Virus inactivation by pepsin treatment at pH 4 of IgG solutions: factors affecting the rate of virus inactivation

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Abstract
Background: IgG preparations have rarely transmitted infectious diseases; however, because such transmission has occurred a few times, manufacturers are required to present experimental proof that their specific production process removes and/or inactivates viruses that may be present in the starting material.Study Design and Methods: The kinetics of virus inactivation mediated by pepsin treatment at pH 4 during the production of intravenous immunoglobulin was assessed with spiking experiments using human immunodeficiency virus, bovine viral diarrhea virus, Semliki Forest virus, and pseudorabies virus. The influence of various factors on the rate of virus inactivation also was studied by modifying the composition of the IgG solutions with respect to IgG, sucrose, and NaCl content.Results: Virus inactivation at 37° C was extremely rapid and resulted in a complete loss of infectivity within 5 minutes to 1 hour. Inactivation was much slower at lower temperatures. Furthermore, inactivation was dependent on the solute composition. Increasing the sucrose content from 0 to 15 percent reduced the rate of inactivation of pseudorabies virus but did not affect the rate of inactivation of Semliki Forest virus. In contrast, increasing the NaCl content from 0 to 150 mM resulted in a reduction in the rate of inactivation of Semliki Forest virus, whereas the rate of inactivation of pseudorabies virus remained unaffected. Moreover, increasing the IgG concentration from 0 to 10 percent resulted in an increased rate of inactivation of pseudorabies virus but a decreased rate of inactivation of Semliki Forest virus.Conclusion: Inactivation of viruses by pepsin treatment at pH 4 essentially is temperature‐dependent, and the reaction rate is selectively influenced by the solute composition of the IgG solution. This has to be taken into account when safety data for different products are compared.