lowest dose no viral excretion could be detected. No clinical symptoms were observed. Subsequently the age periods during which the animals were susceptible to the strain R-2 was investigated. The rabbits seroconverted and shed rotavirus antigen, independent of age of six or 22 weeks. None of the animals had diarrhoea. Administration of strain 82/311 F did not result in viral shedding, independently of dose, but all the animals seroconverted. It was also shown for the strain R-2 that when challenging with the same strain four weeks post inoculation that the animals were protected; no viral shedding was detected at the second infection. Strain 82/311 F gave protection against R-2 when the rabbits were challenged four weeks post inoculation.

Immunological aspects of interaction between rotavirus and the intestine in infancy

Rotaviruses are important pathogens causing severe diarrhoea in human infants and young animals. Available information on the pathogenic mechanisms of and the immune response to rotaviruses is reviewed here. Studies in our laboratory using the suckling mouse model have focused on elucidating the nature of interaction between the virus and the gut, and on the importance of T and B cell mediated immunity in protection and recovery from the disease. Our data suggest that the age dependence of mouse rotavirus (MRV) infection is related to the presence of virus-specific receptors on the enterocytes. The uptake of rotavirus antigens appears to be limited to the epithelium associated with Peyer's patches. The antigen is transported to local and regional lymph nodes. Recent studies have indicated that rotavirus infection also increases the uptake of other macromolecules in the intestine. Rotavirus-specific mucosal IgA response seems to be related to the location and magnitude of MRV antigen in the lymph follicles in different segments of the small intestine. Studies in mice with different types of immunodeficiency suggest that a specific immune response is required for complete resolution of virus infection. Several parameters of immunity to rotavirus infection have been examined and, similar to other reports, local immunity in the intestine appears to have the most important role in protection. It also has been observed that nutritional factors may be important in modifying disease. However, there are still many questions to be answered concerning the role of immunity in mediating the pathogenesis of rotavirus infection.

Neonatal rotavirus infection and its relation to cord blood antibodies

Among 274 neonates born at the maternity services of an urban hospital in India, 36.1% of the infants shed rotavirus in feces (as detected by ELISA) by 72 h of life. The excretion rate increased to 70.3% among the 120 infants who stayed for 5 days or more at the hospital. Diarrhoeal symptoms of mild and self-limited nature were observed only in 19.2% of the rotavirus excretors, the remaining being asymptomatic. Among the 98 infants who received supplement feeds, 49% acquired rotavirus infection as against 24.7% of the 150 exclusively breast fed infants (p less than 0.001). Viral RNA in the feces of all rota positive infants showed the same electropherotype, indicating infection from a common source. The mean percentage rotavirus inhibitory activity of cord sera in the infected and non-infected infants was 50.2 +/- 21.7 and 56.6 +/- 19.2 respectively (p greater than 0.05), suggesting that cord blood antibodies do not offer significant protection against neonatal rotavirus infection.

Persistent rotavirus infection in mice with severe combined immunodeficiency

Rotaviruses are important pathogens of human infants and the infants of many animal species. The disease produced by these viruses can be described as an acute, self-limiting diarrheal disease, with virus replication localized to the differentiated epithelial enterocytes of the small intestine. Immunologically normal infants shed virus for approximately 5 to 12 days after the onset of infection. Recently, it has been shown that rotavirus can produce a chronic infection in severely immunocompromised children, with virus shedding and intermittent diarrhea lasting from 6 weeks to 2 years (G. A. Losonsky, J. P. Johnson, J. A. Winkelstein, and R. H. Yolken, J. Clin. Invest. 76:2362-2367, 1985; F. T. Saulsbury, J. A. Winkelstein, and R. H. Yolken, J. Pediatr. 97:61-65, 1980). These findings point to an important role for the immune system in recovery from the disease. The study described here examined the outcome of murine rotavirus infection in mice with severe combined B- and T-cell immunodeficiency (SCID) and in immunologically normal seronegative BALB/c mice. Persistent rotavirus infection was established in all mice with SCID which had been inoculated orally as pups. Low levels of virus replication and constant fecal virus shedding characterized the chronic infection. This is the first report of a persistent rotavirus infection in an animal model.

Acute gastroenteritis in children attending day-care centres with special reference to rotavirus infections. II. Clinical manifestations

In a prospective study of a cohort of 214 children (aged 6 months-7 years) attending day-care centres, a total of 197 episodes of acute gastroenteritis (GE) occurred in 109 children (i.e. 51% of the participants) during a 12-month observation period. Rotavirus, pathogenic bacteria and Giardia lamblia caused GE in 24%, 6% and 2% of the cases, respectively. The aetiology of the remaining 68% was not discovered. Generally, the symptoms of GE were light and only two episodes led to hospitalization. Thirty-two rotavirus infections were asymptomatic. Two rotavirus GE reinfections occurred. They showed less severe symptoms than the primary infections. The older children (greater than 1.5 years) with rotavirus GE had lighter symptoms than the younger ones (less than or equal to 1.5 years). Compared with children with non-rotavirus GE, those with rotavirus GE showed the following clinical features: (1) Age between 6 months and 2 years. (2) Occurrence of rotavirus GE almost exclusively during the rotavirus season, i.e. January to April (winter). (3) High frequency of vomiting, the onset of which often preceded that of diarrhoea. However, these signs did not form a safe basis for the clinical diagnosis of rotavirus GE. One or more upper respiratory manifestations (URM) were observed in 39% of the children with rotavirus GE and in 36% of those with non-rotavirus GE. The occurrence of URM was age-related being highest in children less than 2 years. Consequently, the existence of a rotavirus syndrome is questioned. It is argued that URM in children with rotavirus GE may be due to a co-infection of the upper respiratory tract by a different micro-organism.

Comparison of methods for detection of serum antibody to murine rotavirus

Mice are frequently used as animal models for the study of rotaviral infections. Since natural infection is common in laboratory mice, it is important that rotaviral studies, as well as other studies utilizing suckling mice, employ animals of known immune status to murine rotavirus. A variety of homologous and heterologous enzyme immunoassay systems and an immunofluorescence technique were thus compared to determine the immunoassay that is most effective at detecting adult mice seropositive for rotaviral antibody. It was determined that a homologous enzyme immunoassay inhibition technique utilizing murine rotavirus-derived reagents was the most efficient serologic assay evaluated. A serologic response was consistently detected by this assay by 5 days after experimental rotaviral inoculation of adult mice. A homologous antibody-binding enzyme immunoassay, a heterologous inhibition enzyme immunoassay utilizing antigenically related simian rotavirus (SA-11) reagents, and an immunofluorescence technique utilizing Nebraska calf diarrhea virus antigens were found to be less sensitive for detecting serum antibody to murine rotavirus.

Protective effect of preexisting rotavirus-specific immunoglobulin A against naturally acquired rotavirus infection in children

The preexisting levels of rotavirus IgA and IgG were measured in 225 children aged 6 months to 7 years in November, ie, before the "rotavirus season" from January to April. During the following 6 months, all episodes of acute gastroenteritis (GE) were evaluated clinically according to a score system and feces was examined for rotavirus, pathogenic bacteria, and parasites. Furthermore, rotavirus GE (n = 45) as well as asymptomatic rotavirus infections (n = 29) were diagnosed serologically. The preexisting concentrations of rotavirus IgA and IgG measured by ELISA were similar in these two groups. However, preexisting rotavirus IgA in the group of children who developed rotavirus GE correlated with less severe symptoms. Thus vomiting was found in 24% and 63% of the children with detectable and undetectable rotavirus IgA, respectively (P less than 0.025). Moreover, according to the total symptom score of rotavirus GE, 52% of the children with detectable preexisting rotavirus IgA had mild symptoms compared with only 13% of those with undetectable concentrations (P less than 0.025). Rotavirus IgG did not have any protective effect. Age per se had a protective effect; older age (greater than 1.5 years) was related to mild symptoms. According to previous studies of local and intestinal antibody response to a rotavirus GE, it is suggested that rotavirus IgA in serum reflects the immunological status of the intestine concerning rotavirus. It is recommended that studies of rotavirus vaccines include rotavirus IgA response and its protective effect.

Sialic acid glycoproteins inhibit in vitro and in vivo replication of rotaviruses

We investigated the interactions of rotaviruses with glycoproteins and cells that support rotaviral replication. We found that a wide range of naturally occurring glycoproteins, including ovalbumins and ovomucoids from chicken and turkey eggs, and mucin derived from bovine submaxillary glands, inhibit the replication of rotaviruses in MA-104 cells. Our studies further indicated that the glycoproteins bind directly to rotaviruses and that virus-glycoprotein binding is dependent largely upon interactions with sialic acid oligosaccharides. We found that accessible sialic acid oligosaccharides are required for efficient rotavirus infection of MA-104 cells, thus demonstrating that sialic acid oligosaccharides play an important role in the interactions of rotaviruses with both glycoproteins and cells that support rotaviral replication. Bovine submaxillary mucin and chicken ovoinhibitor can also prevent the shedding of rotavirus antigen and the development of rotavirus gastroenteritis in a mouse model of rotavirus infection. Our findings document that a range of glycoproteins inhibit the in vivo and in vitro replication of rotaviruses and suggest that the alteration in the quantity or chemical composition of intestinal glycoproteins is a potential means for the modulation of enteric infections.

Observations questioning a protective role for breast-feeding in severe rotavirus diarrhea

To investigate whether breast-feeding protects children against rotavirus diarrhea (RVD), we compared rates of breast-feeding by age and enteric pathogens among 2,276 children with diarrhea 0-4 years of age who attended a diarrhea hospital in Bangladesh. Infants 0-5 months were less likely to be breast-fed than children 6-11 months of age suggesting that some protection against diarrhea with all agents was associated with early breast-feeding. In every age group studied, breast-feeding was more common among children with RVD than among children with non-RVD whereas it was less common among children with cholera and shigellosis. Twenty percent of breast milks consumed by infants less than 1 year of age had high levels of neutralizing activity (greater than or equal to 320) to the Wa strain of rotavirus but this activity did not appear to be protective since the 30 infants with RVD consumed milk which had titers that did not differ significantly from those consumed by 44 infants with diarrhea of other cause. Despite the prolonged breast-feeding which is common in Bangladesh, the mean age of hospitalization with RVD is approximately the same as in countries where the duration of breast-feeding is quite short. None of these 3 independent observations support a protective role for breast-feeding against rotavirus diarrhea after the first months of life.

Variation in virulence of bovine rotaviruses

Forty-six gnotobiotic calves aged less than 16 days or 42-116 days were infected with three strains of bovine rotavirus designated C3-160, CP-1 and PP-1. Each virus was passaged and cloned in cell culture (cloned viruses) but CP-1 and PP-1 were also used before culture (faecal viruses). Infection of calves aged less than 16 days with faecal or cloned CP-1 caused disease whereas cloned C3-160 and faecal or cloned PP-1 caused subclinical infections. The clinical signs of disease were change in faecal colour to pale yellow or cream, increase of 2- to 7-fold in the volume of faecal output and, usually, anorexia. With the virulent CP-1 virus and the avirulent C3-160, similar amounts of virus were excreted in the faeces for 4-6 days. Infection of calves aged 56-116 days with faecal CP-1 produced disease of similar severity to that seen in calves aged 7-10 days infected with the same virus. No differences in clinical signs, virus excretion or levels of convalescent antibody were seen between the two groups. With cloned CP-1, 5 of 8 older calves developed disease but 3 showed only mild signs of infection. It was concluded that two strains of rotavirus caused sub-clinical infections in young calves while a third was virulent in calves up to at least 116 days of age.

Cultivation and characterization of three strains of murine rotavirus

Three distinct strains of murine rotavirus were adapted to growth in cell culture. These strains are genetically related but not identical; they are serotypically heterogeneous. The cultivatable strains were substantially more infectious (approximately 10(6)-fold) for suckling mice than heterologous simian rotaviruses were. Homologous murine rotavirus strains spread from inoculated to uninoculated litter mates and caused diarrhea, while heterologous rotaviruses did not spread and cause illness.

T-cell-deficient mice display normal recovery from experimental rotavirus infection

Rotaviruses are common causes of diarrhea in animals and humans. Little is known, however, about the components of the host response to these viruses. Rotavirus infection was studied in athymic mice experimentally infected with murine rotavirus. Neonatal T-cell-deficient mice experienced a self-limited gastrointestinal infection which was identical to that observed in age-matched immunocompetent mice. Adult T-cell-deficient seronegative mice and age-matched normal mice showed a similar extent of resistance to symptomatic rotavirus infection. In both cases, the infection was resolved without the generation of antirotavirus antibody. These studies indicate that host defense against murine rotavirus requires neither functional T-lymphocytes nor specific antiviral antibody.

Development of resistance of enterocytes to rotavirus in neonatal, agammaglobulinemic piglets

The first part of this report describes the development of a technique for evaluating the growth of rotavirus under controlled conditions that approximate a natural infection. A standard dose of rotavirus (approximately 10(9) viral particles) was injected into ligated segments in the small intestine of newborn, agammaglobulinemic, colostrum-deprived piglets. After various periods postinoculation, the segments were retrieved and the enterocytes were evaluated for the presence of rotaviral antigens by immunofluorescence and rotaviral particles by transmission electron microscopy. Peak immunofluorescence in enterocytes was detected at 8 h postinoculation in the upper and middle jejunum and ileum. Transmission electron microscopy at this time revealed fully formed virions which were not seen in sections examined before this 8-h period. The second part of our study describes the use of ligated segments in determining the susceptibility to rotavirus of enterocytes in piglets ranging in age from newborn to 2 weeks. By the time piglets were 2 days old, enterocytes in the upper half of the small intestines appeared to be resistant to rotavirus, whereas those in the lower half seemed partially resistant. Between 4 and 8 days of age, enterocytes in the lower half also became resistant. Resistance paralleled the loss in capacity of piglets to transport macromolecules through enterocytes and was not correlated with the loss in capacity to internalize macromolecules.

Rotavirus-associated traveler's diarrhea: neutralizing antibody in asymptomatic infections

The sera of patients with traveler's diarrhea were assayed for rotavirus-specific immunoglobulins in enzyme-linked immunosorbent and micro-neutralization assays. The antigenically related simian rotavirus SA-11 was used in both assays. Although similar titers of rotavirus-specific binding immunoglobulin G and A were observed in the sera of both symptomatic and asymptomatic subjects, clinical illness appeared to correlate with the failure to detect increased (greater than or equal to fourfold) titers of neutralizing antibodies in the post- as compared with the pretravel sera.

Virus-specific immunity in neonatal and adult mouse rotavirus infection

Mouse rotavirus (epizootic diarrhea of infant mice) was used as a model to study the role of virus-specific immunity in infection and diarrheal disease. The distribution of viral antigen in intestinal tissues was determined by immunofluorescent staining with anti-simian rotavirus (SA-11) serum. The location and proportion of antigen-positive cells appeared to vary as a function of time postinfection and age of the animal at the time of infection. In animals infected at 1 and 7 days of age, antigen-positive cells (5 to 25%) were first detected (1 day postinfection) in the proximal segment of the small intestine, and infection progressed to the middle and distal segments. At 10 days postinfection, virus-infected cells were no longer observed in the proximal segment. In animals infected at 21 days of age (disease-free), a significantly lower proportion of cells were antigen positive (2 to 5%), and they were restricted to the middle and distal segments of the small intestine. Infection, defined according to the presence of virus and viral antigens in intestinal tissues and by seroconversion in the immunoglobulin M (IgM) isotype as determined by enzyme-linked immunosorbent assay with SA-11 antigen, was observed for all age groups (neonatal to adult), even in the presence of virus-specific serum or intestinal immunoglobulins. On the other hand, diarrheal disease was not detected in neonatal mice (1 to 3 days old) positive for passively acquired virus-specific intestinal IgG. The presence of virus-specific IgA in the intestinal tract at the time of infection did not protect from subsequent diarrheal disease. Virus-specific, cell-mediated immunity, determined by a delayed-type hypersensitivity response, did not develop in neonatal mice infected at 5 and 12 days of age. Reinfection of adult mice was associated with suppression of virus-specific delayed-type hypersensitivity and a significant decrease in the titers of the virus-specific serum IgG and IgA.