Growth of group A rotaviruses in a human liver cell line

Rotavirus Infects Human Biliary Epithelial Cells and Stimulates Secretion of Cytokines IL-6 and IL-8 via MAPK Pathway

Biliary atresia (BA) is an infantile inflammatory cholangiopathy of unknown etiology although epidemiologic studies and animal models utilizing rotavirus (RV) have suggested a role for viral infection. Proinflammatory and profibrotic cytokines have been detected in infants with BA. The purpose of our study was to investigate the susceptibility of human cholangiocytes (H69 cells) to infection with RRV and to determine if this infection resulted in cytokine secretion. Infection of H69 cells by RRV was noncytolytic and resulted in a time-dependent increase in the release of both infectious virions and cytokines IL-6 and IL-8 into the supernate. The greatest difference in cytokine supernatant levels between infected and mock-infected cells was noted at 24 hours postinfection (h p.i.) for IL-8, 556 ± 111 versus 77 ± 68 pg/mL (p < 0.0001), and at 48 h p.i. for IL-6, 459 ± 64 versus 67 ± 2 pg/mL (p < 0.0001). Production of both cytokines following RRV infection was significantly reduced by pretreating the H69 cells with inhibitors of mitogen-activated protein kinase (MAPK). Conclusion. RRV can infect human cholangiocytes resulting in the production of proinflammatory and profibrotic cytokines via the MAPK pathway. RRV-infected H69 cells could be a useful model system for investigating the viral hypothesis of BA.

Prevalence of groups A and C rotavirus antibodies in infants with biliary atresia and cholestatic controls

OBJECTIVE

To analyze the prevalence of acute asymptomatic group A and C rotavirus (RV-A and RV-C) infection in neonates with cholestasis.

STUDY DESIGN

Participants were infants <180 days of age with cholestasis (serum direct or conjugated bilirubin >20% of total and ≥2 mg/dL) enrolled in the Childhood Liver Disease Research and Education Network during RV season (December-May). Forty infants with biliary atresia (BA), age 62 ± 29 days (range, 4.7-13 weeks) and 38 infants with cholestasis, age 67 ± 44 days (range, 3-15.8 weeks) were enrolled.

RESULTS

At enrollment, RV-A IgM positivity rates did not differ between infants with BA (10%) vs those without (18%) (P = .349). RV-C IgM was positive in 0% of infants with BA vs 3% in those without BA (P = .49). RV-A IgG was lower in infants with BA: 51 ± 39 vs 56 ± 44 enzyme-linked immunoassay unit, P = .045 but this difference may lack biological relevance as maternal RV-A IgG titers were similar between groups. Infant RV-A IgM titers at 2-6 months follow-up increased markedly vs at presentation in both infants with BA (50 ± 30 vs 9 ± 9) and those without (43 ± 18 vs 16 ± 20 enzyme-linked immunoassay unit) (P < .0001), without differences between groups.

CONCLUSIONS

RV-A infection in the first 6 months of life is common in infants with cholestasis of any cause. RV-A could have different pathogenetic effects by initiating different hepatic immune responses in infants with vs without BA or could lack pathogenetic significance.

Rotavirus causes hepatic transaminase elevation

Rotavirus is one of the leading causes of acute gastroenteritis among children. While clinical complaints are generally intestinal including vomiting and diarrhea, there is evidence to suggest that disease outside the gastrointestinal tract occurs. This study examines the frequency of hepatic transaminase elevation in children with rotavirus gastroenteritis. Patients identified with rotavirus gastroenteritis by stool antigen testing between November 2005 and March 2006 had available serum analyzed for alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase, total bilirubin, direct bilirubin, and creatinine phoshosphokinase (CPK). Chart review was conducted to identify patients with possible liver injury unrelated to rotavirus. Among the 92 patients identified with rotavirus during the study period, 75 had serum specimens available for testing. Fifteen patients (20%) had elevated ALT and AST, including one patient with an increase in AST, ALT, alkaline phosphatase, and total and direct bilirubin. The mean ALT elevation was 56 IU/L (range, 44 to 114 IU/L), and the mean AST elevation was 80 IU/L (range, 57 to 126 IU/L). Fifty-three patients (71%) had an increase in AST alone, and three patients (4%) had an increase in AST and alkaline phosphatase. The mean AST values in these groups were 61 IU/L (range, 42 to 110 IU/L) and 79 IU/L (range, 59 to 96 IU/L), respectively. In conclusion, rotavirus commonly causes elevation of liver transaminases.

Growth of rotaviruses in primary pancreatic cells

Rotavirus infection in children at risk of developing type 1 diabetes has been temporally associated with development of pancreatic islet autoantibodies. In this study, nonobese diabetic mice were shown to be susceptible to rhesus rotavirus infection and pancreatic islets from nonobese diabetic mice, nonobese diabetes-resistant mice, fetal pigs, and macaque monkeys supported various degrees of rotavirus growth. Human rotaviruses replicated in monkey islets only. This islet susceptibility shows that rotavirus infection of the pancreas in vivo might be possible.

Rotavirus is released from the apical surface of cultured human intestinal cells through nonconventional vesicular transport that bypasses the Golgi apparatus

Rotaviruses are nonenveloped viruses that infect enterocytes of the small intestine and cause severe infantile gastroenteritis. It was previously thought that rotavirus exits cells by lysis, but this behavior does not match the local pathogenesis of the virus. In this study, we have investigated the release of the simian rotavirus strain (RRV) from the polarized intestinal Caco-2 cells. We found that RRV is released almost exclusively from the apical pole of Caco-2 cells before any cells lyse. Using confocal laser scanning microscopy and drugs that inhibit vesicular transport, we studied the RRV transport route from the endoplasmic reticulum (ER) to the apical side of intestinal cells. We demonstrated that RRV exits from the ER through a carbonyl cyanide m-chlorophenylhydrazone-sensitive vesicular transport. RRV staining was never found within the Golgi apparatus or lysosomes, suggesting that the RRV intracellular pathway does not involve these organelles. This finding was confirmed by treatment with monensin or NH4Cl, which do not affect release of RRV. Electron microscopic analysis revealed RRV containing small smooth vesicles in the apical area and free virions outside the cell in the brush border, consistent with a vesicular vectorial transport of virus. These results may provide, for the first time, a cellular explanation of the pathogenesis of rotavirus.

Lack of evidence for rotavirus by polymerase chain reaction/enzyme immunoassay of hepatobiliary samples from children with biliary atresia

The purpose of this study was to analyze hepatobiliary samples of patients with biliary atresia for rotavirus groups. A, B, and C, because group A rotavirus had been used to produce an animal model of the disease and group C rotavirus had been found in hepatobiliary samples from one group of patients. Biliary remnants and liver tissue from 10 biliary atresia and 14 control patients with other liver diseases were examined for rotavirus groups A, B, and C using nonisotopic, reverse transcriptase polymerase chain reaction enzyme immunoassay. Biliary atresia patients had a median age of 3 mo and were from a confined geographic area. Rotaviral stocks from groups A and C were used as polymerase chain reaction-positive controls. The limits of detection for rotaviral RNA from these two groups were respectively, 5 plaque-forming units and 50 tissue culture infectious doses (ID50). Tissue culture was 100-fold less sensitive for groups A and C than the polymerase chain reaction. The nested nonisotopic probes hybridized in solution only with their homologous target DNAs as determined by the enzyme immunoassay, or by Southern blot hybridization. Although it was possible to detect mRNA from a beta-actin housekeeping gene in all of the hepatobiliary samples, no evidence of rotaviral RNA was found in either the biliary atresia or the negative control group. In conclusion, rotavirus is not a common viral etiology of biliary atresia.

Genetic mapping indicates that VP4 is the rotavirus cell attachment protein in vitro and in vivo

To identify the rotavirus protein which mediates attachment to cells in culture, viral reassortants between the simian rotavirus strain RRV and the murine strains EHP and EW or between the simian strain SA-11 and the human strain DS-1 were isolated. These parental strains differ in the requirement for sialic acid to bind and infect cells in culture. Infectivity and binding assays with the parental and reassortant rotaviruses indicate that gene 4 encodes the rotavirus protein which mediates attachment to cells in culture for both sialic acid-dependent and -independent strains. Using ligated intestinal segments of newborn mice and reassortants obtained between the murine strain EW and RRV, we developed an in vivo infectivity assay. In this system, the infectivity of EW was not affected by prior treatment of the enterocytes with neuraminidase, while neuraminidase treatment reduced the infectivity of a reassortant carrying gene 4 from RRV on an EW background more than 80% relative to the controls. Thus, VP4 appears to function as the cell attachment protein in vivo as well as in vitro.

Rotavirus vaccines and vaccination potential

The development of a successful rotavirus vaccine is a complex problem. Our review of rotavirus vaccine development shows that many challenges remain, and priorities for future studies need to be established. For example, the evaluation of administration of a vaccine with OPV or breast milk might receive less emphasis until a vaccine is made that shows clear efficacy against all virus serotypes. Samples remaining from previous trials should be analyzed to determine epitope-specific serum and coproantibody responses to clarify why only some trials were successful. Detailed evaluation of the antigenic properties of the viruses circulating and causing illness in vaccinated children also should be performed for comparisons with the vaccine strains. In future trials, sample collection should include monitoring for asymptomatic infections and cellular immune responses should be analyzed. The diversity of rotavirus serotype distribution must be monitored before, during, and after a trial in the study population and placebo recipients must be matched carefully to vaccine recipients. Epidemiologic and molecular studies should be expanded to document, or disprove, the possibility of animal to human rotavirus transmission, because, if this occurs, vaccine protection may be more difficult in those areas of the world where cohabitation with animals occurs. We also need to have an accurate assessment of the rate of protection that follows natural infections. Is it realistic to try to achieve 90% protective efficacy with a vaccine if natural infections with these enteric pathogens only provide 60% or 70% protection? Subunit vaccines should be considered to be part of vaccine strategies, especially if maternal antibody interferes with the take of live vaccines. The constraints on development of new vaccines are not likely to come from molecular biology. The challenge remains whether the biology and immunology of rotavirus infections can be understood and exploited to permit effective vaccination. Recent advances in developing small animal models for evaluation of vaccine efficacy should facilitate future vaccine development and understanding of the protective immune response(s) (Ward et al. 1990b; Conner et al. 1993).

Extraintestinal rotavirus infections in children with immunodeficiency

Some rotavirus strains, including vaccine candidates, have been demonstrated to cause hepatitis in immunodeficient and malnourished mice and to grow in human liver cells. To determine whether rotavirus spreads outside the intestine in naturally infected children, we examined tissues from four immunodeficient children affected with severe combined immunodeficiency disease, acquired immunodeficiency disease syndrome, or DiGeorge syndrome. Chronic rotavirus-related diarrhea, which persisted until death, had also developed in each child. Using indirect immunoperoxidase techniques, we identified rotavirus antigen in the liver and kidney with a hyperimmune guinea pig antiserum prepared to double-shelled rotavirus particles. Similar immunostaining with an antiserum to a rotavirus nonstructural protein (NS26) provided evidence of active virus replication. The observed reactivity was eliminated specifically when serial sections were immunostained with the same antiserum that had been absorbed with either double-shelled rotavirus particles or NS26. Immunostaining was not observed in the liver of children with other diseases (alpha 1-antitrypsin deficiency, inspissated bile syndrome, and acute rejection of a transplanted liver). These findings demonstrate that rotavirus infections in children can extend beyond the intestinal tract. Further studies are warranted to determine whether extraintestinal rotavirus replication occurs in children without severe immunodeficiency, such as malnourished children.

Comparative growth of different rotavirus strains in differentiated cells (MA104, HepG2, and CaCo-2)

The production of viral antigen after infection of MA104, HepG2 (derived from human liver), and CaCo-2 (derived from human colon) cells with various cultivatable human and animal rotavirus strains was compared using immunofluorescence tests. All rotavirus strains examined expressed antigen in CaCo-2 cells and MA104 cells, but only some virus strains, namely, SA11-Cl3 (simian), RRV (simian), CU-1 (canine), and Ty1 (turkey), produced antigen in numbers of infected HepG2 cells comparable to infections in MA104 and CaCo-2 cells. Fl-14 (equine), OSU (porcine), NCDV (bovine), and Ch2 (chicken) strains were found to infect moderate numbers of HepG2 cells. Most human rotaviruses (representing viruses in serotypes 1, 2, 3, 4, 8, and 9), a simian rotavirus variant (SA11-4F), lapine (Ala, C-11 and R-2) viruses and porcine (Gottfried) virus infections resulted either in no detectable antigen or antigen synthesis in a low percentage of HepG2 cells. Human rotavirus isolates obtained from the stool specimens of an immunocompromised child with rotavirus antigen in his liver showed two different patterns of replication in HepG2 cells. Examination of the replication of a subset of viruses in the liver and intestinal tissues of orally infected suckling mice showed the CU-1 and Ty1 strains replicated well, while the OSU and human rotavirus strains did not. These results indicate that growth restriction in HepG2 cells is not serotype-specific, and growth of a virus in HepG2 cells does not necessarily correlate with the hepatotropic potential of a virus strain. Factors that may influence these differences of virus infectivity in HepG2 cells are discussed.

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.