(293a) Invited Speaker: Understanding Virus Surface Interactions and Stability

Better understanding of virus surface chemistry could lead to improved virus removal techniques, purification methods for viral therapeutics and increased therapeutic stability. To enhance the toolbox of available characterization tools, chemical force microscopy (CFM) is being pioneered for viral particle characterization. CFM measures the adhesion force between a particle, in this case a virus particle, and a functionalized atomic force microscopy (AFM) tip. CFM reduces many of the difficulties of bulk characterization techniques by measuring adhesion of individual virus particles, likely reducing purification affects that can change surface properties. We have used CFM to study the electrostatic and hydrophobic interactions of two model viruses, porcine parvovirus (PPV) and bovine viral diarrhea virus (BVDV). These viruses were chosen because one is non-enveloped and one is enveloped, demonstrating the wide applicability of this method.

Knowledge of the electrostatic differences between the two viruses was used to thermally stabilize the virus particles. This could potentially reduce the need for a cold chain for live attenuated vaccines. The cold chain requires materials to remain below 8°C during transport. The viruses were stabilized by encapsulating them in an electrolyte dense phase. The oppositely charged polypeptides create the dense, coacervate phase. The coacervate is able to capture all detectable virus and can thermally stabilize PPV. The electrostatic differences between the viruses is noted in a shift in the charge fraction needed to encapsulate the two viruses studied.

Taken together, we have used virus surface characterization and virus polypeptide encapsulation to stabilize viruses. Future work will explore other virus surfaces to determine if knowledge of the virus surface electrostatics can be used to engineer the coacervate phase with minimal experiments.