Immunogenicity Of Protein Antigens Research Articles

Hybrid Proteins with Short Conformational Epitopes of the Receptor-Binding Domain of SARS-CoV-2 Spike Protein Promote Production of Virus-Neutralizing Antibodies When Used for Immunization

Based on the previously developed approach, hybrid recombinant proteins containing short conformational epitopes (a.a. 144-153, 337-346, 414-425, 496-507) of the receptor-binding domain (RBD) of SARS-CoV-2 Spike protein (S protein) were synthesized in Escherichia coli cells as potential components of epitope vaccines. Selected epitopes are involved in protein–protein interactions in the S protein complexes with neutralizing antibodies and ACE2 (angiotensin-converting enzyme 2). The recombinant proteins were used for immunization of mice (three doses with 2-week intervals), and the immunogenicity of protein antigens and ability of the resulting sera to interact with inactivated SARS-CoV-2 and RBD produced in eukaryotic cells were examined. All recombinant proteins showed high immunogenicity; the highest titer in the RBD binding assay was demonstrated by the serum obtained after immunization with the protein containing epitope 414-425. At the same time, the titers of sera obtained against other proteins in the RBD and inactivated virus binding assays were significantly lower than the titers of sera obtained with the previously produced four proteins containing the loop-like epitopes 452-494 and 470-491, the conformation of which was fixed with a disulfide bond. We also studied activation of cell-mediated immunity by the recombinant proteins that was monitored as changes in the levels of cytokines in the splenocytes of immunized mice. The most pronounced increase in the cytokine synthesis was observed in response to the proteins containing epitopes with disulfide bonds (452-494, 470-491), as well as epitopes 414-425 and 496-507. For some recombinant proteins with short conformational epitopes, adjuvant optimization allowed to obtained mouse sera displaying virus-neutralizing activity in the microneutralization assay with live SARS-CoV-2 (hCoV-19/Russia/StPetersburg-3524/2020 EPI_ISL_415710 GISAID). The results obtained can be used to develop epitope vaccines for prevention of COVID-19 and other viral infections.

Effectivity of nanovaccine against tick-borne encephalitis

The tubular immunostimulating complex (Tl-complex) is a new nanoparticulate antigen delivery system, which was developed to enhance immunogenicity of different subunit antigens within anti-infectious vaccines and increase their economic efficacy and safety. TI-complexes are self-organized from mixture of triterpene glycosides from Cucumaria japonica, cholesterol and monogalactosyldiacylglycerol (MGDG) from marine macrophytes. MGDG plays role of lipid matrix for subunit protein antigen interrupted in TI-complexes. Microviscosity of MGDG was shown to influence the conformation and immunogenicity of protein antigen. Present work was aimed to study adjuvant effect of Tl-complexes on immunogenicity of chimeric protein antigen based on E protein domain III of tick-borne encephalitis (TBE) virus and OmpF porin of Yersinia pseudotuberculosis depending on MGDGs isolated from different marine algae and seagrass. It was shown that TI-complex including MGDG from Ulva lactuca was most effective. Immunization by chimeric antigen incorporated in TI-complexes provided a high level of animal protection in experimental infection with TBE. Thus, the proposed construction is promising for the development of vaccines against TBE.

The use of a TLR2 agonist‐based adjuvant for enhancing effector and memory CD8 T‐cell responses

We have previously shown that the immunogenicity of protein antigens can be significantly enhanced if electrostatically associated with the Toll-like receptor-2 agonist-based lipopeptide R4Pam2Cys. The precise mechanisms and effectiveness of the cytotoxic T-lymphocyte (CTL)-mediated response facilitated by this agonist, however, have not been studied. Here we show that priming by dendritic cells (DCs) in the draining lymph nodes of animals vaccinated with antigen delivered using R4Pam2Cys results in significantly improved T-cell proliferation and induces their differentiation into polyfunctional effector CTLs characterised by granzyme B expression and the ability to secrete interferon-γ, interleukin-2 and tumor necrosis factor-α 7 days after vaccination. After 30 days, frequencies of antigen-specific CD62(low)CD127(high) (effector memory), CD62(high)CD127(high) (central memory) and CD43(low)CD27(high) CD8(+) T cells, a phenotype associated with strong recall responses against respiratory infections, are also increased compared with responses obtained with antigens formulated in the adjuvants Alum (alhydrogel) and CFA (complete Freund's adjuvant). The phenotypic changes observed in these mice vaccinated using R4Pam2Cys further correlated with their ability to recall specific T cells into the lung to mediate the reduction of pulmonary viral titres following challenge with a chimeric influenza virus containing the K(b)OVA257-264 epitope compared with animals vaccinated using Alum or CFA. The findings from this study not only demonstrate that better T-cell responses can be elicited using R4Pam2Cys compared with classically utilised adjuvants but also highlight the potential effectiveness of this lipopeptide-based adjuvant particularly against viral infections that require resolution through cell-mediated immunity.

Heat shock protein 110 improves the anti-tumor effects of the cytotoxic T lymphocyte epitope E7 in mice

Several strategies have been used to enhance the vaccine-induced immunity of peptide vaccines and effective therapeutic benefits, including the utilization of heat shock proteins (HSP), especially the HSP70 family. HSP110 exhibits a higher binding affinity with protein and is capable of enhancing the immunogenicity of protein antigens; however, whether HSP110 can also increase the efficiency of peptide vaccine remains unclear. Here, we investigated mHSP110 as a chaperone immunoadjuvant to enhance the immune response to HPV16 oncoprotein E7-derived CTL epitopeE749-57 in a mouse model.We developed the HSP110- E749-57 complex and demonstrated that mHSP110 could form complexes with peptide E749-57 using FITC-labeled E749-57 as the tracer. Inoculation of the mHSP110-E749-57 complex was capable of priming strong epitope-specific immune response as determined by its ability to elicit an epitope-specific splenocytes proliferation and a cytotoxic T cell response, and IFN-γ production in splenocytes. Results also showed that immunization with the mHSP110- E749-57 complex completely protected mice against subsequent challenge with tumor cells. More importantly, immunization of this complex also significantly inhibited the growth of established tumors and prolonged the survival time of the tumor-bearing animals. Thus, mHSP110-E749-57 complex vaccine represents a potentially powerful approach for use in the immunotherapy of cervical cancer associated with HPV16 infection. More importantly, the multi-epitopes derived from E7 and other E proteins can be applied to the strategy described in this study to form a multi-antigenic vaccine to induce an improved anti-tumor immune response to cervical cancer in the future.