Recovery of VLP obtained after buffer variations and with the use of stabilizers during storage.

aVarious excipients were evaluated at different concentrations during VLP in storage at 4°C for a time period of 24 weeks after purification. The initial concentration of VLP in all samples was 500 µg mL−1. The experiments were conducted using duplicated lots. The percent of recovery was calculated as the percent of aggregation inhibition in the presence of additive = aggregation inhibition in the presence of additive * 100/concentration of aggregated proteins in the absence of additive where:
aggregation inhibition in the presence of additive = concentration of aggregated proteins in the absence of additive - concentration of aggregated proteins in the presence of additive.
Similar results in terms of recovery were obtained at pH 4 or 7 with the additives assayed. For simplicity, only recoveries at pH 7.0 are shown.
As a control lot, VLP were kept in identical storage conditions without stabilizers in phosphate buffer pH 7.0, 300 mM NaCl. In such case, the recovery of VLP accounted for a 48.5%.