The viral safety of intravenous immune globulin

The viral safety of intravenous immune globulin (IVIG) preparations has been investigated since 1983 when it was discovered that non-A, non-B hepatitis (NANBH) could be transmitted by an experimental IVIG preparation. Recently, it has been demonstrated that the virus causing NANBH is the hepatitis C virus (HCV). A number of subsequent episodes of HCV transmission by IVIG have been reported, but not all the factors that have led to this transmission are clearly understood. However, based on two episodes of HCV transmission by anti-D immune globulin (formulated for intravenous administration), it appears that cold ethanol fractionation is important in ensuring viral safety because both of the implicated anti-D immune globulin preparations were manufactured without cold ethanol fractionation. Other HCV transmission episodes have been associated with chromatography (particularly DEAE-Sephadex chromatography) as a separation step carried out to further purify IgG, after cold ethanol fractionation, and it is possible that such a procedure has only a marginal partitioning capacity for infective HCV virions. The role of anti-HCV screening in improving the viral safety of IVIG preparations remains unclear, but a recent transmission episode by a previously safe IVIG preparation suggests that the absence of anti-HCV antibodies during plasma fractionation may affect the partitioning characteristics of HCV and may also cause a loss of neutralizing antibody against HCV. All of the IVIG preparations associated with HCV transmission have been formulated as freeze-dried preparations and this may have been important in stabilizing HCV during the period prior to administration to patients. No other viruses appear to have been transmitted by IVIG preparations, but prior to seroconversion, HCV-infected plasma donors may continue to contaminate plasma pools used for the manufacture of blood products, despite anti-HCV screening, and additional viral inactivation steps such as incubation at pH4 or solvent-detergent treatment should be incorporated into the production process of all IVIG preparations.