Comparison of electron microscopy, enzyme-linked immunosorbent assay, solid-phase radioimmunoassay, and indirect immunofluorescence for detection of human rotavirus antigen in faeces

Development of one-step real-time reverse transcription polymerase chain reaction assays for rapid detection of porcine group C rotaviruses

Although the widespread occurrence of porcine group C rotaviruses (GCRV) is assumed, precise prevalence remains largely unknown because of the absence of reliable, specific, and rapid diagnostic methods. To detect and quantify porcine GCRV, the authors evaluated and optimized SYBR Green and TaqMan real-time reverse transcription polymerase chain reaction (RT-PCR) assays and applied them to 108 piglet fecal samples. Using serially diluted standard RNA transcripts of porcine GCRV VP6 gene, both SYBR Green and TaqMan real-time RT-PCR assays detected as few as 1 x 10(1) genome copies/microl (correlation coefficiency >0.99), whereas conventional RT-PCR detected 1.0 x 10(3) copies/microl. In addition, the conventional assay detected porcine GCRV in 24% (26/108) of fecal samples, whereas the detection rates of both SYBR Green and TaqMan assays were 72% (78 of 108) and 64% (70 of 108), respectively. The current study indicated that both real-time RT-PCR assays were reliable, specific, and rapid methods for the detection of porcine GCRV in porcine fecal samples.

Rotavirus typing methods and algorithms

Vaccination is the current strategy for control and prevention of severe rotavirus infections, a major cause of acute, dehydrating diarrhoea in young children worldwide. Public health interventions aimed at improving water, food and sanitation are unlikely adequately to control the disease. The development of vaccines against severe rotavirus diarrhoea is based upon homotypic or heterotypic protection provided against either a single common G serotype (monovalent vaccines) or against multiple serotypes (multivalent vaccines). Rotavirus strain surveillance has a high priority in disease control programmes worldwide. The continued identification of the most common G and P serotypes for inclusion in vaccines is an important priority. And subsequent to the introduction of a vaccine candidate, not only monitoring of circulating strains is recommended, but also surveillance of potential reassortment of animal rotavirus genes from the vaccine into human rotavirus strains is critical. Conventional methods used in the characterisation of rotavirus strains, such as enzyme immunoassay serotyping and reverse‐transcription PCR‐based genotyping often fail to identify uncommon and newly appearing strains. The application of newer molecular approaches, including sequencing and oligonucleotide microarray hybridisation, may be required to characterise such strains. The present paper presents a brief overview of the variety of standard methods available, followed by suggestions for a systematic approach for routine rotavirus strain surveillance as well as for characterisation of incompletely typed rotavirus strains. Improved detection and characterisation of incompletely typed strains will help to develop a comprehensive strain surveillance that may be required for tailoring effective rotavirus vaccines. Published in 2004 by John Wiley & Sons, Ltd.

Evaluation of two enzyme immunoassays for detection of human rotaviruses in fecal specimens

The two assays evaluated in this study (the Ridascreen rotavirus and the Pathfinder rotavirus) exhibited comparable sensitivities (100%) but highly divergent positive predictive values (93.74 and 57.7%, respectively) when compared on 393 specimens. This difference should be considered when using these tests on collectives with an unknown or low prevalence.

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.

An assessment of the sensitivity of three methods for the detection of rotavirus

A comparison was made of the sensitivity of a current commercial ELISA for detecting rotavirus in faecal specimens with the more complex, technically demanding systems of electron microscopy and polyacrylamide gel electrophoresis. Even after modification, the ELISA failed to detect 22% of specimens with particles identifiable by electron microscopy. Polyacrylamide gel electrophoresis failed to identify 2 out of 50 specimens with particles present but did distinguish 2 group C rotaviruses.

Rotaviral and coronaviral diarrhea

A number of different viruses can be primary pathogens in the neonatal calf diarrhea complex. By far the most common viruses causing calfhood diarrhea found throughout the world are rotaviruses and coronaviruses. Primary infection of newborn calves with either one of these viruses can cause severe intestinal alterations and diarrhea. Rotaviruses can produce high-morbidity outbreaks of diarrhea in calves under 10 days of age. Morality is variable mainly owing to secondary bacterial infections and electrolyte imbalances. Rotavirus infection of the small intestinal mucosa leads to loss of enterocytes of the upper third of the intestinal villi with subsequent villous atrophy and malabsorption. There is growing evidence that different rotavirus serotypes of different pathogenicity exist. Coronavirus infections can produce high-morbidity outbreaks of diarrhea in calves under 20 days of age, with variable mortality due to secondary complications. Coronaviruses affect not only the small intestinal mucosa, producing significant villous atrophy, but also the colon, causing a very severe intestinal damage that can lead to death due to subsequent electrolyte disturbances. All coronaviruses associated with neonatal calf diarrhea appear to be of the same serotype. The etiologic diagnosis of viral diarrheas of calves requires the support of the laboratory. One of the most useful diagnostic methods is the examination of fecal extracts for the presence of virus particles by electron microscopy. Other antigen-detection procedures like enzyme immunoassays have been found to be useful in the diagnosis of rotaviral diarrheas. The sample of choice for these diagnostic tests is a fresh fecal sample collected directly from the calf as close as possible to the onset of diarrhea. Samples from more than one calf during the outbreak enhance the laboratory ability to establish a proper viral diagnosis.

Detection of rotavirus in faecal specimens by enzyme immunoassay, latex agglutination and electron microscopy

Faecal specimens from 570 patients with gastroenteritis were studied for rotaviruses by enzyme immunoassay (EIA), electron microscopy (EM) and latex agglutination test (LX). Specimens from 127 patients were positive and 379 were negative with all 3 methods. 64 (11%) specimens gave contradictory results in the tests. EIA gave significantly more positive results than EM (168 vs 145). 30 EM-negative and EIA-positive specimens were positive in a confirmatory test. LX was positive in 161 specimens and no significant differences to EM or EIA were observed. There were 16 (2.8%) LX-positive samples that were negative both in EM and EIA. The positivity of these samples could not be confirmed and 15 of them were only slightly positive. Our results can be concluded: (1) Enzyme immunoassay may be more sensitive than electron microscopy but requires a confirmatory test and is tedious when only a few specimens per day are to be examined; (2) LX seems to be suitable for primary screening of faecal specimens for rotavirus; for definitely positive results the test is reliable.

Pseudoreplica electron microscopy for the detection of rotavirus: comparison with high-speed centrifugation electron microscopy and ELISA

Three-hundred and sixty-three stool specimens from patients with diarrhoea were examined for rotaviruses to compare the sensitivity of the pseudoreplica technique (PSD-EM) to that of high-speed centrifugation EM (HSC-EM) in relation to a commercially available (Rotazyme, Abbott) enzyme-linked immunosorbent assay (ELISA). In ELISA-positive cases, both methods were of equal sensitivity. However, in borderline (+/-) and ELISA-negative specimens, PSD-EM detected 31 of 48 (64.6%) and 18 of 229 (8%) positive specimens respectively, compared to only 22 of 48 (45.8%) and one of 229 (0.4%) positives detected by HSC-EM. PSD-EM detected a significantly higher number of positives compared to HSC-EM (p less than 0.05). In view of its simplicity, sensitivity and the fact that a relatively large number of specimens could be processed compared to HSC-EM, we consider that PSD-EM is a much better procedure for routine screening and diagnosis of viral gastroenteritis than HSC-EM.

An improved enzyme-linked immunosorbent assay for the detection of rotavirus in faeces of neonates

A direct enzyme-linked immunosorbent assay (EIA) for the detection of rotavirus in neonatal stools was developed. Rabbit antiserum against SA 11 rotavirus was incorporated as both coating and detector antibody, and rotavirus-negative rabbit serum was applied as a coating antibody control to eliminate false positive results. Pretreatment of stools with EDTA was found to increase both the sensitivity and specificity of the assay. This effect was greatest when 0.25 M EDTA (tetrasodium salt) was included in homogenized stool suspensions before the removal of solid debris by centrifugation. By electron microscopy, this EDTA pretreatment appeared to partly uncoat human rotavirus particles in faeces. Potentially suitable solid phase supports and horseradish peroxidase substrates were evaluated in the development of the assay. Screening of stool samples revealed that repeated freezing and thawing of stools eliminated positive EIA reactions. The SA 11 coating antibody compared favourably with a reference coating antiserum prepared against human faecal rotavirus strains. This EIA showed greater sensitivity for rotavirus detection than electron microscopy of stool concentrates prepared by ultracentrifugation, on testing 143 stools from 99 neonates and children. The assay has been applied successfully to detection of rotavirus in stools of neonates containing meconium, smaller amounts of viral antigen than in older children, and lacteal antirotaviral antibody. It is likely to be particularly useful for cross-infection studies in hospital wards and neonatal nurseries.

Evaluation of a new latex agglutination test for detecting human rotavirus in faeces

Four methods for detecting rotaviruses (latex agglutination, electron microscopy, immunofluorescence and ELISA) have been compared on 57 faecal samples from children with acute diarrhoea. Complete agreement among the four techniques was found in 38 samples. One sample was positive by ELISA and latex agglutination but negative by the other two. For all the other samples there was agreement among three of the techniques only. In a blocking ELISA test, samples positive by ELISA only, turned out to be falsely positive. Assuming true positive or negative for those samples for which at least three techniques were in agreement, electron microscopy, ELISA and latex agglutination were more sensitive (96 per cent) than immunofluorescence (84 per cent). Electron microscopy was the most specific (96.4 per cent), followed by immunofluorescence (92.9 per cent), ELISA (89.4 per cent) and latex agglutination (85.9 per cent).

Replication of human rotavirus in cell culture

Nine strains of human rotavirus were adapted to growth in CV-1 and/or MA-104 cells following pretreatment of virus with trypsin, incorporation of trypsin into culture medium, and use of roller cultures. Immunofluorescence was the most reliable method for the detection of virus replication, although characteristic cytopathic effects were produced sporadically by most isolates. Virus could be readily detected in supernatant fluids of cell cultures and in cell sections by electron microscopy.

Rapid detection of rotavirus in stool by latex agglutination: comparison with radioimmunoassay and electron microscopy and clinical evaluation of the test

A latex agglutination test (LX) using antisera prepared against Nebraska calf diarrhea virus (NCDV) is described for the detection of rotavirus in stool of children with acute gastroenteritis. The test was compared with electron microscopy (EM) and radioimmunoassay (RIA) with 100 stools positive or negative for rotavirus. Out of 53 stools positive in RIA or EM, 49 were positive in LX and 4 were negative. Two specimens negative in EM and RIA were falsely positive in LX. The method was also tested in two clinical series with 115 stools from 101 children. Altogether 67/115 stools were positive in RIA, and 62/115 in LX. Out of 7 stools with contradictory results, 6 were negative in LX but positive in RIA, and 1 was positive in LX but negative in RIA. The results indicate that the LX is suitable for rapid screening of rotavirus gastroenteritis in clinical practice.

Diagnostic virology using electron microscopic techniques

This chapter illustrates the development of the use of electron microscopy in viral diagnosis. The field covered is confined to medical viral diagnosis, but parallel developments have taken place in both veterinary and botanical fields and techniques derived from both these sources are also included where relevant. It is reported that the scanning transmission mode of operation, which can induce image contrast changes electronically, may enhance studies with unstained sections and perhaps facilitate thin section immune electron microscopy (IEM). The application of negative stain IEM has been particularly useful for the study of the antigenic nature of some of the newly discovered noncultivable viruses. Viral antigens can also be detected in thin sections of infected cells by IEM with suitably labeled specific antibodies. Confirmation of viral infection by electron microscopy on tissues originally processed for light microscopy is also frequently useful.

Rotavirus infection in children hospitalized for diarrhoea in Argentina

An epidemiological survey was undertaken to establish the importance of rotavirus as a cause of admission of children to hospital in Buenos Aires, Argentina. Between August 1978 and January 1980 rotavirus infection was detected in 62 (34%) of 180 infants and children admitted to hospital with acute gastro-enteritis. In identification of the virus, electron microscopy (EM) was found to be as sensitive as counterimmunoelectrophoresis (CIE). There was agreement between EM and CIE diagnosis in 90.5% cases. Adenovirus and coronavirus were detected by electron microscopy less often. A serological response to rotavirus was revealed by complement fixation test in 38 (72%) of 53 infected patients. Rotaviruses were detected throughout the year, but peak incidence occurred during the cooler months, May to August. Infection was commoner among children under six months of age. Diarrhoea was generally mild in these children and respiratory illness showed no significant association with rotavirus gastroenteritis. These results indicate that rotaviruses may be a major cause of infantile acute gastroenteritis in Buenos Aires, Argentina especially during the winter.

Detection of rotavirus in faeces by latex agglutination

Human rotavirus (HRV) in faeces of patients may be readily detected with high sensitivity and specificity using latex agglutination (LA) on a glass slide by making use of the cross-reactivity of anti-calf rotavirus (CRV) antibody. Latex particles were coated with anti-CRV immunoglobin. The antibody coated particles (AC-L) are specifically agglutinated by both CRV and HRV, and the agglutination is evident macroscopically within a minute. To examine the sensitivity and reliability of the LA method compared to other methods, HRV in faecal extracts of 48 infants with acute gastroenteritis was sought by the LA, reversed passive haemagglutination (RPHA) and electron microscope (EM) methods. Samples positive by the EM method were all positive by the LA method, and samples negative by EM were all negative by LA. The LA method is suitable for application as a simple clinical diagnostic test.

Optimized enzyme-linked immunosorbent assay for detection of human and bovine rotavirus in stools: Comparison with electron-microscopy, immunoelectro-osmophoresis, and fluorescent antibody techniques

Detection of human and bovine rotavirus in stools is described using a double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) with poly-styrene microtest plates as solid phase, immunoglobulin fraction of rabbit antiserum to rotavirus (human) as catching antibody, and the same reagent labelled with horseradish peroxidase as conjugate. The ELISA has been optimized with regard to simplicity, rapidity, sensitivity, and specificity. In a comparative study, stool specimens from 81 infants and children and 92 neonatal calves with diarrhoea were tested for rotavirus by ELISA, electron microscopy (EM), immunoelectro-osmophoresis (IEOP), and fluorescent antibody technique (FA). The relative sensitivity of the different assays for human and bovine rotavirus was: EM 68%, 76%; IEOP 80%, 76%; FA not determined, 85%; and ELISA 86%, 98%, respectively. Less than 1 ng of purified human rotavirus could be detected in ELISA, whereas 100 ng was the minimal amount detected by IEOP. It is concluded that the developed ELISA is a simple, rapid, reliable, and sensitive method for the diagnosis of human and bovine rotavirus infections.

Recherche de virus en microscopie électronique dans les selles d'enfants atteints de gastro-entérite aiguë hivernale

During two successive winters, faecal extracts from 110 children under 3 years of age were examined by electron microscopy with negative contrast. In a first group of 22 children hospitalised for various medical disorders, no virus particles were detected. In the second group of 88 children with acute gastroenteritis, we found viruses in 31,8 % of the faecal extracts, Rotavirus were detected in 22,7 % of the specimens and various particles (Adenovirus, Astrovirus, Coronavirus) in 9,1 % of the specimens.