West Nile virus and the safety of plasma derivatives: verification of high safety margins, and the validity of predictions based on model virus data.

BACKGROUND: During the 2002 West Nile virus (WNV) epidemic in the US, virus transmission through solid organ transplantation and transfusion of blood components was observed. This raised concerns about the safety of plasma derivatives. To verify the safety margins of these products, which were initially shown with a panel of model viruses including some very similar to WNV, the effectiveness of the virus inactivation procedures incorporated into their manufacturing processes was reinvestigated. STUDY DESIGN AND METHODS: An infectivity assay for 1999 New York isolate of WNV was established to investigate virus inactivation steps commonly used during the manufacture of plasma derivatives, such as pasteurization for human albumin, S/D treatment for IVIG and FVIII, vapor heating for FVIII inhibitor-bypassing activity, and incubation at low pH for IVIG. RESULTS: The results show that WNV behaves exactly as had been predicted based on available data for similar model viruses; that is, it is readily inactivated by all the commonly used virus inactivation procedures tested. CONCLUSION: Our investigation verifies the safety margins of plasma derivatives against a potential transmission of WNV and that the model virus concept is valid for predicting the behavior of closely related viruses.