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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - FusionPAMPs (New generation of chimeric TLR2-NOD agonist compounds for vaccine adjuvants)

Teaser

Summary

New vaccine modalities need to be developed that can activate more potently the immune system, in this regard, adjuvants augment adaptive immune responses and can improve vaccine performance. Aluminum salt (alum) is the most commonly used adjuvant for human vaccination. However, it drives primarily TH2-effector responses and is not effective for vaccines that target mucosal surfaces. Thus, safe and potent adjuvants need to be developed that can increase and direct vaccines specific immunity. Recent advances in our understanding of innate immune responses are providing opportunities to design better adjuvants. In this regard, within this project, we have design novel chimeric compounds to synergistically activate several pattern recognition receptors (PRRs). These compounds will activate TLR2 and NOD1/NOD2, two major classes of PRRs stimulated in response to bacterial infection.

This project is important for the society because there is an unmet need for the development of vaccine modalities able to activate more potently the immune system. Thus, the design of new adjuvants able to boost the immune response and provide better protection against bacterial infection is important to reduce mortality and morbidity. This is especially important in high-risk groups, as babies and elderly people which in particular suffer from immune-senescence and they respond less potently to vaccination than young people and adults.

In view of the above-mentioned need for the development of new vaccine modalities, the goal of this project has been to generate safe and potent adjuvants that in conjunction with a specific antigen will elicit protective immunity. The project had the following main objectives:
(a) Synthesize a panel of chimeric agonists (fusion PAMPs) for TLR2-NOD2 and TLR2-NOD1 innate immune receptors.
(b) Determine the adjuvant function and pattern recognition receptor requirements of the synthetic compounds by examining cytokine production and T-cell activation by DCs.
(c) Examine the immune activating and protective properties of the chimeric compounds in a mouse model.

The results obtained during the development of this project validate the hypothesis of the project, the covalent attachment of NOD and TLR2 agonist results in efficient cross talk of signal transduction pathways and in synergistic immune activation. We found that the chimeric compounds induce higher production of IL-6 and TFNÎ± than the NOD or TLR2 agonists alone. These studies are very promising and can be used for the design of new adjuvant modalities that will improve vaccines performance.

Work performed

During the reporting period, the researcher has been working towards the achievement of each listed objective. For this, a battery of novel chimeric compounds in which agonists of TLR2 and NOD receptors where covalent linked was synthesized following the procedures exposed in the final report (Objective 1). In addition, cell biology studies were performed to compare the ability of the different chimeric and single PRR agonists to stimulate the production of cytokines in primary DCs assessing the synergistic activity of the chimeric compounds. Stimulation of bone-marrow-derived macrophages with our fusion PAMPs showed that four of the six MDP-lipopeptide chimeric compounds are very active when compares to stimulation with MDP or TLR2 agonist alone, which is very promising for their use as a vaccine adjuvants. In addition, we found that the number of lysine residues is key for TLR activation. Compounds in which the lipopeptide part displays 2 or 4 Lysine residues are the most active chimeric agonist (Objective 2). In vivo experiments will be performed in the next months to examine the immune activating and protective properties of the chimeric compounds in a mouse model (Objective 3).

The results are expected to be published in two high-impact journals, as Angewandte Chemie International Edition and Journal of American Chemical Society, in OPEN ACCESS format, covered by Utrecht University. In addition, the researcher followed the plan for the dissemination and exploitation of results designed in the proposal and some of the results have been presented in several conferences (4th Science for Life Conference and 2nd Biennial UIPS Symposium. Bioinspired Therapies). The UE funding has been and will be acknowledged in all dissemination activities and publications.

Final results

In this project, new adjuvants derived by the covalent linking of two Pathogen-associated molecular patterns PAMPs (fusion PAMPs), TLR2 and NOD chimeric agonists had been prepared to ensure that immune cells are being exposed to both, resulting in efficient cross talk of signal transduction pathways and in synergistic immune activation. This is a completely new approach since current methods rely on the stimulation of a single PRR. Our new chimeric compounds can be employed at lower adjuvant concentrations, minimizing unwanted side effects. Preliminary results indicated that the covalent attachment NOD and TLR agonist induces stronger the immune response than the unlinked agonist alone. These results are expected to have a big impact on the development of a new class of vaccine adjuvants that may find wide application in the development of prophylactic as well as therapeutic vaccines. This can pave the way for more efficient vaccines making people lives better.