Human viral gastroenteritis

Human adenoviruses: A suspect behind the outbreak of acute hepatitis in children amid the COVID-19 pandemic

As of 10 May 2022, at least 450 cases of pediatric patients with acute hepatitis of unknown cause have been reported worldwide. Human adenoviruses (HAdVs) have been detected in at least 74 cases, including the F type HAdV41 in 18 cases, which indicates that adenoviruses may be associated with this mysterious childhood hepatitis, although other infectious agents or environmental factors cannot be excluded. In this review, we provide a brief introduction of the basic features of HAdVs and describe diseases caused by different HAdVs in humans, aiming to help understand the biology and potential risk of HAdVs and cope with the outbreak of acute child hepatitis.

Molecular and serologic characterization of rotavirus from children with acute gastroenteritis in northern Iran, Gorgan

BACKGROUND

The pattern and distribution of human rotavirus genotypes in young children in developing countries play an important role in epidemiological studies, as well as providing a strategy for the development of future rotavirus vaccine.

METHODS

We evaluated stool samples from 349 children with acute gastroenteritis from Northern Iran (Gorgan city, Golestan province). Polyacrylamide Gel Electrophoresis (PAGE) and Latex Agglutination Test (LAT) were utilized to determine the prevalence of human rotavirus in fecal samples. Moreover semi-multiplex RT-PCR technique was carried out in order to determine the P and G genotypes of human rotavirus in rotavirus-positive samples.

RESULTS

A total of 46 rotavirus-positive samples were G and P genotyped. Whereas 28 (60.8%) fecal specimens contained only one rotavirus strain, 14 (30.4%) were mixed rotavirus infections and 4 (8.8%) was non-typeable. Overall, during the study, 57.82% of strains identified as genotype G1, G2 (18.70%), G3 (4.69%), G4 (3.13%), G8 (3.13%), G9 (6.26%) and non-typeable G (6.26%). From all these mentioned rotavirus strains, 46 were characterized as P [8] (97.80%) and P [4] (2.20%).Our analysis of the G and P genotyping of strains from all 46 rotavirus-infected children has revealed that 4/46(6.26%) of G type strains were non-typeable. The predominant single G/P combination was G1P [8] (57.82%), followed by, G2P [8] (16.98%), G2P [4] (1.72%), G3P [8] (4.69%), G4P [8] (3.13%) G8P [8] (3.13%), G9P [8] (6.26%) and four cases of non-typeable G (6.26%). Rotavirus was detected in 39 specimens (11.17%) by PAGE and in 38 specimens (10.88%) by LAT. Both tests were 100% specific; however, the LAT was 82.61% sensitive compared to the PAGE, which was 84.78% sensitive.

CONCLUSIONS

The results suggest that to characterize rotavirus strains as well as design new effective vaccines for children with acute gastroenteritis, a large-scale study is needed in future.

Norovirus

Norovirus, an RNA virus of the family Caliciviridae, is a human enteric pathogen that causes substantial morbidity across both health care and community settings. Several factors enhance the transmissibility of norovirus, including the small inoculum required to produce infection (<100 viral particles), prolonged viral shedding, and its ability to survive in the environment. In this review, we describe the basic virology and immunology of noroviruses, the clinical disease resulting from infection and its diagnosis and management, as well as host and pathogen factors that complicate vaccine development. Additionally, we discuss overall epidemiology, infection control strategies, and global reporting efforts aimed at controlling this worldwide cause of acute gastroenteritis. Prompt implementation of infection control measures remains the mainstay of norovirus outbreak management.

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.

Towards a rational strategy for monitoring of microbiological quality of ambient waters

Water is one of the main sources of human exposure to microbiological hazards. Although legislation establishes regulatory standards in terms of fecal indicator bacteria to assess the microbiological quality of water, these do not necessarily predict the presence of pathogens such as parasites and viruses. Better surveillance and management strategies are needed to assess the risk of pathogens' waterborne transmission. We established a baseline dataset to characterize river water quality, identify changes over time, and design a rational monitoring strategy. Data from a year-long monthly monitoring campaign of the polluted Arenales River (Argentina), were analyzed to statistically correlate physicochemical and microbiological variables, the seasonal and longitudinal variations of the water quality and determine the similarity between study sites. The measured variables (sixteen) reflected the deterioration in the river quality through the city. Different viruses and parasites found did not correlate with the concentration of total and thermotolerant coliforms. There was significant seasonal variation for temperature, turbidity, conductivity, dissolved oxygen, enterococci, and norovirus. Strong correlations between some variables were found; we selected eight variables (dissolved oxygen, conductivity, turbidity, total and thermotolerant coliforms, Enterococcus, and adenovirus and Microsporidium as viral and parasitological indicators, respectively) for future monitoring. There was similarity between the monitoring locations, which were grouped into four clusters validated by cophenetic correlation and supported by discriminant analysis. This allowed us to reduce the number of sites, from eleven down to five. Sixty seven percent of the total variance and the correlation structure between variables were explained using five principal components. All these analyses led to a new long-term systematic monitoring scheme. A rational monitoring strategy based on the selection of the most suitable monitoring points and of the most significant variables to measure, will result in optimal use of the limited resources available to adequately protect the public and environmental health.

Minimum Infective Dose of the Major Human Respiratory and Enteric Viruses Transmitted Through Food and the Environment

Viruses are a significant cause of morbidity and mortality around the world. Determining the minimum dose of virus particles that can initiate infection, termed the minimum infective dose (MID), is important for the development of risk assessment models in the fields of food and water treatment and the implementation of appropriate infection control strategies in healthcare settings. Both respiratory and enteric viruses can be shed at high titers from infected individuals even when the infection is asymptomatic. Presence of pre-existing antibodies has been shown to affect the infectious dose and to be protective against reinfection for many, but not all viruses. Most respiratory viruses appear to be as infective in humans as in tissue culture. Doses of <1 TCID₅₀ of influenza virus, rhinovirus, and adenovirus were reported to infect 50% of the tested population. Similarly, low doses of the enteric viruses, norovirus, rotavirus, echovirus, poliovirus, and hepatitis A virus, caused infection in at least some of the volunteers tested. A number of factors may influence viruses' infectivity in experimentally infected human volunteers. These include host and pathogen factors as well as the experimental methodology. As a result, the reported infective doses of human viruses have to be interpreted with caution.

Multivariate logistic regression for predicting total culturable virus presence at the intake of a potable-water treatment plant: novel application of the atypical coliform/total coliform ratio

Predicting the presence of enteric viruses in surface waters is a complex modeling problem. Multiple water quality parameters that indicate the presence of human fecal material, the load of fecal material, and the amount of time fecal material has been in the environment are needed. This paper presents the results of a multiyear study of raw-water quality at the inlet of a potable-water plant that related 17 physical, chemical, and biological indices to the presence of enteric viruses as indicated by cytopathic changes in cell cultures. It was found that several simple, multivariate logistic regression models that could reliably identify observations of the presence or absence of total culturable virus could be fitted. The best models developed combined a fecal age indicator (the atypical coliform [AC]/total coliform [TC] ratio), the detectable presence of a human-associated sterol (epicoprostanol) to indicate the fecal source, and one of several fecal load indicators (the levels of Giardia species cysts, coliform bacteria, and coprostanol). The best fit to the data was found when the AC/TC ratio, the presence of epicoprostanol, and the density of fecal coliform bacteria were input into a simple, multivariate logistic regression equation, resulting in 84.5% and 78.6% accuracies for the identification of the presence and absence of total culturable virus, respectively. The AC/TC ratio was the most influential input variable in all of the models generated, but producing the best prediction required additional input related to the fecal source and the fecal load. The potential for replacing microbial indicators of fecal load with levels of coprostanol was proposed and evaluated by multivariate logistic regression modeling for the presence and absence of virus.

A multiplex reverse transcription-PCR method for detection of human enteric viruses in groundwater

Untreated groundwater is responsible for about half of the waterborne disease outbreaks in the United States. Human enteric viruses are thought to be leading etiological agents of many of these outbreaks, but there is relatively little information on the types and levels of viruses found in groundwater. To address this problem, monthly samples from 29 groundwater sites were analyzed for 1 year for enteroviruses, hepatitis A virus, Norwalk virus, reoviruses, and rotaviruses by multiplex reverse transcription-PCR (RT-PCR). A procedure with which to remove environmental RT-PCR inhibitors from groundwater samples was developed. The procedure allowed an average of 71 liters of the original groundwater to be assayed per RT-PCR, with an average virus recovery rate of 74%, based on seeded samples. Human enteric viruses were detected in 16% of the groundwater samples analyzed, with reoviruses being the most frequently detected virus group.

A multiplex reverse transcription-PCR method for detection of human enteric viruses in groundwater

Untreated groundwater is responsible for about half of the waterborne disease outbreaks in the United States. Human enteric viruses are thought to be leading etiological agents of many of these outbreaks, but there is relatively little information on the types and levels of viruses found in groundwater. To address this problem, monthly samples from 29 groundwater sites were analyzed for 1 year for enteroviruses, hepatitis A virus, Norwalk virus, reoviruses, and rotaviruses by multiplex reverse transcription-PCR (RT-PCR). A procedure with which to remove environmental RT-PCR inhibitors from groundwater samples was developed. The procedure allowed an average of 71 liters of the original groundwater to be assayed per RT-PCR, with an average virus recovery rate of 74%, based on seeded samples. Human enteric viruses were detected in 16% of the groundwater samples analyzed, with reoviruses being the most frequently detected virus group.

VI, 3. Molecular biology and epidemiology of Aichi virus and other diarrhoeogenic enteroviruses

The virion of the Aichi virus contains a single-stranded RNA molecule as the genome. The homology of Aichi virus structural proteins (VP0, VP3, and VP1) with corresponding polypeptides of other picornaviruses varies between 19% and 32%. The epidemiology of the Aichi virus as a medically important pathogen has not been well defined. Stool samples from adult patients in six oyster-associated gastroenteritis outbreaks were examined for variation, based on their reactivity with a monoclonal antibody raised against the standard strain (A486/88) and on reverse transcription-polymerase chain reactions (RT-PCR) of three genomic regions. Antibody to the Aichi virus could be detected using a neutralization test and an enzyme-linked immunosorbent assay (ELISA). These methods were used for the identification of Aichi virus infection in paired serum samples. The chapter concludes with a discussion on other diarrheagenic enteroviruses.

Diagnosis of noncultivatable gastroenteritis viruses, the human caliciviruses

Gastroenteritis is one of the most common illnesses of humans, and many different viruses have been causally associated with this disease. Of those enteric viruses that have been established as etiologic agents of gastroenteritis, only the human caliciviruses cannot be cultivated in vitro. The cloning of Norwalk virus and subsequently of other human caliciviruses has led to the development of several new diagnostic assays. Antigen detection enzyme immunoassays (EIAs) using polyclonal hyperimmune animal sera and antibody detection EIAs using recombinant virus-like particles have supplanted the use of human-derived reagents, but the use of these assays has been restricted to research laboratories. Reverse transcription-PCR assays for the detection of human caliciviruses are more widely available, and these assays have been used to identify virus in clinical specimens as well as in food, water, and other environmental samples. The application of these newer assays has significantly increased the recognition of the importance of human caliciviruses as causes of sporadic and outbreak-associated gastroenteritis.

Application of a reverse transcription-PCR for identification and differentiation of Aichi virus, a new member of the Picornavirus family associated with gastroenteritis in humans

Aichi viruses isolated in Vero cells from seven patients in five gastroenteritis outbreaks in Japan, five Japanese returning from Southeast Asian countries, and five local children in Pakistan with gastroenteritis were examined for differentiation based on their reactivities with a monoclonal antibody to a standard strain (A846/88) and a reverse transcription-PCR (RT-PCR) of three genomic regions. The RNA sequences were determined for 519 bases of these 17 isolates at the putative junction between the C terminus of 3C and the N terminus of 3D. The analyses revealed an approximately 90% homology between these isolates, which were then divided into two groups: group 1 (genotype A) included six isolates from four outbreaks and one isolate from a traveler and group 2 (genotype B) included one isolate from the other outbreak, four isolates from returning travelers, and all of the isolates from the Pakistani children. Based on the isolate sequences, a primer pair and a biotin-labeled probe were designed for amplification and detection of 223 bases at the 3C-3D junction of Aichi virus RNA in fecal specimens. The Aichi virus RNA was detected in 54 (55%) of 99 fecal specimens from the patients in 12 (32%) of 37 outbreaks of gastroenteritis in Japan. Of the 12 outbreaks, 11 were suspected to be due to genotype A. These results indicated that RT-PCR can be a useful tool to detect Aichi virus in stool samples and that a sequence analysis of PCR products can be employed to identify the prevalent strain in each incident.

Antibodies to enteric adenoviruses (Ad40 and Ad41) in sera from Iranian children

BACKGROUND

There is strong epidemiologic and serologic evidence that infection with the enteric adenoviruses can result in severe gastroenteritis in children.

OBJECTIVES

This study was performed to determine the prevalence of enteric adenovirus infection in Iran.

STUDY DESIGN

One hundred and twenty-seven single sera from children up to 7 years of age, collected from healthy Iranian children in 1993-1994, were tested for antibodies to enteric adenoviruses by neutralization tests.

RESULT AND CONCLUSION

Antibodies to enteric adenoviruses have been detected in about one-half of sera. It is concluded that infection by these viruses is common among children in Iran.

VP7 and VP4 genotyping of human group A rotavirus in Buenos Aires, Argentina

Specific and sensitive tests for the detection and typing of group A rotavirus strains are needed for a more comprehensive knowledge of the epidemiology of rotaviral infection. In this study 500 stool specimens taken from 1996 to 1998 from children with acute diarrhea in Buenos Aires were examined. Group A rotavirus was unequivocally demonstrated in 62% of the samples tested by enzyme-linked immunosorbent assay (ELISA) for detection of VP6 antigen, polyacrylamide gel electrophoresis of double-stranded RNA, and reverse transcription-PCR (RT-PCR) for amplification of the VP7:G (1, 062 bp) and VP4:P (876 bp) genes. Only five positive specimens were found by RT-PCR but not by ELISA. G and P typing was carried out by nested amplification of variable sequences of the VP7 and the VP4 genes with six G- and five P-type-specific primers (multiplex PCR). Results obtained by this method showed the prevalence of the following G and P types: G1, 39%; G2, 43%; G4, 4%; P[8], 16%; P[4], 71%. Unexpectedly, the G-P type combination most frequently found was G2P[4] (43%) rather than G1P[8] (12%), which is the most commonly found worldwide. Unusual strains of the type G1P[4] accounted for 14% of the total, while mixed infections with more than one type were found in 10% of the samples. Detection of fecal rotavirus-specific immunoglobulin M (IgM) and IgA antibodies in consecutive samples of two patients taken at daily intervals demonstrated that high levels of IgM and IgA antibodies were detected on day 1 after the onset of disease and that the samples remained positive for about 10 days, after which virus shedding was no longer observed. Multiplex PCR offers a sensitive and specific alternative to determine the prevalence of group A rotavirus G and P types and to identify the emergence of uncommon strains, whereas detection of fecal IgM and IgA antibodies represents a useful supplement to virus detection for the diagnosis of current or recently acquired infections.

Complete nucleotide sequence and genetic organization of Aichi virus, a distinct member of the Picornaviridae associated with acute gastroenteritis in humans

The complete nucleotide sequence of a novel enteric virus, Aichi virus, associated with nonbacterial acute gastroenteritis in humans was determined. The Aichi virus genome proved to be a single-stranded positive-sense RNA molecule with 8,251 bases excluding a poly(A) tail; it contains a large open reading frame with 7,302 nucleotides that encodes a potential polyprotein precursor of 2,433 amino acids. The genome contains a 5' nontranslated region (NTR) with 712 bases and a 3' NTR with 240 bases followed by a poly(A) tail. The structure of the genome, VPg-5' NTR-leader protein-structural proteins-nonstructural proteins-3' NTR-poly(A), was found to be typical of a picornavirus. The VP0-VP3 and VP3-VP1 cleavage sites were determined to be Q-H and Q-T, respectively, by N-terminal amino acid sequence analyses using purified virion proteins. Possible cleavage sites, Q-G, Q-A, and Q-S, which cleave P2 and P3 polyproteins were found to be similar to those of picornaviruses. A dendrogram based on 3Dpol proteins indicated that Aichi virus is genetically distinct from the known six genera of picornaviruses including entero-, rhino-, cardio-, aphtho-, and hepatovirus and echovirus 22. Considering this together with other properties of the virus (T. Yamashita, S. Kobayashi, K. Sakae, S. Nakata, S. Chiba, Y. Ishihara, and S. Isomura, J. Infect. Dis. 164:954-957, 1991), we propose that Aichi virus be regarded as a new genus of the family Picornaviridae.

Oral immunization with recombinant Norwalk virus-like particles induces a systemic and mucosal immune response in mice

Recombinant Norwalk virus-like particles (rNV VLPs) produced in insect cells were evaluated as an oral immunogen in CD1 and BALB/c mice by monitoring rNV-specific serum total and subclass immunoglobulin G (IgG) and intestinal IgA responses. Dose and kinetics of response were evaluated in the presence and absence of the mucosal adjuvant cholera toxin (CT). rNV-specific serum IgG and intestinal IgA were detected in the absence of CT, and the number of responders was not significantly different from that of mice administered VLPs with CT at most doses. The use of CT was associated with induction of higher levels of IgG in serum; this effect was greater at higher doses of VLPs. IgG in serum was detected in the majority of animals by 9 days postimmunization (dpi), and intestinal IgA responses were detected by 24 dpi. In the absence of CT, IgG2b was the dominant IgG subclass response in both mouse strains. Thus, nonreplicating rNV VLPs are immunogenic when administered orally in the absence of any delivery system or mucosal adjuvant. These studies demonstrate that rNV VLPs are an excellent model to study the oral delivery of antigen, and they are a potential mucosal vaccine for NV infections.

Antibody-secreting cell responses and protective immunity assessed in gnotobiotic pigs inoculated orally or intramuscularly with inactivated human rotavirus

Newborn gnotobiotic pigs were inoculated twice perorally (p.o.) (group 1) or intramuscularly (i.m.) (group 2) or three times i.m. (group 3) with inactivated Wa strain human rotavirus and challenged with virulent Wa human rotavirus 20 to 24 days later. To assess correlates of protection, antibody-secreting cells (ASC) were enumerated in intestinal and systemic lymphoid tissues from pigs in each group at selected postinoculation days (PID) or postchallenge days. Few virus-specific ASC were detected in any tissues of group 1 pigs prior to challenge. By comparison, groups 2 and 3 had significantly greater numbers of virus-specific immunoglobulin M (IgM) ASC in intestinal and splenic tissues at PID 8 and significantly greater numbers of virus-specific IgG ASC and IgG memory B cells in spleen and blood at challenge. However, as for group 1, few virus-specific IgA ASC or IgA memory B cells were detected in any tissues of group 2 and 3 pigs. Neither p.o. nor i.m. inoculation conferred significant protection against virulent Wa rotavirus challenge (0 to 6% protection rate), and all groups showed significant anamnestic virus-specific IgG and IgA ASC responses. Hence, high numbers of IgG ASC or memory IgG ASC in the systemic lymphoid tissues at the time of challenge did not correlate with protection. Further, our findings suggest that inactivated Wa human rotavirus administered either p.o. or parenterally is significantly less effective in inducing intestinal IgA ASC responses and conferring protective immunity than live Wa human rotavirus inoculated orally, as reported earlier (L. Yuan, L. A. Ward, B. I. Rosen, T. L. To, and L. J. Saif, J. Virol. 70:3075-3083, 1996). Thus, more efficient mucosal delivery systems and rotavirus vaccination strategies are needed to induce intestinal IgA ASC responses, identified previously as a correlate of protective immunity to rotavirus.

Human serum immunoglobulin counteracts rotaviral infection in Caco-2 cells

Oral administration of human serum immunoglobulin reduces the duration of diarrhea and of rotaviral excretion in children. To investigate the in vitro effects of immunoglobulin on virus-enterocyte interaction, Caco-2 cells were infected with Rotavirus strain SA11. Immunoglobulin was added prior to and at various times postinfection. Indirect immunofluorescence was performed with an antibody against VP-6 rotaviral antigen. Cell viability and monolayer transepithelial electrical resistance (TEER) were monitored. Immunofluorescence showed a perinuclear distribution in 90% of cells. Rotavirus infection induced a progressive decrease in TEER and a parallel reduction in cell viability, depending on viral load. Preincubation of the virus with immunoglobulin prevented cell infection as judged by immunofluorescence. Immunoglobulin addition to infected cells partially prevented the decrease in TEER and induced a later shift of TEER toward increasing values, suggesting restoration of monolayer's integrity. The efficacy of immunoglobulin depended on its concentration and on the time of its addition. These results indicate that immunoglobulin is effective in preventing infection and in reducing cell damage, through a direct anti-Rotavirus action and may indicate that immunoglobulin should be administered in the early phase of diarrhea, to reduce the severity of Rotavirus infection.

Viral gastroenteritis: small round structured viruses, caliciviruses and astroviruses. Part II. The epidemiological perspective

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Viral gastroenteritis: small round structured viruses, caliciviruses and astroviruses. Part I. The clinical and diagnostic perspective

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Systematic and intestinal antibody-secreting cell responses and correlates of protective immunity to human rotavirus in a gnotobiotic pig model of disease

Neonatal gnotobiotic pigs orally inoculated with virulent (intestinal-suspension) Wa strain human rotavirus (which mimics human natural infection) developed diarrhea, and most pigs which recovered (87% protection rate) were immune to disease upon homologous virulent virus challenge at postinoculation day (PID) 21. Pigs inoculated with cell culture-attenuated Wa rotavirus (which mimics live oral vaccines) developed subclinical infections and seroconverted but were only partially protected against challenge (33% protection rate). Isotype-specific antibody-secreting cells (ASC were enumerated at selected PID in intestinal (duodenal and ileal lamina propria and mesenteric lymph node [MLN]) and systemic (spleen and blood) lymphoid tissues by using enzyme-linked immunospot assays. At challenge (PID 21), the numbers of virus-specific immunoglobulin A (IgA) ASC, but not IgG ASC, in intestines and blood were significantly greater in virulent-Wa rotavirus-inoculated pigs than in attenuated-Wa rotavirus-inoculated pigs and were correlated (correlation coefficients: for duodenum and ileum, 0.9; for MLN, 0.8; for blood, 0.6) with the degree of protection induced. After challenge, the numbers of IgA and IgG virus-specific ASC and serum-neutralizing antibodies increased significantly in the attenuated-Wa rotavirus-inoculated pigs but not in the virulent-Wa rotavirus-inoculated pigs (except in the spleen and except for IgA ASC in the duodenum). The transient appearance of IgA ASC in the blood mirrored the IgA ASC responses in the gut, albeit at a lower level, suggesting that IgA ASC in the blood of humans could serve as an indicator for IgA ASC responses in the intestine after rotavirus infection. To our knowledge, this is the first report to study and identify intestinal IgA ASC as a correlate of protective active immunity in an animal model of human-rotavirus-induced disease.

Enumeration of isotype-specific antibody-secreting cells derived from gnotobiotic piglets inoculated with porcine rotaviruses

In order to evaluate mucosal antibody responses to rotavirus, an enzyme-linked immunospot (ELISPOT) assay was adapted to enumerate antibody-secreting cells (ASC) in the mesenteric lymph nodes (MLN), lamina propria (LP) of the small intestine and spleens of gnotobiotic pigs orally inoculated with porcine rotaviruses (SB1A and Gottfried). Rotavirus-specific IgM ASC occurred by post-inoculation day (PID) 3, and numbers peaked in spleen and MLN tissues by PID 7 and in intestinal LP by PID 7-14. Numbers of rotavirus specific IgA and IgG ASC in these tissues peaked at PID 14-21. Rotavirus specific IgA ASC were predominant in the gut and IgA to IgG rotavirus specific ASC ratios were highest for all rotavirus antigen coatings in the gut LP. However, the relative ratios of specific IgA to IgG ASC were lower (ratios of 5 to 7) against combined structural and nonstructural viral antigens (rotavirus-infected fixed cell ELISPOT plates) than ratios (13 to 46) against only viral structural antigens (rotavirus-coated ELISPOT plates), indicating that there were proportionately more specific IgG ASC to the nonstructural viral antigens in the LP, the tissue adjacent to the site of rotavirus replication in the intestine. In the node cells (spleen and MLN) rotavirus-specific IgA to IgG ASC ratios were lowest and against the various ELISPOT rotavirus coatings ranged from 0.7 to 4. Gnotobiotic piglets inoculated at different ages with porcine rotaviruses generally showed similar specific immunoglobulin (Ig) ASC responses to rotavirus infection, along with similar diarrhea and virus shedding patterns in the different age groups. However, the numbers of specific IgA ASC in the MLN of 3-4 week old pigs were higher than those of 3-5 day old pigs. Although challenge of SB1A or Gottfried rotavirus-inoculated pigs with SB1A (G4P7) or Gottfried (G4P6) rotavirus revealed a high degree of protection from diarrhea and virus shedding, greater numbers of specific IgM ASC were observed in spleen after challenge of SB1A-inoculated pigs with Gottfried rotavirus (same G type, distinct P type). Thus, by using the ELISPOT technique, we successfully measured intestinal mucosal antibody-related responses to rotavirus in gnotobiotic pigs. Moreover, our results support the use of gnotobiotic piglets as an animal model to evaluate active antibody responses and protection against rotavirus infection and disease.

Direct detection and characterization of rotavirus into subgroups by dot blot hybridization and correlation with ‘long’ and ‘short’ electropherotypes

BACKGROUND

Enzyme-linked immunosorbent assay (ELISA) and polyacrylamide gel electrophoresis (PAGE) of viral RNA are well-established methods for detection of rotavirus in stool samples. Dot-blot hybridization has also been found to be a sensitive and specific technique for detection and characterization of rotaviruses.

OBJECTIVES

To compare the performance of dot blot hybridization with ELISA and PAGE for detection of rotavirus in stool samples. To assess the use of dot blot hybridization for characterization of rotaviruses into subgroups.

STUDY DESIGN

Stool samples were collected from 214 children presenting to the hospital with acute diarrhoea. These were assayed for rotavirus by ELISA and PAGE. Dot-blot hybridization was done with full length cloned radiolabelled c-DNA probes of gene segment 6 of SA-11 (subgroup I) and Wa (subgroup II) rotaviruses.

RESULTS

Out of 214 stool samples 134 were found to be positive for rotavirus by one of the three methods. Among these 134 positive specimens 114 were positive by dot blot hybridization, this included 18 specimens which were positive only by dot blot assay. One-hundred-and-twelve of these 114 specimens could be subgrouped. Fifteen of these were classified as subgroup I, 97 as subgroup II and two had a dual subgroup specificity. Three subgroup 1 strains had a 'long' RNA pattern, whereas one subgroup II strain had a 'short' RNA pattern which has not been reported earlier for human rotaviruses.

CONCLUSION

Dot blot hybridization as described here is a sensitive and specific assay for detection and subgrouping of rotaviruses. However, as there is a considerable genomic diversity among rotaviruses, the panel should include probes from all the genotypes of gene segment 6.

Prevalence of newly isolated, cytopathic small round virus (Aichi strain) in Japan

Cytopathic small round virus (Aichi strain), isolated from a patient with oyster-associated gastroenteritis, showed no reaction in the polymerase chain reaction method for enteroviruses or in the enzyme-linked immunosorbent assay (ELISA) for the five serotypes of astroviruses. Our ELISA was sensitive in detecting the Aichi strain antigen in stool samples, but there was no reaction in this ELISA with any non-Aichi strains of enteric viruses, with such origins as enterovirus, rotavirus, Norwalk virus, calicivirus, or astrovirus. In the ELISA, 13 of 47 stool samples from adult patients in five of nine oyster-associated gastroenteritis outbreaks were positive, but only 1 of 397 pediatric stool samples in Aichi Prefecture was positive. The prevalence rate for Aichi strain antibody was found to be 7.2% for persons aged 7 months to 4 years. The prevalence rate for antibody to Aichi strain increased with age, to about 80% in persons 35 years old. On the basis of the results of the present study, it was hypothesized that Aichi strain could be a new type of small round virus that mainly produces diarrhea in patients in the 15- to 34-year-old age group, 50 to 76% of whom possess neutralizing antibody.

Genomic concatemerization/deletion in rotaviruses: a new mechanism for generating rapid genetic change of potential epidemiological importance

Three variants of group A rotavirus with large changes in their gene 5 structures have been analyzed at the molecular level. The first of these, P9 delta 5, was obtained during plaque purification undertaken as part of the biological cloning of a field isolate of virus. The gene 5 homolog in this isolate migrated just ahead of the normal segment 6 RNA, giving an estimated size of 1,300 bp. Molecular cloning and sequencing of this homolog revealed it to have a single 308-bp deletion in the center of the normal gene 5 sequence extending between nucleotides 460 and 768 of the normal gene sequence. This deletion caused a frameshift in the gene such that a stop codon was encountered 8 amino acids downstream of the deletion point, giving a predicted size for the protein product of this gene of 150 amino acids compared with the 490 amino acids of its normal-size counterpart. Attempts to detect this shortened protein in virus-infected cells were not successful, indicating that it was much less stable than the full-length protein and/or had suffered a large change in its antigenicity. The second two variants, brvA and brvE, were generated in an earlier study following the high-multiplicity passage of the UKtc strain of bovine rotavirus. Polyacrylamide gel electrophoresis analysis of these nondefective variants showed that brvA had a gene 5 homolog approximately equal in size to the normal RNA segment 2 (approximately 2,700 bp) and that brvE had a size of approximately 2,300 bp. Both variants showed changes in their gene 5 protein products, with brvA mimicking P9 delta 5 in failing to produce a detectable product whereas brvE produced a new virus-specific protein approximately 80 kDa in size. Full-length cDNA clones of the brvE gene 5 homolog were isolated, and analysis of their structure revealed a head-to-tail concatemerization of the normal gene 5 sequence with the first copy of the concatemer covering nucleotides 1 to 808 and the second covering nucleotides 92 to 1579, giving a total length of 2,296 bp. Sequencing across the junction region of the two copies of the gene showed that they were joined in frame to give a predicted combined open reading frame of 728 amino acids with the amino-terminal region consisting of amino acids 1 to 258 fused at the carboxy terminus to amino acids 21 to 490.(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of Norwalk virus in stool specimens by reverse transcriptase-polymerase chain reaction and nonradioactive oligoprobes

A reverse transcriptase (RT)-polymerase chain reaction (PCR)-oligoprobe (OP), or RT-PCR-OP, method was developed for the detection of the Norwalk virus, which causes acute, epidemic gastroenteritis, in stool specimens. The Norwalk virus genome regions encoding the following two proteins were amplified by RT-PCR: the RNA polymerase (260-bp product) and a putative immunogenic protein (224-bp product). The resulting DNA fragments (amplicons) were hybridized to a digoxigenin-labeled internal OP specific to each amplicon. The detection limit of Norwalk virus, as determined by the endpoint of RT-PCR amplification for serially diluted, positive stool specimens, was similar to the actual virion titer as estimated by electron microscopy and at least 100-fold greater than the titer determined by radioimmunoassay (RIA). The RT-PCR-OP assay was specific for Norwalk virus and negative for other enteric viruses, including human and animal caliciviruses, hepatitis E virus, Snow Mountain agent, astroviruses, 16 human enteroviruses, and 5 human rotaviruses. Components of fecal specimens that interfere with RT-PCR were removed successfully by Sephadex G-200 gel chromatography. Of 20 stool specimens from human volunteers that were positive for Norwalk virus by RIA, a specific RT-PCR-OP result was obtained in 95% (19 of 20) of the samples by using the immunogenic protein primers and 75% (15 of 20) by using the polymerase primers. Twenty-six stool specimens from asymptomatic children and adults were negative by the Norwalk virus RT-PCR-OP. RT-PCR-OP detected Norwalk virus in the 4 of 21 coded fecal specimens that were also positive by enzyme immunoassay. Two samples that were positive by RIA or enzyme immunoassay were negative by RT-PCR, perhaps because viral RNA was not present or RT-PCR inhibitors were not adequately removed.

Rotavirus and bacterial enteropathogens causing acute diarrhea

The etiology of rotavirus in acute diarrhoeal illness in children 0-5 years of age, admitted to the Pediatric wards of Kasturba Medical College Hospital, Manipal was studied, over a period of one year. Rotavirus in the faecal samples detected by the slide latex agglutination test accounted for 14.9% of the diarrheas with maximum incidence in the 7-12 months of age group (57.5%). Bacterial enteropathogens continued to play a significant role in diarrheal diseases. Salmonella enteritis was found more in the age group 0-6 months and shigellosis in 37-60 months. In a control study of 100 children who had no diarrhea, 2 were found positive for rotaviruses.

Identification in porcine faeces of a novel virus with a bisegmented double stranded RNA genome

Polyacrylamide gel electrophoresis of nucleic acids extracted from porcine faecal samples revealed in several samples the presence of two discrete bands. The bands were resistant to digestion with of DNase I and RNase T1, but not with RNase A in low salt conditions, indicating that they consisted of double stranded (ds) RNA. The two bands from different samples varied in sizes, in a range between 2.4-2.6 kbp and 1.7-1.9 kbp for the slow and fast moving band respectively. The bands cosedimented in CsCl gradients at an average density of 1.415 g/ml with icosahedral virus particles of a diameter of 34 nm and a triangulation number equal to 3. Aggregates of virus, which appeared to be immunocomplexes, were seen in one sample. From 244 faecal samples collected in one farm, 27 (11.1%) were found to contain the characteristic dsRNA pattern, with a higher prevalence in samples from animals 15 to 35 days old. The agent was equally distributed among samples from diarrhoeic or non-diarrhoeic animals. These results confirm the circulation among pigs of a novel virus, possibly of vertebrates, with a bisegmented double stranded RNA genome, similar to viruses previously described in humans, wild rats, guinea pigs, pigs, and chickens, for which the name "picobirnavirus" has been proposed.

Some infectious causes of diarrhea in young farm animals

Escherichia coli, rotaviruses, and Cryptosporidium parvum are discussed in this review as they relate to enteric disease in calves, lambs, and pigs. These microorganisms are frequently incriminated as causative agents in diarrheas among neonatal food animals, and in some cases different strains or serotypes of the same organism cause diarrhea in humans. E. coli causes diarrhea by mechanisms that include production of heat-labile or heat-stable enterotoxins and synthesis of potent cytotoxins, and some strains cause diarrhea by yet undetermined mechanisms. Rotaviruses and C. parvum induce various degrees of villous atrophy. Rotaviruses infect and replicate within the cytoplasm of enterocytes, whereas C. parvum resides in an intracellular, extracytoplasmic location. E. coli, rotavirus, and C. parvum infections are of concern to producers, veterinarians, and public health officials. These agents are a major cause of economic loss to the producer because of costs associated with therapy, reduced performance, and high morbidity and mortality rates. Moreover, diarrheic animals may harbor, incubate, and act as a source to healthy animals and humans of some of these agents.

Adenovirus types 40 and 41 and rotaviruses associated with diarrhea in children from Guatemala

From March 1987 to February 1988, fecal excretion of adenovirus types 40 and 41 and rotavirus serotypes in 194 children (age, 0 to 3 years) from a rural community of Guatemala was monitored. In total, 458 samples taken during 385 episodes of diarrhea and 191 specimens obtained during symptom-free periods were examined by enzyme-linked immunosorbent assay. Fifty-seven children hospitalized because of diarrhea were also studied. Among the rural children, 43 (22.2%) excreted adenovirus types 40 and 41 and 20 (10.3%) shed rotaviruses. Adenovirus types 40 and 41 were associated with 54 (14.0%) illnesses, and rotaviruses were associated with 18 (4.7%) illnesses. Asymptomatic infections with adenovirus types 40 and 41 were documented in nine children and with rotaviruses in two children. Fifteen typeable rotaviruses were identified as serotype 2. In the hospital population, 36 (63.2%) children had viral infections. Rotaviruses were identified in 29 (50.9%) and adenovirus types 40 and 41 were identified in 15 (31.2%) of 48 subjects tested. Dual infections by these viruses were found in eight children. Of 22 typeable strains of rotaviruses, 9 (34.6%) were serotype 1, 12 (46.1%) were serotype 2, and 1 (3.8%) was serotype 3. All the children infected with serotype 2 rotavirus were coinfected with other enteric pathogens, while only three (37.5%) of those infected with rotavirus serotype 1 excreted another pathogen. Adenovirus types 40 and 41 are an important cause of gastroenteritis in both ambulatory and hospitalized Guatemalan children. There seems to be a difference in the pathogenicity among rotavirus serotypes.

Microbiologic and clinical evidence supporting the role of Aeromonas caviae as a pediatric enteric pathogen

Aeromonas caviae was recovered as the sole potential enteric pathogen from the stools of 14 of 17 symptomatic children (10 younger than 1 year of age) while Aeromonas hydrophila, Aeromonas sobria, and Plesiomonas shigelloides were isolated once each. The infants from whom A. caviae was isolated all presented with a watery diarrhea lasting 1 to 3 weeks. None of these infants was breast-fed, and all had a stool pH of greater than 7.5. All of the A. caviae isolates, including a reference strain (ATCC 15468), adhered to HEp-2 cells, and preliminary data showed that they produced a cytotoxin as well. Because A. caviae can survive at an elevated pH, as found in the gastrointestinal tract of formula-fed infants, and because of the adherence and cytotoxin production capabilities of the species, it should be regarded as an enteric pathogen in pediatric patients and most probably among adults as well.

Extramucosal spread and development of hepatitis in immunodeficient and normal mice infected with rhesus rotavirus

The pathogenic profiles of two heterologous animal rotaviruses, rhesus rotavirus strain MMU 18006 and bovine rotavirus strain WC3, were evaluated in mice with severe combined immunodeficiency (SCID mice) and normal BALB/c mice. Control animals were inoculated with homologous murine strain EDIM 5099 or a tissue culture-adapted murine rotavirus. Heterologous infection with rhesus rotavirus resulted in hepatitis in 84% of SCID and 21% of BALB/c mice, with mortality rates of 27 and 0%, respectively. Surviving SCID animals developed chronic liver disease, while symptoms in BALB/c mice resolved in 2 to 4 weeks after onset. Histopathologic examination revealed a diffuse hepatitis with focal areas of parenchymal necrosis. Rotavirus was detected in liver tissue from 100% of 29 SCID and 85% (11 of 13) BALB/c animals tested by cell culture infectivity, immunofluorescence, or electron microscopy. No extramucosal spread of virus or hepatitis was observed after infection with heterologous bovine strain WC3 or homologous murine rotaviruses. This finding of a novel rotavirus-induced disease manifestation suggests altered tissue tropism in a heterologous host for a group of viruses previously shown to replicate exclusively in the gut mucosa. The implications of our observations suggest that in human vaccine trials utilizing heterologous rotavirus strains, special attention should be paid to children with immunodeficiency disorders, and screening for hepatic function should be included in vaccine protocols.

Rotavirus gene structure and function

Knowledge of the structure and function of the genes and proteins of the rotaviruses has expanded rapidly. Information obtained in the last 5 years has revealed unexpected and unique molecular properties of rotavirus proteins of general interest to virologists, biochemists, and cell biologists. Rotaviruses share some features of replication with reoviruses, yet antigenic and molecular properties of the outer capsid proteins, VP4 (a protein whose cleavage is required for infectivity, possibly by mediating fusion with the cell membrane) and VP7 (a glycoprotein), show more similarities with those of other viruses such as the orthomyxoviruses, paramyxoviruses, and alphaviruses. Rotavirus morphogenesis is a unique process, during which immature subviral particles bud through the membrane of the endoplasmic reticulum (ER). During this process, transiently enveloped particles form, the outer capsid proteins are assembled onto particles, and mature particles accumulate in the lumen of the ER. Two ER-specific viral glycoproteins are involved in virus maturation, and these glycoproteins have been shown to be useful models for studying protein targeting and retention in the ER and for studying mechanisms of virus budding. New ideas and approaches to understanding how each gene functions to replicate and assemble the segmented viral genome have emerged from knowledge of the primary structure of rotavirus genes and their proteins and from knowledge of the properties of domains on individual proteins. Localization of type-specific and cross-reactive neutralizing epitopes on the outer capsid proteins is becoming increasingly useful in dissecting the protective immune response, including evaluation of vaccine trials, with the practical possibility of enhancing the production of new, more effective vaccines. Finally, future analyses with recently characterized immunologic and gene probes and new animal models can be expected to provide a basic understanding of what regulates the primary interactions of these viruses with the gastrointestinal tract and the subsequent responses of infected hosts.

Western blot (immunoblot) assay of small, round-structured virus associated with an acute gastroenteritis outbreak in Tokyo

Small, round-structured virus (SRSV) was detected in a stool specimen of a patient during an acute gastroenteritis outbreak in Tokyo and was tentatively named SRSV-9. SRSV-9 was purified by sucrose velocity gradient centrifugation after CsCl density gradient centrifugation. The buoyant density of SRSV-9 appeared to be 1.36 g/ml in CsCl. A Western blot (immunoblot) assay using the biotin-avidin system revealed that SRSV-9 was antigenically related to the Hawaii agent but distinct from the Norwalk agent and contained a single major structural protein with a molecular size of 63.0 +/- 0.6 kilodaltons. The prevalence of SRSV-9 infection in Tokyo was surveyed by the Western blot antibody assay by using a crude virus preparation as the antigen. Seroconversion was observed in 56.5% of the patients involved in the outbreaks from which SRSV was detected by electron microscopy.

Characterization by enzyme-linked immunosorbent assay using subgroup- and serotype-specific monoclonal antibodies of human rotavirus obtained from diarrheic patients in Bangladesh

By enzyme-linked immunosorbent assay with group A-, subgroup-, and serotype-specific monoclonal antibodies (MAbs), we tested 414 stool specimens collected from pediatric and adult patients hospitalized with acute gastroenteritis between January and June 1988. Of 414 specimens tested, 124 (30%) were positive for group A rotavirus. The subgroup was determined in 110 specimens (88.7%); 16.1% were subgroup I, and 72.6% were subgroup II. Two specimens reacted with both subgroup I- and subgroup II-specific MAbs. Serotype determinations showed that serotype 1 (38.4%) was predominant over serotypes 2 (28.2%), 3 (2.5%), and 4 (23%). Three specimens reacted with more than one serotype-specific MAb. While the frequency of serotype 1 was highest in the two hospitals in Mymensingh, serotype 2 was most prevalent in one hospital in Dhaka. All human rotavirus strains with subgroup I and serotype 2 specificities showed a short electropherotype, and all but one strain with subgroup II and serotype 1, 3, or 4 specificities exhibited a long electropherotype.

Detection of human rotavirus by using an alkaline phosphatase-conjugated synthetic DNA probe in comparison with enzyme-linked immunoassay and polyacrylamide gel analysis

An alkaline phosphatase-conjugated synthetic oligodeoxyribonucleotide probe was compared with polyacrylamide gel electrophoresis (PAGE) detection of rotavirus RNA as well as an enzyme-linked immunosorbent assay (ELISA) for the detection of rotavirus in stools from young children with gastroenteritis. The synthetic probe did not cross-react with bacterial causative agents of diarrheal disease. Extraction of viral RNA from stool samples with a phenol-chloroform mixture was suitable for most samples. In some cases fecal pigments interfered with the reaction of the probe with viral RNA. The use of ion-exchange chromatography to further purify viral RNA removed contaminating pigments and increased the sensitivity of the probe assay. Of 260 stool specimens, 77 (30%) were positive for rotavirus when tested by PAGE analysis of rotavirus RNA. The synthetic probe identified 71 rotavirus specimens when RNA obtained by phenol-chloroform extraction followed by chromatographic purification was used (sensitivity, 91.0%; specificity, 96.7%). The ELISA results also agreed well with the electrophoretic analysis (sensitivity, 98.7%; specificity 94%) and the probe assay (sensitivity, 90%; specificity, 100%). Discordant results between the ELISA and the probe assay were examined further by electron microscopy and PAGE analysis of viral RNA. The positive and negative predictive values of the probe assay in comparison with PAGE were 92.2 and 96.1%, respectively. Rotaviruses showing both long and short RNA electrophoretic patterns were detected by the probe. The probe assay coupled with chromatographic purification of rotavirus RNA is an effective method for detecting rotavirus and compares favorably with PAGE analysis and ELISA.

An outbreak of acute infectious nonbacterial gastroenteritis in a high school in Maryland

An outbreak of acute infectious nonbacterial gastroenteritis (AING) occurred in a high school in Maryland in 1984. Thirty-six percent of students surveyed met the case definition of gastroenteritis, as did 24 percent of school employees. Eating lunch in the cafeteria on January 30 was significantly associated with illness. After controlling for other food items consumed during the January 30 lunch, only the sandwiches were significantly associated with illness, but the source of the contamination was not identified. Four of 17 serum pairs from sick students and none of the 8 serum pairs from exposed controls (a nonsignificant difference) showed at least a 4-fold rise in antibody titre to Norwalk virus between acute- and convalescent-phase specimens. This outbreak of AING is believed to be the first to implicate epidemiologically sandwiches as vehicles of transmission. The outbreak highlights the need for investigators to look for a viral etiology in gastroenteritis outbreaks.

Genome variants of human adenovirus types 40 and 41 (subgroup F) in Japan

Nineteen strains of fecal adenovirus were typed as adenovirus type 40 (Ad40) by restriction enzyme analysis of the DNA, using SmaI. The DNAs of the strains were further compared by digestion with four other enzymes, namely, HindIII, EcoRI, BglI, and BamHI. At least two different restriction profiles were found to exist for BamHI. Of the 19 strains studied, 17 had the same combination of profiles for all of the enzymes. Thirteen strains of fecal adenovirus were typed as Ad41 by restriction enzyme analysis of the DNA, using SmaI. The DNAs of the strains were further compared by digestion with four other enzymes, as for Ad40. At least two different restriction profiles were found to exist for each enzyme. Of 13 strains, 9 had the same cleavage sites for all of the enzymes, indicating a close relationship. Two strains were genome variants which deviated from the common genome on digestion of the DNA with HindIII. One strain was a genome variant which deviated from the common genome on digestion of the DNA with HindIII and EcoRI. The last one had a combination of restriction sites which was not identical to those of other strains on digestion of the DNA with SmaI. All 13 Ad41 strains studied were easily distinguished from Ad40 strains by using any of the five restriction enzymes.

Contemporary issues: diseases with a food vector

Foodborne disease has become a contemporary issue. Several large, well-publicized outbreaks of foodborne disease have heightened public awareness that harmful microorganisms may be present in food and that chronic as well as acute disease may be caused by foodborne microbes. The field of food microbiology has likewise experienced a resurgence of interest. New tools, such as recombinant deoxyribonucleic acid technology and monoclonal antibody production, used to elucidate microbial virulence factors have facilitated identification of disease-causing microbes once thought to be harmless and demonstrated the complexity of individual virulence mechanisms previously considered to be well understood. Foodborne pathogens are also causing disease via some surprising food vectors, such as chopped, bottled garlic and sauteed onions. In addition to acute gastrointestinal disturbances, certain microorganisms may, through complex interactions with the human immune response, cause chronic diseases that affect several major organ systems. These microbes are serving as models in studies of molecular mimicry and genetic interrelatedness of procaryotes and eucaryotes. Other recently recognized attributes of foodborne microorganisms, such as the heat shock phenomenon and the possible nonculturability of some bacteria, may affect their ability to cause disease in humans. Because foodborne disease is a major cause of morbidity and mortality, the study of these diseases and their causative microorganisms presents a unique challenge to many professionals in the subdisciplines of microbiology, epidemiology, and clinical medicine.

Two forms of VP7 are involved in assembly of SA11 rotavirus in endoplasmic reticulum

Two pools of the glycoprotein VP7 were detected in the endoplasmic reticulum (ER) of SA11 rotavirus-infected cells. One portion of the newly synthesized protein with VP3 composed the virus outer capsid, while the rest remained associated with the membrane. The two populations could be separated biochemically by fluorocarbon extraction or by immunological methods which used two classes of antibodies. A monoclonal antibody with neutralizing activity recognized VP7 only as displayed on intact virus particles, while a polyclonal antiserum precipitated predominantly the unassembled ER form of the protein and precipitated virus-assembled VP7 poorly. Virus-associated VP7 was localized by immunofluorescence to small punctate structures, presumably corresponding to accumulated virus particles, and to regions of the ER surrounding viroplasmic inclusions, whereas the membrane-associated molecules were distributed in an arborizing reticular pattern throughout the ER. VP3 and the nonstructural glycoprotein NCVP5 displayed a localization similar to that of virus-associated VP7. Intracellular virus particles were isolated from infected cells to determine the kinetics of assembly of VP7 and of the other structural proteins into virions. It was found that incorporation of the inner capsid proteins into single-shelled particles occurred rapidly, while VP7 and VP3 appeared in mature double-shelled particles with a lag time of 10 to 15 min. In addition, the alpha-mannosidase processing kinetics of virus-associated VP7 oligosaccharides showed a 15-min lag compared with that of the membrane-associated form, suggesting that the latter is the precursor to virion VP7. This lag may represent the time required for virus budding and outer capsid assembly.

Development of neutralizing antibodies and group A common antibodies against natural infections with human rotavirus

We determined the levels of group A common and neutralizing antibodies against human rotavirus in paired serum specimens obtained from 38 infants within 12 days of the onset of diarrhea. Thirty of the infants excreted rotavirus in stools, and eight did not. Nine patients (30%) with rotavirus diarrhea and seven patients (88%) with diarrhea due to other causes had detectable levels (greater than or equal to 1: 80) of immunoglobulin (IgG) common antibodies in acute-phase sera. All the patients with rotavirus diarrhea showed at least fourfold rises in titers of IgG or IgM common antibodies or both, while only two control patients showed significant rises in either IgG or IgM common antibodies in their convalescent-phase sera. Of the 19 patients excreting "short" electropherotypes of rotavirus, 18 showed at least fourfold rises in titers of neutralizing antibodies against serotype 2 human rotavirus but not against serotype 1, 3, or 4. Nine of the ten patients excreting "long" electropherotypes showed significant rises in neutralizing antibodies against serotype 3, and the other patient showed a significant rise in neutralizing antibodies against serotype 1. One patient excreted long and short electropherotypes simultaneously, and he also showed a significant rise in neutralizing antibodies against serotype 2 and 3 viruses. The control patients with diarrhea did not show significant changes in titers of antibodies against any of the serotypes. These results demonstrated that the neutralizing antibody response within 2 weeks after clinical onset is specific for the infecting serotype of rotavirus.

Identification of cross-reactive and serotype 2-specific neutralization epitopes on VP3 of human rotavirus

The group A rotaviruses are composed of at least seven serotypes. Serotype specificity is defined mainly by an outer capsid protein, VP7. In contrast, the other surface protein, VP3 (775 amino acids), appears to be associated with both serotype-specific and heterotypic immunity. To identify the cross-reactive and serotype-specific neutralization epitopes on VP3 of human rotavirus, we sequenced the VP3 gene of antigenic mutants resistant to each of seven anti-VP3 neutralizing monoclonal antibodies (N-MAbs) which exhibited heterotypic or serotype 2-specific reactivity, and we defined three distinct neutralization epitopes on VP3. The mutants sustained single amino acid substitutions at position 305, 392, 433, or 439. Amino acid position 305 was critical to epitope I, whereas amino acid position 433 was critical to epitope III. In contrast, epitope II appeared to be more dependent upon conformation and protein folding because both amino acid positions 392 and 439 appeared to be critical. These four positions clustered in a relatively limited area of VP5, the larger of the two cleavage products of VP3. At the positions where amino acid substitutions occurred, there was a correlation between amino acid sequence homology among different serotypes and the reactivity patterns of various viruses with the N-MAbs used for selection of mutants. A synthetic peptide (amino acids 296 to 313) which included the sequence of epitope I reacted with its corresponding N-MAb, suggesting that the region contains a sequential antigenic determinant. These data may prove useful in current efforts to develop vaccines against human rotavirus infection.

Evaluation of seven immunoassays for detection of rotavirus in pediatric stool samples

The performance of seven commercially manufactured rotavirus assays was evaluated with 144 pediatric stool specimens and compared with electron microscopy (EM) findings. The four enzyme-linked immunosorbent assays used were Rotazyme II, Pathfinder, IDL rotavirus immunoassay, and Enzygnost (Behring) rotavirus assay. The three latex tests were Meritec rotavirus detection test, Virogen Rotatest, and Bartels rotavirus latex test. Test outcomes were compared with EM on the basis of sensitivity, specificity, positive-negative predictive value, and the kappa statistic. Relative to EM, Meritec had the highest specificity (97%), followed by Virogen (95%), IDL (91%), Pathfinder (85%), Behring (81%), Bartels (72%), and Rotazyme (71%). The sensitivities were as follows: Rotazyme (92%), Pathfinder (89%), Bartels (86%), Virogen (86%), Behring (82%), Meritec (71%), and IDL (75%). Patient age and sex did not influence test results. Owing to the absence of a true standard, the tests were also compared with each other on the basis of the kappa statistic, the frequency of positive test results, and the frequency of samples in which a test differed from all other tests. Using these measures, the assays could be classified into three groups with progressively decreasing utility: group 1 (Virogen, Meritec, IDL, and EM), group 2 (Pathfinder and Behring), and group 3 (Rotazyme and Bartels). Laboratory criteria were also compared. Latex tests were faster and required less equipment than enzyme-linked immunosorbent assays. The Virogen latex assay showed the best overall performance, which made it our choice for rapid and accurate rotavirus diagnosis. However, in children who have gastrointestinal symptoms with negative rotavirus test results, EM will be useful until such time as immunological tests for other enteric viruses are available.

A three-year diagnostic and epidemiological study on viral infantile diarrhoea in Rome

Rotavirus infection was demonstrated in 168 (29.3%) of 573 children hospitalized for acute diarrhoea in Rome between January 1982 and December 1984. Laboratory diagnosis of these infections was made by transmission electron microscopy and enzyme immunoassay techniques with an overall agreement of 91.3%. Astroviruses, adenoviruses and small round viruses were detected in the faeces of 36 patients (6.4%). Whereas in 1982 rotavirus positive patients were clustered in the winter and following spring, in the following years cases were recorded all year round. The median age of patients with rotavirus infections was 17, 10 and 11.5 months in 1982, 1983 and 1984, respectively. In addition, a smaller number of rotavirus positive cases were admitted in 1983 when compared to those admitted during the previous as well as the subsequent years. It is suggested that a herd immunity was induced in the population by epidemic spread of rotavirus in the first half of 1982.

Infection immunity of piglets to either VP3 or VP7 outer capsid protein confers resistance to challenge with a virulent rotavirus bearing the corresponding antigen

A single-gene substitution reassortant 11-1 was generated from two porcine rotaviruses, OSU (serotype 5) and Gottfried (serotype 4). This reassortant derived 10 genes, including gene 4 encoding VP3, from the OSU strain and only gene 9, encoding a major neutralization glycoprotein (VP7), from the Gottfried strain and was thus designated VP3:5; VP7:4. Oral administration of this reassortant to colostrum-deprived gnotobiotic newborn pigs induced a high level of neutralizing antibodies not only to Gottfried VP7 but also to OSU VP3, thus demonstrating that VP3 is as potent an immunogen as VP7 in inducing neutralizing antibodies during experimental oral infection. Gnotobiotic piglets infected previously with the reassortant were completely resistant to oral challenge with the virulent Gottfried strain (VP3:4; VP7:4), as indicated by failure of symptoms to develop and lack of virus shedding. Similarly, prior infection with the reassortant induced almost complete protection against diarrhea and significant restriction of virus replication after oral challenge with the virulent OSU strain (VP3:5; VP7:5). Thus, it appears that (i) the immune system of the piglet responds equally well to two rotavirus outer capsid proteins, VP3 and VP7, during primary enteric rotavirus infection; (ii) antibody to VP3 and antibody to VP7 are each associated with resistance to diarrhea; and (iii) infection with a reassortant rotavirus bearing VP3 and VP7 neutralization antigens derived from two viruses of different serotype induces immunity to both parental viruses. The relevance of these findings to the development of effective reassortant rotavirus vaccines is discussed.