Determination of Conformational and Functional Stability of Potential Plague Vaccine Candidate in Formulation

Generally, protein-based vaccines are available in liquid form and are highly susceptible to instability under elevated temperature changes including freezing conditions. There is a need to create a convenient formulation of protein/peptides that can be stored at ambient conditions without loss of activity or production of adverse effects. The efficiency of naturally occurring biocompatible polymer dextran in improving the shelf-life and biological activity of a highly thermally unstable plague vaccine candidate protein called Low Calcium Response V antigen (LcrV), which can be stored at room temperature (30 +/- 2 degrees C), has been evaluated. To determine the preferential interactions with molecular-level insight into solvent-protein interactions, analytical techniques such asspectroscopy, particle size distribution, gel electrophoresis, microscopy, and thermal analysis have been performed along with the evaluation of humoral immune response, invivo. The analytical methods demonstrate the structural stability of the LcrV protein by expressing its interaction with the excipients in the formulation. The invivo studies elicited the biological activity of the formulated antigen with a significantly higher humoral immune response (p-value = 0.047) when compared to the native, adjuvanted antigen. We propose dextran as a potential biopolymer with its co-excipient sodium chloride (NaCl) to provide protein compactness, i.e., prevent protein unfolding by molecular crowding or masking mechanism using preferential hydrophobic interaction for up to three weeks at room temperature (30 +/- 2 degrees C).

Automated summary

This study evaluates the use of the biocompatible polymer dextran to improve the shelf-life and biological activity of a thermally unstable plague vaccine protein called LcrV. Analytical techniques and in vivo evaluations demonstrate the structural stability of LcrV protein and its significantly higher immune response when formulated with dextran as compared to the native antigen. Dextran, along with sodium chloride, is proposed as a potential biopolymer to provide compactness and prevent protein unfolding at room temperature for up to three weeks.