Prions--clinical significance, epidemiology and possibilities of transmission through blood and blood products

Abstract

Prions play a leading role in development of transmissible spongiform encephalopathies (TSE). These infectious particles, smaller than viruses and viroids, consist of special kind of proteins and don't contain nucleic acids. Due to that, they are named defective viruses. Prion protein determined as PrPcs was isolated in infective material of all known prion diseases. This represents an abnormal conformer of PrPc prion protein, normally synthesized in all cells, predominantly in neurons of vertebrates. Transmissible spongiform encephalopathies are neurodegenarative diseases whose pathogenesis includes modification of secondary structure of normal glycoprotein--prion protein. In human peripheral blood, PrP are expressed in T and B lymphocytes, NK cells, monocytes, dendritic cells, platelets and plasma. Investigations of transmission of prions to experimental animals, showed that lymphoid tissues are infectious in the earliest phase of the disease. Experimental transmission of sporadic Creutzfeldt-Jakob disease (CJD) by intracerebral inoculation of experimental animals with whole blood, buffy coat, platelet concentrates, plasma, early cohn fractions and albumin preparations, has been reported. A small number of clinical studies reported transmission of CJD by human blood, urine and lymphoid tissues and the role of B lymphocytes in neuroinvasion and transmission of prions. Thus, importance of prion diseases in blood transfusion is obvious, latrogenic transmission of prion diseases by blood and blood products, can't be neglected. Moreover, it is necessary to find markers in prion diseases as well as new technologies and methodologies in blood transfusion practice to minimize the theoretical risk of transmission of prion diseases by blood and blood products.