Prions and blood products

The transmission of Creutzfeldt-Jakob disease (CJD) by human pituitary-deri ved growth hormone has led to concerns that blood products might also provi de a route for the iatrogenic transmission of CJD. A number of actions have been implemented by regulatory authorities to address such concerns, and n umerous studies have been undertaken to determine whether or not there is a risk of CJD being transmitted in this manner. To date, no excess risk has been identified, leading to a growing consensus that there is little or no risk of long established forms of CJD being transmitted to recipients of bl ood products. This opinion does nor extend to new variant CJD (vCJD) which is found predominantly in the UK and is believed to have resulted from the transmission of bovine spongiform encephalopathy (BSE) to humans. Unlike th at of CJD, the prevalence of vCJD is not known. In addition, the detection of abnormal prion protein in the tonsils of vCJD-infected individuals has l ed to speculation that blood infectivity may be greater than in patients wi th CJD. A number of precautionary measures have been taken to address the p ossibility that vCJD may be transmissible by blood products; however, furth er scientific advances are needed to enable this risk to be defined. A suit able screening test is required to identify any infected blood donors, part icularly where cellular blood components are being derived from populations believed to be at risk from BSE infection. Recent experimental data sugges t that process operations used in the manufacture of plasma products may be capable of removing prion agents to a significant extent. However, further work is required to confirm these observations and to determine whether or not all potential vCJD infectivity would be removed by these means.