Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is the main pathogen that causes COVID-19,which is fast-mutating and highly transmissible.The infection has led to a global epidemic.As the main preventive and control measure,vaccination plays a critical role in fighting a-gainst COVID-19.Although a large number of epitope-based and mucosal vaccines have been stud-ied,few peptide epitope vaccines targeting the mucosa and their functional evaluation have been re-ported.In this study,we used SARS-CoV-2 structural protein M peptide epitope predicted by the IEDB database as an antigenic target to design the MS-3S gene containing 3 050 and 1 229 signal peptides and DCpep optimized for insertion into MS2 phage coat proteins.The expression plasmid pSIP:MS-3S was constructed by cloning the PCR fragments seamlessly and was transformed into Lactiplantibacillus plantarum 18 to obtain the recombinant bacterium LP18:MS-3S.Expression conditions such as induction time,inducer concentration,rotational speed and initial pH were opti-mized.The intranasal immunization experiments were performed to examine the vaccine efficacy.The results showed that the 916 bp-long target gene MS-3S modified and optimized was amplified and used to successfully construct the recombinant bacterial strain LP18:MS-3S.The optimal con-ditions for recombinant protein expression were obtained and verified by Western blot,flow cy-tometry,immunofluorescence and other detection methods.The optimal expression conditions were determined as follows:induction time was 4 h with 100 pg/L of SppIP as the optimal induction concentration.Antibody-specific for the epitope was verified by ELISA experiments in serum,alve-olar lavage fluid and fecal dilutions of mice.In summary,a recombinant bacterial strain expressing the epitope antigen of the SARS-CoV-2 M protein peptide was constructed.The obtained protein can induce the body to produce humoral and mucosal immunity,which lays the foundation for the development of a vaccine candidate for the mucosal immunity of COVID-19.
维普
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