West Nile virus: recent experience with the model virus approach.

During recent West Nile Virus (WNV) epidemics in the USA, virus transmissions through transfusion of blood components have been observed, also raising concerns about the safety of plasma derivatives. To verify the safety margins of these products, as initially shown using model viruses very similar to WNV, virus inactivation procedures incorporated into their manufacturing processes were re-investigated using WNV directly. The results show that WNV behaves exactly as had been predicted based on available data for similar ("model") viruses, i.e. it is readily inactivated by e.g. pasteurisation of human albumin, solvent-detergent treatment of intravenous immunoglobulin and factor VIII, vapour heating of factor VIII inhibitor by-passing activity, and incubation of intravenous immunoglobulin at low pH. Our investigation thus verifies the safety margins of plasma derivatives against Flaviviruses in general, and now WNV in particular. Also, use of the model virus concept was confirmed to be well capable of predicting the behaviour of a certain virus based on available data for closely related viruses.