Physical Stabilization of Norwalk Virus‐Like Particles*

Virus‐like particles (VLPs) used as vaccine antigens often elicit strong immune responses due to their intrinsic repetitive, high‐density display of epitopes, and the fact that the mammalian immune system is highly attuned to recognizing particles in the size range of viruses (20-150 nm). To retain these immunogenic qualities, vaccines that utilize virus‐like particle (VLP) antigens should be formulated to stabilize both native conformational epitopes and the overall particulate nature of the VLP. This work describes a systematic approach for identifying potential stabilizers for formulation of Norwalk VLPs (NV‐VLPs) in aqueous suspension. A number of excipients were screened for their ability to inhibit aggregation of NV‐VLPs under conditions known to induce aggregation. Those compounds shown to inhibit aggregation were further evaluated under conditions of thermal stress and the NV‐VLP structure was monitored using biophysical techniques such as CD, ANS fluorescence, and DSC to provide insight into the mechanisms by which stability was conferred. Increased thermal stability in the presence of chitosan glutamate, sucrose, and trehalose was correlated with stabilization of secondary and tertiary structural elements of NV‐VLPs. These excipients may be useful for formulation of a stable NV‐VLP vaccine. © 2008 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:4208-4218, 2008