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A single functional group substitution in c5a breaks B cell and T cell tolerance and protects against experimental
Christoph Kessel1, Kutty S Nandakumar, Francis B Peters
1Karolinska Institute, Stockholm, Sweden.
Objective:
A deficiency in C5 protects against arthritis development. However, there is currently no approach successfully translating these findings into arthritis therapy, as by targeting the key component, C5a. The aim of this study was to develop a vaccination strategy targeting C5a as therapy for patients with rheumatoid arthritis.
Methods:
An anti-C5a vaccine was generated by incorporating the unnatural amino acid p-nitrophenylalanine (4NPA) into selected sites in the murine C5a molecule. C5a-4NPA variants were screened for their immunogenicity in mice on different arthritis-susceptible class II major histocompatibility complex (MHC) backgrounds. A candidate vaccine was tested for its impact on disease in a murine model of collagen-induced arthritis (CIA). Immunity toward endogenous C5a as well as type II collagen was monitored and characterized.
Results:
Replacing a single tyrosine residue in position 35 (Y(35) ) with 4NPA allowed the generation of an anti-C5a vaccine, which partly protected mice against the development of CIA while strongly ameliorating the severity of clinical disease. Although differing in just 3 atoms from wild-type C5a (wtC5a), C5aY(35) 4NPA induced loss of T cell and B cell tolerance toward the endogenous protein in mice expressing class II MHC H-2(q) molecules. Despite differential B cell epitope recognition, antibodies induced by both wtC5a and C5aY(35) 4NPA neutralized C5a. Thus, anti-wtC5a IgG titers during arthritis priming were potentially of critical importance for disease protection, because high titers of C5a-neutralizing antibodies after disease onset were unable to reverse the course of arthritis.
Conclusion:
The results of this study suggest that the most effective anti-C5a treatment in arthritis can be accomplished using a preventive vaccination strategy, and that treatment using conventional biologic or small molecule strategies targeting the C5a/C5aR axis may miss the optimal window for therapeutic intervention during the subclinical priming phase of the disease.
Insights
Developing a novel anti-C5a vaccine targeting complement component 5a (C5a) showed promise in preventing rheumatoid arthritis. This preventive vaccination strategy may be more effective than later treatments for rheumatoid arthritis.
Area of Science:
- Immunology
- Rheumatology
- Vaccine Development
Background:
- Complement component 5a (C5a) plays a crucial role in arthritis development.
- Current therapies targeting C5a have not been successfully translated into effective treatments for rheumatoid arthritis.
- A preventive vaccination strategy targeting C5a is explored for rheumatoid arthritis therapy.
Purpose of the Study:
- To develop a vaccination strategy targeting C5a for rheumatoid arthritis therapy.
- To assess the efficacy of an anti-C5a vaccine in a murine model of arthritis.
Main Methods:
- An anti-C5a vaccine was created using unnatural amino acids (p-nitrophenylalanine, 4NPA) incorporated into murine C5a.
- Vaccine immunogenicity was tested in mice on arthritis-susceptible MHC backgrounds.
- The candidate vaccine's impact on collagen-induced arthritis (CIA) was evaluated.
Main Results:
- A modified C5a (C5aY(35)4NPA) vaccine partially protected mice against CIA and reduced disease severity.
- The vaccine induced loss of tolerance to endogenous C5a in specific mouse strains.
- Induced antibodies neutralized C5a, with early antibody titers being critical for protection.
Conclusions:
- Preventive vaccination targeting C5a is a potentially effective strategy for arthritis treatment.
- Conventional C5a/C5aR targeting therapies may be less effective if not administered during the subclinical phase.
- This study highlights the importance of the timing of therapeutic intervention in arthritis.
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