Antibody response in vaccinated pregnant mares to recent G3BP[12] and G14P[12] equine rotaviruses

Genetic and antigenic characterization of two diarrhoeicdominant rotavirus A genotypes G3P[12] and G14P[12] circulating in the global equine population

Equine rotavirus species A (ERVA) G3P[12] and G14P[12] are two dominant genotypes that cause foal diarrhoea with a significant economic impact on the global equine industry. ERVA can also serve as a source of novel (equine-like) rotavirus species A (RVA) reassortants with zoonotic potential as those identified previously in 2013-2019 when equine G3-like RVA was responsible for worldwide outbreaks of severe gastroenteritis and hospitalizations in children. One hurdle to ERVA research is that the standard cell culture system optimized for human rotavirus replication is not efficient for isolating ERVA. Here, using an engineered cell line defective in antiviral innate immunity, we showed that both equine G3P[12] and G14P[12] strains can be rapidly isolated from diarrhoeic foals. The genome sequence analysis revealed that both G3P[12] and G14P[12] strains share the identical genotypic constellation except for VP7 and VP6 segments in which G3P[12] possessed VP7 of genotype G3 and VP6 of genotype I6 and G14P[12] had the combination of VP7 of genotype G14 and VP6 of genotype I2. Further characterization demonstrated that two ERVA genotypes have a limited cross-neutralization. The lack of an in vitro broad cross-protection between both genotypes supported the increased recent diarrhoea outbreaks due to equine G14P[12] in foals born to dams immunized with the inactivated monovalent equine G3P[12] vaccine. Finally, using the structural modelling approach, we provided the genetic basis of the antigenic divergence between ERVA G3P[12] and G14P[12] strains. The results of this study will provide a framework for further investigation of infection biology, pathogenesis and cross-protection of equine rotaviruses.

Equine Rotavirus A under the One Health Lens: Potential Impacts on Public Health

Group A rotaviruses are a well-known cause of viral gastroenteritis in infants and children, as well as in many mammalian species and birds, affecting them at a young age. This group of viruses has a double-stranded, segmented RNA genome with high genetic diversity linked to point mutations, recombination, and, importantly, reassortment. While initial molecular investigations undertaken in the 1900s suggested host range restriction among group A rotaviruses based on the fact that different gene segments were distributed among different animal species, recent molecular surveillance and genome constellation genotyping studies conducted by the Rotavirus Classification Working Group (RCWG) have shown that animal rotaviruses serve as a source of diversification of human rotavirus A, highlighting their zoonotic potential. Rotaviruses occurring in various animal species have been linked with contributing genetic material to human rotaviruses, including horses, with the most recent identification of equine-like G3 rotavirus A infecting children. The goal of this article is to review relevant information related to rotavirus structure/genomic organization, epidemiology (with a focus on human and equine rotavirus A), evolution, inter-species transmission, and the potential zoonotic role of equine and other animal rotaviruses. Diagnostics, surveillance and the current status of human and livestock vaccines against RVA are also reviewed.

Quadruplex Real-Time TaqMan® RT-qPCR Assay for Differentiation of Equine Group A and B Rotaviruses and Identification of Group A G3 and G14 Genotypes

Equine rotavirus A (ERVA) is the leading cause of diarrhea in foals, with G3P[12] and G14P[12] genotypes being the most prevalent. Recently, equine G3-like RVA was recognized as an emerging infection in children, and a group B equine rotavirus (ERVB) was identified as an emergent cause of foal diarrhea in the US. Thus, there is a need to adapt molecular diagnostic tools for improved detection and surveillance to identify emerging strains, understand their molecular epidemiology, and inform future vaccine development. We developed a quadruplex TaqMan® RT-qPCR assay for differentiation of ERVA and ERVB and simultaneous G-typing of ERVA strains, evaluated its analytical and clinical performance, and compared it to (1) a previously established ERVA triplex RT-qPCR assay and (2) standard RT-PCR assay and Sanger sequencing of PCR products. This quadruplex RT-qPCR assay demonstrated high sensitivity (>90%)/specificity (100%) for every target and high overall agreement (>96%). Comparison between the triplex and quadruplex assays revealed only a slightly higher sensitivity for the ERVA NSP3 target using the triplex format (p-value 0.008) while no significant differences were detected for other targets. This quadruplex RT-qPCR assay will significantly enhance rapid surveillance of both ERVA and ERVB circulating and emerging strains with potential for interspecies transmission.

Equine rotavirus infection

This review briefly describes the virus classification, clinical signs, epidemiology, diagnosis, disinfection, and vaccines related equine group A rotavirus (RVA) infection. Equine RVA is one of the most important pathogens causing diarrhoea in foals. The main transmission route is faecal–oral, and the clinical signs are diarrhoea, fever, lethargy, and anorexia (decreased suckling). Some human RVA rapid antigen detection kits based on the principles of the immunochromatographic assay are useful for the diagnosis of equine RVA infection. The kits are used in daily clinical practice because of their rapidity and ease of handling. Equine RVA is a non-enveloped virus and is more resistant to disinfectants than enveloped viruses such as equine influenza virus and equine herpesvirus. Although amphoteric soaps and quaternary ammonium compounds are commonly used in veterinary hygiene, they are generally ineffective against equine RVA. Alcohol products, aldehydes, and chlorine- and iodine-based compounds are effective against equine RVA. Inactivated vaccines have been used for equine RVA infection in some countries. Pregnant mares are intramuscularly inoculated with a vaccine, and thus their colostrum has abundant antibodies against RVA at the time of birth. According to G and P classification defined in accordance with the VP7 and VP4 genes, respectively, the predominant equine RVAs circulating in horse populations globally are G3P[12] and G14P[12] equine RVAs, but the vaccines contain only the G3P[12] equine RVA strain. Ideally, a G14P[12] equine RVA should be added as a vaccine strain to obtain a better vaccine effect.

Development and evaluation of a one-step multiplex real-time TaqMan® RT-qPCR assay for the detection and genotyping of equine G3 and G14 rotaviruses in fecal samples

BACKGROUND

Equine rotavirus A (ERVA) is the leading cause of diarrhea in neonatal foals and has a negative impact on equine breeding enterprises worldwide. Among ERVA strains infecting foals, the genotypes G3P[12] and G14P[12] are the most prevalent, while infections by strains with other genomic arrangements are infrequent. The identification of circulating strains of ERVA is critical for diagnostic and surveillance purposes, as well as to understand their molecular epidemiology. Current genotyping methods available for ERVA and rotaviruses affecting other animal species rely on Sanger sequencing and are significantly time-consuming, costly and labor intensive. Here, we developed the first one-step multiplex TaqMan® real-time reverse transcription polymerase chain reaction (RT-qPCR) assay targeting the NSP3 and VP7 genes of ERVA G3 and G14 genotypes for the rapid detection and G-typing directly from fecal specimens.

METHODS

A one-step multiplex TaqMan® RT-qPCR assay targeting the NSP3 and VP7 genes of ERVA G3 and G14 genotypes was designed. The analytical sensitivity was assessed using serial dilutions of in vitro transcribed RNA containing the target sequences while the analytical specificity was determined using RNA and DNA derived from a panel of group A rotaviruses along with other equine viruses and bacteria. The clinical performance of this multiplex assay was evaluated using a panel of 177 fecal samples and compared to a VP7-specific standard RT-PCR assay and Sanger sequencing. Limits of detection (LOD), sensitivity, specificity, and agreement were determined.

RESULTS

The multiplex G3 and G14 VP7 assays demonstrated high specificity and efficiency, with perfect linearity. A 100-fold difference in their analytical sensitivity was observed when compared to the singleplex assays; however, this difference did not have an impact on the clinical performance. Clinical performance of the multiplex RT-qPCR assay demonstrated that this assay had a high sensitivity/specificity for every target (100% for NSP3, > 90% for G3 VP7 and > 99% for G14 VP7, respectively) and high overall agreement (> 98%) compared to conventional RT-PCR and sequencing.

CONCLUSIONS

This new multiplex RT-qPCR assay constitutes a useful, very reliable tool that could significantly aid in the rapid detection and G-typing of ERVA strains circulating in the field.

Evaluation of inactivated vaccines against equine group A rotaviruses by use of a suckling mouse model

BACKGROUND

Equine group A rotaviruses (RVAs) cause diarrhea in suckling foals. The dominant RVAs circulating among horses worldwide, including Japan, are G3P[12] and/or G14P[12] genotypes. Inactivated vaccines containing a G3P[12] RVA are commercially available in some countries for prevention of diarrhea caused by equine RVAs. However, there is no reported evidence whether vaccines containing a G3P[12] RVA are effective against G14P[12] RVAs or whether using a G14P[12] RVA results in a more effective vaccine. This study used a suckling mouse model to evaluate the effectiveness of inactivated vaccines containing G3P[12] (G3 vaccine) or G14P[12] (G14 vaccine) RVAs against G3P[12] and G14P[12] RVAs.

METHODS

Female mice were inoculated twice with G3 or G14 vaccines, and were then mated. After parturition, suckling mice were challenged with one of either two G3P[12] RVAs, two G14P[12] RVAs, or one G13P[18] RVA. After virus inoculation, suckling mice were observed for diarrhea, and the incidence rates of diarrhea in the vaccinated groups were compared with those in the non-vaccinated groups.

RESULTS

Following G3P[12] RVA challenge, suckling mice in the G3 and G14 vaccinated groups had significantly lower rates of diarrhea incidence than did those in the non-vaccinated group, and the rates in the G3 vaccinated group tended to be lower than in the G14 vaccinated group. Following G14P[12] RVA challenge, suckling mice in the G14 vaccinated group had significantly lower rates of diarrhea incidence than did those in the non-vaccinated and G3 vaccinated groups. The G3 and G14 vaccines did not reduce the rate when challenged with the G13P[18] RVA.

CONCLUSION

The mouse model showed that the G3 and G14 vaccines were both effective against G3P[12] RVAs, and that the G14 vaccine was effective against G14P[12] RVAs. These results suggest that at least a G14 RVA strain should be included in as a vaccine strain.

Detection, molecular characterization and phylogenetic analysis of G3P[12] and G14P[12] equine rotavirus strains co-circulating in central Kentucky

Equine rotavirus A (ERVA) is the leading cause of diarrhea in neonatal foals and a major health problem to the equine breeding industry worldwide. The G3P[12] and G14P[12] ERVA genotypes are the most prevalent in foals with diarrhea. Control and prevention strategies include vaccination of pregnant mares with an inactivated vaccine containing a prototype ERVA G3P[12] strain with limited and controversial field efficacy. Here, we performed the molecular characterization of ERVA strains circulating in central Kentucky using fecal samples collected during the 2017 foaling season. The data indicated for the first time that the G14P[12] genotype is predominant in this region in contrast to a previous serotyping study where only G3 genotype strains were reported. Overall, analysis of antigenic sites in the VP7 protein demonstrated the presence of several amino acid substitutions in the epitopes exposed on the surface including a non-conserved N-linked glycosylation site (D123N) in G14P[12] strains, while changes in antigenic sites of VP8* were minor. Also, we report the successful isolation of three ERVA G14P[12] strains which presented a high identity with other G14 strains from around the world. These may constitute ideal reference strains to comparatively study the molecular biology of G3 and G14 strains and perform vaccine efficacy studies following heterologous challenge in the future.

Molecular characterization of equine rotaviruses isolated in Europe in 2013: implications for vaccination

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Diarrhea samples from 65 foals were collected in Europe and screened for rotavirus.

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From 26 qPCR positive stool samples, 11 could be (partially) genotyped.

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In addition to the common G3/G14P[12] strains, the rare P[18] genotype was detected.

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A vaccine based on an inactivated G3P[12] genotype is still relevant in Europe.

Equine group A rotavirus (RVAs) mainly cause disease in foals under the age of 3 months. Only sporadic data are available on the circulation of RVAs in equine populations in Europe. In this study, 65 diarrheic samples from foals under 4 months of age were collected in Belgium (n = 32), Germany (n = 17), Slovenia (n = 5), Sweden (n = 4), Hungary (n = 3), Italy (n = 2), France (n = 1) and The Netherlands (n = 1). Forty percent of these samples (n = 26) were found to be RVA positive by a quantitative RT-PCR assay. The viral load in 11 of these samples was sufficiently high to be (partially) genotyped. G3, G14 and P[12] were the main genotypes detected, and phylogenetic analyses revealed that they were closely related to contemporary equine RVA strains detected in Europe as well as in Brazil and South Africa. Regional variation was observed with only G14 and P[12] being detected in Germany, whereas mainly G3P[12] was encountered in Belgium. Surprisingly the only G14P[12] RVA strain detected in Belgium was also found to possess the very rare P[18] genotype, which has been described only once from equine RVA strain L338 detected in the UK in 1991. Despite the identification of this uncommon P[18] genotype, G3P[12] and G14P[12] RVA strains remained the most important genotypes in Europe during the study period. Based on this finding and the knowledge that G3P[12] and G14P[12] serotypes are partially cross-reactive it can be assumed that a vaccine based on an inactivated virus of the G3P[12] genotype is still relevant in the current European epidemiological situation, although the addition of a G14 strain would most likely be beneficial.

Virucidal effect of commercially available disinfectants on equine group A rotavirus

Although many disinfectants are commercially available in the veterinary field, information on the virucidal effects of disinfectants against equine group A rotavirus (RVA) is limited. We evaluated the performance of commercially available disinfectants against equine RVA. Chlorine- and iodine-based disinfectants showed virucidal effects, but these were reduced by the presence of organic matter. Glutaraldehyde had a virucidal effect regardless of the presence of organic matter, but the effect was reduced by low temperature or short reaction time, or both. Benzalkonium chloride had the greatest virucidal effect among the three quaternary ammonium compounds examined, but its effect was reduced by the presence of organic matter or by low temperature or a short reaction time. These findings will be useful for preventing the spread of equine RVA infection.

Global distribution of group A rotavirus strains in horses: a systematic review

Group A rotavirus (RVA) is a major cause of diarrhea and diarrhea-related mortality in foals in parts of the world. In addition to careful horse farm management, vaccination is the only known alternative to reduce the RVA associated disease burden on horse farms. The precise evaluation of vaccine effectiveness against circulating strains needs enhanced surveillance of equine RVAs in areas where vaccine is already available or vaccine introduction is anticipated. Therefore, we undertook the overview of relevant information on epidemiology of equine RVA strains through systematic search of public literature databases. Our findings indicated that over 99% of equine RVA strains characterized during the past three decades belonged to two common genotypes, G3P[12] and G14P[12], whereas most of the minority equine RVA strains were probably introduced from a heterologous host by interspecies transmission. These baseline data on RVA strains in horses shall contribute to a better understanding of the spatiotemporal dynamics of strain prevalence in vaccinated and non-vaccinated herds.

Whole genomic analyses of equine group A rotaviruses from Japan: evidence for bovine-to-equine interspecies transmission and reassortment events

Equine group A rotaviruses (RVA) are a major cause of severe diarrhea in foals. The whole genomes of only six common and three unusual equine RVA strains have been analyzed so far. To date, there are no reports on whole genomic analyses of equine RVAs from Asian countries. We report here the whole genomic analyses of three common (strains RVA/Horse-tc/JPN/BI/1981/G3P[12], RVA/Horse-tc/JPN/HH-22/1989/G3P[12] and RVA/Horse-tc/JPN/CH-3/1987/G14P[12]) and an unusual (RVA/Horse-tc/JPN/OH-4/1982/G6P[5]) equine RVA strains isolated from diarrheic foals in Japan. Strains BI, HH-22 and CH-3 shared a largely conserved genotype constellation (G3/G14-P[12]-I2/I6-R2-C2-M3-A10-N2-T3-E2-H7) with each other and with those of common equine RVAs from other continents. Phylogenetically, most of the genes of BI, HH-22 and CH-3 were closely related to those of other common equine RVAs. On the other hand, the NSP2 genes of BI and CH-3 formed a distinct lineage, and were distantly related to the other, major equine RVA cluster within the NSP2-N2 genotype. The NSP4 gene of HH-22 appeared to originate from possible reassortment events involving common equine RVAs and co-circulating bovine or bovine-like equine RVAs, revealing the presence of a bovine RVA-like NSP4 gene on a typical equine RVA genetic backbone. All the 11 gene segments of the unusual equine RVA strain OH-4 were found to be more closely related to those of bovine and bovine-like human RVAs than to those of other RVAs, providing the first conclusive evidence for artiodactyl(likely bovine)-to-equine interspecies transmission events. Taken together, these observations provided important insights into the genetic diversity of equine RVAs.

Equine rotaviruses--current understanding and continuing challenges

Equine rotaviruses were first detected in foals over 30 years ago and remain a major cause of infectious diarrhoea in foals. During this time, there has been substantial progress in the development of sensitive methods to detect rotaviruses in foals, enabling surveillance of the genotypes present in various horse populations. However, there has been limited epidemiological investigation into the significance of these circulating genotypes, their correlation with disease and the use of vaccination in these animal populations. Our knowledge of the pathogenesis of rotavirus infection in foals is based on a limited number of studies on a small number of foals and, therefore, most of our understanding in this area has been extrapolated from studies in other species. Questions such as the concentrations of rotavirus particles shed in the faeces of infected foals, both with and without diarrhoea, and factors determining the presence or absence of clinical disease remain to be investigated, as does the relative and absolute efficacy of currently available vaccines. The answer to these questions may help direct research into the development of more effective control measures.