Detection of Chronic Wasting Disease Prions in Fetal Tissues of Free-Ranging White-Tailed Deer

Abstract

The transmission of chronic wasting disease (CWD) has largely been attributed to contact with infectious prions shed in excretions (saliva, urine, feces, blood) by direct animal-to-animal exposure or indirect contact with the environment. Less-well studied has been the role that mother-to-offspring transmission may play in the facile transmission of CWD, and whether mother-to-offspring transmission before birth may contribute to the extensive spread of CWD. We thereby focused on a population of free-ranging white-tailed deer from West Virginia, USA, in which CWD has been detected. Fetal tissues, ranging from 113 to 158 days of gestation, were harvested from the uteri of CWD+ dams in the asymptomatic phase of infection. Using serial protein misfolding amplification (sPMCA), we detected evidence of prion seeds in 7 of 14 fetuses (50%) from 7 of 9 pregnancies (78%), with the earliest detection at 113 gestational days. This is the first report of CWD detection in free ranging white-tailed deer fetal tissues. Further investigation within cervid populations across North America will help define the role and impact of mother-to-offspring vertical transmission of CWD.

Keywords: RT-QuIC; chronic wasting disease; fetal tissues; mother-to-offspring transmission; prions; sPMCA.

Figure 1

PrP^CWD detection in free-ranging white-tailed deer fetal tissues following seven rounds of sPMCA (method 1). Representative western blots for detection of PrP^CWD in liver (LI), popliteal lymph node (POP), and thymus (THY). sPMCA controls (10% homogenate, 7 rounds sPMCA) show complete proteinase K (PK) digestion of negative white-tailed deer brain homogenate (−C) and PK-resistant PrP^CWD in CWD+ brain homogenate (+C). Samples 1–9 were harvested from West Virginia; samples 10–13 were harvested from a non-endemic state, Georgia. Unamplified western blot assay controls show complete PK-digestion of CWD-negative white-tailed deer brain homogenate (−C; lane 2) and PK-resistant PrP^CWD in CWD+ white-tailed deer brain homogenate (+C; lane 4) (10% homogenate, undiluted, no sPMCA). PrP^CWD was not detected in brain (BR). * = sPMCA positive. NBH = normal brain homogenate. Sample type is identified along the top row of each western blot.

Figure 2

Detection of prion seeding activity by sPMCA/RT-QuIC (sPMCA method 2) in tissues harvested from fetuses of asymptomatic free-ranging CWD+ white-tailed deer does. Round 5 sPMCA reactions of fetal tissue samples (popliteal lymph node, ileum, and thymus) were analyzed by RT-QuIC. Statistically significant seeding activity was detected in all three fetal tissues analyzed. Asterisks indicate significance level (**** p < 0.0001, *** p < 0.001, ** p < 0.01).