2182: mRNA Vaccine Against Fibroblast Activation Protein Ameliorates Murine Models of Inflammatory Arthritis

Xiaowei Zhang¹, Antony Jozic¹, Pingfang Song¹, Qiang Xu², Xiaofei Shi³, Hong Wang⁴, Lindsey Bishop¹, Hillary Struthers¹, John Rutledge⁵, Shuang Chen¹, Fei Xu¹, Meaghan Hancock¹, Daocheng Zhu⁶, Gaurav Sahay¹ and Cong-Qiu Chu¹, ¹Oregon Health & Science University, Portland, OR, ²Guangzhou University of Chinese Medicine, Guangzhou, China, ³Henan University of Science and Technology, Luoyang, China, ⁴Wenzhou Medical University, Wenzhou, China, ⁵Portland VA Research Foundation, Portland, ⁶Shanghai Kexin Biotechnology, Shanghai, China

Background/Purpose: Synovial fibroblasts in patients with rheumatoid arthritis (RA) contribute substantially to the perpetuation of synovitis and invasion to cartilage and bone, and have been targets for developing novel therapies for RA. RA synovial fibroblasts express high levels of fibroblast activation protein (FAP) and this expression is relatively highly specific. Here we explored a strategy to ablate synovial fibroblasts by provoking immune response to FAP for developing a therapy in experimental arthritis.

Methods: A consensus cDNA sequence for FAP was generated and FAP protein (consensus FAP, cFAP) was expressed and tested for protection against collagen-induced arthritis (CIA). Mouse cytomegalovirus (MCMV) vector carrying cFAP cDNA was also generated and tested for protection against CIA. mRNA derived from the consensus cDNA was generated and encapsulated by lipid nanoparticles (LNP). cFAP mRNA-LNP was injected intramuscularly (IM) at week 0 and week 3. Two weeks after the last injection of cFAP mRNA-LNP, CIA was induced by intradermal injection of collagen type II in complete Freund's adjuvant or collagen antibody-induced arthritis (CAIA) induced by intraperitoneal injection of a cocktail of monoclonal anti-collagen type II antibodies in DBA/1 mice; incidence and severity of arthritis were assessed clinically and histologically. Serum anti-FAP antibodies were quantified by ELISA.

Results: Immunization with cFAP in aluminum based adjuvant reduced the incidence of CIA to 20% versus 80% in bovine albumin immunized group. MCMV-cFAP infected mice also showed a reduced incidence of CIA to 40% versus 100% in MCMV vector infected mice. cFAP mRNA-LNP was first tested and confirmed for expression of cFAP protein in vitro in human embryonic kidney cells. Mice with IM injection of cFAP mRNA-LNP generated antibodies to cFAP and mouse FAP (mFAP), whereas those with enhanced green fluorescent protein (EGFP) mRNA-LNP injection generated antibodies to EGFP but not to cFAP or mFAP. We then tested whether cFAP mRNA-LNP vaccine will be able to suppress arthritis. After two doses of cFAP mRNA-LNP vaccine (n=10), 60% of mice developed CIA while 100% of mice in GFP mRNA-LNP vaccine (n=8) or PBS treated (n=8) groups developed CIA (Figure 1A); those animals that developed arthritis in cFAP mRNA-LNP treated group had a less severe course of the disease (Figure 1B). In CAIA model, cFAP mRNA-LNP vaccine did not have effect on prevention of arthritis, but was able to reduce the severity of arthritis (Figure 1C and D).

Conclusion: cFAP delivered by mRNA-LNP was able to provoke host immune response in vivo and ameliorate murine models of inflammatory arthritis. These results suggest that FAP expressed by synovial fibroblasts can be used as a target for developing therapeutics interrupting fibroblasts for arthritis.
Figure 1. Effect of cFAP mRNA-LNP vaccination on arthritis. (A and B) Male DBA/1 mice were injected intramuscularly (IM) with 1.5 µg cFAP mRNA-LNP or EGFP mRNA-LNP or PBS at week 0 and week 3. Two weeks after the last LNP-mRNA injection, mice were injected with chicken collagen type II emulsified in complete Freund’s adjuvant for induction of collagen-induced arthritis. (C and D) Two weeks after IM injection of mRNA-LNP, mice were injected intraperitoneally with anti-collagen type II monoclonal antibody cocktail (Arthrogen-CIA 5 Clone cocktail, Chondrex) and LPS. Onset and severity of arthritis were assessed clinically (n=5-10 mice in each group; *p < 0.01, **p < 0.05).
Disclosures: X. Zhang, None; A. Jozic, None; P. Song, None; Q. Xu, None; X. Shi, None; H. Wang, None; L. Bishop, None; H. Struthers, None; J. Rutledge, None; S. Chen, None; F. Xu, None; M. Hancock, None; D. Zhu, None; G. Sahay, None; C. Chu, None.