Downloaded from www.microbiologyresearch.org by IP: 54.226.47.109 On: Tue, 18 Jul 2017 17:08:52 Short Communication Cell-surface expression of PrP C and the presence of scrapie prions in the blood of goats Rohana P. Dassanayake, 1 David A. Schneider, 2 Lynn M. Herrmann-Hoesing, 2 Thomas C. Truscott, 2 William C. Davis 1 and Katherine I. O’Rourke 1,2 Correspondence Rohana P. Dassanayake rohana1@vetmed.wsu.edu Received 21 October 2011 Accepted 20 January 2012 1 Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA 2 Animal Disease Research Unit, Agricultural Research Service, US Department of Agriculture, Pullman, WA 99164-6630, USA Although host-encoded prion protein (PrP C ) expression in ovine PBMCs and prion infectivity in scrapie-infected sheep blood have been demonstrated, such studies have not been reported in goats. Therefore, this study characterized cell-surface expression of PrP C on PBMC subsets derived from normal goats and sheep, by flow cytometry, and determined prion infectivity in blood from a scrapie-infected goat using a transfusion bioassay in goat kids. Cell-surface PrP C expression was detected on all subsets of goat PBMCs. The highest PrP C cell-surface expression was found in CD2 + T lymphocytes in goats. Transmission of infection was detected in all three recipients who received whole blood from a goat with classical scrapie. It was concluded that caprine PBMCs express PrP C similarly to sheep but with relative differences among PBMCs subsets, and that blood-borne infectious prions can be detected in scrapie-infected goats. Thus, similar to sheep, goat blood may be a suitable diagnostic target for the detection of scrapie infection. Prion diseases, or transmissible spongiform encephalopa- thies, are unique fatal neurodegenerative disorders that affect a number of different species including goats and sheep (scrapie), cattle (bovine spongiform encephalopathy, BSE), deer, elk and moose (chronic wasting disease), humans (Creutzfeldt–Jakob disease) and mink (transmis- sible mink encephalopathy). The infectious agent is largely proteinaceous and consists primarily of a conformational isoform (PrP Sc ) of the host-encoded prion protein PrP C (Prusiner, 1982). A characteristic feature of transmissible spongiform encephalopathies is the accumulation of PrP Sc in the central nervous system (Bolton et al., 1982). In goats and sheep with classical scrapie disease, PrP Sc also accumulates in the lymphoreticular system (Valdez et al., 2003; van Keulen et al., 1996). Detection of PrP Sc in brain and lymphoid tissues by immunoassay has been a reliable diagnostic marker for prion disease. Accumulation of PrP Sc in host tissues requires cellular expression of PrP C (Bu ¨eler et al., 1993). PrP C is a glycosyl- phosphatidylinositol-anchored protein attached predomi- nantly on the extracellular surface of the plasma membrane (Stahl et al., 1987). In sheep, PrP C is widely expressed by many cell types including neurons and leukocytes (Gossner et al., 2009; Halliday et al., 2005; Herrmann et al., 2001). In goats, only expression of PrP C in brain tissue (Vorberg et al., 1999), cells in the mammary gland (Didier et al., 2008) and milk (Didier et al., 2008; Franscini et al., 2006) has been reported to date. The early detection of PrP Sc in lymph nodes of goats and sheep with classical scrapie, humans with variant Creutzfeldt– Jakob disease, cervids with chronic wasting disease and in most rodent scrapie models suggests that infectious prions are disseminated in extraneural tissues via the circulatory and lymphatic systems. The presence of prions in the blood of sheep with classical scrapie or experimentally induced BSE has been confirmed in transfusion bioassays in which recipient lambs were inoculated with whole blood, purified leukocytes, plasma or platelets from infected donor sheep (Houston et al., 2000, 2008; Hunter et al., 2002; McCutcheon et al., 2011). It is noteworthy that, although BSE-infected sheep blood is infectious to sheep, BSE-infected cattle blood is not infectious to cattle. Using the same bioassay procedure, we recently determined in sheep with classical scrapie that relatively high levels of infectivity are associated with the CD72 + pan-B lymphocytes and also with the CD21 + subset (Dassanayake et al., 2011). However, prion infectivity could not be detected in serum or blood clots derived from goats with classical scrapie in an early study utilizing non-transgenic mice as bioassay recipients (Hadlow et al., 1980). Details of the methods and mAbs used in this study are available with the online version of this paper. Journal of General Virology (2012), 93, 1127–1131 DOI 10.1099/vir.0.039032-0 039032 Printed in Great Britain 1127