Study of the Immunogenicity of Combination of Recombinant RBD (Omicron) and Nucleocapsid Proteins of SARS-CoV-2 Expressed in Pichia Pastoris

Shakhnoz Azimova1 Sobirdjan Sasmakov1 Farkhod Eshboev1 , * Open Modal Jaloliddin Abdurakhmanov1 Oybek Ashirov1 Shukhrat Khasanov1 Artyom Makhnyov1 Asadali Baymirzaev1 Orzigul Alimukhamedova1 Tulkin Sadullaev1 Elvira Yusupova1 Khusan Nasriddinov1 Ekaterina Terenteva1 Mukaddas Umarova1 Umida Khamidova1 Galina Piyakina1 Elena Lysova1 Saidazim Ikramov1 Nigora Tosheva1 Khayotjon Dolimov1 Saodat Gaynazarova1 Aygul Yarilkaganova1 Authors Info & Affiliations
The Open Biochemistry Journal 30 Nov 2023 RESEARCH ARTICLE DOI: 10.2174/011874091X273716231122102205



SARS-CoV-2 is a virus responsible for the COVID-19 pandemic that began in late 2019. This pandemic has had a devastating impact worldwide, resulting in over 6.95 million deaths. The development of effective vaccines against the virus is crucial for preventing infection and reducing the severity of the disease. Objective: This study aimed to obtain the recombinant receptor-binding domain (RBD) and the nucleocapsid (N) proteins of SARS-CoV-2 as well as assess the immunogenicity of the combination of these recombinant proteins.


The recombinant plasmids encoding the receptor-binding domain (RBD) of the spike protein of the Omicron variant and the nucleocapsid protein of SARS-CoV-2 were cloned into the yeast Pichia pastoris. The optimal fermentation conditions were established for recombinant P. pastoris strains. The methods for the isolation and purification of the target recombinant RBD and nucleocapsid proteins were developed. The immunogenicity of the purified recombinant proteins was evaluated by injecting them into mice and analyzing the specific IgG antibody responses using ELISA.


The study found that RBD and N proteins, as well as their combination, showed antigenic specificity and were highly immunogenic in mice. The immunogenicity was measured by determining the antibody titer, which represents the concentration of antibodies produced in response to the antigen. The antibody titers were 1:60000 for both RBD and N proteins, and 1:80000 for their combination.


These findings suggest that the expressed proteins could be potential candidates for the development of vaccines or immunological diagnostic test kits for combatting or detecting the Omicron variant of SARS-CoV-2.

Keywords: Nucleocapsid, RBD, SARS-CoV-2, Omicron, Pichia pastoris, Recombinant protein, Immunogenicity.
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