Chronic wasting disease (CWD) is an emergent, rapidly spreading prion disease of cervids. Shedding of infectious prions in saliva and urine is thought to be an important factor in CWD transmission. To help to elucidate this issue, we applied an in vitro amplification assay to determine the onset, duration, and magnitude of prion shedding in longitudinally collected saliva and urine samples from CWD-exposed white-tailed deer. We detected prion shedding as early as 3 months after CWD exposure and sustained shedding throughout the disease course. We estimated that the 50% lethal dose (LD 50 ) for cervidized transgenic mice would be contained in 1 ml of infected deer saliva or 10 ml of urine. Given the average course of infection and daily production of these body fluids, an infected deer would shed thousands of prion infectious doses over the course of CWD infection. The direct and indirect environmental impacts of this magnitude of prion shedding on cervid and noncervid species are surely significant. IMPORTANCEChronic wasting disease (CWD) is an emerging and uniformly fatal prion disease affecting free-ranging deer and elk and is now recognized in 22 U.S. states and 2 Canadian provinces. It is unique among prion diseases in that it is transmitted naturally through wild populations. A major hypothesis to explain CWD's florid spread is that prions are shed in excreta and transmitted via direct or indirect environmental contact. Here we use a rapid in vitro assay to show that infectious doses of CWD prions are in fact shed throughout the multiyear disease course in deer. This finding is an important advance in assessing the risks posed by shed CWD prions to animals as well as humans. Chronic wasting disease (CWD) is an emergent transmissible spongiform encephalopathy affecting free-ranging populations of mule deer (Odocoileus hemionus), white-tailed deer (Odocoileus virginianus), elk (Cervus canadensis), and moose (Alces alces) in North America (1, 2). CWD is the only known prion disease to spread horizontally through wild populations, in which it continues to expand in prevalence and range in North America (3). As a prion disease, CWD is caused by a pathogenic, misfolded conformation of the normal, natively folded cellular protein PrP C to a pathogenic prion conformer (variously designated PrP CWD , PrP SC , or PrP D ) (2, 4-7). A leading hypothesis for the facile spread of CWD in wild populations is that the accumulation and excretion of CWD prions in bodily fluids facilitate both direct animal-to-animal transfer and substantial environmental contamination leading to indirect infection (8-10). Infectious CWD prions have been identified in urine, saliva, blood, and feces by bioassay of deer or cervid PrP Cexpressing transgenic mice (11-16). Prions bound to soil are remarkably stable, retaining infectivity even after a decade (9,(17)(18)(19)(20). Moreover, some evidence suggests that prions bound to soil may increase infectivity through an unknown mechanism (21). Understanding the kinetics and magnitude of C...

No abstract

Yellow fever virus (YFV), a member of the genus Flavivirus, is a mosquito-borne virus found in tropical regions of Africa and South America that causes severe hepatic disease and death in humans. Despite the availability of effective vaccines, YFV is responsible for an estimated 200,000 cases and 30,000 deaths annually. There are currently no prophylactic or therapeutic strategies approved for use in human YFV infections. Furthermore, implementation of YFV17D-204 vaccination campaigns has become problematic due to an increase in reported post-vaccinal adverse events. We have created human/murine chimeric MAbs of a YFV-reactive murine monoclonal antibody (mMAb), 2C9, that was previously shown to protect mice from lethal YFV infection and to have therapeutic activity. The new chimeric (c)MAbs were constructed by fusion of the m2C9 IgG gene variable regions with the constant regions of human IgG and IgM and expressed in Sp2 murine myelomas. The 2C9 cMAbs (2C9-cIgG and 2C9-cIgM) reacted with 17D-204 vaccine strain in an enzyme-linked immunosorbent assay and neutralized virus in vitro similarly to the parent m2C9. Both m2C9 and 2C9-cIgG when administered prophylactically 24 hours prior to infection protected AG129 mice from peripheral 17D-204 challenge at antibody concentrations ≥ 1.27 μg/mouse; however, the 2C9-cIgM did not protect even at a dose of 127 μg/mouse. The 17D-204 infection of AG129 mice is otherwise uniformly lethal. While the m2C9 was shown previously to be therapeutically effective in YFV-infected BALB/c mice at day 4 post-infection, the m2C9 and 2C9-cIgG demonstrated therapeutic activity only when administered 1 day post-infection in 17D-204-infected AG129 mice.