Experimental Verification of a Traceback Phenomenon in Prion Infection
Posted Jan 23 2010 6:50pm
J. Virol. doi:10.1128/JVI.02387-09 Copyright (c) 2010, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.
Experimental Verification of a Traceback Phenomenon in Prion Infection
Atsushi Kobayashi, Nobuyuki Sakuma, Yuichi Matsuura, Shirou Mohri, Adriano Aguzzi, and Tetsuyuki Kitamoto* Division of CJD Science and Technology, Department of Prion Research, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan; Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, Japan; Institute of Neuropathology, University Hospital Zurich, CH-8002 Zurich, Switzerland
* To whom correspondence should be addressed. Email: email@example.com.
The clinicopathological phenotypes of sporadic Creutzfeldt-Jakob disease (sCJD) correlate with the allelotypes (M or V) of the polymorphic codon 129 of the human prion protein (PrP) gene and the electrophoretic mobility patterns of abnormal prion protein (PrPSc). Transmission of sCJD prions to mice expressing human PrP with a heterologous genotype (referred to as cross-sequence transmission) results in prolonged incubation periods. We previously reported that cross-sequence transmission can generate a new prion strain with unique transmissibility designated as a traceback phenomenon. To verify experimentally the traceback of sCJD-VV2 prions, we inoculated sCJD-VV2 prions into mice expressing human PrP with the 129M/M genotype. These 129M/M mice showed altered neuropathology and a novel PrPSc type after a long incubation period. We then passaged the brain homogenate from the 129M/M mouse inoculated with sCJD-VV2 prions into further 129M/M or 129V/V mice. Despite cross-sequence transmission, 129V/V mice were highly susceptible to these prions compared to the 129M/M mice. The neuropathology and PrPSc type of the 129V/V mice inoculated with the 129M/M mouse-passaged sCJD-VV2 prions were identical to those of the 129V/V mice inoculated with sCJD-VV2 prions. Moreover, we generated for the first time type 2 PrPSc-specific antibody in addition to type 1 PrPSc-specific antibody and discovered that drastic changes in the PrPSc subpopulation underlie the traceback phenomenon. Here we report the first direct evidence of the traceback in prion infection.
Source: Neuropathology, Volume 29, Number 5, October 2009 , pp. 619-624(6)
Publisher: Blackwell Publishing
The transmission of prions to animals with incongruent prion protein (PrP) gene (referred to as cross-sequence transmission) results in a relatively long incubation period and can generate a new prion strain with unique transmissibility designated as a traceback phenomenon. For example, cross-sequence transmission of bovine spongiform encephalopathy (BSE) prions to human generated variant Creutzfeldt-Jakob disease (vCJD) prions which retained the transmissibility to mice expressing bovine PrP. This finding suggests that traceback studies could enable us to identify the origin of prions. There are two distinct phenotypes in dura mater graft-associated Creutzfeldt-Jakob disease (dCJD), with the majority represented by a non-plaque-type of dCJD (np-dCJD) and the minority by a plaque-type of dCJD (p-dCJD). To identify the origin of p-dCJD, we performed a traceback study using mice expressing human PrP with methionine homozygosity (129M/M) or valine homozygosity (129V/V) at polymorphic codon 129. The characteristics of p-dCJD such as the accumulation of abnormal isoform of PrP (PrPSc) intermediate in size between type 1 and type 2, and plaque-type PrP deposition in the brain were maintained after transmission to the 129M/M mice. Furthermore, the 129V/V mice were more susceptible to p-dCJD prions than the 129M/M mice and produced type 2 PrPSc that were identical in size to those from the 129V/V mice inoculated with sporadic CJD prions from a patient with 129V/V and type 2 PrPSc (sCJD-VV2). In addition, we performed intracerebral transmission of sCJD-VV2 prions to the 129M/M mice as an experimental model for p-dCJD. These 129M/M mice showed the accumulation of the intermediate type PrPSc and plaque-type PrP deposition in the brain. These results suggest that p-dCJD could be caused by cross-sequence transmission of sCJD-VV2 prions to individuals with the 129M/M genotype. Keywords: Creutzfeldt-Jakob disease; polymorphism; prion protein; traceback; transmission
Document Type: Research article
Affiliations: 1: Division of CJD Science and Technology, Department of Prion Research, Tohoku University Graduate School of Medicine, Miyagi, and 2: Prion Disease Research Center, National Institute of Animal Health, Ibaraki, Japan
Cross-sequence Transmission of Sporadic Creutzfeldt-Jakob Disease Creates a New Prion Strain* Atsushi Kobayashi‡, Masahiro Asano‡, Shirou Mohri§ and Tetsuyuki Kitamoto‡1 + Author Affiliations
‡Division of CJD Science and Technology, Department of Prion Research, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan and §Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Ibaraki 305-0856, Japan 1 To whom correspondence should be addressed: Div. of CJD Science and Technology, Dept. of Prion Research, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai 980-8575, Japan. Tel.: 81-22-717-8143; Fax: 81-22-717-8148; E-mail: firstname.lastname@example.org.
Next Section Abstract The genotype (methionine or valine) at polymorphic codon 129 of the human prion protein (PrP) gene and the type (type 1 or type 2) of abnormal isoform of PrP (PrPSc) are major determinants of the clinicopathological phenotypes of sporadic Creutzfeldt-Jakob disease (sCJD). Here we found that the transmission of sCJD prions from a patient with valine homozygosity (129V/V) and type 2 PrPSc (sCJD-VV2 prions) to mice expressing human PrP with methionine homozygosity (129M/M) generated unusual PrPSc intermediate in size between type 1 and type 2. The intermediate type PrPSc was seen in all examined dura mater graft-associated CJD cases with 129M/M and plaque-type PrP deposits (p-dCJD). p-dCJD prions and sCJD-VV2 prions exhibited similar transmissibility and neuropathology, and the identical type of PrPSc when inoculated into PrP-humanized mice with 129M/M or 129V/V. These findings suggest that p-dCJD could be caused by cross-sequence transmission of sCJD-VV2 prions.
Besides p-dCJD, a few iatrogenic CJD cases with the 129M/M genotype and plaque-type PrP deposits in the brain have been reported in human growth hormone-related CJD (34, 35). The present results lead us to surmise that the human growth hormone-related CJD cases with 129M/M and plaque-type PrP deposits might be caused by the cross-sequence transmission of sCJD-VV2 prions.
Through cross-sequence transmission, sCJD-VV2 prions acquired new conformational properties as reflected by the upward shift of the size of PrPres. A similar shift of the PrPres size through cross-sequence transmission has been reported in mice inoculated with vCJD prions (29, 36) or hamster scrapie strain Sc237 (37, 38). Moreover, the altered size of mouse-passaged Sc237 PrPres reverts to those of hamster-passaged Sc237 PrPres through transmission to hamsters (37). In accordance with these findings, the intermediate type PrPres reverted to type 2 when MM[VV2]2Sh+ prions or p-dCJD prions were transmitted to the humanized mice with 129V/V in this study. The most plausible explanation for these findings is that adaptation to the new host PrPC and/or selection of a PrPSc subpopulation from the whole heterogeneous population result in the emergence of a new prion strain with altered conformational properties, and that the emerging prion strain retains the memory of the parental prions within its conformational properties and/or its PrPSc subpopulation. Therefore, if the emerging prion strain is transmitted to the original host, the parental prions may re-emerge and become dominant.
The above concept is supported by the “traceback” phenomenon (8), e.g. knock-in mice and transgenic mice expressing bovine PrP are highly susceptible to vCJD prions as well as bovine spongiform encephalopathy prions (8, 39). Consistent with a report using transgenic mice expressing human PrP with 129M or 129V (12), the humanized mice with 129V/V in our study were more susceptible to sCJD-VV2 prions than the humanized mice with 129M/M. Furthermore, the humanized mice with 129V/V showed high susceptibility to MM[VV2]2Sh+ prions and p-dCJD prions despite cross-sequence transmission. These phenomena can be explained as follows. Because MM[VV2]2Sh+ prions and p-dCJD prions retained the memory of the parental sCJD-VV2 prions, the humanized mice with 129V/V were highly susceptible to these prions as well as sCJD-VV2 prions. Our results demonstrate that traceback studies can be a powerful tool to identify the origin of prions.
In this study, the strain-dependent traits of sCJD-MM1 prions were inherited through cross-sequence transmission without any modification. The humanized mice with 129V/V produced type 1 PrPres after inoculation with sCJD-MM1 prions. Because sCJD-VV1 cases are extremely rare (at most 1–2% of the total number of sCJD cases) and characterized by early onset (mean age at onset, 39.3 years) (5), our results raise the possibility that CJD cases classified as VV1 may include cases caused by iatrogenic transmission of sCJD-MM1 prions or food-borne infection by type 1 prions from animals, e.g. chronic wasting disease prions in cervid. In fact, two CJD-VV1 patients who hunted deer or consumed venison have been reported (40, 41). The results of the present study emphasize the need for traceback studies and careful re-examination of the biochemical properties of sCJD-VV1 prions.
In conclusion, cross-sequence transmission of sCJD-VV2 prions generates a new prion strain with altered conformational properties and disease phenotypes as p-dCJD prions. Furthermore, the newly generated prions have unique transmissibility including the traceback phenomenon. In the future, if atypical prion strains emerge through cross-sequence transmission, especially from animals, traceback studies will enable us to identify the origin of the prions.
Since Gambetti's team wrote a paper describing an initial 11 cases referred to his centre between 2002 and 2006 (Annals of Neurology, vol 63, p 697), another five have come to light. "So it is possible that it could be just the tip of the iceberg," Gambetti says.
HUMAN and ANIMAL TSE Classifications i.e. mad cow disease and the UKBSEnvCJD only theory JUNE 2008
Tissue infectivity and strain typing of the many variants Manuscript of the human and animal TSEs are paramount in all variants of all TSE. There must be a proper classification that will differentiate between all these human TSE in order to do this. With the CDI and other more sensitive testing coming about, I only hope that my proposal will some day be taken seriously. ...
Elsevier Editorial System(tm) for The Lancet Infectious Diseases Manuscript Draft Manuscript Number: Title: HUMAN and ANIMAL TSE Classifications i.e. mad cow disease and the UKBSEnvCJD only theory Article Type: Personal View Corresponding Author: Mr. Terry S. Singeltary, Corresponding Author's Institution: na First Author: Terry S Singeltary, none Order of Authors: Terry S Singeltary, none; Terry S. Singeltary Abstract: TSEs have been rampant in the USA for decades in many species, and they all have been rendered and fed back to animals for human/animal consumption. I propose that the current diagnostic criteria for human TSEs only enhances and helps the spreading of human TSE from the continued belief of the UKBSEnvCJD only theory in 2007.