Progress in prostate cancer research is presently limited by a shortage of reliable in vitro model systems. We describe a novel self-assembling peptide, bQ13, which forms nanofibers and gels useful for the 3D culture of prostate cancer spheroids, with improved cytocompatibility compared to related fibrillizing peptides. The mechanical properties of bQ13 gels could be controlled by adjusting peptide concentration, with storage moduli ranging between 1–10 kPa. bQ13’s ability to remain soluble at mildly basic pH considerably improved the viability of encapsulated cells compared to other self-assembling nanofiber-forming peptides. LNCaP cells formed spheroids in bQ13 gels with similar morphologies and sizes to those formed in Matrigel or RADA16-I. Moreover, prostate-specific antigen (PSA) was produced by LNCaP cells in all matrices, and PSA production was more responsive to enzalutamide treatment in bQ13 gels than in other fibrillized peptide gels. bQ13 represents an attractive platform for further tailoring within 3D cell culture systems.

Supramolecular materials composed of proteins and peptides have been receiving considerable attention toward a range of diseases and conditions from vaccines to drug delivery. Owing to the relative newness of this class of materials, the bulk of work to date has been preclinical. However, examples of approved treatments particularly in vaccines, dentistry, and hemostasis demonstrate the translational potential of supramolecular polypeptides. Critical milestones in the clinical development of this class of materials and currently approved supramolecular polypeptide therapies are described in this study. Additional examples of not-yet-approved materials that are steadily advancing toward clinical use are also featured. Spherical assemblies such as virus-like particles, designed protein nanoparticles, and spherical peptide amphiphiles are highlighted, followed by fiber-forming systems such as fibrillizing peptides, fiber-forming peptide-amphiphiles, and filamentous bacteriophages.

Subunit vaccines inducing antibodies against tumor-specific antigens have yet to be clinically successful. Here, we use a supramolecular α-helical peptide nanofiber approach to design epitope-specific vaccines raising simultaneous B cell, CD8 + T cell, and CD4 + T cell responses against combinations of selected epitopes and show that the concurrent induction of these responses generates strong antitumor effects in mice, with significant improvements over antibody or CD8 + T cell–based vaccines alone, in both prophylactic and therapeutic subcutaneous melanoma models. Nanofiber vaccine–induced antibodies mediated in vitro tumoricidal antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). The addition of immune checkpoint and phagocytosis checkpoint blockade antibodies further improved the therapeutic effect of the nanofiber vaccines against murine melanoma. These findings highlight the potential clinical benefit of vaccine-induced antibody responses for tumor treatments, provided that they are accompanied by simultaneous CD8 + and CD4 + responses, and they illustrate a multiepitope cancer vaccine design approach using supramolecular nanomaterials.

Current treatments for chronic immune-mediated diseases such as psoriasis, rheumatoid arthritis, or Crohn's disease commonly rely on cytokine neutralization using monoclonal antibodies; however, such approaches have drawbacks. Frequent repeated dosing can lead to the formation of anti-drug antibodies and patient compliance issues, and it is difficult to identify a single antibody that is broadly efficacious across diverse patient populations. As an alternative to monoclonal antibody therapy, anti-cytokine immunization is a potential means for long-term therapeutic control of chronic inflammatory diseases. Here we report a supramolecular peptide-based approach for raising antibodies against IL-17 and demonstrate its efficacy in a murine model of psoriasis. B-cell epitopes from IL-17 were co-assembled with the universal T-cell epitope PADRE using the Q11 self-assembling peptide nanofiber system. These materials, with or without adjuvants, raised antibody responses against IL-17. Exploiting the modularity of the system, multifactorial experimental designs were used to select formulations maximizing titer and avidity. In a mouse model of psoriasis induced by imiquimod, unadjuvanted nanofibers had therapeutic efficacy, which could be enhanced with alum adjuvant but reversed with CpG adjuvant. Measurements of antibody subclass induced by adjuvanted and unadjuvanted formulations revealed strong correlations between therapeutic efficacy and titers of IgG1 (improved efficacy) or IgG2b (worsened efficacy). These findings have important implications for the development of anti-cytokine active immunotherapies and suggest that immune phenotype is an important metric for eliciting therapeutic anti-cytokine antibody responses.

A major challenge in developing an effective vaccine against HIV-1 is the genetic diversity of its viral envelope. Because of the broad range of sequences exhibited by HIV-1 strains, protective antibodies must be able to bind and neutralize a widely mutated viral envelope protein. No vaccine has yet been designed which induces broadly neutralizing or protective immune responses against HIV in humans. Nanomaterial-based vaccines have shown the ability to generate antibody and cellular immune responses of increased breadth and neutralization potency. Thus, we have developed supramolecular nanofiber-based immunogens bearing the HIV gp120 envelope glycoprotein. These immunogens generated antibody responses that had increased magnitude and binding breadth compared to soluble gp120. By varying gp120 density on nanofibers, we determined that increased antigen valency was associated with increased antibody magnitude and germinal center responses. This study presents a proof-of-concept for a nanofiber vaccine platform generating broad, high binding antibody responses against the HIV-1 envelope glycoprotein.

Complement protein C3dg, a key linkage between innate and adaptive immunity, is capable of stimulating both humoral and cell-mediated immune responses, leading to considerable interest in its use as a molecular adjuvant. However, the potential of C3dg as an adjuvant is limited without ways of controllably assembling multiple copies of it into vaccine platforms. Here, we report a strategy to assemble C3dg into supramolecular nanofibers with excellent compositional control, using β-tail fusion tags. These assemblies were investigated as therapeutic active immunotherapies, which may offer advantages over existing biologics, particularly toward chronic inflammatory diseases. Supramolecular assemblies based on the Q11 peptide system containing β-tail–tagged C3dg, B cell epitopes from TNF, and the universal T cell epitope PADRE raised strong antibody responses against both TNF and C3dg, and prophylactic immunization with these materials significantly improved protection in a lethal TNF-mediated inflammation model. Additionally, in a murine model of psoriasis induced by imiquimod, the C3dg-adjuvanted nanofiber vaccine performed as well as anti-TNF monoclonal antibodies. Nanofibers containing only β-tail–C3dg and lacking the TNF B cell epitope also showed improvements in both models, suggesting that supramolecular C3dg, by itself, played an important therapeutic role. We observed that immunization with β-tail–C3dg caused the expansion of an autoreactive C3dg-specific T cell population, which may act to dampen the immune response, preventing excessive inflammation. These findings indicate that molecular assemblies displaying C3dg warrant further development as active immunotherapies.