The development of anti-cocaine vaccines that counteract the rewarding effects of the drug are currently being investigated as adjunct therapies for prevention of relapse in abstinent users. However, cocaine is weakly immunogenic and requires conjugation to carrier proteins and coadministration with strong adjuvants, which carry the risk of local reactogenicity and systemic toxicity. Here we report synthetic and multivalent self-assembling peptide nanofibers as adjuvant-free carriers for cocaine vaccines. A novel cocaine hapten modified at the P3 site was conjugated to the N-terminus of an amphipathic self-assembling domain KFE8. In aqueous buffers the cocaine-KFE8 conjugate assembled into β-sheet rich nanofibers, which raised anti-cocaine antibodies without the need for added adjuvants in mice. Vaccinated mice were treated with cocaine and a significant negative correlation was observed between antibody levels and cocaine-evoked hyperactivity. These totally synthetic and multivalent nanofibers with well-defined chemical composition represent the first generation of adjuvant-free cocaine vaccines.

BackgroundMelanoma is one of the few types of cancer with an increasing annual incidence. While a number of immunotherapies for melanoma have been associated with significant clinical benefit, including high-dose IL-2 and cytotoxic T lymphocyte antigen 4 (CTLA-4) blockade, clinical response to either of these single agents has been limited to 11-20% of treated patients. Therefore, in this study, we sought to test the hypothesis that the combination of IL-2 and CTLA-4 blockade could mediate a more profound therapeutic response.MethodsHere, B6 mice were challenged with poorly immunogenic B16 melanoma on day 0, and treated with CTLA-4 blocking antibody (100 μg/mouse) on days 3, 6, and 9, and IL-2 (100,000 units) twice daily on days 4–8, or both.ResultsA highly significant synergistic effect that delayed tumor growth and prolonged survival was demonstrated with the combination immunotherapy compared to either monotherapy alone. The therapeutic effect of combination immunotherapy was dependent on both CD8+ T and NK cells and co-depletion of these subsets (but not either one alone) abrogated the therapeutic effect. CTLA-4 blockade increased immune cell infiltration (including CD8+ T cells and NK cells) in the tumor and IL-2 reduced the proportion of highly differentiated/exhausted tumor-infiltrating NK cells.ConclusionsThese results have implications for the design of clinical trials in patients with metastatic melanoma and provide new insights into how the immune system may be mediating anti-tumor activity with combination IL-2 and CTLA-4 blockade in melanoma.Electronic supplementary materialThe online version of this article (doi:10.1186/s40425-015-0063-3) contains supplementary material, which is available to authorized users.

D-Amino acid analogs of peptides and proteins are attractive for applications in biotechnology and medicine due to their reduced proteolytic sensitivity. Here, we report that self-assembling peptide nanofibers composed of D-amino acids act as immune adjuvants, and investigate their ability to induce antibody responses in comparison to their L-amino acid counterparts. The model antigenic peptide OVA (chicken egg ovalbumin aa 323−339) from chicken egg ovalbumin, known to elicit antibody responses in mice, was linked to an L-or Damino acid self-assembling peptide domain to generate enantiomeric nanofibers displaying the same epitope. The chiral nature of the fusion peptides was confirmed by circular dichrosim spectroscopy and transmission electron microscopy studies indicated that OVA-bearing enantiomers self-assembled into nanofibers with similar morphologies. In mice, D-amino acid peptide nanofibers displaying OVA elicited stronger antibody responses, equivalent levels of CD4+ T cell responses, and long-term antigen-presentation in vivo compared to L-amino acid nanofibers. Our findings indicate that self-assembling peptides composed of D-amino acids are strong immune adjuvants and that biomaterial stereochemistry can be used as a design tool to program adaptive immune responses for vaccine development.

To combat mucosal pathogens that cause gastrointestinal (GI) infections, local mucosal immunity is required which is best achieved through oral vaccination.