Immunogenicity of DNA vaccine encoding spike protein against Middle East respiratory syndrome coronavirus in mammalian model

Abstract

Background: The Middle East respiratory syndrome coronavirus (MERS-CoV) is currently a major threat to public health worldwide. There are, as of yet, no licensed MERS-CoV vaccines or therapeutics. The rapid development and deployment of low-cost and effective vaccines against emerging variants has renewed interest in DNA vaccine technology. So, the aim of the current study is the generation and immunological evaluation of DNA vaccine candidates against MERS-CoV. Methods: The spike gene was selected to generate the DNA vaccine, which encodes the spike protein of coronaviruses that plays a pivotal role in viral entry into host cells and serves as a primary target for host immune responses. Moreover, the antibody responses post-immunization with spike-DNA fragment and inactivated coronaviruses vaccines was explored, using a microneutralization assay with severe acute respiratory syndrome (SARS-CoV-2), and the log2 antibody titers at different time points (0, 2, 4, 6, and 8 weeks) post-vaccination was measured. Results: The inactivated MERS-CoV and pCDNA3.1-S-MERS-CoV vaccines maintained steady log2 antibody titers, showing no specific response to SARS-CoV-2 in the control group (PBS). Microneutralization against MERS-CoV showed no significant antibody titers for Inactivated SARS-CoV-2, suggesting no cross-reactivity. Sustained antibody titers for Inactivated MERS-CoV indicate vaccine-induced stability. Conclusion: This study sheds light on antibody responses induced by these vaccines against MERS-CoV, aiding rapid development and deployment of low-cost and effective vaccines. These insights are crucial for optimizing vaccine strategies, particularly in the context of the evolving MERS-CoV pandemic.