Comparative Immunology, Microbiology and Infectious Diseases
Persistence and chronic urinary shedding of the aphthovirus equine rhinitis A virus
Introduction
Equine rhinitis A virus (ERAV) is a respiratory pathogen of horses classified in the family Picornaviridae, genus Aphthovirus, alongside foot-and-mouth disease virus (FMDV) [1], a systemic pathogen of cloven hoofed animals. ERAV shares many pathogenic features with the prototype aphthovirus FMDV such as a respiratory infection, establishment of viraemia and persistent infection [1]. Furthermore, the key FMDV virulence factors, Lpro and 3Cpro share significant functional similarity to the homologue ERAV proteins [2]. Further investigation into the pathogenesis of ERAV may also highlight additional parallels between these two aphthoviruses, which has previously been described ERAV as a surrogate for FMDV, without the requirement for high-level biocontainment [3], [4], [5].
Sporadic outbreaks of acute febrile respiratory disease following ERAV infection have been reported [6], [7], [8], [9], [10], although, given the high seroprevalence of ERAV within the population, sub-clinical infections of ERAV are likely to be common [8], [11], [12]. It is difficult, however, to establish an estimate of the prevalence of disease caused by ERAV, due to difficulties associated with isolation and propagation of this non-cytopathic virus [7]. Furthermore, recent ERAV challenge studies using highly cell culture adapted virus inoculums have resulted in sub-clinical infections [13], in contrast to the acute febrile respiratory disease observed in the early challenge studies [14]. There has been limited investigation of the host, viral and other factors that may explain the disparate outcomes of experimental infection.
Early experimental challenge studies that documented viraemia and urinary shedding in guinea pigs and rabbits [15] suggested the progression of ERAV infection in a small animal model may be similar to that observed in the horse.
This study describes an investigation into the pathogenesis of ERAV both in the natural host and a small animal model alternative (CBA mice). Using these two models the pathogenesis of ERAV is compared to that of the prototype member, FMDV.
Section snippets
Cells
Viruses were propagated in primary equine foetal kidney (EFK) cells and Vero cells. Cell monolayers were grown in a base media of Dulbecco's minimal essential medium (DMEM, Sigma) containing 5 mM sodium bicarbonate, 10 mM HEPES and 50 μg/ml ampicillin. Uninfected cells were cultured in growth media containing 4 (Vero) or 10% (v/v) (EFK) foetal bovine serum (FBS). Virus was propagated in maintenance media containing 0.5% (v/v) FBS. Virus titrations and neutralisation assays were performed in assay
RT-qPCR sensitivity and specificity
A RT-qPCR assay was designed to target the non-structural internal ribosomal entry site (IRES) of ERAV. The assay was linear over 7 orders of magnitude extending 108–102 copies of in vitro transcribed RNA/RT-qPCR reaction and could detect 10–0.8 TCID50, of virus per reaction, which is 1000 times more virus than previously published assays [19]. The ERAV RT-qPCR assay was highly reproducible with a low inter-assay variation (0.40–2.5 cv% median 0.52) and low intra-assay variation (0.5–1.8 cv%
Discussion
ERAV has been classified as an aphthovirus alongside FMDV since 1996, and although several physical and structural features are conserved among these viruses [1], [2], [3], [4], [5], it is largely unknown whether these also translate into consistencies in pathogenesis. Furthermore the significance of ERAV as a pathogen and a cause of poor performance in horses may be underestimated in part, due to a lack of understanding of the dynamics of viral shedding following infection and sensitive
Acknowledgements
Project funding was from the Australian Research Council and Pfizer Animal Health. S.E.L was a recipient of an Australian Postgraduate Award (Industry) scholarship with Pfizer Animal Health as the industry partner. We thank Drs Gary Muscatello (The University of Sydney), Laura Fenell (The University of Melbourne), John Moody (CSL Ltd.) and Bob Geyer (The University of Melbourne) for assistance with animal experiments, and Nino Ficorilli and Cynthia Brown, Department of Veterinary Science, The
References (25)
- et al.
Equine rhinitis A virus-like particle expressing DNA vaccine induces a virus neutralising immune response in mice
Virus Research
(2011) - et al.
Osteopontin and skeletal muscle myoblasts: association with muscle regeneration and regulation of myoblast function in vitro
International Journal of Biochemistry and Cell Biology
(2008) Differential diagnosis of polyuria/polydipsia
- et al.
The pathogenesis and diagnosis of foot-and-mouth disease
Journal of Comparative Pathology
(2003) - et al.
Prevalence of serum neutralising antibody to equine rhinitis A virus (ERAV), equine rhinitis B virus 1 (ERBV1) and ERBV2
Veterinary Microbiology
(2007) - et al.
Equine rhinovirus 1 is more closely related to foot-and-mouth disease virus than to other picornaviruses
Proceedings of the National Academy of Sciences of the United States of America
(1996) - et al.
Conservation of L and 3C proteinase activities across distantly related aphthoviruses
Journal of General Virology
(2002) - et al.
The crystal structure of equine rhinitis A virus in complex with its sialic acid receptor
Journal of General Virology
(2010) - et al.
Cell entry of the aphthovirus equine rhinitis A virus is dependent on endosome acidification
Journal of Virology
(2010) - et al.
Equine rhinitis A virus and its low pH empty particle: clues towards an aphthovirus entry mechanism?
PLoS Pathogens
(2009)
Isolation and characterisation of an equine rhinovirus
Zentralblaat fur Veterinarmedizin Reihe B
Identification of noncytopathic equine rhinovirus 1 as a cause of acute febrile respiratory disease in horses
Journal of Clinical Microbiology
Cited by (17)
Use of Biologics in the Prevention of Infectious Diseases
2019, Large Animal Internal MedicineDiseases of the Respiratory System
2019, Large Animal Internal MedicineDisorders of the Respiratory System
2018, Equine Internal Medicine: Fourth EditionVeterinary Medicine, Eleventh Edition
2016, Veterinary Medicine, Eleventh EditionUpdate on viral diseases of the equine respiratory tract
2015, Veterinary Clinics of North America - Equine Practice