Enhanced protection in mice induced by immunization with inactivated whole viruses compare to spike protein of middle east respiratory syndrome coronavirus

Figures & data

Fig. 1 Vaccine candidates and immunization schedule.

Western blot analyses of Middle East respiratory syndrome coronavirus (MERS-CoV) S and inactivated whole MERS-CoV(IV) vaccines using mouse anti-S (a) and anti-NP monoclonal antibodies (mAbs) (b). Schematic of the study (c)

Fig. 2 Antigen-specific IgG response after vaccination.

Anti-S (a) and anti-NP (b) specific IgGs were detected at 2, 6, and 10 weeks. S protein-specific antibody isotypes induced by vaccination after 10 weeks (c). Values are the means ± standard error of the mean (SEM). Significant values are defined by *P < 0.05, **P < 0.01 and ***P < 0.001

Fig. 3 Envelope (E) and membrane (M)-specific immune responses following vaccination with IV vaccine as determined by Western blotting (WB) and indirect immunofluorescence assay (IFA).

Samples were collected from 293 T cells that were transiently transfected with the pCAGGS-E (E), pCAGGS-M (M) or control plasmid pCAGGS at 24 h post-transfection and subjected to WB (a) or IFA (b) using IV-immunized mouse serum at a 1:400 dilution as the primary antibody

Fig. 4 Neutralizing antibodies induced by S protein and IV vaccine against MERS-CoV pseudovirus particles and MERS-CoV.

Neutralizing antibody titers against MERS-CoV pseudovirus particles. (a, b) and MERS-CoV (c, d) were determined by plaque reduction neutralization assays at 6 and 10 weeks. Representative results of the plaque reduction neutralization (PRNT) assay for the detection of neutralization activity in the sera of mice (e). Approximately 30 pfu of the virus stock (hCoV-EMC) was used to infect Vero cells in 12-well plates with or without heat-inactivated sera from immunized mice 2 weeks after the third immunization. PRNT50 was calculated after the plaques were counted. Significant values are defined by **p < 0.01.

Fig. 5 The IV formulation provides enhanced protection in mice compared to the S formulation, indicating ameliorated lung pathology, reduced viral titers and expression of virus antigens in the lungs of mice with IV or S.

Representative results of hematoxylin-eosin (HE) staining (×400) in the lungs of mock-treated or immunized mice (a). Immunohistochemistry staining (×400) with anti-S and anti-NP mAbs (b). Lung virus titers 3 days after MERS-CoV challenge (c) as detected by virus isolation and titration at day 3 post-challenge. Values are the means ± SEM. Significant values are defined by ***P < 0.001