Abstract
Chronic wasting disease (CWD) is the most contagious prion disease. It is expanding rapidly in North America, was found recently in Europe, and the potential for transmission to humans cannot be excluded yet. We hypothesized that it is possible to prevent peripheral CWD infection and CWD prion shedding by inducing auto-antibodies against the cellular prion protein (PrPC) by active vaccination. Our objective is to overcome self-tolerance against PrP by using a multimeric recombinant PrP (recPrP) as an immunogen. We expressed in E. coli, purified and refolded four immunogens: cervid and murine recPrP in monomeric and dimeric form. Testing immunogenicity in sera of the vaccinated transgenic mice expressing cervid PrP revealed that all four immunogens effectively overcame self-tolerance against the prion protein as shown by high antibody titers. Confocal microscopy analysis revealed effective binding of post-immune sera to surface-located PrPC in both murine and cervid PrP expressing cultured cells. Remarkably, the post-immune auto-antibodies effectively inhibited CWD-induced prion conversion in RT-QuIC assay when incubated with either PrP substrate or CWD seed. Furthermore, they mitigated prion propagation in CWD-infected cervid-PrP expressing RK13 cells. Together, multimeric recombinant cervid PrP effectively overcomes self-tolerance to PrP and induces auto-antibodies that interfere with CWD conversion in vitro.
Highlights
Chronic wasting disease (CWD) is a rapidly expanding fatal transmissible spongiform encephalopathy (TSE) or prion disease affecting free-ranging and captive cervids
Coomassie staining of SDSPAGE showed that the yield of monomeric immunogens (Dmo and mice vaccinated with mouse (Mmo)) was greater than that of dimeric ones (Ddi and mouse dimer (Mdi)), all immunogens were of high purity (Fig. 1b)
We found that CpG was a better adjuvant for deer dimer (Ddi) recombinant PrP substrate (rPrP) than alum, with no differences for deer monomer (Dmo) rPrP (Fig. 1e)
Summary
Chronic wasting disease (CWD) is a rapidly expanding fatal transmissible spongiform encephalopathy (TSE) or prion disease affecting free-ranging and captive cervids (deer, elk and moose). There is a solid body of evidence that passive and active immunization has the potential to block prion propagation in murine-adapted scrapie in vivo models[8,9,10,11,12]. One study used a synthetic peptide vaccine approach and did not show any success in protection of mule deer against CWD15. Deer were immunized orally with an attenuated Salmonella typhimurium vector vaccine expressing cervid PrP. This study provides a solid proof-of-concept that active vaccination has the potential to interfere in CWD infection. Having a solid proof-of-concept for our self-vaccination approach in wild-type mice, led us to test whether multimeric cervid PrP can be used for active vaccination against CWD in a transgenic mouse model susceptible to CWD prions
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