Alteration of the Chronic Wasting Disease Species Barrier byIn VitroPrion Amplification

Abstract

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy (TSE) of cervids now detected in 19 states of the United States, three Canadian provinces, and South Korea. Whether noncervid species can be infected by CWD and thereby serve as reservoirs for the infection is not known. To investigate this issue, we previously used serial protein misfolding cyclic amplification (sPMCA) to demonstrate that CWD prions can amplify in brain homogenates from several species sympatric with cervids, including prairie voles (Microtus ochrogaster) and field mice (Peromyscus spp.). Here, we show that prairie voles are susceptible to mule deer CWD prions in vivo and that sPMCA amplification of CWD prions in vole brain enhances the infectivity of CWD for this species. Prairie voles inoculated with sPMCA products developed clinical signs of TSE disease approximately 300 days prior to, and more consistently than, those inoculated with CWD prions from deer brain. Moreover, the deposition patterns and biochemical properties of protease-resistant form of PrP (PrP RES ) in the brains of affected voles differed from those in cervidized transgenic (CerPrP) mice infected with CWD. In addition, voles inoculated orally with sPMCA products developed clinical signs of TSE and were positive for PrP RES deposition, whereas those inoculated orally with deer-origin CWD prions did not. These results demonstrate that transspecies sPMCA of CWD prions can enhance the infectivity and adapt the host range of CWD prions and thereby may be useful to assess determinants of prion species barriers.Chronic wasting disease (CWD) is a fatal transmissible spongiform encephalopathy (TSE) of cervids, including deer, elk, and moose. CWD is the only TSE found in free-ranging wildlife; its spread in nature may reflect the dissemination of prions from saliva and excreta of infected cervids (10,20,22,28,36) and/or the persistence of infectious prions in the environment (15,23,30). While the known natural host range for CWD is limited to cervids, recent studies have expanded the number of noncervid species (ferrets, mink, hamsters, cattle, sheep, Peromyscus spp. mice, and voles) that can be infected experimentally (3, 11-14, 26, 32). It is not known whether noncervid species may contribute to the spread of CWD as reservoirs or vectors; however, interspecies transmission of prion diseases (e.g., from deer to noncervids) is less efficient than intraspecies transmission, a phenomenon commonly referred to as a species barrier. Species barriers may be mediated by differences in cellular PrP (PrP C ) sequence (5, 13, 16), inoculum titer, route of inoculation, and other still unknown factors (4,13,16,24,25).We recently demonstrated (18) that PrP C from several noncervid species, including prairie voles (Microtus ochrogaster) and prairie deer mice (Peromyscus maniculatus bairdii), can be converted to the protease-resistant form of PrP (PrP RES ) in vitro by serial protein misfolding cyclic amplification (sPMCA). Heisey et al. (14) have since shown that other vol...

Cross-species transmission of CWD prions

“…[22][23][24] However, intracerebral CWD inoculation caused prion infection in voles, hamsters, ferrets, sheep, cats, mink, and cattle, with variable attack rates. [25][26][27][28][29][30][31][32][33] Wild type mice and raccoons resisted CWD prion infection (Table 1). 16,34,35 An extensive study of CWD susceptibility in transgenic mice expressing ovine and bovine PrP C revealed no mice with prion disease, supporting the strong barrier to CWD infection observed in sheep and cattle.…”

Scientific Opinion on a request for a review of a scientific publication concerning the zoonotic potential of ovine scrapie prions

“…This effect has been shown with CWD in ferrets (Kurt et al, 2007) and prairie voles (Kurt et al, 2011), RML (a laboratory scrapie strain) in cervid transgenic mice (Green et al, 2008), mouse scrapie in hamster (Castilla et al, 2008b), and feline spongiform encephalopathy (FSE) in bovine transgenic mice (Eiden et al, 2010). Even PrP c from dog and rabbit, species which are not susceptible to TSE under natural conditions, could be converted by using scrapie (rabbit, Chianini et al, 2012) or BSE prions as seed (rabbit and dog, Vidal et al, 2013b).…”

“… Serial PMCA amplification of CWD prions in vole brain substrate enhanced not only their infectivity for voles in vivo, but also showed a biochemical pattern different from voles infected with deer CWD (Kurt et al, 2011).…”

“…Several authors have described an adaptation of the amplified PrP Sc to the new host, a process which normally requires several subpassages in animals (Castilla et al, 2008b;Green et al, 2008;Meyerett et al, 2008;Barria et al, 2011;Kurt et al, 2011). In these experiments novel prion strains arose with distinct biochemical and biological properties, even with altered species barriers:…”

PrPSc-specific antibodies do not induce prion disease or misfolding of PrPCin highly susceptible Tga20 mice

“…20 These observations agree with relatively stringent constraints on successful template-directed misfolding across species in vivo. However, serial PMCA assays or the products of these assays are able to more readily surmount species barriers, 21,22 and different prion strains vary in their cross-species transmissibility, 23 suggesting that the minimum requirements for template directed misfolding can be less stringent. Furthermore, the recent finding that lymphoid tissues are more permissive to replication of CWD prions than brain, 24 suggests that the safety of any immunotherapy approach should be carefully considered.…”