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

Virus-like particles (VLPs) offer an attractive possibility for the development of vaccines. Recombinant core antigen (HBc) of Hepatitis B virus (HBV) was expressed in different systems, and the E. coli expression system was shown to be effective for the production of HBc VLPs. Here, we used HBc of the HBV genotype G (HBc/G) as a technologically promising VLP carrier for the presentation of spike RBM and nucleocapsid protein-derived peptides of the SARS-CoV-2 Delta variant for subsequent immunological evaluations of obtained fusion proteins. The major immunodominant region (MIR) of the HBc/G protein was modified through the insertion of a receptor binding motif (RBM) from the S protein or B-cell epitope-containing peptide from the N protein. The C-terminus of the two truncated HBc/G proteins was used for the insertion of a group of five cytotoxic T lymphocyte (CTL) epitopes from the N protein. After expression in E. coli, the MIR-derived proteins were found to be insoluble and were recovered through step-wise solubilization with urea, followed by refolding. Despite the lack of correct VLPs, the chimeric proteins induced high levels of antibodies in BALB/c mice. These antibodies specifically recognized either eukaryotically expressed hRBD or bacterially expressed N protein (2-220) of SARS-CoV-2. CTL-epitope-containing proteins were purified as VLPs. The production of cytokines was analyzed through flow cytometry after stimulation of T-cells with target CTL peptides. Only a protein with a deleted polyarginine (PA) domain was able to induce the specific activation of T-cells. At the same time, the T-cell response against the carrier HBc/G protein was detected for both proteins. The neutralization of SARS-CoV-2 pseudotyped murine retrovirus with anti-HBc/G-RBM sera was found to be low.

Human immunodeficiency virus and hepatitis B genotype G/A2 recombinant co-infection: a case study.

BACKGROUND: Hepatitis B virus (HBV) genotypes have distinct geographical distributions and are associated with different clinical courses. HBV genotype G (HBV/G) is extremely rare among Human immunodeficiency virus (HIV) infected populations in Japan. Genetic analysis and clinical course of recombinant forms with HBV/G infection are seldom reported in the literature. CASE PRESENTATION: A 36-year old homosexual man with HIV infection was referred to a general hospital for assessment of chronic HBV infection. We cloned full-length HBV isolates and determined the complete genome sequences of 2 obtained clones, although mixture of multiple variant with different length is detected by HBV-DNA genotyping. The Bootscaning analysis using a full-length HBV genome revealed the clones represented as the HBV/A2 and the HBV/G/A2 recombinant strain. The HBV-DNA decreased from >9.1 to 2.5 log copies/mL after 24 months of antiretroviral therapy. CONCLUSIONS: This patient was co-infected with HBV/A2 and HBV/G/A2 recombinant strain. This recombinant strain was not identical to HBV/G/A2 strains previously reported from Japan. Recombination with other genotypes could alter the clinical manifestations of chronic hepatitis B in people living with HIV.