Removal of viral contaminants from therapeutic protein solutions.

The presence of adventitious viruses in various blood or cell culture-derived therapeutic protein solutions poses serious health risks. Ideally, it would be desirable to process these solutions in such a way that the infectious agents are eliminated or inactivated, while maintaining the therapeutic efficacy of these preparations. Adsorption processes are not widely used for virus removal primarily because suitable and efficient adsorbents are not available. The overall goal of this thesis is to develop two types of adsorbents that can potentially serve this purpose. A quaternary ammonium chloride (QAC)-treated adsorbent was shown to possess an exceedingly high affinity for enveloped viruses based upon both hydrophobic and electrostatic interactions. Although most virions were still infectious while attached onto the QAC-treated surface, they were inactivated as they were eluted from the surface. The mechanism of inactivation was found to involve disruption of the viral envelope with subsequent release of nucleocapsid. The major drawback of using QAC-treated beads, was the non-specific binding of protein molecules to the reactive surface. As a consequence, QAC-treated beads can be applied only to those solutions that contain low protein content. To alleviate the problem of protein fouling, a novel approach of biospecific adsorption was examined in which cellular receptors on cell membrane are used as affinity lig and s to adsorb, and thus remove, both free virions and virus-infected cells from complex protein solutions. The biospecific adsorbent was prepared by immobilizing cells or cell membranes that bear the complementary receptors for target viruses onto inert polymer support surfaces, and then chemically cross-linking the cellular proteins with glutaraldehyde. The stabilization process was shown not to impede the affinity adsorption process as measured in herpes simplex virus and human cytomegalovirus model systems. Cellular receptor adsorbent prepared in this manner have the advantages of high binding specificity, broad adsorption spectrum, ease of preparation. A stochastic approach that describes a diffusion-adsorption model system was undertaken to examine the interactions between free virus particles and a reactive surface. The sticking probability of virus adsorption was determined by fitting the experimental data with the Monte Carlo simulation results. Effects of various process parameters also were examined in the simulation studies.PhDChemical engineeringUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/161984/1/8821664.pd