The Immune System in the Pathogenesis and Prevention of Prion Diseases

Abstract

Bovine spongiform encephalopathy (BSE) remains a significant threat to both human and animal health in the United States and in particular a threat to the agriculture industry. The diagnosis of BSE in a single cow within the United States in 2003 led to net losses of billions of dollars and additional studies have pointed to significant sociological consequences of BSE cases in Canada, particularly in terms of the dissolution of rural communities. Unlike other infectious diseases, BSE and other prion diseases are caused by a misfolded protein (PrPSc) that is highly resistant to normal nucleic acid-based disinfection and sterilization procedures. Disease progression is linked to the progressive conversion of a normal cellular molecule (PrPC) into the infectious form (PrPSc) mainly on cells of the immune and neurological systems, leading to formation of multimolecular fibrils associated with progressive neurodegeneration and dementia. Due to the unique nature of this infectious particle and the fact that the disease is caused by a misfolded form of a normal self-protein, development of vaccines and other therapeutics have been challenging. The molecular mechanisms behind PrPSc targeting to lymph node germinal centers and the failure of immune recognition, remain unclear. Here, we review the current knowledge of prion disease biology, the role of the immune system in disease transmission and pathogenesis and efforts towards development of therapeutics and vaccines. While feed-based control of BSE has been successful in limiting transmission and spread of the disease, the recent description of apparently spontaneous and/or genetic forms of BSE underlies the importance of continued research into tools to counter this unique disease threat to the world economy as well as animal and human health.