Subject: cwd genetic susceptibility
Genetic susceptibility to chronic wasting disease in free-ranging white-tailed deer: Complement component C1q and Prnp polymorphisms§
Julie A. Blanchong a, *, Dennis M. Heisey b , Kim T. Scribner c , Scot V. Libants d , Chad Johnson e , Judd M. Aiken e , Julia A. Langenberg f , Michael D. Samuel g
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Identifying the genetic basis for heterogeneity in disease susceptibility or progression can improve our understanding of individual variation in disease susceptibility in both free-ranging and captive populations. What this individual variation in disease susceptibility means for the trajectory of disease in a population, however, is not straightforward. For example, the greater, but not complete, resistance to CWD in deer with at least one Serine (S) at amino acid 96 of the Prnp gene appears to be associated with slower progression of disease (e.g., Johnson et al., 2006; Keane et al., 2008a). If slower disease progression results in longer-lived, infected deer with longer periods of infectiousness, resistance may lead to increased disease transmission rates, higher prion concentrations in the environment, and increased prevalence, as has been observed in some captive deer herds (Miller et al., 2006; Keane et al., 2008a). Alternatively, if the slower progression of disease in resistant deer is not associated with longer periods of infectiousness, but might instead indicate a higher dose of PrPCWD is required for infection, transmission rates in the population could decline especially if, as in Wisconsin, deer suffer high rates of mortality from other sources (e.g., hunting). Clearly, determining the relationship between genetic susceptibility to infection, dose requirements, disease progression, and the period of PrPCWD infectiousness are key components for understanding the consequences of CWD to free-ranging populations.
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http://forest.wisc.edu/files/pdfs/samuel...c%20wasting.pdfhttp://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1083&context=nrem_pubshttp://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2017.4667/epdfhttp://www.tandfonline.com/doi/full/10.1080/19336896.2015.1115179https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4964855/pdf/kprn-09-06-1115179.pdfhttp://www.sciencedirect.com/science/article/pii/S1567134809001956?via%3Dihub
Prion protein gene sequence and chronic wasting disease susceptibility in white-tailed deer (Odocoileus virginianus)
Adam L Brandt,1 Amy C Kelly,1 Michelle L Green,1,2 Paul Shelton,3 Jan Novakofski,2,* and Nohra E Mateus-Pinilla1,2 Author information ► Article notes ► Copyright and License information ►
The sequence of the prion protein gene (PRNP) affects susceptibility to spongiform encephalopathies, or prion diseases in many species. In white-tailed deer, both coding and non-coding single nucleotide polymorphisms have been identified in this gene that correlate to chronic wasting disease (CWD) susceptibility. Previous studies examined individual nucleotide or amino acid mutations; here we examine all nucleotide polymorphisms and their combined effects on CWD. A 626 bp region of PRNP was examined from 703 free-ranging white-tailed deer. Deer were sampled between 2002 and 2010 by hunter harvest or government culling in Illinois and Wisconsin. Fourteen variable nucleotide positions were identified (4 new and 10 previously reported). We identified 68 diplotypes comprised of 24 predicted haplotypes, with the most common diplotype occurring in 123 individuals. Diplotypes that were found exclusively among positive or negative animals were rare, each occurring in less than 1% of the deer studied. Only one haplotype (C, odds ratio 0.240) and 2 diplotypes (AC and BC, odds ratios of 0.161 and 0.108 respectively) has significant associations with CWD resistance. Each contains mutations (one synonymous nucleotide 555C/T and one nonsynonymous nucleotide 286G/A) at positions reported to be significantly associated with reduced CWD susceptibility. Results suggest that deer populations with higher frequencies of haplotype C or diplotypes AC and BC might have a reduced risk for CWD infection – while populations with lower frequencies may have higher risk for infection. Understanding the genetic basis of CWD has improved our ability to assess herd susceptibility and direct management efforts within CWD infected areas.
KEYWORDS: CWD, diplotype, G96S, PRNP, prion, synonymous polymorphism, haplotype
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A solid understanding of the genetics of CWD in white-tailed deer is vital to improve management of CWD on the landscape. Most TSEs are found in domestic or captive animals where management of infected individuals is feasible. For example, scrapie infected flocks can be handled through a process generally involving genetic testing, removal and destruction of infected or suspect animals, followed by decontamination of facilities and equipment.55Containment of free ranging deer in wild populations potentially infected with CWD and decontamination of the environment is not reasonably possible. The long term effects of CWD are not yet known but it is conceivable that an unmanaged infected population would be gradually extirpated as the disease progresses56,57 or at least reduced to low densities with high disease prevalence.58,59 Either outcome would have severe ecological effects (e.g., deer play a major role in affecting plant communities60 and as a prey source61,62) as well as negative economic impacts to hunting. Overall disease prevalence has remained at relatively low levels in Illinois compared to Wisconsin.11 It is important to note that at the time of sampling, CWD had been found in 6 Illinois counties and has since been detected in 14.9Complete eradication of CWD among free ranging white-tailed deer may not be possible; however, an active containment effort in Illinois appears to have prevented significant increases in prevalence.9,11,12 Further examination of PRNP haplotype and diplotype frequencies across northern Illinois and southern Wisconsin in conjunction with population structure and movement45,63,64 will be useful in identifying localities with greater or reduced susceptibility risk. Effectiveness of CWD containment efforts can be aided through genetic testing and redirecting management resources.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4964855/***at present, no cervid PrP allele conferring absolute resistance to prion infection has been identified.
P-145 Estimating chronic wasting disease resistance in cervids using real time quaking- induced conversion
Nicholas J Haley1, Rachel Rielinqer2, Kristen A Davenport3, W. David Walter4, Katherine I O'Rourke5, Gordon Mitchell6, Juergen A Richt2 1 Department of Microbiology and Immunology, Midwestern University, United States; 2Department of Diagnostic Medicine and Pathobiology, Kansas State University; 3Prion Research Center; Colorado State University; 4U.S. Geological Survey, Pennsylvania Cooperative Fish and Wildlife Research Unit; 5Agricultural Research Service, United States Department of Agriculture; 6Canadian Food Inspection Agency, National and OlE Reference Laboratory for Scrapie and CWD
In mammalian species, the susceptibility to prion diseases is affected, in part, by the sequence of the host's prion protein (PrP). In sheep, a gradation from scrapie susceptible to resistant has been established both in vivo and in vitro based on the amino acids present at PrP positions 136, 154, and 171, which has led to global breeding programs to reduce the prevalence of scrapie in domestic sheep. In cervids, resistance is commonly characterized as a delayed progression of chronic wasting disease (CWD); at present, no cervid PrP allele conferring absolute resistance to prion infection has been identified. To model the susceptibility of various naturally-occurring and hypothetical cervid PrP alleles in vitro, we compared the amplification rates and efficiency of various CWD isolates in recombinant PrPC using real time quaking-induced conversion. We hypothesized that amplification metrics of these isolates in cervid PrP substrates would correlate to in vivo susceptibility - allowing susceptibility prediction for alleles found at 10 frequency in nature, and that there would be an additive effect of multiple resistant codons in hypothetical alleles. Our studies demonstrate that in vitro amplification metrics predict in vivo susceptibility, and that alleles with multiple codons, each influencing resistance independently, do not necessarily contribute additively to resistance. Importantly, we found that the white-tailed deer 226K substrate exhibited the slowest amplification rate among those evaluated, suggesting that further investigation of this allele and its resistance in vivo are warranted to determine if absolute resistance to CWD is possible.
***at present, no cervid PrP allele conferring absolute resistance to prion infection has been identified.
PRION 2016 CONFERENCE TOKYO
http://prion2016.org/dl/newsletter_03.pdf ''There are no known familial or genetic TSEs of animals, although polymorphisms in the PRNP gene of some species (sheep for example) may influence the length of the incubation period and occurrence of disease.''
c) The commonest form of CJD occurs as a sporadic disease, the cause of which is unknown, although genetic factors (particularly the codon 129 polymorphism in the prion protein gene (PRNP)) influence disease susceptibility. The familial forms of human TSEs (see Box 1) appear to have a solely genetic origin and are closely associated with mutations or insertions in the PRNP gene. Most, but not all, of the familial forms of human TSEs have been transmitted experimentally to animals. There are no known familial or genetic TSEs of animals, although polymorphisms in the PRNP gene of some species (sheep for example) may influence the length of the incubation period and occurrence of disease.
https://www.gov.uk/government/uploads/sy...ntroduction.pdfhttp://chronic-wasting-disease.blogspot.com/
