Short incubation periods of atypical H-BSE to cattle with EK211 and KK211 prion protein genotypes after intracranial inoculation

Authors: Cassmann, Eric; FREESE, LEXI - Oak Ridge Institute For Science And Education (ORISE); BECKY, KELSEY - Oak Ridge Institute For Science And Education (ORISE); Greenlee, Justin

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2023
Publication Date: 11/3/2023
Citation: Cassmann, E.D., Freese, L.J., Becky, K.A., Greenlee, J.J. 2023. Short incubation periods of atypical H-BSE to cattle with EK211 and KK211 prion protein genotypes after intracranial inoculation. Frontiers in Veterinary Science. https://doi.org/10.3389/fvets.2023.1301998.
DOI: https://doi.org/10.3389/fvets.2023.1301998

Interpretive Summary: Classical Bovine Spongiform Encephalopathy (C-BSE) is a prion disease of cattle that was responsible for the “mad cow disease” epizootic in Europe in the 1980’s. C-BSE was determined to be the cause of the human prion disease vCJD. Since the epizootic, atypical spontaneous strains of BSE were identified. H-BSE is one of those strains. Much research has explored the origins of C-BSE, and strain emergence from atypical H-BSE is one hypothesis. Furthermore, the identification of any positive BSE case elicits a significant effort by regulators to differentiate C-BSE from atypical BSE. In 2006, a H-BSE case was determined to have a germline mutation in the prion protein gene analogous to a hereditary human prion disease. The consequences of this germline mutation are still under investigation and subject of this research. We report the transmission of H-BSE from cattle with and without the germline prion protein mutation (E211K) to cattle with various prion genotypes: EE211 (wild-type), EK211, and KK211. The molecular phenotype was different in KK211 cattle when assessed by the western blot electrophoretic profile. We also described a significantly shorter incubation period in K211 cattle compared to prion wild-type cattle. Finally, we explored the possibility of C-BSE strain emergence after serial passages of H-BSE K211 in cattle; molecular phenotypes of experimental cattle did not provide evidence of C-BSE strain emergence in this model. In summary, H-BSE in wild-type prion genotype cattle was different than in cattle with the K211 prion genotype, but we did not uncover evidence of C-BSE strain emergence after multiple passages in H-BSE inoculated cattle. This information may be important to prion researchers, veterinary diagnostic laboratories, and those involved with establishing regulatory guidelines.

Technical Abstract: In 2006 a case of atypical H-type BSE (H-BSE) was associated with a germline mutation in the PRNP gene that resulted in a lysine substitution for glutamic acid (E) at codon 211 (E211K). The E211K polymorphism in cattle is analogous to E200K in humans that develop genetic Creutzfeldt-Jakob disease (CJD). In the present study, we aimed to determine the effect of the E211K polymorphism on the incubation time in cattle inoculated with the agent of H-BSE, characterize the molecular profile of H-BSE in KK211 and EK211 genotype cattle, and assess the influence of serial passage on BSE strain. Eight cattle, representing three PRNP genotype groups (EE211, EK211, and KK211), were intracranially inoculated with 0.1 gram of brain homogenate derived from either a E211K or EE211 prion protein genotype donor steer with H-BSE. The E211K H-BSE inoculum was derived from a field case (US2006) with the E211K polymorphism; the EE211 H-BSE inoculum was derived from a field case (US2004) in a wild-type bovid. All cattle developed clinical disease, post-mortem samples were collected, and prion disease was confirmed with enzyme immunoassay, anti-PrPSc immunohistochemistry, and western blot. Western blot molecular analysis was distinct in a steer with KK211 H-BSE compared to EK211 and EE211 cattle. Incubation periods were significantly shorter in cattle with EK211 and KK211 genotypes compared to EE211. The inoculum type did not significantly influence the incubation period of cattle. This study demonstrates a shorter incubation period of H-BSE in cattle with the K211 genotype in both the homozygous and heterozygous state.