RABV antigenic peptide loaded polymeric nanoparticle production, characterization, and preliminary investigation of its biological activity

Nanoparticle-based antigen carrier systems have become a significant area of research with the advancement of nanotechnology. Biodegradable polymers have emerged as particularly promising carrier vehicles due to their ability to address the limitations of existing vaccine systems. In this study, we successfully encapsulated the G5-24 linear peptide, located between amino acids 253 and 275 in the primary sequence of the rabies virus G protein, into biodegradable and biocompatible PLGA copolymer using the double emulsion solvent evaporation method. The resulting nanoparticles had a size of approximately 230.9 ± 0.9074 nm, with a PDI value of 0.168 ± 0.017 and a zeta potential value of -9.86 ± 0.132 mV. SEM images confirmed that the synthesized nanoparticles were uniform in size and distribution. Additionally, FTIR spectra indicated successful peptide loading into the nanoparticles. The encapsulation efficiency of the peptide-loaded nanoparticles was 73.3%, with a peptide loading capacity of 48.2% and a reaction yield of 30.4%. Peptide release studies demonstrated that 65.55% of the peptide was released in a controlled manner over 28 d, following a 'biphasic burst release' profile consistent with the degradation profile of PLGA. This controlled release is particularly beneficial for vaccine studies. Cytotoxicity tests revealed that the R-NP formulation did not induce cytotoxicity in fibroblast cells and enhanced NO production in macrophages, indicating its potential for vaccine development.

Synthetic peptides derived from predicted B cell epitopes of nervous necrosis virus (NNV) show antigenicity and elicit immunogenic responses in Asian seabass (Lates calcarifer)

Nervous necrosis virus (NNV) has spread throughout the world, affecting more than 120 freshwater and marine fish species. While vaccination effectively prevents disease outbreaks, the difficulty of producing sufficient viruses using cell lines continues to be a significant disadvantage for producing inactivated vaccines. This study, therefore, explored the application of synthetic peptides as potential vaccine candidates for the prevention of NNV in Asian seabass (Lates calcarifer). Using the epitope prediction tool and molecular docking, three predicted immunogenic B cell epitopes (30-32 aa) derived from NNV coat protein were selected and synthesised, corresponding to amino acid positions 5 to 34 (P1), 133 to 162 (P2) and 181 to 212 (P3). All the predicted peptides interact with Asian sea bass's MHC class II by docking. The antigenicity of these peptides was determined through ELISA and all peptides were able to react with NNV-specific antibodies. Subsequently, the immunogenicity of these synthetic peptides was investigated by immunisation of Asian seabass with individual peptides (30 μg/fish) and a peptide cocktail (P1+P2+P3, 10 μg each/fish) by intraperitoneal injection, followed by a booster dose at day 28 post-primary immunisation. There was a subset of immunised fish that were able to induce upregulation of immune genes (IL-1β, TNFα, MHCI, MHCII β, CD4, CD8, and IgM-like) in the head kidney and spleen post immunization. Importantly, antibodies derived from fish immunised with synthetic peptides reacted with whole NNV virions, and sera from P1 group could neutralise NNV in an in vitro assay. Taken together, these findings indicate that synthetic linear peptides based on predicted B cell epitopes exhibited both antigenic and immunogenic properties, suggesting that they could be potential vaccine candidates for the prevention of NNV in fish.

Peptides for Vaccine Development

This review discusses peptide epitopes used as antigens in the development of vaccines in clinical trials as well as future vaccine candidates. It covers peptides used in potential immunotherapies for infectious diseases including SARS-CoV-2, influenza, hepatitis B and C, HIV, malaria, and others. In addition, peptides for cancer vaccines that target examples of overexpressed proteins are summarized, including human epidermal growth factor receptor 2 (HER-2), mucin 1 (MUC1), folate receptor, and others. The uses of peptides to target cancers caused by infective agents, for example, cervical cancer caused by human papilloma virus (HPV), are also discussed. This review also provides an overview of model peptide epitopes used to stimulate non-specific immune responses, and of self-adjuvanting peptides, as well as the influence of other adjuvants on peptide formulations. As highlighted in this review, several peptide immunotherapies are in advanced clinical trials as vaccines, and there is great potential for future therapies due the specificity of the response that can be achieved using peptide epitopes.

Armamentarium of Cryoprotectants in Peptide Vaccines: Mechanistic Insight, Challenges, Opportunities and Future Prospects

Vaccines are designed to leverage the immune system and produce long-lasting protection against specific diseases. Peptide vaccines are regarded as safe and effective way of circumventing problems such as mild allergic reactions associated with conventional vaccines. The biggest challenges associated with formulation of peptide vaccines are stability issues and conformational changes which lead to destruction of their activity when exposed to lyophilization process that may act as stressors. Lyophilization process is aimed at removal of water which involves freezing, primary drying and secondary drying. To safeguard the peptide molecules from such stresses, cryoprotectants are used to offer them viability and structural stability. This paper is an attempt to understand the physicochemical properties of peptide vaccines, mechanism of cryoprotection under the shed of water replacement, water substitution theory and cation-pi interaction theory of amino acids which aims at shielding the peptide from external environment by formation of hydrogen bonds, covalent bonds or cation-pi interaction between cryoprotectant and peptide followed by selection criteria of cryoprotectants and their utility in peptide vaccines development along with challenges and opportunities.

Lipopeptides for Vaccine Development

The development of lipopeptides (lipidated peptides) for vaccines is discussed, including their role as antigens and/or adjuvants. Distinct classes of lipopeptide architectures are covered including simple linear and ligated constructs and lipid core peptides. The design, synthesis, and immunological responses of the important class of glycerol-based Toll-like receptor agonist lipopeptides such as Pam₃CSK₄, which contains three palmitoyl chains and a CSK₄ hexapeptide sequence, and many derivatives of this model immunogenic compound are also reviewed. Self-assembled lipopeptide structures including spherical and worm-like micelles that have been shown to act as vaccine agents are also described. The work discussed includes examples of lipopeptides developed with model antigens, as well as for immunotherapies to treat many infectious diseases including malaria, influenza, hepatitis, COVID-19, and many others, as well as cancer immunotherapies. Some of these have proceeded to clinical development. The research discussed highlights the huge potential of, and diversity of roles for, lipopeptides in contemporary and future vaccine development.

Immunological properties of gold nanoparticles

In the past decade, gold nanoparticles have attracted strong interest from the nanobiotechnological community owing to the significant progress made in robust and easy-to-make synthesis technologies, in surface functionalization, and in promising biomedical applications. These include bioimaging, gene diagnostics, analytical sensing, photothermal treatment of tumors, and targeted delivery of various biomolecular and chemical cargos. For the last-named application, gold nanoparticles should be properly fabricated to deliver the cargo into the targeted cells through effective endocytosis. In this review, we discuss recent progress in understanding the selective penetration of gold nanoparticles into immune cells. The interaction of gold nanoparticles with immune cell receptors is discussed. As distinct from other published reviews, we present a summary of the immunological properties of gold nanoparticles. This review also summarizes what is known about the application of gold nanoparticles as an antigen carrier and adjuvant in immunization for the preparation of antibodies in vivo. For each of the above topics, the basic principles, recent advances, and current challenges are discussed. Thus, this review presents a detailed analysis of data on interaction of gold nanoparticles with immune cells. Emphasis is placed on the systematization of data over production of antibodies by using gold nanoparticles and adjuvant properties of gold nanoparticles. Specifically, we start our discussion with current data on interaction of various gold nanoparticles with immune cells. The next section describes existing technologies to improve production of antibodies in vivo by using gold nanoparticles conjugated with specific ligands. Finally, we describe what is known about adjuvant properties of bare gold or functionalized nanoparticles. In the Conclusion section, we present a short summary of reported data and some challenges and perspectives.

An efficient, chemically-defined semisynthetic lipid-adjuvanted nanoparticulate vaccine development system

A novel vaccine development platform that enables the site-specific conjugation of synthetic lipid adjuvants to recombinant proteins was produced. This technology facilitates the simple and efficient production of homogeneous, chemically-defined, semisynthetic lipoprotein vaccines. Using a polytope 'string-of-beads' approach, a synthetic gene incorporating seven Streptococcus pyogenes M protein strain-specific antigens, and a conserved M protein antigen (J14) was produced, expressed, and attached to a lipoamino acid based adjuvant (lipid core peptide; LCP). Nanoparticles (40 nm diameter) of an optimal size for stimulating antibody-mediated immunity were formed upon the addition of these lipoproteins to aqueous buffer (PBS). Systemic antigen-specific IgG antibodies were raised against all eight antigens in C57BL/6J mice, without the need to formulate with additional adjuvant. These antibodies bound cell surface M proteins of S. pyogenes strains represented within the polytope sequence, with higher antibody levels observed where a dendritic cell targeting peptide (DCpep) was incorporated within the LCP adjuvant.

FROM THE CLINICAL EDITOR

In this study, a novel vaccine development system is presented, combining adjuvants with recombinant protein antigens, and presenting the antigen in a nanoparticle system optimized for antibody production. They demonstrate efficient vaccination in a murine model system without the need for additional adjuvants.