Abstract
Objectives: Here, we prepared a liposome-based vaccine formulation containing Middle East Respiratory Syndrome Coronavirus papain-like protease (MERS-CoV-PLpro). Methods: A persistent leukopenic condition was induced in mice by injecting cyclophosphamide (CYP) three days before each dose of immunization. Mice were immunized on days 0, 14 and 21 with alpha- GalCer-bearing MERS-CoV PLpro-encapsulated DPPC-liposomes (alpha-GalCer-MERS-PLpro-liposomes or MERS-CoV PLpo-encapsulated DPPC-liposomes (MERS-PLpro-liposomes), whereas the antigen emulsified in Alum (MERS-PLpro-Alum) was taken as a control. On day 26, the blood was taken from the immunized mice to analyze IgG titer, whereas the splenocytes were used to analyze the lymphocyte proliferation and the level of cytokines. In order to assess the memory immune response, mice were given a booster dose after 150 days of the last immunization. Results: The higher levels of MERS-CoV-PLpro-specific antibody titer, IgG2a and lymphocyte proliferation were noticed in mice immunized with alpha-GalCer-MERS-PLpro-liposomes. Besides, the splenocytes from mice immunized with alpha-GalCer-MERS-PLpro-liposomes produced larger amounts of IFN-gamma as compared to the splenocytes from MERS-PLpro-liposomes or MERS- PLpro-Alum immunized mice. Importantly, an efficient antigen-specific memory immune response was observed in alpha-GalCer-MERS-PLpro-liposomes immunized mice. Conclusions: These findings suggest that alpha-GalCer-MERS-PLpro-liposomes may substantiate to be a successful vaccine formulation against MERS-CoV infection, particularly in immunocompromised individuals. (c) 2022 The Authors. Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).