Table I.
Update on MERS-CoV vaccines based on viral S protein and its fragments
| Vaccine type | Name | Immune responses | Protection | References |
|---|---|---|---|---|
| MERS-CoV vaccines based on full-length or truncated S protein | ||||
| DNA | MERS DNA | Induced S-specific cellular immune responses and IgG Abs in NHPs which are specific to full-length S protein, S1 or S2 subunit, and RBD fragment, neutralizing live MERS-CoV infection | Protected NHPs against MERS-CoV infection, with reduced clinical symptoms, decreased viral load, and alleviated severity of pathological signs | 57 |
| DNA-protein | pSΔER-pSΔTM | Induced S-specific T-cell responses and S/S1/RBD-specific IgG Abs in mice, with neutralizing activity against infection of multiple pseudotyped MERS-CoVs and live MERS-CoV strain | Protected hDPP4-Tg mice against MERS-CoV infection, with reduced weight loss and complete survival | 71 |
| Viral vector | rAd/spike PIV5/MERS-S ChAdOx1-MERS | rAd/spike induced S-specific T-cell responses and S1-specific Abs (IgG, IgA), neutralizing pseudotyped MERS-CoV infection; PIV5/MERS-S induced S-specific T cell responses and neutralizing Abs in mice against pseudotyped MERS-CoV infection; ChAdOx1-MERS enhanced neutralizing Abs in seropositive dromedary camels against pseudotyped MERS-CoV infection | PIV5/MERS-S protected hDPP4-KI mice against mouse-adapted MERS-CoV infection, improving virus clearance and having minimal eosinophils in the lungs; ChAdOx1-MERS reduced virus shedding and nasal discharge in dromedary camels | 58,76,77 |
| MERS-CoV vaccines based on the RBD fragment | ||||
| Protein | S RBD-HBD 2 | Induced RBD-specific IgG and IgA Abs in mice after intranasal immunization | Protected hDPP4-Tg mice from MERS-CoV challenge, with better protection via the intranasal route than the intramuscular route | 59 |
| Nanoparticle | RBD-LS RBD-NP(cdGMP) | RBD-LS induced S1-specific IgG and neutralizing Abs in rabbits against clade A (EMC2012) and clade B (Qatar15/2015) live MERS-CoV infection; RBD-NP(cdGMP) induced RBD-specific T cell responses, IgG Abs, and neutralizing Abs in mice against live MERS-CoV infection | RBD-LS protected rabbits against MERS-CoV infection, preventing virus shedding and infection; RBD-NP(cdGMP) protected hDPP4-Tg mice from MERS-CoV challenge, without inducing eosinophilic immunopathology | 60,72 |
| Viral or bacterial vector | RV/MERSMERS BLP RVΔP-MERS/S1 | Induced higher S-specific T-cell responses (for RV/MERS), RBD-specific IgG Abs, and rapid (for RV/MERS) or higher (for MERS BLP) neutralizing Abs in mice against pseudotyped MERS-CoV infection; RVΔP-MERS/S1 induced neutralizing Abs against both MERS-CoV and RV infection | N/A | 74,75 |
| MERS-CoV vaccines based on other S fragments (such as S1 subunit) | ||||
| DNA | AcHERV-MERS-S1 pcDNA3.1-S1 pS1 | Induced S1/RBD-specific T-cell responses and/or S-specific IgG and neutralizing Abs in mice against infection of multiple pseudotyped MERS-CoV strains with human and camel origins or live MERS-CoV strain | Protected hDPP4-Tg mice from MERS-CoV challenge, with reduced weight loss and complete survival; Protected Ad5-hDPP4-transduced mice from MERS-CoV infection | 61,65,66 |
Abbreviations: Abs, antibodies; BLP, bacterium-like particle; hDPP4, dipeptidyl peptidase 4; hDPP4-KI, human DPP4-knock-in mice; hDPP4-Tg, human DPP4-transgenic mice; LS, lumazine synthase; N/A, not available; NHPs, nonhuman primates; PIV5, parainfluenza virus 5; rAd, recombinant adenovirus; RBD, receptor-binding domain; RV, rabies virus; S, spike.