A novel Rabies/SARS-CoV-2 fusion glycoprotein for VLPs expression: a potential vaccine candidate for COVID19

GARAY, ERNESTO; FONTANA, DIEGO; VILLARRAZA, CARLOS JAVIER; FUSELLI, ANTONELA; GUGLIOTTA, AGUSTINA; ANTUÑA, SEBASTÍAN; GASTALDI, VICTORIA; TARDIVO, MARÍA BELÉN; RODRÍGUEZ, MARÍA CELESTE; CEAGLIO, NATALIA; PRIETO, CLAUDIO

Santa Fe

Simposio; IX Simposio Latinoamericano de Tecnología de Cultivos Celulares - IX SLATCC 2022; 2022

Centro Biotecnológico del Litoral - FBCB - UNL

Virus-like particles (VLPs) are highly immunogenic nanoparticles that have been widely used forvaccine applications. For COVID19, VLPs have been engineered to obtain vaccine candidates through expression of SARS-CoV-2 S, M, E and N proteins. The production of these native VLPs is challenging, as multiple proteins must be expressed to assure VLP budding. As an alternative, we designed a novel rabies glycoprotein, fused to the SARS-CoV-2 Spike ectodomain stabilized in the pre-fusion conformation, with the goal to express and characterize chimeric VLPs (cVLPs) as a COVID19 vaccine candidate. The fusion protein was expressed in HEK293 cells, and its plasma membrane localization was confirmed by immunofluorescence. Using anti-RBD mAbs and convalescent plasma we specifically detect the exposition of key SARS-CoV-2 antigenic epitopes in its structure. Moreover, the correct interaction between our fusion protein with ACE2 receptor was confirmed in HEK293-ACE2 cells transduction assay, using pseudotyped GFP expressing lentiviruses. Further, cVLPs were expressed, purified and its morphology was assessed by transmission electron microscopy (TEM) and immunoTEM. Finally, the immunogenicity of cVLPs was evaluated in mice vaccinated with two doses of VLPs, 3 weeks apart. Specific antibodies response was detected using either purified RBD or the trimeric spike protein in ELISA assays. High antibody titers were observed, even 3 months after priming. Furthermore, after a booster the animals showed a significative increment of the antibody titers, higher than the obtained 15 days after second dose. In conclusion, we were able to obtain a novel cVLP that presents SARS-CoV-2 native-like morphology and induces a specific humoral immune response in mice, becoming a promising candidate for vaccine applications.