Faecal and pharyngeal shedding of rotavirus and rotavirus IgA in children with diarrhoea

Use of Pathogen-Specific Antibody Biomarkers to Estimate Waterborne Infections in Population-Based Settings

PURPOSE OF REVIEW

This review discusses the utility of pathogen-specific antibody biomarkers for improving estimates of the population burden of waterborne infections, assessing the fraction of infections that can be prevented by specific water treatments, and understanding transmission routes and the natural history and ecology of disease in different populations (including asymptomatic infection rates).

RECENT FINDINGS

We review recent literature on the application of pathogen-specific antibody response data to estimate incidence and prevalence of acute infections and their utility to assess the contributions of waterborne transmission pathways. Advantages and technical challenges associated with the use of serum versus minimally invasive salivary antibody biomarkers in cross-sectional and prospective surveys are discussed. We highlight recent advances and challenges and outline future directions for research, development, and application of antibody-based and other immunological biomarkers of waterborne infections.

Comparison of α-glucosyl hesperidin of citrus fruits and epigallocatechin gallate of green tea on the Loss of Rotavirus Infectivity in Cell Culture

A number of secondary plant metabolites (e.g., flavonoids) possess antiviral/antimicrobial activity. Most flavonoids, however, are difficult to study, as they are immiscible in water-based systems. The relatively new semisynthetic α-glucosyl hesperitin (GH), and the natural plant product epigallocatechin gallate (EGCG) are unique among most flavonoids, as these flavonoids are highly soluble. The antiviral activity of these plant metabolites were investigated using the rotavirus as a model enteric virus system. Direct loss of virus structural integrity in cell-free suspension and titration of amplified RTV in host cell cultures was measured by a quantitative enzyme-linked immunosorbent assay (qEIA). After 30 min. 100 × 10(3) μg/ml GH reduced RTV antigen levels by ca. 90%. The same compound reduced infectivity (replication in cell culture) by a similar order of magnitude 3 to 4 days post inoculation. After 3 days in culture, EGCG concentrations of 80, 160, and 320 μg/ml reduced RTV infectivity titer levels to ca. 50, 20, and 15% of the control, respectively. Loss of RTV infectivity titers occurred following viral treatment by parallel testing of both GH and EGCG, with the latter, markedly more effective. Cytotoxicity testing showed no adverse effects by the phenolic concentrations used in this study. The unique chemical structure of each flavonoid rather than each phenolic's inherent solubility may be ascribed to those marked differences between each molecule's antiviral (anti-RTV) effects. The solubility of EGCG and GH obviated our need to use potentially confounding or obfuscating carrier molecules (e.g., methanol, ethanol, DMSO) denoting our use of a pure system environ. Our work further denotes the need to address the unique chemical nature of secondary plant metabolites before any broad generalizations in flavonoid (antiviral) activity may be proposed.

Effect of pH on anti-rotavirus activity by comestible juices and proanthocyanidins in a cell-free assay system

Cranberry (Vaccinium macrocarpon) and grape (Vitis labrusca) juices, and these species' secondary plant metabolites [i.e., proanthocyanidins (PACs)] possess antiviral activity. An understanding of the mechanism(s) responsible for these juices and their polyphenolic constituents' direct effect on enteric virus integrity, however, remains poorly defined. Using the rotavirus (RTV) as a model enteric virus system, the direct effect of manufacturer-supplied and commercially purchased juices [Ocean Spray Pure Cranberry 100 % Unsweetened Juice (CJ), Welch's 100 % Grape Juice (GJ), 100 % Concord (PG) and 100 % Niagara juices (NG)] and these species' cranberry (C-PACs) and grape PACs (G-PACs) was investigated. Loss of viral capsid integrity in cell-free suspension by juices and their PACs, and as a factor of pH, was identified by an antigen (RTV) capture enzyme-linked immunosorbent assay. At native and an artificially increased suspension at or near pH 7, loss of viral infectivity occurred after 5 min, in the order CJ > NG = GJ > PG, and PG > GJ = NG = CJ, respectively. Antiviral activity of CJ was inversely related to pH. Grape, but not cranberry PACs, displayed a comparatively greater anti-RTV activity at a suspension pH of 6.7. Anti-RTV activity of C-PACs was regained upon reduction of RTV-cranberry PAC suspensions to pH 4. An alteration or modification of Type A PAC (of V. macrocarpon) structural integrity at or near physiologic pH is suggested to have impacted on this molecule's antivirus activity. Type B PACs (of V. labrusca) were refractive to alternations of pH. Significantly, findings from pure system RTV-PAC testing paralleled and in turn, supported those RTV-juice antiviral studies. Electron microscopy showed an enshroudment by PACs of RTV particles, suggesting a blockage of viral antigenic binding determinants. The implications of our work are significant, especially in the interpretation of PAC (and PAC-containing food)-RTV interactions in the differing [pH] conditions of the gastrointestinal tract.

Gastrointestinal flora and gastrointestinal status in children with autism--comparisons to typical children and correlation with autism severity

Background

Children with autism have often been reported to have gastrointestinal problems that are more frequent and more severe than in children from the general population.

Methods

Gastrointestinal flora and gastrointestinal status were assessed from stool samples of 58 children with Autism Spectrum Disorders (ASD) and 39 healthy typical children of similar ages. Stool testing included bacterial and yeast culture tests, lysozyme, lactoferrin, secretory IgA, elastase, digestion markers, short chain fatty acids (SCFA's), pH, and blood presence. Gastrointestinal symptoms were assessed with a modified six-item GI Severity Index (6-GSI) questionnaire, and autistic symptoms were assessed with the Autism Treatment Evaluation Checklist (ATEC).

Results

Gastrointestinal symptoms (assessed by the 6-GSI) were strongly correlated with the severity of autism (assessed by the ATEC), (r = 0.59, p < 0.001). Children with 6-GSI scores above 3 had much higher ATEC Total scores than those with 6-GSI-scores of 3 or lower (81.5 +/- 28 vs. 49.0 +/- 21, p = 0.00002).

Children with autism had much lower levels of total short chain fatty acids (-27%, p = 0.00002), including lower levels of acetate, proprionate, and valerate; this difference was greater in the children with autism taking probiotics, but also significant in those not taking probiotics. Children with autism had lower levels of species of Bifidobacter (-43%, p = 0.002) and higher levels of species of Lactobacillus (+100%, p = 0.00002), but similar levels of other bacteria and yeast using standard culture growth-based techniques. Lysozyme was somewhat lower in children with autism (-27%, p = 0.04), possibly associated with probiotic usage. Other markers of digestive function were similar in both groups.

Conclusions

The strong correlation of gastrointestinal symptoms with autism severity indicates that children with more severe autism are likely to have more severe gastrointestinal symptoms and vice versa. It is possible that autism symptoms are exacerbated or even partially due to the underlying gastrointestinal problems. The low level of SCFA's was partly associated with increased probiotic use, and probably partly due to either lower production (less sacchrolytic fermentation by beneficial bacteria and/or lower intake of soluble fiber) and/or greater absorption into the body (due to longer transit time and/or increased gut permeability).

Intestinal IgA response and immunity to rotavirus infection in normal and antibody-deficient chickens

Rotavirus inoculation by oesophageal cannulation resulted in subclinical infection without decreasing intestinal D-xylose absorption in both intact and embryonally bursectomised, antibody-deficient (EBx) 8-week-old specific-pathogen-free chickens. In intact chickens, rotavirus-specific IgM, IgG and IgA responses were detected in serum, while the intestinal antibody response consisted almost entirely of IgA Serum IgG and intestinal IgA levels were increased for at least 70 days following a single inoculation with the virus. Intact chickens recovered from a primary rotavirus infection between 4 and 14 days post inoculation (dpi) and developed resistance to homotypic challenge between 14 and 28 dpi. These responses were only slightly delayed in EBx birds, which recovered from primary infection between 8 and 28 dpi and developed resistance between 14 and 42 dpi. This suggested that the intestinal IgA response in chickens participated in both recovery from and resistance to rotavirus infection, but that it was not the only mediator of recovery and resistance.

Epidemiology of rotavirus infections in The Netherlands

This paper reviews published and unpublished data from epidemiological and virological studies of rotavirus in the Netherlands to identify gaps in our knowledge; it includes analysis of surveillance data for seasonality and age groups at risk. Rotavirus was found in approximately 5% of stool specimens from people consulting a physician for gastroenteritis. Of these cases, 38% were under 5 y of age. A clear seasonality was observed, with a peak in rotavirus activity in winter and early spring. In one hospital-based study between 1976 and 1983, rotavirus was found in 30% of children under 3 y of age hospitalized for gastroenteritis. In addition, nosocomial infections have been documented. Analysis of monthly data from laboratory surveillance from 1981 to 1996 showed that between 6 and 16% of stool samples tested positive for rotavirus, again with a clear seasonal distribution. A total of 98% of rotavirus strains that were typed were G-type 1-4. We conclude that more recent data about hospitalization rates are needed for a well-founded cost-benefit analysis.

Extended excretion of rotavirus after severe diarrhoea in young children

BACKGROUND

Rotaviruses are the major cause of severe childhood diarrhoea. Knowledge of the natural history of infection, including duration of intestinal virus shedding, is important in the understanding of transmission, sources of infection, and immune responses.

METHODS

We carried out a study of rotavirus excretion in 37 children admitted to hospital with severe rotavirus diarrhoea. Sequential faecal specimens were collected from each child during 100 days of surveillance, and screened for rotavirus by EIA and by amplification of genome double-stranded RNA by reverse-transcription PCR. IgA coproantibody was estimated by EIA.

FINDINGS

Duration of rotavirus excretion ranged from 4 to 57 days after onset of diarrhoea. Excretion ceased within 10 days in 16 (43%) children, and within 20 days in 26 (70%) children. Extended excretion was detected for 25-57 days in the remaining 11 (30%) children owing mainly to continued excretion of the primary infecting strain. Extended excretion was significantly associated with antirotavirus IgA coproantibody boosts during 100 days of surveillance (p=0.001, log-rank test), and with recurrence of mild diarrhoea symptoms during convalescence (p=0.006, Fisher's exact test).

INTERPRETATION

Severe rotavirus disease in young children may be followed by extended excretion of rotavirus. The risk of transmission to others may be greater than previously believed. Extended excretion could also explain some cases of the postgastroenteritis syndrome.

Serum IgA immune response to individual rotavirus polypeptides in young children with rotavirus infection

A human IgA-radioimmunoprecipitation assay (IgA-RIPA) utilizing the galactose-binding lectin jacalin from the jack-fruit Artrocarpus integrifolia was developed. Among the human immunoglobulins, jacalin binds specifically to immunoglobulin A. The IgA-RIPA was used to characterize the serum IgA response to individual rotavirus polypeptides in nine paired sera from children (8-34 months of age) with an acute rotavirus infection. In acute sera the IgA response was mainly directed against the inner capsid proteins VP2 and VP6, with VP2 surprisingly being the most immunogenic protein while in the convalescent sera, the IgA response was directed not only against structural but also against non-structural proteins.

The rotavirus genus

Human rotaviruses, discovered nearly 20 years ago, have been proven to be major cause of paediatric diarrhoeal disease morbidity and mortality. The clinical significance of these viruses stimulated basic studies on their biology, molecular and antigenic properties and epidemiology. General features, clinical relevance, epidemiologic pattern and laboratory diagnosis of human rotavirus infections are here reviewed.

Serial observations of chronic rotavirus infection in an immunodeficient child

Chronic rotavirus infection of an infant with severe combined immunodeficiency (SCID) was studied by virological examinations in association with long-term observation of his symptoms and immune status. During eleven months of hospitalization, the patient was suffering from incurable severe diarrhea with persisting excretion of rotaviruses detected by electron microscopy and the reversed-passive hemagglutination (R-PHA) test and had transient hepatitis symptom despite multiple administrations of human gammaglobulin and high calorie fluids. The detected viruses were morphologically recognized as rotavirus with double capsid structure. Polyacrylamide gel electrophoretic (PAGE) analysis of their genomic RNAs showed the long electropherotype of group A virus with abnormal migration profiles changing considerably from the early to the late phase of illness: (1) The 11th segment became undetectable; (2) the molecular weight of the 6th segment slightly increased; (3) seven to fourteen extra segments appeared; and (4) PAGE patterns of viral genomic RNAs changed every three or four months. These findings suggest that chronic infection with rotavirus accompanied the generation of extra viral genomic segments and their unusual assortments in an immunodeficient host.

Induction and persistence of local rotavirus antibodies in relation to serum antibodies

The induction and persistence of local rotavirus antibodies, including stool IgA, jejunal IgA, and jejunal neutralizing antibody, were evaluated in 14 adult volunteers infected with the CJN strain of human rotavirus. In addition, the relationships between local rotavirus IgA and serum rotavirus IgA, IgG, and neutralizing antibody were determined. Both stool and serum rotavirus IgA appeared to have similar kinetics. Both antibodies peaked by days 14-17 after inoculation in all subjects, then decreased rapidly. By days 26-28, titers had fallen to 13% and 30% of their respective peaks. Serum rotavirus IgG peaked somewhat later, occurring in five subjects on days 26-28. Serum neutralizing antibody peaked on days 26-28 in all but three subjects. Both serum IgG and neutralizing antibodies also declined more slowly than rotavirus IgA. Although all antibody concentrations had decreased to only a fraction of their peak responses by days 270-365 after rotavirus inoculation they remained higher than baseline levels. For example, stool rotavirus IgA concentrations were 13.5-fold higher than baseline, while jejunal rotavirus IgA and neutralizing antibody were 8.9- and 4.3-fold above baseline, respectively. Similarly, serum antibodies remained 3.7- to 11.2-fold higher than baseline at 270-365 days after rotavirus inoculation. These studies imply that serum rotavirus IgA is a good indicator of local antibody responses. Furthermore, although both serum and local antibody titers peaked within 2-4 weeks after infection, these antibodies persisted at above baseline concentrations for at least 9-12 months after infection.

Human viral gastroenteritis

During the last 15 years, several different groups of fastidious viruses that are responsible for a large proportion of acute viral gastroenteritis cases have been discovered by the electron microscopic examination of stool specimens. This disease is one of the most prevalent and serious clinical syndromes seen around the world, especially in children. Rotaviruses, in the family Reoviridae, and fastidious fecal adenoviruses account for much of the viral gastroenteritis in infants and young children, whereas the small caliciviruses and unclassified astroviruses, and possibly enteric coronaviruses, are responsible for significantly fewer cases overall. In addition to electron microscopy, enzyme immunoassays and other rapid antigen detection systems have been developed to detect rotaviruses and fastidious fecal adenoviruses in the stool specimens of both nonhospitalized patients and those hospitalized for dehydration and electrolyte imbalance. Experimental rotavirus vaccines have also been developed, due to the prevalence and seriousness of rotavirus infection. The small, unclassified Norwalk virus and morphologically similar viruses are responsible for large and small outbreaks of acute gastroenteritis in older children, adolescents, and adults. Hospitalization of older patients infected with these viruses is usually not required, and their laboratory diagnoses have been limited primarily to research laboratories.

Diarrheal diseases in Brazil: clinical features of rotavirus-associated gastroenteritis in children

This study was undertaken to detect the presence of rotavirus in the stools of children with gastroenteritis, using the enzyme-linked-immunosorbent assay (ELISA), and to compare the signs and symptoms of rotavirus-positive and -negative children. Over a period of fifteen months, 367 children ranging in age from less than 1 month to 5 years or more with diarrhea and 86 children, in the same age group, without diarrhea and respiratory infections, used as controls, were evaluated. Human rotavirus was detected in 15.8% of children with diarrhea attending out-patient clinics and in 28.9% of patients seen by general practitioners. In the control groups, the percentages of identification of rotavirus were 1.4% and 5.5% respectively. Frequency of other enteropathogens was determined. The hydration state of diarrheal cases, different clinical symptoms and the type of medical attendance distinguished the rotavirus positive from the rotavirus negative patients.

Comparison of serum and mucosal antibody responses following severe acute rotavirus gastroenteritis in young children

The development of mucosal immunity is presumed to be the most important marker of rotavirus infection. The practical difficulties of obtaining small-bowel secretions stimulated this study of the antibody response to acute rotavirus infection at other sites. Forty-four infants admitted to the hospital with rotavirus gastroenteritis had serum, saliva, and feces collected at the acute phase (median, 5.5 days), during convalescence (median, 33.5 days), and 4 months later (median, 12.2 weeks). A subgroup of 19 children also had duodenal juice collected in parallel. Rotavirus-specific immunoglobulin G (IgG), IgA, secretory immunoglobulin, and IgM were measured and compared in all samples. The results showed that the estimation of antirotavirus serum IgM, serum IgG, duodenal juice IgA, and duodenal juice IgM by an enzyme immunoassay indicated an immune response to severe primary rotavirus infection in all children. Four months later, the levels of serum IgG and IgA served as the most sensitive markers of the preceding rotavirus infection. The predictive accuracies of immune responses at different sites in relation to a positive IgA immune response in the duodenum were calculated. Fecal IgA predicted duodenal IgA rotavirus antibodies with accuracies of 86% at 1 month and 92% at 4 months. The high sensitivity of serum IgM and IgG in detecting rotavirus infection and the high predictive accuracy of fecal IgA as an indicator of duodenal IgA abrogates the need for duodenal intubation to detect (or monitor) an immune response to rotavirus infection. This finding has important practical implications for epidemiological studies of acute diarrhea in children and in rotavirus vaccine trials.

Use of serotype-specific monoclonal antibodies to study the epidemiology of rotavirus infection

The development of an enzyme immunoassay (EIA) capable of serotyping human rotavirus (HRV) in faecal extracts has enabled us to retrospectively study the epidemiology of rotavirus infection in Melbourne. Of 552 stored specimens obtained from individuals with rotavirus-associated gastroenteritis between 1975 and 1986, the serotype could be determined in 62%. Infection was most prevalent in two groups, neonates and children aged between 12 and 24 months. In these groups infection was due to different serotypes, type 1 in older children and an untypable virus in infants. Serotype 1 strains were detected in greater numbers than the other serotypes and circulated in each year of the study. Serotype 2 rotaviruses were associated with a large epidemic in 1978, but have been detected only rarely since.

Development of nasal, fecal and serum isotype-specific antibodies in calves challenged with bovine coronavirus or rotavirus

Unsuckled specific pathogen free calves were inoculated at 3-4 weeks of age, either intranasally (IN) or orally (O) with bovine coronavirus or O plus IN (O/IN) or O with bovine rotavirus. Shedding of virus in nasal or fecal samples, and virus-infected nasal epithelial cells were detected using immunofluorescent staining (IF), ELISA or immune electron microscopy (IEM). Isotype-specific antibody titers in sera, nasal and fecal samples were determined by ELISA. Calves inoculated with coronavirus shed virus in feces and virus was detected in nasal epithelial cells. Nasal shedding persisted longer in IN-inoculated calves than in O-inoculated calves and longer than fecal shedding in both IN and O-inoculated calves. Diarrhea occurred in all calves, but there were no signs of respiratory disease. Calves inoculated with rotavirus had similar patterns of diarrhea and fecal shedding, but generally of shorter duration than in coronavirus-inoculated calves. No nasal shedding of rotavirus was detected. Peak IgM antibody responses, in most calves, were detected in fecal and nasal speciments at 7-10 days post-exposure (DPE), preceeding peak IgA responses which occurred at 10-14 DPE. The nasal antibody responses occurred in all virus-inoculated calves even in the absence of nasal shedding of virus in rotavirus-inoculated calves. Calves inoculated with coronavirus had higher titers of IgM and IgA antibodies in fecal and nasal samples than rotavirus-inoculated calves. In most inoculated calves, maximal titers of IgM or IgA antibodies correlated with the cessation of fecal or nasal virus shedding. A similar sequence of appearance of IgM and IgA antibodies occurred in serum, but IgA antibodies persisted for a shorter period than in fecal or nasal samples. Serum IgG1 antibody responses generally preceeded IgG2 responses and were predominant in most calves after 14-21 DPE.

Involvement of infants, children, and adults in a rotavirus gastroenteritis outbreak in a kibbutz in southern Israel

An outbreak of acute gastroenteritis in a kibbutz in southern Israel, characterized by diarrhea, fever, vomiting, and abdominal pain, involved 32 kibbutz members of all ages. Nineteen percent of the children and 3.5% of the adults were ill. Transmission of the illness occurred in direct proportion to the degree of close contact, involving first infants, then mothers and nursery staff, and only later youngsters, adolescents, and fathers. Stool samples obtained from 32 kibbutz members with clinical illness and from 44 asymptomatic close contacts were examined for the presence of rotavirus antigen. Fifty-six percent of symptomatic members were positive for rotavirus antigen as compared with 4.5% of asymptomatic close contacts. Positivity of stool samples correlated inversely with the number of days elapsed after onset of illness until the sample was obtained. Serologic studies carried out on acute and convalescent sera of symptomatic and asymptomatic subjects further supported a rotavirus etiology for the outbreak. RNA profiles of stool sample extracts obtained by polyacrylamide gel electrophoresis and silver staining indicate that one electropherotype may have been responsible for the outbreak.