Fig 1.
Vaccine constructs and vaccination schedule.
A) Schematic illustration of CORAVAX, the rabies virus-based SARS-CoV-2 vaccine construct wherein a SARS-CoV-2 S1 RABV G chimeric protein cDNA was inserted between the N and P genes of the SAD-B19-derived RABV virus vaccine vector BNSP333 and control vaccine FILORAB1, the rabies virus-based EBOLA vaccine used in this study. B) Syrian hamsters were immunized on day 0 and day 28 with 10 μg chemically inactivated CORAVAX or FILORAB1 with MPLA-AddaVax adjuvant. The animals were challenged on day 60 with a dose of 105 PFU of the SARS-CoV-2 isolate USA_WA1/2020. Serum was collected from each hamster at days -2, 26, 56, 63, and 75 for analysis. Animals were necropsied at days 63 (day 3 p.c.) and 75 (day 15 p.c.).
Fig 2.
Serum samples collected from each hamster were evaluated for SARS-CoV-2 S-specific immune responses by A) ELISA, Anti-SARS CoV-2 S1 IgG responses represented as EC50 titers over time, B) ELISA, Anti-SARS CoV-2 IgG2/3 responses, C) Virus neutralizing antibodies, and D) ELISA, Anti-SARS COV- 2 S RBD IgG responses. The CORAVAX vaccine group is shown in blue and the FILORAB1 group in black. For A-D, mean titers ± SD are depicted for each group per time point. P values determined by Mann-Whitney test. Only significant differences are depicted.
Fig 3.
Rabies virus neutralizing antibodies Hamster day 56 sera were assessed for RABV VNA.
Dotted line represent 0.5 I.U/mL. Only significant differences are depicted.
Fig 4.
Hamster body weight after SARS CoV-2 infection.
Hamsters were vaccinated at day 0 and day 28, challenged intranasally with 105 PFU SARS-CoV-2 at day 60. Percent change in body weight. CORAVAX vaccine group is shown in blue and FILORAB1 group in black. N = 12 for FILORAB1 group (6 hamsters euthanized at day 3 p.c.) and N = 11 for CORAVAX group (6 hamsters euthanized at day 3 p.c.). Body weight P value determined by Wilcoxon test. P > 0.123 (ns), P < 0.033 (*), P < 0.002 (**), P < 0.001 (***).
Fig 5.
SARS-CoV-2 tissue viral load in hamsters.
Hamsters were challenged intranasally with 105 PFU SARS-CoV-2, and half of the animals in each group were euthanized at days 3 and 15 p.c. Right lungs (A, C) and nasal turbinates (B, D) from each animal were homogenized in media and viral loads were determined by plaque assays on Vero E6 cells (A, B) or by qRT-PCR (C, D). The limit of detection for the plaque assay was 70 PFU per lung and 35 PFU per nasal turbinate. The limit of detection for the qRT-PCR assay is 10 copies. The CORAVAX vaccine group is shown in blue and the FILORAB1 group in black. Data represent mean ± S.D., N = 6 for FILORAB1 group day 3 and day 15 time points, and N = 6 for CORAVAX group day 3 and N = 5 for CORAVAX group day 15 time points. P values determined by Mann-Whitney test. Only significant differences are depicted.
Fig 6.
Representative histological images of SARS-CoV-2 infection in control and vaccinated hamster lungs. A and B, low magnification images, day 3 p.c. lungs. A: FILORAB1 control, B: CORAVAX vaccinated. C and D, high magnification of A and B detailing specific pathological features, location indicated by asterisks on low magnification images. Infiltration of parenchyma and airways by mononuclear inflammatory cells is prominent in control animal. Notable improvement in airway infiltration observed in vaccinated animals. Varying degrees of consolidation and septal thickening are present in control and vaccinated animals. E and F, low magnification images, day 15 p.c. lungs. E: FILORAB1 control, F: CORAVAX vaccinated. G and H, high magnification of E and F detailing specific pathological features, location indicated by asterisks (*) on low magnification images. Significant airway infiltration is absent in all animals, but other aspects of inflammatory pathology persist, such as epithelial hyperplasia Overall consolidation improved in vaccinated animals but did not reach statistical significance.
Fig 7.
Comparative pathology scores for lungs from CORAVAX vaccinated and control hamsters post SARS-CoV-2 challenge.
Scores at 3 days (A) and 15 days (B) p.c. Scores are displayed for overall lung pathology and individual criteria, including consolidation or extent of inflammation, type inflammatory foci, airway pathology, and septal thickening. The pathology scores (mean) were calculated based on the criteria described in S1 Table. The CORAVAX vaccine group is shown in blue and the control group in black. Data represent mean ± S.D., N = 6 for FILORAB1 group day 3 and day 15 time points and N = 6 for CORAVAX vaccine group at day 3 and N = 5 for CORAVAX day 15 time points. P > 0.123 (ns), P < 0.033 (*), P < 0.002 (**), P < 0.001 (***). Only significant differences are depicted.