Location: Virus and Prion ResearchTitle: A comparison of classical and H-type bovine spongiform encephalopathy associated with E211K prion protein polymorphism in wild type and EK211 cattle following intracranial inoculation Author
Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2016
Publication Date: 9/15/2016
Citation: Moore, S.J., West Greenlee, M.H., Smith, J.D., Vrentas, C.E., Nicholson, E.M., Greenlee, J.J. 2016. A comparison of classical and H-type bovine spongiform encephalopathy associated with E211K prion protein polymorphism in wild type and EK211 cattle following intracranial inoculation. Frontiers in Veterinary Science. 3:78. Interpretive Summary: Cases of bovine spongiform encephalopathy (BSE) or mad cow disease can be subclassified into at least 3 distinct disease forms with the predominate form known as classical BSE and the others collectively referred to as atypical BSE. Atypical BSE can be further subdivided into H-type and L-type cases that are distinct from classical BSE and from each other. Both of the atypical BSE subtypes are believed to occur spontaneously, whereas classical BSE is spread through feeding contaminated meat and bone meal to cattle. Work by other research groups suggests that the stability of the distinguishing features of atypical BSE cases (phenotypical stability) can change to closely resemble classical BSE after experimental passage implicating atypical BSE as a possible origin of classical BSE. Interestingly, one case of H-type BSE in the US was associated with an inherited mutation in the prion protein gene referred to as E211K. The purpose of this work was to compare wild type and cattle with the E211K mutation after experimental inoculation with either classical BSE or H-BSE from the original E211K case. This study demonstrates that the disease features of E211K BSE-H remain stable when transmitted to cattle without the K211 polymorphism. In addition, passage of classical BSE to cattle with the K211 polymorphism results in disease with features consistent with classical BSE and not a switch to atypical BSE-H as a result of the K211 polymorphism. As the origin of classical, feedborne BSE remains unknown and low numbers of atypical BSE are diagnosed each year, parties with interest in the cattle and beef industries and regulatory officials responsible for safe feeding practices of cattle will be interested in this work.
Technical Abstract: In 2006, a case of H-type bovine spongiform encephalopathy (BSE-H) was diagnosed in a cow that was associated with a heritable polymorphism in the bovine prion protein gene (PRNP) resulting in a lysine for glutamine amino acid substitution at codon 211 (called E211K) of the prion protein. Although the prevalence of this polymorphism is low, cattle carrying the K211 allele may be predisposed to rapid onset of BSE-H when exposed or to the potential development of a genetic BSE. This study was conducted to better understand the relationship between the K211 polymorphism and its effect on BSE phenotype. BSE-H from the US 2006 case was inoculated intracranially (IC) in one PRNP wild type (EE211) calf and one EK211 calf. In addition, one wild type calf and one EK211 calf were inoculated IC with brain homogenate from a US 2003 classical BSE case. All cattle developed clinical disease. The survival times of the E211K BSE-H inoculated EK211 calf (10 months) was shorter than the wild type calf (18 months). This genotype effect was not observed in classical BSE inoculated cattle (both 26 months). Significant changes in retinal function were observed in H-type BSE challenged cattle only. Cattle challenged with the same inoculum showed similar severity and neuroanatomical distribution of vacuolation and disease-associated prion protein deposition in the brain, though differences in neuropathology were observed between E211K BSE-H and classical BSE inoculated animals. Western blot results for brain tissue from challenged animals were consistent with the inoculum strains. This study demonstrates that the phenotype of E211K BSE-H remains stable when transmitted to cattle without the K211 polymorphism, and exhibits a number of features that differ from classical BSE in both wild type and heterozygous EK211 animals.