Inactivation of hepatitis A virus in plasma products by vapor heating.

BACKGROUND: The transmission of hepatitis A virus (HAV) has been associated with the use of a number of solvent/detergent-treated factor VIII concentrates and possibly a factor IX concentrate. These reports have emphasized the necessity of using virus-inactivation methods for plasma products that are capable of inactivating nonenveloped viruses such as HAV. STUDY DESIGN AND METHODS: A simple, highly accurate titration procedure for HAV, which allows extensive kinetic investigations of virus-inactivation procedures, has been developed. This system has now been used to evaluate the efficacy of vapor heating in inactivating HAV after the addition of the virus to a range of human plasma products. RESULTS: It was demonstrated that HAV was significantly more thermostable than other picornaviruses, which reinforced the fact that such viruses cannot be used as model viruses for HAV-inactivation studies. A one-step vapor-heating procedure was demonstrated to inactivate between 5.9 and > 6.3 log10 of HAV in different products. A two-step vapor-heating procedure had the capacity to inactivate between > 8.7 and > 10.4 log10 of HAV. Both procedures were more effective in inactivating HAV than was the pasteurization procedure used for virus inactivation in human albumin solutions. CONCLUSION: These data demonstrate the efficacy of vapor heating in inactivating high-titer HAV after the spiking of plasma products with virus. This study confirms and explains the results of controlled clinical trials and long-term clinical usage with respect to the lack of HAV transmission by such vapor-heated products.

Determination of the inactivation kinetics of hepatitis A virus in human plasma products using a simple TCID50 assay.

The transmission of hepatitis A virus (HAV) associated with use of FVIII concentrates has been reported in a number of European countries. All of these cases were associated with products inactivated by use of solvent detergent treatment. These reports have emphasized the necessity of evaluating virus inactivation methodologies for their ability to inactivate HAV. Such studies had previously been hampered by the difficulties associated with titration of HAV, because of the minimal cytopathic effect of most strains of virus on tissue culture cells. We have developed a simple, rapid, TCID50 virus titration system using a cytopathic strain of HAV which allows extensive kinetic studies of HAV inactivation. This has been compared with the standard radioimmunofocus forming (RFF) assay which is presently used for HAV titration. The reproducibility of the TCID50 assay was demonstrated to be equal to that of the RFF assay and the 95% confidence intervals for titres determined by both assays were also equal. The thermal stability of the cytopathic strain was studied and shown to be equivalent to that of a noncytopathic strain. The kinetics of HAV inactivation by heating in aqueous solution were compared to those of HIV-1 and a number of model viruses. It was demonstrated that HAV was highly stable, with 5 hours heat treatment at 60 degrees C in aqueous solution being required to inactivate 5.8 log10 virus. In contrast to heating in aqueous solution, lyophilization followed by 1 hour vapor heating at 60 degrees C was sufficient to inactivate 5.9 log10 HAV.