Immunogenicity Evaluation of Thermostable Microparticles Entrapping Receptor Binding Domain of SARS-CoV-2 by Single Point Administration

Receptor binding domain (RBD) of SARS-CoV-2 is a prime vaccine target against which neutralizing antibody responses are directed. Purified RBD as a vaccine candidate warrants administration of multiple doses along with adjuvants and use of delivery systems to improve its immunogenicity. The present investigation examines the immunogenicity of RBD delivered by biodegradable polymer particles from single dose administration. Mice upon single point immunization of RBD entrapped microparticles generated improved antibody response. The polymer microparticles showed better temperature stability and could be stored at 37 degrees for one month without any considerable loss of immunogenicity. Further, immunization with microparticles could elicit memory antibody response upon challenge after four months of single dose administration. Thus, using microparticles entrapping RBD as a vaccine candidate confer improved immunogenicity, temperature stability and recall response. These thermostable microparticles seem to be a potentially cost-effective approach which can help in dose reduction, provide a wider access of vaccines and accelerate the end of global pandemic.