Delivery of MERS antigen encapsulated in α-GalCer-bearing liposomes elicits stronger antigen-specific immune responses

Abstract

Alpha-Galactosylceramide (α-GalCer) effectively activates the natural killer T (NKT) cells to secrete remarkable amounts of Th1 and Th2 cytokines and therefore, acts as a potential immunoadjuvant in vaccine formulation. In the present study, we prepared α-GalCer-bearing or α-GalCer-free liposomes and loaded them with Middle East Respiratory Syndrome Coronavirus papain-like protease (α-GalCer-Lip-MERS-CoV PLpro or Lip-MERS-CoV PLpro). These formulations were injected in mice to investigate the antigen-specific humoral and cell-mediated immune responses. The immunisation with α-GalCer-Lip-MERS-CoV PLpro or Lip-MERS-CoV PLpro did not induce any notable toxicity in immunised mice. The results demonstrated that mice immunised with α-GalCer-Lip-MERS-CoV PLpro showed greater antigen-specific antibody titre, switching of IgG isotyping to IgG2a subclass and higher lymphocyte proliferation. Moreover, the splenocytes from α-GalCer-Lip-MERS-CoV PLpro immunised mice secreted greater levels of IFN-γ, IL-4, IL-2 and IL-12. Interestingly, a booster dose induced stronger memory immune responses in mice previously immunised with α-GalCer-Lip-MERS-CoV PLpro. In summary, α-GalCer-Lip-MERS-CoV PLpro may prove to be a promising vaccine formulation to protect the individuals against MERS-CoV infection.

Keywords:

• Liposome
• vaccine delivery
• α-GalCer
• adjuvant
• immune response
• vaccination
• antiviral immunity

Disclosure statement

The authors declare no conflict of interest.

Additional information

Funding

The authors gratefully acknowledge the Deanship of Scientific Research, Qassim University, for the financial support of this research study under the Interdisciplinary Grant [No. 5575-cams1-2019-2-2-I] during the 2019 academic year.