Fig. 2.

Thermostability, immunogenicity, and protective efficiency of spray-dried MS2-16L2 VLPs after storage for 34 months at room temperature. A) Spray-dried VLPs were reconstituted in sterile phosphate buffered saline solution and the VLPs were observed under an electron microscope at 70,000x. B) Balb/c mice were immunized twice with 5 µg of MS2-16L2 VLPs (from 2 A), fresh liquid MS2-16L2 VLPs or control MS2 VLPs (with alum hydroxide). Sera were collected two weeks after the last immunization and anti-L2 IgG antibody titers were determined by ELISA using HPV 16L2 (amino acid 17–31) as a target peptide. Statistical analysis was done using two-tailed unpaired t-test. C) Immunized mice in B were infected with 6.4×10⁶ PsV infectious units of HPV16, 4 months after immunizations. Luciferase activity, average radiance, and statistical analysis were determined as described in Fig. 1 legend.