Figure 7.
Applying RBD capsid decoration at boost significantly increases SARS-CoV-2 specific antibody and T cell responses in an adenovirus vector prime-boost regimen
(A) BALB/c mice (n = 12) were immunized intramuscularly with Ad(Spike)-DogTag on D0 and then on D21 given a second intramuscular immunization of either Ad(Spike)-DogTag (group 1, n = 6) or Ad(Spike)-DogTag:DogCatcher-RBD (group 2, n = 6). All vaccines were administered at a dose of 108 infectious units. (B) Serum IgG antibody responses to RBD measured by endpoint ELISA. Responses measured post prime on D20 (Ad(Spike)-DogTag) are compared with responses on D35 after homologous (Ad(Spike)-DogTag, Ad(Spike)-DogTag), or heterologous (Ad(Spike)-DogTag, Ad(Spike)-DogTag:DogCatcher-RBD) prime boost. Fold change in median titer post boost is shown. Horizontal bars show median responses. Statistical analyses performed by Kruskal-Wallis with Dunn’s test for multiple comparisons, ∗p < 0.05; ∗∗∗∗p < 0.0001. Dashed line represents limit of detection. (C) IFNγ-ELISpot response in spleen at D35 against peptide pools spanning full-length (1–1,273) SARS-CoV-2 S (summed responses from two peptide pools spanning residues 1–643 and 633–1,273 are shown). (D) IFNγ-ELISpot response in spleen at D35 against peptide pool spanning C-terminal residues 633–1,273 of SARS-CoV-2 S only (i.e., not including RBD domain). In (C)–(D), horizontal bars show median responses and statistical analyses performed by Mann-Whitney test, ∗∗p < 0.01.