Evaluation of a latex agglutination kit (Virogen Rotatest) for detection of bovine rotavirus in fecal samples

Determining genetic diversity of prevalent G and P genotype of Bovine Rotavirus A from neonatal calves of Gujarat, India

IMPORTANCE

Neonatal calf diarrhea is a major cause of mortality in newborn calves worldwide, posing a significant challenge in bovine herds. Group A Bovine Rotaviruses (BRVA) are the primary contributors to severe gastroenteritis in calves under two months old.

OBJECTIVES

This study examined the prevalence and molecular characterization of BRVA in neonatal calves in Gujarat, India.

METHODS

Sixty-nine diarrheic fecal samples were collected and subjected to various molecular methods of BRVA detection, isolation, and characterization.

RESULTS

The latex agglutination test (LAT), electropherotyping (RNA-PAGE), and reverse transcription polymerase chain reaction revealed positivity rates of 39.13%, 20.30%, and 37.70%, respectively. RNA-PAGE identified 11 bands with a 4:2:3:2 migration pattern, indicative of the segmented genome of BRVA. BRVA was successfully isolated from LAT-positive samples, with 26 samples exhibiting clear cytopathic effects upon passage in MA-104 cell lines. Genotyping identified G10 as the predominant G genotype, with P[11] genotypes comprising 76.92% of the isolates. The most common G/P combination was G10P[11], highlighting its zoonotic potential.

CONCLUSIONS AND RELEVANCE

These findings underscore the importance of molecular detection and genotyping for effective vaccine development. This study provides crucial insights into the prevalent G and P genotypes of BRVA in Gujarat, India, aiding in the development of targeted control measures.

Establishment of an Indirect ELISA Method for the Detection of the Bovine Rotavirus VP6 Protein

The objective of this study was to develop an indirect ELISA utilizing a polyclonal antibody against bovine rotavirus (BRV) VP6 protein. To achieve this, pcDNA3.1-VP6, a recombinant eukaryotic expression plasmid, was constructed based on the sequence of the conserved BRV gene VP6 and was transfected into CHO-K1 cells using the transient transfection method. The VP6 protein was purified as the coating antigen using nickel ion affinity chromatography, and an indirect ELISA was subsequently established. The study found that the optimal concentration of coating for the VP6 protein was 1 μg/mL. The optimal blocking solution was 3% skim milk, and the blocking time was 120 min. The secondary antibody was diluted to 1:4000, and the incubation time for the secondary antibody was 30 min. A positive result was indicated when the serum OD450 was greater than or equal to 0.357. The coefficients of variation were less than 10% both within and between batches, indicating the good reproducibility of the method. The study found that the test result was positive when the serum dilution was 217, indicating the high sensitivity of the method. A total of 24 positive sera and 40 negative sera were tested using the well-established ELISA. The study also established an indirect ELISA assay with good specificity and sensitivity for the detection of antibodies to bovine rotavirus. Overall, the results suggest that the indirect ELISA method developed in this study is an effective test for detecting such antibodies.

Development and evaluation of polyclonal antibodies based antigen capture ELISA for detection of porcine rotavirus

Rotaviruses are rising as zoonotic viruses worldwide, causing the lethal dehydrating diarrhea in children, piglets, and other livestock of economic importance. A simple, swift, cost-effective, highly specific, and sensitive antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) was developed for detection of porcine rotavirus-A (PoRVA) by employing rabbit (capture antibody) and murine polyclonal antibodies (detector antibody) produced against VP6 of PoRVA (RVA/Pig-tc/CHN/TM-a/2009/G9P23). Reactivity of the both polyclonal antibodies was confirmed by using an indirect ELISA, western-blot analysis and indirect fluorescence assay against rVP6 protein and PoRVA. The detection limit of AC-ELISA was found 50 ng/ml of PoRVA protein. The relative sensitivity and specificity of this in-house AC-ELISA were evaluated for detection of PoRVA from 295 porcine diarrhea samples, and results were compared with that of RT-PCR and TaqMan RT-qPCR. The relative sensitivity and specificity of AC-ELISA compared with those of TaqMan RT-qPCR were found as 94.4 and 99.2%, respectively, with the strong agreement (κ -0.58) between these two techniques. Furthermore, AC-ELISA could not detect any cross-reactivity with porcine epidemic diarrhea virus, transmissible gastro-enteritis virus, pseudo rabies virus and porcine circovirus-2. This in-house AC-ELISA efficiently detected PoRVA from clinical samples, which suggests that this technique can be used for large-scale surveillance and timely detection of rotavirus infection in the porcine farms.

Advanced sequence optimization for the high efficient yield of human group A rotavirus VP6 recombinant protein in Escherichia coli and its use as immunogen

Rotavirus is the important etiological agents of infectious diarrhea among children under 5 years old. Rotaviruses are divided into 10 serogroups (A-J) and each group is based on genetic properties of major structural protein VP6. We designed a novel VP6 sequence optimization to increase the expression level of this protein. Numerous factors such as codon adaptation index, codon pair bias, and guanine-cytosine content were adapted based on Escherichiacoli codon usage. In addition, the ribosome binding site (RBS) of pET-15b was redesigned by the RBS calculator and the secondary structure of VP6 messenger RNA was optimized in the whole length of the coding sequence. Various factors including isopropyl beta- d-thiogalactoside (IPTG) concentration, temperature, and induction time were analyzed for the optimization of the best expression in E. coli by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blotting. The recombinant VP6 (rVP6) protein was purified by the Ni-sepharose and then the hyperimmune sera were generated against rVP6 in rabbits. Among three different temperatures, IPTG concentrations, and postinductions, the level of rVP6 was higher at 37°C, 1 mM of IPTG, and 8 h, respectively. Also, the high expression level of rVP6 was obtained in the insoluble aggregate form (43.8 g/L). After purification, the yield of rVP6 was 10.83 g/L. The rVP6 specific antiserum was confirmed by both immunofluorescent and western blotting. The versatile sequence optimization was the reason to produce a high level of rVP6 compared to other reports and can potentially apply to produce cheaper commercial kits to diagnose serological tests and new rotavirus vaccines.

Molecular and non-molecular approaches to etiologic diagnosis of gastroenteritis

Gastroenteritis is a major cause of mortality and morbidity globally and rapid identification of the causative pathogen is important for appropriate treatment and patient management, implementation of effective infection control measures, reducing hospital length of stay, and reducing overall medical costs. Although stool culture and microscopic examination of diarrheal stool has been the primary method for laboratory diagnosis, culture-independent proteomic and genomic tests are receiving increased attention. Antigen tests for stool pathogens are routinely implemented as rapid and simple analytics whereas molecular tests are now available in various formats from high complexity to waived point-of-care tests. In addition, metagenomic next-generation sequencing stands poised for use as a method for both diagnosis and routine characterization of the gut microbiome in the very near future. Analysis of host biomarkers as indicators of infection status and pathogenesis may also become important for prediction, diagnosis, and monitoring of gastrointestinal infection. Here we review current methods and emerging technologies for the etiologic diagnosis of gastroenteritis in the clinical laboratory. Benefits and limitations of these evolving methods are highlighted.

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.

Development and Validation of Monoclonal Antibody-Based Antigen Capture ELISA for Detection of Group A Porcine Rotavirus

Porcine rotavirus-A (PoRVA) is one of the common causes of mild to severe dehydrating diarrhea, leading to losses in weaning and postweaning piglets. A rapid, highly specific, and sensitive antigen-capture enzyme-linked immunosorbent assay (AC-ELISA) was developed for detection of PoRVA, by using VP6 (a highly conserved and antigenic protein of group-A rotavirus)-directed rabbit polyclonal antibodies (capture antibody) and murine monoclonal antibodies (detector antibody). The detection limit of AC-ELISA was found to be equal to that of conventional reverse transcription-polymerase chain reaction (RT-PCR; about 10^2.5 TCID₅₀/mL). For validation of the in-house AC-ELISA, 295 porcine fecal/diarrhea samples, collected from different provinces of China, were evaluated and compared with conventional RT-PCR and TaqMan RT-quantitative PCR (qPCR). The sensitivity and specificity of this in-house AC-ELISA relative to RT-qPCR were found to be 91.67% and 100%, respectively, with the strong agreement (kappa = 0.972) between these two techniques. Total detection rate with AC-ELISA, conventional RT-PCR, and RT-qPCR were found to be 11.2%, 11.5%, and 12.2%, respectively, without any statistical significant difference. Moreover, AC-ELISA failed to detect any cross-reactivity with porcine epidemic diarrhea virus, transmissible gastroenteritis virus, pseudorabies virus, and porcine circovirus-2. These results suggested that our developed method was rapid, highly specific, and sensitive, which may help in large-scale surveillance, timely detection, and preventive control of rotavirus infection in porcine farms.

Diarrhoea caused by rotavirus in a regional Peruvian hospital: determination of circulating genotypes

BACKGROUND

Gastroenteritis caused by rotavirus is responsible for approximately 810 deaths per year in children under 5 years of age in Peru and emerging rotavirus genotypes have led to concerns regarding cross-protection by the vaccines available. Moreover, there are no reports on the molecular epidemiology of rotavirus diarrhoea in Peru.

METHODS

A total of 131 stool samples were obtained from children under 5 years hospitalised from January 2010 to December 2012 in the Hospital Regional de Cajamarca (Peru). ELISA and RT-PCR techniques were performed for rotavirus detection. G and P typing of rotavirus-positive samples were performed by semi-nested multiplex RT-PCR, and sequencing was performed to confirm the PCR results.

RESULTS

Of the 117 samples available, 22 (18.8%) tested positive for rotavirus by ELISA and 42 (35.9%) tested positive by RT-PCR. Among the G genotypes identified, G9 (35.7%; 15/42) and G12 (33.3%; 14/42) were the most prevalent, with the most common combination being G12/P[6] (23.8%; 10/42).

CONCLUSIONS

A high prevalence of the G12/P[6] genotype was detected. It is known that this genotype is not covered by the current vaccines available. More in-depth studies are needed to determine the current rotavirus genotypes presents in Peru.

Rapid detection of human rotavirus using NSP4 gene specific reverse transcription loop-mediated isothermal amplification assay

The seasonal outbreaks of human rotavirus (RV) infection occur every winter. Most patients are diagnosed clinically by a rapid latex agglutination detection kit or polymerase chain reaction assays for RV from stool samples, but some problems have been reported on the specificity and sensitivity of such rapid detection assays. To ratify these issues, a sensitive, specific, simple, and rapid nucleic acid based diagnostic method is expected to be introduced and the reverse transcription loop-mediated isothermal amplification (RT-LAMP) was developed to detect the RV in human stool samples by incubation at 60 °C for 1 h and amplification was confirmed by electrophoretic laddering, restriction enzyme digestion, and hydroxynapthol blue discoloration. The assay established in this study was found to detect only the RVs and no cross-reaction with other viruses, demonstrating its high specificity. By using serial samples dilution as template, the detection limit of LAMP was 10 times more than that of PCR. The results showed the potential clinical feasibility of RT-LAMP as a useful diagnostic tool for the detection of RV with high sensitivity in comparison to conventional RT-PCR.

Sensitivity and specificity of PS/AA-modified nanoparticles used in malaria detection

Polystyrene (PS) nanoparticle (NP) copolymerized with acrylic acid (AA) and coloured monomer, i.e. 2,3,6,7-tetra(2,2'-bithiophene)-1,4,5,8-naphthalenetetracarboxylic-N,N'-di(2-methylallyl)-bisimide (ALN8T), was synthesized via the miniemulsion polymerization. Before applying for malaria antigen detection, the blue NP was conjugated with human polyclonal malaria IgG antibody (Ab) specific to Plasmodium falciparum. For the conjugation, three methods, i.e. physical adsorption, covalent coupling and affinity binding via streptavidin (SA) and biotin interaction, were employed. The optimum ratio of Ab to NPs used in each immobilization procedure and the latex agglutination test based on the reaction between Ab conjugated NPs and malaria patient plasma were investigated. All Ab-latex conjugates provided the high sensitivity for the detection of P. falciparum malaria plasma. The highest specificity to P. falciparum was obtained from using Ab-NPs conjugated via the SA-biotin interaction.

Comparison of three diagnostic techniques for detection of rotavirus and coronavirus in calf faeces in Australia

Objective  Compare real‐time reverse transcription polymerase chain reaction (qRT‐PCR), a commercially available enzyme‐linked immunosorbent assay (ELISA) and lateral flow immunochromatography assay (LAT) for the detection of rotavirus and coronavirus in faecal samples collected from diarrhoeic calves.

Design  Prospective survey.

Method  Samples were tested at two separate facilities using a commercial ELISA and an in‐house qRT‐PCR. Simple logistic regression was performed to examine the relationship between the two tests. A subset of samples was screened using qRT‐PCR, ELISA and a commercial LAT dipstick (132 faecal samples were tested for coronavirus and 122 samples for rotavirus).

Results  Of the 586 samples tested, 131 (22.39%) and 468 (79.86%) were positive for coronavirus and group A rotavirus, respectively, using qRT‐PCR. The number of samples positive on ELISA for coronavirus and rotavirus was 73 (12.46%) and 225 (38.40%), respectively. Using LAT, 30 (22.73%) and 43 (35.35%) samples were positive for coronavirus and rotavirus, respectively. Simple linear regression revealed a statistically significant (P < 0.05) but weak (r²=−0.07 and −0.40) correlation between the rotavirus/coronavirus qRT‐PCR and ELISA, respectively. There was also poor agreement between the LAT and qRT‐PCR assays.

Conclusion  The sensitivity and specificity of the commercial ELISA and LAT assays evaluated in this study were low compared with qRT‐PCR. The low positive and negative predictive values of the assays suggests that they were of limited diagnostic benefit in the population sampled.

Viral and bacterial infections associated with camel (Camelus dromedarius) calf diarrhea in North Province, Saudi Arabia

Diarrhea and deaths in new-born camel calves were noticed by veterinary investigators and pastoralist in Saudi Arabia to be very high. Hence, it is thought to be necessary to investigate this problem from the virological and bacteriological point of view. The role of pathogenic bacteria and viruses in six different towns of North Province (Al-Assafia, Arar, Domat Aljandal, Hail, Skaka and Khoa) in Saudi Arabia was studied. Survey was conducted in diarrheic camel calves aged 12 months or younger. In our study calf diarrhea was reported in 184 out of 2308 camels examined clinically during one year, the prevalence of diarrhea was found to be 8.0% in calves ranging from one month to one year. In the present study group A rotavirus and Brucella abortus were detected in 14.7% and 8.98%, respectively, using ELISA technique. Escherichia coli was isolated from diarrheic calf camel (58.2%) 99/170 samples during dry and wet season. Salmonella spp. and Enterococcus spp. were detected in 12% and 8.8% of the specimens, respectively. In this study enterotoxogenic E. coli (ET E. coli) was isolated from 7% of diarrheic camel, which indicates the strong correlation between the camel calf diarrhea and the detection of enterotoxogenic E. coli. This study represented the first report for the detection of group A rotavirus and B. abortus antigen and antibodies in calf camels in Saudi Arabia. It is recommended that the disease should be controlled by vaccination in calf camels.

Development of a latex agglutination test for norovirus detection

Norovirus (NoV) is the leading cause of acute gastroenteritis worldwide. Currently, reverse transcription polymerase chain reaction (RT-PCR) is used commonly to detect NoVs in both clinical and environmental samples. However, RT-PCR requires expensive equipment and cannot be performed on site. In this study, a latex agglutination test (LAT) using antibody-labeled latex beads for detecting NoVs was developed. Two kinds of polyclonal antibodies, one generated from synthetic peptides and the other from E. coli-expressed NoV capsid proteins, were used to develop the LAT. Each of these polyclonal antibodies was immobilized on the surface of latex beads and tested for the ability to detect NoVs. Under optimized conditions, our LAT detected GII.4 NoV at concentrations as low as 3.3x10(5) RT-PCR units/ml in stool samples. The detection limit for the LAT was approximately 1.7 103 RT-PCR units. Forty-eight stool samples were tested for NoVs using this LAT. In comparison with an RT-PCR assay, the sensitivity and specificity of the LAT were 35% and 100%, respectively. With further optimization, this LAT used with appropriate antibodies could be applied for convenient detection of NoVs in clinical diagnosis and food monitoring.

Genotype 1 and genotype 2 bovine noroviruses are antigenically distinct but share a cross-reactive epitope with human noroviruses

The bovine enteric caliciviruses Bo/Jena/1980/DE and Bo/Newbury2/1976/UK represent two distinct genotypes within a new genogroup, genogroup III, in the genus Norovirus of the family Caliciviridae. In the present study, the antigenic relatedness of these two genotypes was determined for the first time to enable the development of tests to detect and differentiate between both genotypes. Two approaches were used. First, cross-reactivity was examined by enzyme-linked immunosorbent assay (ELISA) using recombinant virus-like particles (VLPs) and convalescent-phase sera from calves infected with either Jena (genotype 1) or Newbury2 (genotype 2). Second, cross-reactivity was examined between the two genotypes with a monoclonal antibody, CM39, derived using Jena VLPs. The two genotypes, Jena and Newbury2, were antigenically distinct with little or no cross-reactivity by ELISA to the heterologous VLPs using convalescent calf sera that had homologous immunoglobulin G titers of log10 3.1 to 3.3. CM39 reacted with both Jena and heterologous Newbury2 VLPs. The CM39 epitope was mapped to nine amino acids (31PTAGAQIAA39) in the Jena capsid protein, which was not fully conserved for Newbury2 (31PTAGAPVAA39). Molecular modeling showed that the CM39 epitope was located within the NH2-terminal arm inside the virus capsid. Surprisingly, CM39 also reacted with VLPs from two genogroup II/3 human noroviruses by ELISA and Western blotting. Thus, although the bovine noroviruses Jena and Newbury2 corresponded to two distinct antigenic types or serotypes, they shared at least one cross-reactive epitope. These findings have relevance for epidemiological studies to determine the prevalence of bovine norovirus serotypes and to develop vaccines to bovine noroviruses.

Verification of sensitivity and specificity of group a rotavirus detection in piglets faeces with monoclonal blocking ELISA methods

Monoclonal antibodies to group A rotavirus Vp6 protein were prepared and used for verification of three blocking enzyme‐linked immunosorbent assay (ELISA) modifications to detect rotavirus A. Selected competitive blocking ELISA (CB‐ELISA) and electron microscopy (EM) were used for examination of 194 field faecal samples of piglets affected with diarrhoea. Rotavirus was detected in 43 samples (22.2%) by CB‐ELISA method, whereas in 26 (13.4%) samples by EM examination. However, of 26 samples positive by EM, rotavirus A was detected by CB‐ELISA in 19 (73.1%) samples; indicating the share of group A rotavirus in all cases of gastroenteritis caused by rotavirus. The sensitivity and specificity of the CB‐ELISA was verified both by inclusion of control samples containing transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhoea virus (PEDV) in each analysis and by comparative examination of samples with the commercial ELISA kit. The CB‐ELISA sensitivity was positively affected by examination of samples in the presence of chelating agent.

Detection of PCR amplicons from bacterial pathogens using microsphere agglutination

For rapid and inexpensive detection of polymerase chain reaction (PCR) amplicons, a novel microsphere agglutination assay has been developed. PCR is carried out using biotinylated forward and reverse primers, and the amplified DNA fragments are able to agglutinate streptavidin-coated microspheres (5.7 microm in diameter). Purification of PCR amplicons is unnecessary when initial primer concentrations are 250 nM. Agglutination can be identified visually within 2 min without any additional equipment or reagents. Using listeriolysin (lisA)-specific biotinylated primers, we have successfully detected and identified Listeria monocytogenes lisA+ cells among Salmonella typhimurium, Staphylococcus aureus, Campylobacter jejuni and Escherichia coli O157:H7 cells. The simplicity of this protocol considerably reduces the time and cost of diagnostic PCR experiments. This procedure is potentially useful for various studies and field applications.

Evaluation of a human group a rotavirus assay for on-site detection of bovine rotavirus

Neonatal diarrhea induced by bovine group A rotavirus causes significant economic loss in the dairy and beef industry due to increased morbidity and mortality, treatment costs, and reduced growth rates. The objective of this study was to evaluate a human group A rotavirus assay (ImmunoCardSTAT Rotavirus [ICS-RV]) as an on-site diagnostic test for bovine rotavirus. When used with a collection of bovine diarrhea samples submitted to the Virology Section of the Diagnostic Center for Population and Animal Health at Michigan State University and compared to a bovine group A rotavirus-specific reverse transcription-PCR (RT-PCR), the ICS-RV assay had a sensitivity and specificity of 87.0 and 93.6%, respectively. A commercially available group A rotavirus enzyme-linked immunosorbent assay (ELISA) (Pathfinder; Sanofi Diagnostics, Redmond, Wash.), when used with the same fecal sample collection and compared to the same RT-PCR, had a sensitivity and specificity of 78.3 and 67.7%, respectively. Subsequently, the ICS-RV assay, RT-PCR, and a different commercially available group A rotavirus ELISA (Rotaclone; Meridian Diagnostics, Cincinnati, Ohio) were used to evaluate fecal samples collected from neonatal calves experimentally infected with bovine rotavirus. When diarrheic fecal samples that were positive for bovine rotavirus by RT-PCR were evaluated, the ICS-RV assay and the Rotaclone assay detected bovine rotavirus 85 and 95% of the time, respectively. Based on these studies, the ICS-RV assay appears to be an excellent test for detecting group A bovine rotaviruses. This assay may be useful as an on-site diagnostic test for veterinarians as an aid in the management of bovine neonatal diarrhea.

Development, evaluation, and application of lateral-flow immunoassay (immunochromatography) for detection of rotavirus in bovine fecal samples

A lateral-flow immunoassay (LFT) was developed to detect bovine rotavirus in fecal samples. Using samples (n = 74) from diarrheic calves, a comparison of the LFT with a commercial latex agglutination test (LAT) and transmission electron microscopy (EM) was conducted. When EM was used as the reference method, initial studies of 29 samples indicated 70 and 80% sensitivities of the LFT and LAT, respectively, with both being 100% specific. When the LAT was the reference test, the LFT was 75% sensitive and 91% specific. Additional specimens (n = 45) were tested by the LFT and LAT alone, and results were identical for both methods.