SARS-CoV-2 RBD Conjugated to Polyglucin, Spermidine, and dsRNA Elicits a Strong Immune Response in Mice

• Published in: Vaccines (Basel) Vol. 11; no. 4; p. 808
• Main Authors: Volosnikova, Ekaterina A., Merkuleva, Iuliia A., Esina, Tatiana I., Shcherbakov, Dmitry N., Borgoyakova, Mariya B., Isaeva, Anastasiya A., Nesmeyanova, Valentina S., Volkova, Natalia V., Belenkaya, Svetlana V., Zaykovskaya, Anna V., Pyankov, Oleg V., Starostina, Ekaterina V., Zadorozhny, Alexey M., Zaitsev, Boris N., Karpenko, Larisa I., Ilyichev, Alexander A., Danilenko, Elena D.
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.04.2023; MDPI
• Subjects: adjuvant; Adjuvants; Aluminum; Animals; Antibodies; Antibody-drug conjugates; Antigens; CD4 antigen; CD8 antigen; Cloning; Comparative analysis; Coronaviruses; COVID-19; COVID-19 vaccines; Dosage and administration; Double-stranded RNA; Immune response; Immune response (humoral); Immune system; Immunization; Immunogenicity; Immunoglobulin G; Laboratory animals; Lymphocytes; Lymphocytes T; Nanoparticles; Neutralizing; Polyamines; Proteins; RBD; receptor-binding domain; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2; Spermidine; Spike protein; Testing; Vaccines; Vectors (Biology); Viral diseases; Yeast; Russia; United States > US; Germany; COVID-19; SARS-CoV-2; RBD; adjuvant; receptor-binding domain
• ISSN: 2076-393X; 2076-393X
• DOI: 10.3390/vaccines11040808

Despite the rapid development and approval of several COVID vaccines based on the full-length spike protein, there is a need for safe, potent, and high-volume vaccines. Considering the predominance of the production of neutralizing antibodies targeting the receptor-binding domain (RBD) of S-protein after natural infection or vaccination, it makes sense to choose RBD as a vaccine immunogen. However, due to its small size, RBD exhibits relatively poor immunogenicity. Searching for novel adjuvants for RBD-based vaccine formulations is considered a good strategy for enhancing its immunogenicity. Herein, we assess the immunogenicity of severe acute respiratory syndrome coronavirus 2 RBD conjugated to a polyglucin:spermidine complex (PGS) and dsRNA (RBD-PGS + dsRNA) in a mouse model. BALB/c mice were immunized intramuscularly twice, with a 2-week interval, with 50 µg of RBD, RBD with Al(OH)3, or conjugated RBD. A comparative analysis of serum RBD-specific IgG and neutralizing antibody titers showed that PGS, PGS + dsRNA, and Al(OH)3 enhanced the specific humoral response in animals. There was no significant difference between the groups immunized with RBD-PGS + dsRNA and RBD with Al(OH)3. Additionally, the study of the T-cell response in animals showed that, unlike adjuvants, the RBD-PGS + dsRNA conjugate stimulates the production of specific CD4+ and CD8+ T cells in animals.