Abstract
Subunit vaccines consist of non-genetic material, such as peptides or proteins. They are considered safe because they have fewer side effects; however, they have low immunogenicity when used alone. We aimed to enhance the immune response of peptide-based vaccines by using self-assembled multimeric peptide amphiphiles (PAs). We designed two epitope PAs by conjugating epitope peptides from Enterovirus 71 (EV71) virus particle (VP) 1 and VP3 capsid proteins with different fatty acid chain lengths (VP1PA and VP3PA). These PAs self-assembled into supramolecular structures at a physiological pH, and the resulting structures were characterized using atomic force microscopy. Multi-epitope PAs (m-PAs) consisted of a 1:1 mixture of VP1PA and VP3PA solutions. To evaluate immunogenicity, m-PA constructs were injected with adjuvant subcutaneously into female Balb/c mice. Levels of antigen-specific immunoglobulin G (IgG) and IgG1 in m-PA-injected mice serum samples were analyzed using ELISA and Western blotting. Additionally, cytokine production stimulated by each antigen was measured in splenocytes cultured from immunized mice groups. We found that m-PA showed improved humoral and cellular immune responses compared to the control and peptide groups. The sera from m-PA immunized mice group could neutralize EV71 infection and protect host cells. Thus, self-assembled m-PAs can promote a protective immune response and can be developed as a potential platform technology to produce peptide vaccines against infectious viral diseases.
Highlights
Vaccines play an essential role in preventing infectious diseases
The control PAs (CPAs) were GGGCCK-palmitic acid (CPA-C16) and GGGCCK-stearic acid (CPA-C18) without the epitope peptides (Figure 2b,d). Both the solution of VP1PA:CPA-16 and VP3PA:CPA-18, each at a molar ratio of 6:4, turned turbid, and a white precipitate was observed at the physiological pH 7.4 (Figure 3a)
atomic force microscopy (AFM) images showed that VP1PA and VP3PA assembled into nanofibers with relatively uniform diameter (131.8 ± 16.8 nm for VP1PA and 77.1 ± 17.8 nm for VP3PA) at a concentration of 1 μg/mL in drop-cast samples (Figure 3b,c)
Summary
Vaccines play an essential role in preventing infectious diseases. At present, 300 years after the first vaccine was released, vaccination prevents 2–3 million deaths annually, according to the WHO [1,2]. The majority of vaccines against infectious diseases consist of inactivated or live attenuated pathogens [1,3] These conventional vaccines are potent but are not always safe; they may cause the disease itself or contain contaminants that cause adverse effects [4,5]. The immunogenicity of subunit vaccines differs based on the antigen used and are generally less immunogenic than inactive or attenuated pathogens and often cannot confer optimal protection [6]. For this reason, various approaches to increase the immunogenicity of peptide vaccines have been tried. Antigenic materials composed of epitope peptides linked to lipopeptides, polymer-based nanoparticles, and virus-like particles have been found to induce robust antibody and cellular immune responses [7,8,9,10,11]
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