Chimeric Hepatitis B core virus-like particles harboring SARS-CoV2 epitope elicit a humoral immune response in mice

Abstract

Background Virus-like particles are an interesting vector platform for vaccine development. Particularly, Hepatitis B virus core antigen has been used as a promising VLP platform. It is highly expressed in different recombinant expression systems, such as E. coli, and self-assembled in vitro. It effectively improves the immunogenicity of foreign antigenic epitopes on its surface. Various foreign antigens from bacteria, viruses, and protozoa can be genetically inserted into such nanoparticles. The effective immunogenicity due to VLP vaccines has been reported. However, no research has been performed on the SARS-CoV2 vaccine within this unique platform through genetic engineering. Considering the high yield of target proteins, low cost of production, and feasibility of scaling up, E. coli is an outstanding expression platform to develop such vaccines. Therefore, in this investigation, we planned to study and develop a unique HBc VLP-based vaccine against SARS-Cov2 utilizing the E. coli expression system due to its importance. Results Insertion of the selected epitope was done into the major immunodominant region (MIR) of truncated (149 residues) hepatitis B core capsid protein. The chimeric protein was constructed in PET28a+ and expressed through the bacterial E. coli BL21 expression system. However, the protein was expressed in inclusion body forms and extracted following urea denaturation from the insoluble phase. Following the extraction, the vaccine protein was purified using Ni2 + iminodiacetic acid (IDA) affinity chromatography. SDS-PAGE and western blotting were used to confirm the protein expression. Regarding the denaturation step, the unavoidable refolding process was carried out, so that the chimeric VLP reassembled in native conformation. Based on the transmission electron microscopy (TEM) analysis, the HBC VLP was successfully assembled. Confirming the assembled chimeric VLP, we explored the immunogenic effectivity of the vaccine through mice immunization with two-dose vaccination with and without adjuvant. The utilization of adjuvant was suggested to assess the effect of adjuvant on improving the immune elicitation of chimeric VLP-based vaccine. Immunization analysis based on anti-spike specific IgG antibody showed a significant increase in antibody production in harvested serum from immunized mice with HBc-VLP harboring antigenic epitope compared to HBc-VLP- and PBS-injected mice. Conclusions The results approved the successful production and the effectiveness of the vaccine in terms of humoral IgG antibody production. Therefore, this platform can be considered a promising strategy for developing safe and reasonable vaccines; however, more complementary immunological evaluations are needed.

Toward a SARS-CoV-2 VLP Vaccine: HBc/G as a Carrier for SARS-CoV-2 Spike RBM and Nucleocapsid Protein-Derived Peptides

“…Until now, only two studies have been published on genetically engineered HBc-protein-based SARS-CoV-2 vaccines produced in E. coli [ 58 , 59 ]. Sazegary et al [ 58 ] used the short RLNEVAKNL epitope of the SARS-CoV-2 S protein with G4SG4 linkers on both sides of the epitope for insertion into the MIR of a truncated, HBc149 protein. This chimeric protein was again found to make an inclusion body in the host cells and was extracted with urea in a way similar to that used in our study.…”

“…Soluble VLPs were found only for our HBc/G fusion proteins that carried a CTL epitope string at the C-terminus of the truncated HBc/G proteins HBc/G 161 and HBc/G175. Until now, only two studies have been published on genetically engineered HBcprotein-based SARS-CoV-2 vaccines produced in E. coli [58,59]. Sazegary et al [58] used the short RLNEVAKNL epitope of the SARS-CoV-2 S protein with G4SG4 linkers on both sides of the epitope for insertion into the MIR of a truncated, HBc149 protein.…”

“…Until now, only two studies have been published on genetically engineered HBcprotein-based SARS-CoV-2 vaccines produced in E. coli [58,59]. Sazegary et al [58] used the short RLNEVAKNL epitope of the SARS-CoV-2 S protein with G4SG4 linkers on both sides of the epitope for insertion into the MIR of a truncated, HBc149 protein. This chimeric protein was again found to make an inclusion body in the host cells and was extracted with urea in a way similar to that used in our study.…”

Production of Promising Heat-Labile Enterotoxin (LT) B Subunit-Based Self-Assembled Bioconjugate Nanovaccines against Infectious Diseases

“…For prophylactic vaccines, proteinaceous NPs have received more attention for their greater safety and biocompatibility. As such, various virus-like particles, such as HBc, AP205, and Qβ, have been adopted in SARS-CoV2 vaccine research [16][17][18]. Additionally, ferritin-NPs, which can induce a receptor-mediated immune response, have been used to produce SARS-CoV-2, influenza, HIV-1, Epstein-Barr, and hepatitis C virus vaccines [19][20][21][22][23].…”

Tailored Viral-like Particles as Drivers of Medical Breakthroughs

“…These VLPs are mostly explored for vaccination purposes, and due to their chimeric nature, are not described with surface functionalization. Chimeric VLPs include VLPs combining HIV-1 Gag and a fusion rabies glycoprotein [ 59 ] and VLPs with a Hepatitis B core bearing a SARS-CoV-2 epitope [ 60 ], among others).…”