Bivalent mucosal peptide vaccines administered using the LCP carrier system stimulate protective immune responses against Streptococcus pyogenes infection.

Despite the broad knowledge about the pathogenicity of Streptococcus pyogenes there is still a controversy about the correlate of protection in GAS infections. We aimed in further improving the immune responses stimulated against GAS comparing different vaccine formulations including bis-(3',5')-cyclic dimeric adenosine monophosphate (c-di-AMP) and BPPCysMPEG, a derivative of the macrophage-activating lipopeptide (MALP-2), as adjuvants, respectively, to be administered with and without the universal T helper cell epitope P25 along with the optimized B cell epitope J14 of the M protein and B and T cell epitopes of SfbI. Lipopeptide based nano carrier systems (LCP) were used for efficient antigen delivery across the mucosal barrier. The stimulated immune responses were efficient in protecting mice against a respiratory challenge with a lethal dose of a heterologous S. pyogenes strain. Moreover, combination of the LCP based peptide vaccine with c-di-AMP allowed reduction of antigen dose at the same time maintaining vaccine efficacy.

The application of self-assembled nanostructures in peptide-based subunit vaccine development.

Peptide based-vaccines are becoming one of the most widely investigated prophylactic and therapeutic health care interventions against a variety of diseases, including cancer. However, the lack of a safe and highly efficient adjuvant (immune stimulant) is regarded as the biggest obstacle to vaccine development. The incorporation of a peptide antigen in a nanostructure-based delivery system was recently shown to overcome this obstacle. Nanostructures are often formed from antigens conjugated to molecules such as polymers, lipids, and peptide, with the help of self-assembly phenomenon. This review describes the application of self-assembly process for the production of peptide-based vaccine candidates and the ability of these nanostructures to stimulate humoral and cellular immune responses.

The use of a conformational cathepsin D-derived epitope for vaccine development against Schistosoma mansoni.

Schistosomiasis is caused by the infection from Schistosoma species. Among these, Schistosoma mansoni is one of the major species that infects millions of people worldwide. The use of praziquantel is effective in clearing the infestation but treatment of a large and widespread population in endemic areas is unsustainable. Thus, synergistic approach of using drug and vaccination can serve as an alternative to the current treatment. In this study, we have developed vaccine candidates that composed of three components: a B-cell epitope derived from S. mansoni cathepsin D protein (Sm-CatD) flanked by GCN4 helix promoting peptide; a promiscuous T-helper epitope (P25); and a lipid core peptide system, in attempt to develop self-adjuvanting vaccine candidates against the schistosome. Physicochemical properties of the vaccine candidates were analysed and antibodies to each construct were raised in BALB/c mice. The vaccine candidates were able to self-assemble into particles that induced high titres of IgG without the use of additional adjuvant. The antibody levels were comparable to that induced by peptide formulated with strong but toxic Freund's adjuvant. The integration of a GCN4 sequence induced the helical conformation of the epitope, while the addition of the T helper peptide was very effective in inducing consistent IgG-specific antibodies response amongst mice. These findings are particularly encouraging for the development of efficient and immunogenic vaccine against schistosomiasis.

Cyclization enhances function of linear anti-arthritic peptides.

This study describes the biophysical and immunomodulatory features of a cyclic peptide termed C1 which consists of alternating d-, l-amino acids and is capable of inhibiting IL-2 production in vitro and reducing the induction and extent of T-cell mediated inflammation in animal models. Solid-state nuclear magnetic resonance demonstrates that the peptide orders the lipid bilayer, suggesting a transmembrane orientation, and this is supported by surface plasmon resonance indicating strong binding affinity of C1 to model membranes. In vitro cell viability and proliferation assays show that C1 does not disrupt the integrity of cell surface membranes. Permeation studies of C1 and analogs across human epidermis cells show that the stability and skin permeability are enhanced by cyclization. Treatment with C1 in an asthma and in an arthritis animal model resulted in a suppressed immune response. Cyclization may be a useful means of enhancing biological linear peptide activity and improving delivery.

The topology, in model membranes, of the core peptide derived from the T-cell receptor transmembrane domain.

The T-cell receptor-CD3 complex (TCR-CD3) serves a critical role in protecting organisms from infectious agents. The TCR is a heterodimer composed of α- and ß-chains, which are responsible for antigen recognition. Within the transmembrane domain of the α-subunit, a region has been identified to be crucial for the assembly and function of the TCR. This region, termed core peptide (CP), consists of nine amino acids (GLRILLLKV), two of which are charged (lysine and arginine) and are crucial for the interaction with CD3. Earlier studies have shown that a synthetic peptide corresponding to the CP sequence can suppress the immune response in animal models of T-cell-mediated inflammation, by disrupting proper assembly of the TCR. As a step towards the understanding of the source of the CP activity, we focused on CP in egg phosphatidylcholine/cholesterol (9:1, mol/mol) model membranes and determined its secondary structure, oligomerization state, and orientation with respect to the membrane. To achieve this goal, 15-residue segments of TCRα, containing the CP, were synthesized and spin-labeled at different locations with a nitroxide derivative. Electron spin-echo envelope modulation spectroscopy was used to probe the position and orientation of the peptides within the membrane, and double electron-electron resonance measurements were used to probe its conformation and oligomerization state. We found that the peptide is predominantly helical in a membrane environment and tends to form oligomers (mostly dimers) that are parallel to the membrane plane.

The combination of Neosartorya (Aspergillus) fischeri antifungal proteins with rationally designed γ-core peptide derivatives is effective for plant and crop protection.

Plant pathogenic fungi are responsible for enormous crop losses worldwide. Overcoming this problem is challenging as these fungi can be highly resistant to approved chemical fungicides. There is thus a need to develop and introduce fundamentally new plant and crop protection strategies for sustainable agricultural production. Highly stable extracellular antifungal proteins (AFPs) and their rationally designed peptide derivatives (PDs) constitute feasible options to meet this challenge. In the present study, their potential for topical application to protect plants and crops as combinatorial biofungicides is supported by the investigation of two Neosartorya (Aspergillus) fischeri AFPs (NFAP and NFAP2) and their γ-core PDs. Previously, the biofungicidal potential of NFAP, its rationally designed γ-core PD (γNFAP-opt), and NFAP2 was reported. Susceptibility tests in the present study extended the in vitro antifungal spectrum of NFAP2 and its γ-core PD (γNFAP2-opt) to Botrytis, Cladosporium, and Fusarium spp. Besides, in vitro additive or indifferent interactions, and synergism were observed when NFAP or NFAP2 was applied in combination with γNFAP-opt. Except for γNFAP2-opt, the investigated proteins and peptides did not show any toxicity to tomato plant leaves. The application of NFAP in combination with γNFAP-opt effectively inhibited conidial germination, biofilm formation, and hyphal extension of the necrotrophic mold Botrytis cinerea on tomato plant leaves. However, the same combination only partially impeded the B. cinerea-mediated decay of tomato fruits, but mitigated the symptoms. Our results highlight the feasibility of using the combination of AFP and PD as biofungicide for the fungal infection control in plants and crops. Supplementary Information: The online version contains supplementary material available at 10.1007/s10526-022-10132-y.

Transcriptome sequencing analysis of the MSDIN gene family encoding cyclic peptides in lethal Amanita fuligineoides.

Amanita fuligineoides, a lethal mushroom discovered in China, contains abundant cyclic peptide toxins that can cause fatal poisoning. However, the MSDIN gene family encoding for these cyclic peptides in A. fuligineoides has not been systematically studied. In this research, the transcriptome sequencing of A. fuligineoides was performed and its MSDIN family members were analyzed. A total of 4.41 Gb data containing 30833 unigenes was obtained; sequence alignments throughout several databases were done to obtain their functional annotations. Based on these annotations, MSDIN genes were found and verified by RT-PCR. A total of 29 different core peptides were obtained: 3 toxin genes, encoding ß-amanitin (ß-AMA), phalloidin (PHD), and phallacidin (PCD), and 26 genes encoding unknown cyclic peptides, 20 of which are reported for the first time and may encode for novel cyclic peptides. Analysis of the predicted precursor peptides indicated that octocyclic peptides were the main MSDIN peptides synthesized by A. fuligineoides, accounting for the 45%. A phylogenetic analysis suggested that studied precursor peptides could be clustered into 7 clades, which might represent different functionalities. Results suggested that A. fuligineoides might have a strong capacity to synthesize cyclopeptides, laying the foundation for their excavation and utilization.

Current status and future prospects of protein vaccine candidates against Schistosoma mansoni infection.

Schistosomiasis is an acute and chronic tropical parasitic disease caused by blood dwelling worm of the genus Schistosoma. It is the most destructive disease globally and is a major cause of morbidity and mortality for developing countries. Three main species of schistosomes infect human beings from which S. mansoni is the most common and widespread. Over the last several decades, chemotherapy using praziquantel has been a commonly used strategy for the treatment and control of schistosomiasis. However, control programs focused exclusively on chemotherapy have been challenging because of the frequency and rapidity of reinfection and these programs were expensive. Thus, new schistosomiasis control strategies will be needed. Vaccination strategy would be an ideal tool for a significant and sustainable reduction in the transmission and disease burden of schistosomiasis. An effective anti schistosome vaccine would greatly contribute to decreasing schistosomiasis-associated morbidity via protective immune responses leading to reduced worm burdens and decreased egg production. Vaccine development is a long process that can take decades. There have been three candidate vaccines that have been produced by Good Manufacturing Procedure and entered human clinical trials for S. mansoni are Sm14, SmTSP-2, and Sm-p80. Other candidates that are in pre-clinical trials at various stages include paramyosin, Sm29, SmKI-1, and Sm23. Since the growth of several new technologies, including genomics, transcriptomics, microarrays, immunomic profiling, and proteomics, have helped in the identification of promising new target schistosome antigens. Therefore, this review considers the present status of protein vaccine candidates against Schistosoma mansoni and provides some insight on prospects vaccine design and discovery.

Multilayer engineered nanoliposomes as a novel tool for oral delivery of lipopeptide-based vaccines against group A Streptococcus.

AIM: To develop an oral nanovaccine delivery system for lipopeptide-based vaccine candidate against group A Streptococcus. MATERIALS & METHODS: Lipid-core peptide-1-loaded nanoliposomes were prepared as a template and coated with opposite-charged polyelectrolytes to produce particles with size <200 nm. Efficacy of this oral nanovaccine delivery system was evaluated in mice model. RESULTS: Polymer-coated liposomes produced significantly higher antigen-specific mucosal IgA and systemic IgG titers in comparison to vaccine formulated with a strong mucosal adjuvant upon oral immunization in mice. Moreover, high levels of systemic antibody titers were retained even at day 185 postprimary immunization. CONCLUSION: Efficient oral delivery platform for lipopeptide-based vaccines has been developed.

Systematic evaluation of self-adjuvanting lipopeptide nano-vaccine platforms for the induction of potent CD8(+) T-cell responses.

AIM: Systematically evaluate lipid core peptide vaccine delivery platforms to identify core features promoting strong CD8(+) T-cell responses. MATERIALS & METHODS: Three different self-adjuvanting lipid core peptide nanovaccines each comprising four copies of the dominant ovalbumin CD8(+) T-cell epitope and varying in the utilization of a polylysine or glucose core with 2-amino-hexadecanoic acid (C16) or 2-amino-dodecanoic acid (C12) lipids were synthesized. Vaccines were tested for ability to induce CD8(+) T-cell responses and inhibit tumor growth in vivo. RESULTS: The construct utilizing C12 lipids and polylysine core induced very robust effector T cells shown to have in vivo effector capability as demonstrated by in vivo cytotoxicity and ability to inhibit tumor growth as well as modulation of dendritic cell activation. CONCLUSION: The C12 polylysine platform was an effective configuration for induction of potent CD8(+) T-cell responses.

Amyloid fibril formation from a 9 amino acid peptide, 55th-63rd residues of human lysozyme.

Hen egg white lysozyme (HEWL) readily forms amyloid fibrils in vitro. We have previously identified a core structure, termed HEWL K-peptide, involved in fibril formation. Two major peptides, peptide #3 (50th-102nd residues of human lysozyme (hLZ)) and peptide #5 (54th-102nd residues), were isolated from the hLZ amyloid fibrils that had been exposed to pH 2.0 and 58 °C, and precipitated by ultra-centrifugation. These peptides cover most of the beta-domain and C-helix of hLZ including a 9 residues sequence corresponds to a human counterpart of HEWL K-peptide, GIFQINSRY (55th-63rd residues of hLZ, thus named "human K-peptide"). Chemically synthesized human K-peptide readily formed amyloid fibrils, as in HEWL K-peptide. It was demonstrated that both at least 9 residue length and Phe residue at 3rd position of the human K-peptide were crucial for amyloidogenesis in vitro. Short peptides covering COOH-terminal region of peptides #3 and #5 did not form amyloid fibrils. These data suggested that human K-peptide region with high propensity of amyloidogenesis plays a key role as a fibril-forming core sequence of hLZ. Interestingly, human K-peptide region is flanked by two predicted semi-disordered regions (39th-52nd and 67th-75th residues). We discuss the possible role of these regions.

Novel T-cell inhibiting peptides delay the onset of Type 1 diabetes in non-obese diabetic mice.

The aim of this study was to investigate the effectiveness of immunomodulatory peptides in preventing the spontaneous onset of Type 1 diabetes in NOD mice. Two such peptides, CP and C1, were injected intraperitoneally in NOD mice three times a week starting at two different time points, nine weeks and 11 weeks of age, and blood sugar levels monitored for the development of diabetes. CP was shown to be effective in delaying the onset of diabetes compared to control (P = 0.006). The timing of peptide administration was crucial since delay in treatment did not prevent the onset of diabetes (nine weeks versus 11 weeks of age). C1 was effective in delaying the onset of Type 1 diabetes with borderline significance when given at week 11 (P = 0.05). These findings confirm the efficacy of these peptides in the prevention and possible treatment for Type 1 diabetes and thereby create new opportunities for genetic manipulation.