Fig. 1.

Adjuvants impact the durability of protection conferred by eVLP vaccination.

(a) C57BL/6 mice were vaccinated IM two times with 10 μg of eVLP and challenged four (short-term) weeks or twenty-two (long-term) weeks after the vaccine boost. Data in A are pooled from 8 individual studies with 6–10 animals/group. Fisher's exact test: survival in the short-term group was significantly higher than in the long-term group (p < 0.0001). (b) C57BL/6 mice were vaccinated IM two times with 10 μg of eVLP and challenged at the indicated days after the second vaccination. n = 9 or 10/group. Cochran-Armitage test: percentage surviving declined as time to challenge increased (p = 0.0046). There was a significant difference (p = 0.03) between survival on Day 77 and Day 175. (c) Serum samples collected from animals in (B) one week prior to challenge were subjected to an ELISA for the evaluation of anti-GP IgG, IgG1, and IgG2c antibody titers. Red symbols indicate titers of animals that succumbed to challenge while black indicate titers of survivors; red symbols with black outlines indicate that one of these two animals succumbed to challenge, but animal tags were indeterminate after challenge. Median and IQR shown. (d) C57BL/6 mice were vaccinated two times (IM) with VLP, with or without the indicated adjuvants. Animals were challenged twenty-two weeks after the vaccine boost. Data in D are pooled from at least 4 separate studies with a total of at least 35 animals per group. P-values comparing VLP alone to vaccination with VLP and adjuvant are shown, calculated using Fisher's exact tests with stepdown Bonferroni correction. V = VLP, VP = VLP + PolyICLC, VC = VLP + CpG, VM = VLP + MPLA, and VA = VLP + alhydrogel.