MERS-CoV‒Specific T-Cell Responses in Camels after Single MVA-MERS-S Vaccination

Abstract

We developed an ELISPOT assay for evaluating Middle East respiratory syndrome coronavirus (MERS-CoV)‒specific T-cell responses in dromedary camels. After single modified vaccinia virus Ankara-MERS-S vaccination, seropositive camels showed increased levels of MERS-CoV‒specific T cells and antibodies, indicating suitability of camel vaccinations in disease-endemic areas as a promising approach to control infection.

Keywords: Dubai; ELISPOT assay; MERS-CoV; MVA; MVA expressing full-length MERS-CoV spike protein as antigen; MVA-MERS-S; Middle East respiratory syndrome coronavirus; T-cell responses; coronavirus; dromedary camels; modified vaccinia virus Ankara; respiratory infections; spike protein; vaccination; viruses; zoonoses.

Figure 1

Antigen-specific humoral immunity after MVA-MERS-S vaccination in dromedary camels, Dubai, United Arab Emirates. MERS-CoV seropositive and naive dromedary camels were immunized once with 2.5 x 10⁸ plaque-forming units of MVA-MERS-S or MVA as a vector control. Serum samples were collected on day 0 and on day 15 after single-shot vaccination. Black indicates serum samples analyzed for MERS-CoV S1 IgG by ELISA of MVA–vaccinated animals and red indicates for MVA-MERS-S–vaccinated animals. Box plots show individual values (dots), median values (horizontal lines within boxes), first and third quartiles (box tops and bottoms), and minimums and maximums of value distribution (error bars). LOD, limit of detection; MERS-CoV, Middle East respiratory syndrome coronavirus; MVA, modified vaccinia virus Ankara; MVA-MERS-S, modified vaccinia virus Ankara expressing full-length MERS-CoV spike protein as antigen.

Figure 2

Antigen-specific cellular immunity after MVA-MERS-S vaccination in dromedary camels, Dubai, United Arab Emirates. PBMCs were isolated from blood samples on different days post‒single-shot vaccination and IFN-γ SFCs were measured by ELISpot assay after restimulation of PBMCs from different time points with overlapping peptides comprising the MERS-CoV S1 (A) and MERS-CoV-S2 (B) protein subunit. Box plots show individual values (dots), median values (horizontal lines within boxes), first and third quartiles (box tops and bottoms), and minimums and maximums of value distribution (error bars). IFN-γ, interferon-γ; MERS-CoV, Middle East respiratory syndrome coronavirus; MVA, modified vaccinia virus Ankara; MVA-MERS-S, modified vaccinia virus Ankara expressing full-length MERS-CoV spike protein as antigen; PBMCs, peripheral blood mononuclear cells; SFCs, spot-forming T cells.