Rapid and label-free A2 peptide epitope decorated CoFe2O4-C60 nanocomposite-based electrochemical immunosensor for detecting Visceral Leishmaniasis

Diagnosis of Visceral Leishmaniasis is challenging due to the shared clinical features with malaria, typhoid, and tuberculosis. A CoFe2O4-C60 nanocomposite-based immunosensor decorated with a sensitive A2 peptide antigen was fabricated to detect anti-A2 antibodies for application in visceral leishmaniasis diagnosis. The flame-synthesised nanocomposite was characterised using Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy and electrochemical impedance spectroscopy (EIS) techniques. N terminated specific A2 peptide epitope antigen (NH2-QSVGPLSVGP-OH) was synthesised and characterised by high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectroscopy (LC-MS). Using EDC/NHS, A2 peptide antigen (Apg) was immobilised on the CoFe2O4-C60-modified electrode. The performance of the immunosensor, Apg-CoFe2O4-C60NP/GCE, was evaluated by testing its ability to detect varying concentrations of anti-A2 antibody solution in PBS and spiked serum with 1 mM [Fe(CN)6]3-/4- in 0.01 M PBS (pH 7.4) as supporting electrolyte. using differential pulse voltammetry. The immunosensor showed excellent reproducibility and a linear range of 10-10-10-1 µg/mL, with an experimental detection limit of 30.34 fg/mL. These results suggest that the fabricated sensor has great potential as a tool for diagnosing visceral leishmaniasis.

Supramolecular assembly of a trivalent peptide hydrogel vaccine for cancer immunotherapy

Vaccination shows great promise in cancer immunotherapy. However, the induction of robust and broad therapeutic CD8 T cell immunity against tumors is challenging due to the essential heterogenicity of tumor antigen expression. Recently, bioinspired materials have reshaped the field of cancer nanomedicine. Herein, a bioinspired nanofibrous trivalent peptide hydrogel vaccine was constructed using the spontaneous supramolecular co-assembly of three antigenic epitope-conjugated peptides, which could mimic the fibrillar structure and biological function of the extracellular matrix and naturally occurring protein assembly. The hydrogel vaccine could be accurately and flexibly adjusted to load each antigenic peptide at a defined ratio, which facilitated the antigen presentation of dendritic cells and significantly improved the initiation of CD8 T cell response and the secretion of interferon-γ (IFN-γ). C57BL/6 mice were immunized with the trivalent peptide hydrogel vaccine, where it elicited a high broad-spectrum antitumor CD8 T cell response that significantly inhibited the growth of B16 tumors in the absence of additional immunoadjuvants or delivery systems. In summary, the supramolecular assembly of triple antigenic epitope-conjugated peptides offers a simple, customizable, and versatile approach for the development of cancer vaccines with remarkable therapeutic efficacy, thereby providing a highly versatile platform for the application of personalized multivalent tumor vaccines. STATEMENT OF SIGNIFICANCE: (1) We report a feasible, versatile and bioinspired approach to manufacture a multivalent peptide-based hydrogel cancer vaccine in the absence of additional adjuvants, which closely mimics immune niches, co-delivers antigen epitopes, greatly promotes antigen presentation to DCs and their subsequent homing to dLNs and elicits a broad-spectrum antitumor CD8 T cell response, resulting in significant inhibition of B16 tumor growth. (2) This feasible and efficient co-assembly strategy provides an attractive platform for engineering a range of multivalent vaccines at defined ratios to further enhance antigen-specific T cell responses. This approach may also be used for personalized immunotherapy with neo-epitopes.

High-performance immune diagnosis of tuberculosis: Use of phage display and synthetic peptide in an optimized experimental design

Immunoassays are practical and cost-effective approaches suitable for large-scale tuberculosis (TB) screening. This study identified new peptide mimotopes of Mycobacterium tuberculosis and applied them in the serodiagnosis of TB. Thereby, linear (X₁₅, X₈CX₈) and constrained (LX-4 and LX-8) phage display peptide libraries were screened with purified Immunoglobulin G antibodies from TB-positive patients, and eight mimotopes were selected. The mimotope peptides were screened using the SPOT-synthesis technique followed by immunoblotting. Peptides P.Mt.PD.4 and P.Mt.PD.7 demonstrated the highest binding affinity and were chemically synthesized and used as antigens for enzyme-linked immunosorbent assay (ELISA) assays. Experimental designs were used to optimize the assays and to assess each variable's influence. Peptide P.Mt.PD.7 was differentiated between positive and negative samples and achieved 100% sensitivity and specificity when tested on a 100-sera panel. Therefore, the selected peptide was applied to the ELISA assay as a screening method for diagnosing TB represents a potential tool for helping to combat the disease.

Structural Prediction of Peptide-MHC Binding Modes

The immune system is constantly protecting its host from the invasion of pathogens and the development of cancer cells. The specific CD8⁺ T-cell immune response against virus-infected cells and tumor cells is based on the T-cell receptor recognition of antigenic peptides bound to class I major histocompatibility complexes (MHC) at the surface of antigen presenting cells. Consequently, the peptide binding specificities of the highly polymorphic MHC have important implications for the design of vaccines, for the treatment of autoimmune diseases, and for personalized cancer immunotherapy. Evidence-based machine-learning approaches have been successfully used for the prediction of peptide binders and are currently being developed for the prediction of peptide immunogenicity. However, understanding and modeling the structural details of peptide/MHC binding is crucial for a better understanding of the molecular mechanisms triggering the immunological processes, estimating peptide/MHC affinity using universal physics-based approaches, and driving the design of novel peptide ligands. Unfortunately, due to the large diversity of MHC allotypes and possible peptides, the growing number of 3D structures of peptide/MHC (pMHC) complexes in the Protein Data Bank only covers a small fraction of the possibilities. Consequently, there is a growing need for rapid and efficient approaches to predict 3D structures of pMHC complexes. Here, we review the key characteristics of the 3D structure of pMHC complexes before listing databases and other sources of information on pMHC structures and MHC specificities. Finally, we discuss some of the most prominent pMHC docking software.

Histone Protein Epitope Mapping for Autoantibody Recognition in Rheumatoid Arthritis

Deiminated proteins are the target of diagnostic anti-citrullinated peptide/protein autoantibodies (ACPA) in rheumatoid arthritis (RA). Deiminated histone H4 contained in the neutrophil extracellular traps reacts with ACPA, becoming an interesting diagnostic antigen for RA. The identification of the ACPA binding site in histone H4 was performed experimentally by mapping the complete sequence. The method describes the synthesis of an overlapping peptide library covering the entire deiminated sequence of H4 and its further evaluation in ELISA. A detailed description of an ELISA protocol to test RA patients' sera against the synthesized peptides and ACPA is provided.

Poly(propylacrylic acid)-peptide nanoplexes as a platform for enhancing the immunogenicity of neoantigen cancer vaccines

Cancer vaccines targeting patient-specific tumor neoantigens have recently emerged as a promising component of the rapidly expanding immunotherapeutic armamentarium. However, neoantigenic peptides typically elicit weak CD8⁺ T cell responses, and so there is a need for universally applicable vaccine delivery strategies to enhance the immunogenicity of these peptides. Ideally, such vaccines could also be rapidly fabricated using chemically synthesized peptide antigens customized to an individual patient. Here, we describe a strategy for simple and rapid packaging of peptide antigens into pH-responsive nanoparticles with endosomal escape activity. Electrostatically-stabilized polyplex nanoparticles (nanoplexes) can be assembled instantaneously by mixing decalysine-modified antigenic peptides and poly(propylacrylic acid) (pPAA), a polyanion with pH-dependent, membrane destabilizing activity. These nanoplexes increase and prolong antigen uptake and presentation on MHC-I (major histocompatibility complex class I) molecules expressed by dendritic cells, resulting in enhanced activation of CD8⁺ T cells. Using an intranasal immunization route, nanoplex vaccines inhibit formation of lung metastases in a murine melanoma model. Additionally, nanoplex vaccines strongly synergize with the adjuvant α-galactosylceramide (α-GalCer) in stimulating robust CD8⁺ T cell responses, significantly increasing survival time in mice with established melanoma tumors. Collectively, these findings demonstrate that peptide/pPAA nanoplexes offer a facile and versatile platform for enhancing CD8⁺ T cell responses to peptide antigens, with potential to complement ongoing advancements in the development of neoantigen-targeted cancer vaccines.

Nanomaterial-dependent immunoregulation of dendritic cells and its effects on biological activities of contraceptive nanovaccines

Nanovehicles are promising delivery systems for various vaccines. Nevertheless, different biophysicochemical properties of nanoparticles (NPs), dominating their in vitro and in vivo performances for vaccination, remain unclear. We attempted to elucidate the effects of NPs and their pH-sensitivity on in vitro and in vivo efficacy of resulting prophylactic nanovaccines containing a contraceptive peptide (FSHR). To this end, pH-responsive and non-responsive nanovaccines were produced using acetalated β-cyclodextrin (Ac-bCD) and poly(lactic-co-glycolic acid) (PLGA), respectively. Meanwhile, FSHR derived from an epitope of the follicle-stimulating hormone receptor was used as the model antigen. FSHR-containing Ac-bCD and PLGA NPs were successfully prepared by a nanoemulsion technique, leading to well-shaped nanovaccines with high loading efficiency. The pH-sensitivity of Ac-bCD and PLGA nanovaccines was examined by in vitro hydrolysis and antigen release studies. Nanovaccines could be effectively engulfed by dendritic cells (DCs) via endocytosis in both dose and time dependent manners, and their intracellular trafficking was closely related to the pH-sensitivity of the carrier materials. Furthermore, nanovaccines could induce the secretion of inflammatory cytokines by DCs and T cells co-cultured with the stimulated DCs. In vivo evaluations demonstrated that nanovaccines were more potent than that based on the complete Freund's adjuvant, with respect to inducing anti-FSHR antibody, reducing the sperm count, inhibiting the sperm motility, and increasing the teratosperm rate. Immunization of male mice with nanovaccines notably decreased the parturition incidence of the mated females. Consequently, both in vitro and in vivo activities of FSHR could be considerably augmented by NPs. More importantly, our studies indicated that the pH-responsive nanovaccine was not superior over the non-responsive counterpart for the examined peptide antigen.