title: Lyssavirus infection: 'low dose, multiple exposure' in the mouse model.
abstract: The European bat lyssaviruses (EBLV-1 and EBLV-2) are zoonotic pathogens present within bat populations across Europe. The maintenance and transmission of lyssaviruses within bat colonies is poorly understood. Cases of repeated isolation of lyssaviruses from bat roosts have raised questions regarding the maintenance and intraspecies transmissibility of these viruses within colonies. Furthermore, the significance of seropositive bats in colonies remains unclear. Due to the protected nature of European bat species, and hence restrictions to working with the natural host for lyssaviruses, this study analysed the outcome following repeat inoculation of low doses of lyssaviruses in a murine model. A standardized dose of virus, EBLV-1, EBLV-2 or a 'street strain' of rabies (RABV), was administered via a peripheral route to attempt to mimic what is hypothesized as natural infection. Each mouse (n=10/virus/group/dilution) received four inoculations, two doses in each footpad over a period of four months, alternating footpad with each inoculation. Mice were tail bled between inoculations to evaluate antibody responses to infection. Mice succumbed to infection after each inoculation with 26.6% of mice developing clinical disease following the initial exposure across all dilutions (RABV, 32.5% (n=13/40); EBLV-1, 35% (n=13/40); EBLV-2, 12.5% (n=5/40)). Interestingly, the lowest dose caused clinical disease in some mice upon first exposure ((RABV, 20% (n=2/10) after first inoculation; RABV, 12.5% (n=1/8) after second inoculation; EBLV-2, 10% (n=1/10) after primary inoculation). Furthermore, five mice developed clinical disease following the second exposure to live virus (RABV, n=1; EBLV-1, n=1; EBLV-2, n=3) although histopathological examination indicated that the primary inoculation was the most probably cause of death due to levels of inflammation and virus antigen distribution observed. All the remaining mice (RABV, n=26; EBLV-1, n=26; EBLV-2, n=29) survived the tertiary and quaternary inoculations although the serological response did not necessarily reflect the repeated exposure. We conclude that despite repeated exposure, neither clinical disease nor serological response can be predicted and that further studies are required to understand the mechanisms behind survival following multiple exposures to lyssaviruses.
authors.affiliation: Wildlife Zoonoses and Vector Borne Diseases Research Group, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom. Electronic address: ashley.banyard@ahvla.gsi.gov.uk.
authors.forename: Ashley C
authors.initials: AC
authors.lastname: Banyard
authors.affiliation: Wildlife Zoonoses and Vector Borne Diseases Research Group, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Derek M
authors.initials: DM
authors.lastname: Healy
authors.affiliation: Wildlife Zoonoses and Vector Borne Diseases Research Group, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Brookes
authors.affiliation: Wildlife Zoonoses and Vector Borne Diseases Research Group, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Katja
authors.initials: K
authors.lastname: Voller
authors.affiliation: Pathology Unit, Department of Specialist Scientific Support, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Hicks
authors.affiliation: Pathology Unit, Department of Specialist Scientific Support, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Núñez
authors.affiliation: Wildlife Zoonoses and Vector Borne Diseases Research Group, Animal Health and Veterinary Laboratories Agency, Woodham Lane, New Haw, Surrey KT15 3NB, United Kingdom; Department of Clinical Infections, University of Liverpool, Microbiology and Immunology, United Kingdom.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Fooks
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology / Q000821:virology; D002685:Chiroptera / Q000821:virology; D004195:Disease Models, Animal; D005260:Female; D018114:Lyssavirus / Q000302:isolation & purification / Q000502:physiology*; D051379:Mice; D018353:Rhabdoviridae Infections / Q000401:mortality / Q000473:pathology / Q000821:virology*; D014779:Virus Replication
keywords: Exposure; Lyssavirus; Mouse; Pathogenicity; Rabies; Virus