Superior immune responses induced by intranasal immunization with recombinant adenovirus-based vaccine expressing full-length Spike protein of Middle East respiratory syndrome coronavirus
Fig 3
The neutralizing capacity directed against MERS Spike pseudotyped virus.
Groups of mice were immunized as indicated in Fig 2. On day 7 after the last immunization, sera and BALFs were collected from each group. Serially diluted sera and BALFs were evaluated for their neutralizing activity against MERS Spike pseudotyped virus in Huh 7.5 cells. The transduction percentage was calculated by measuring GFP expression in comparison with the expression in the control pseudovirus-infected cells. The dotted horizontal line indicates 50% neutralization. (A) Neutralization activities in serially diluted sera. (B) The IC50 (50% inhibitory concentration) neutralization titers in the sera. (C) The neutralization activities in serially diluted BALFs. Data are representative of at least two independent experiments with similar results and average SEM value of four mice. (D) NHNE cells (106 cells/well) were inoculated with 300 μl of virus solution (MERS-CoV 10μl/PBS 10 ml) and N2 gene level of MERS-CoV was assessed at 1 day post-infection using real-time PCR. To prove the effect of neutralizing antibody for MERS-CoV spike protein, targeted antibody of MERS-CoV spike protein was diluted to 1:10, 1:50, 1:250 and the diluted antibodies were mixed with the virus solution at a ratio of 1:1 and maintained for 1 hour before infection to NHNE cells. Then, N2 gene level of MERS-CoV was assessed at 1 day post-infection using real-time PCR. The same experiments were carried out using mock antibody and the result was compared with that of targeted antibody for MERS-CoV spike protein. ns, not significant; ***p<0.001; **p<0.01; *p<0.05.