Absence of detectable viremia in plasma and peripheral blood mononuclear cells from smallpox vaccinees: implications for blood safety.

Background: Mass smallpox vaccination with live vaccinia virus has been considered as a preventive measure to counter bioterrorism involving smallpox. This has raised concerns about the possibility of vaccinia virus being transmitted from vaccinated blood donors to recipients. The results of this study could be used to define an appropriate deferral period for blood donors (vaccinated against smallpox) to ensure safety of the blood supply.

Development and evaluation of HIV-1 subtype RNA panels for the standardization of HIV-1 NAT assays.

Multiple nucleic acid-based techniques (NAT) have been implemented for testing blood and plasma donors for HIV-1 RNA which may be detected at an earlier stage of infection when HIV antigen or antibody is absent or below the limit of detection of current assays. The available NAT assays are based on different technologies. In order to evaluate the performance of nucleic acid-based techniques (NAT assays) and to allow accurate comparisons of results from different assays, it is essential to have well characterized specimens with known copy numbers as a standard.

Computerized morphometric analysis of pathological prion protein deposition in scrapie-infected hamster brain.

Transmissible spongiform encephalopathies (TSEs or prion diseases) are characterized by a constellation of typical though variable pathological changes in the brain. Deposition of disease-associated abnormal prion protein (PrP(Sc)) is the pathological feature of TSEs most consistent and accessible for quantification. However, the evaluation of PrP(Sc) deposits detected by immunohistochemical techniques has been traditionally based on arbitrarily assigned semiquantitative scores.

The clearance of viruses and transmissible spongiform encephalopathy agents from biologicals.

The viral and transmissible spongiform encephalopathy (TSE) safety of therapeutics of biological origin (biologicals) is greatly influenced by the nature and degree of variability of the source material and by the mode of purification. Plasma-derived and recombinant DNA products currently have good viral safety records, but challenges remain. In general, large enveloped viruses are easier to remove from biologicals than small 'naked' viruses.

The rat-based neurovirulence safety test for the assessment of mumps virus neurovirulence in humans: an international collaborative study.

Because of the highly neurotropic and neurovirulent properties of wild-type mumps viruses, most national regulatory organizations require neurovirulence testing of virus seeds used in the production of mumps vaccines. Such testing has historically been performed in monkeys; however, some data suggest that testing in monkeys does not necessarily discriminate among the relative neurovirulent risks of mumps virus strains. To address this problem, a collaborative study was initiated by the National Institute for Biological Standards and Control in the United Kingdom and the Food and Drug Administration in the United States, to test a novel rat-based mumps virus neurovirulence safety test.

Mouse neurotoxicity test for vaccinia-based smallpox vaccines.

The only US FDA licensed smallpox vaccine, Dryvax, was associated with rare but serious neurological adverse events. After smallpox was eradicated in the United States, mass vaccination ceased in 1971. As counter-bioterrorism/biowarfare measures, new smallpox vaccines are now being investigated.