Poly(I:C) and R848 ligands show better adjuvanticity to induce B and T cell responses against the antigen(s)

Advances in the Functionalization of Vaccine Delivery Systems: Innovative Strategies and Translational Perspectives

The development of effective vaccines requires a rational design that considers the interaction between antigens, their vectors, and the immune system in addition to the activation of pathways that induce a safe and specific immune response. The efficacy of a vaccine formulation depends on the nature of the antigen, the protection offered by the delivery system, the ability to potentiate the immune response, and the precise release of the immunogen. Carrier systems such as lipid nanoparticles, polymers, exosomes, and microorganisms can be functionalized by chemical, physical, or biological methods to generate selective and improved biodistribution profiles. These methods enhance interaction with target cells, thereby improving immunological efficacy. The conjugation of specific ligands or the modification of parameters such as shape, charge, and size of vectors can enhance the specificity, stability, and efficiency of antigen transport to cellular compartments, thereby facilitating a robust immune response. This study examines modifications in vaccine delivery systems, focusing on biomolecules and physicochemical changes that enhance antigen presentation. Additionally, we examine innovative methods, including microneedles, electroporation, and needle-free systems that show potential for enhancing the immune response.

Anti-Tumor Efficacy of a Mesothelin-Based Nanovaccine in a KPC Orthotopic Mouse Model of Pancreatic Cancer

Background/Objectives: Immunotherapy has shown promising results in some cancers, but its efficacy remains limited in pancreatic ductal adenocarcinoma (PDAC). Vaccines in nanoparticle form (nanovaccines) can incorporate immunostimulating components to induce a potent immune response. As mesothelin (MSLN) is a tumor-associated antigen overexpressed in PDAC, we evaluated the effect of MSLN nanovaccine in a syngeneic orthotopic KPC-PDAC mouse model. Methods: An MSLN peptide combining three MSLN epitopes and two adjuvants, poly I:C and R848, was encapsulated in PLGA-chitosan nanoparticles to generate the nanovaccine. Results: The MSLN nanovaccine was successfully taken up by dendritic cells in vitro and was found in inguinal lymph nodes 24 h after subcutaneous injection into C57BL/6 mice. Nanovaccine re-stimulation of splenocytes from vaccinated mice led to increased levels of interferon-γ in vitro compared to unstimulated splenocytes. Higher levels of MSLN-specific IgM and IgG antibodies were detected in the serum of vaccinated mice compared to that of control mice. Three vaccination regimens were tested: a prophylactic scheme that included vaccination before tumor induction and two therapeutic schemes involving early and late vaccination after tumor cell inoculation. MSLN nanovaccination inhibited KPC tumor progression and metastasis and induced higher CD8+ T cell infiltration in the tumor that developed in response to prophylactic and early therapeutic schedules but not in response to a later vaccination approach. Although the nanovaccine treatment elicited higher humoral and cellular antigen-specific responses in tumor-bearing mice for both vaccination strategies, the therapeutic vaccination also increased the expression of exhaustion markers in CD8+ T cells. Conclusions: Our results support the relevance of an MSLN-based nanovaccine as a new immunotherapy treatment for PDAC and propose an innovative method of vaccine delivery using NPs.

Poly I:C vaccination drives transient CXCL9 expression near B cell follicles in the lymph node through type-I and type-II interferon signaling

Subunit vaccines drive immune cell-cell interactions in the lymph node (LN), yet it remains unclear how distinct adjuvants influence the chemokines responsible for this interaction in the tissue. Here, we tested the hypothesis that classic Th1-polarizing vaccines elicit a unique chemokine signature in the LN compared to other adjuvants. Polyinosinic:polycytidylic acid (Poly I:C) vaccination resulted in dynamic upregulation of CXCL9 that was localized in the interfollicular region, a response not observed after vaccination with alum or a combination of alum and poly I:C. Experiments using in vivo mouse models and live ex vivo LN slices revealed that poly I:C vaccination resulted in a type-I IFN response in the LN that led to the secretion of IFNγ, and type-I IFN and IFNγ were required for CXCL9 expression in this context. CXCL9 expression in the LN was correlated with an IgG2c antibody polarization after vaccination; however, genetic depletion of the receptor for CXCL9 did not prevent the development of this polarization. Additionally, we measured secretion of CXCL9 from ex vivo LN slices after stimulation with a variety of adjuvants and confirmed that adjuvants that induced IFNγ responses also promoted CXCL9 expression. Taken together, these results identify a CXCL9 signature in a suite of Th1-polarizing adjuvants and determined the pathway involved in driving CXCL9 in the LN, opening avenues to target this chemokine pathway in future vaccines.

Impact of N-Terminal PEGylation on Synthesis and Purification of Peptide-Based Cancer Epitopes for Pancreatic Ductal Adenocarcinoma (PDAC)

Peptide-based cancer vaccines have shown promising results in preclinical trials focusing on tumor immunotherapy. However, the presence of hydrophobic amino acid segments within these peptide sequences poses challenges in their synthesis, purification, and solubility, thereby hindering their potential use as cancer vaccines. In this study, we successfully synthesized peptide sequences derived from mesothelin (MSLN), a tumor-associated antigen overexpressed in pancreatic ductal adenocarcinoma (PDAC) by conjugating them with monodisperse polyethylene glycol (PEG). By PEGylating mesothelin epitopes of varying lengths (ranging from 9 to 38 amino acids) and hydrophobicity (60-90%), we achieved an effective method to improve the peptide yield and facilitate the processes of synthesis and purification. PEGylation significantly enhanced the solubility, facilitating the single-step purification of lengthy hydrophobic peptides. Most importantly, PEGylation did not compromise cell viability and had little to no effect on the immunogenicity of the peptides. In contrast, the addition of a palmitoyl group to increase immunogenicity led to reduced yield and solubility. Overall, PEGylation proves to be an effective technique for enhancing the solubility and broadening the range of utility of diverse long hydrophobic peptides.