CpG-B ODN Mediated Protection from Systemic Lupus Erythematosus

PROJECT SUMMARY Systemic lupus erythematosus (SLE) is a chronic autoimmune disease with no known cure. Current therapies focus on symptom relief with corticosteroids or immunosuppressants but have significant side effects. The gut microbiome plays an important role in immune regulation, and modulation of the gut microflora could provide a novel avenue for SLE therapy. The Luo Lab has demonstrated that bacterial DNA (bDNA) can stimulate IL-10 production and regulatory B cell (Breg) proliferation, which are both associated with improved lupus symptoms. Toll-like receptor 9 (TLR9) is an endosomal sensor that recognizes bDNA and is associated with less severe lupus symptoms. CpG-B oligonucleotides (ODNs) are short nucleotide sequences that mimic bDNA and agonize TLR9. We have shown that CpG-B ODNs can robustly induce IL-10 production and Breg proliferation in vitro through two distinct, TLR9-dependent mechanisms: a B cell intrinsic mechanism, where TLR9 is agonized in B cells themselves, and a B cell extrinsic mechanism, where TLR9 is agonized in a secondary cell type, creating IL-6 that subsequently expands Bregs. IL-6 can expand Bregs but is also capable of expanding inflammatory cell subsets. We have in vivo data to show that increased IL-6 is associated with increased Bregs but is also associated with increased renal damage in lupus prone (MRL/lpr) mice. Therefore, we aim to enhance the IL-6 independent, B cell intrinsic mechanism, while limiting the IL-6 dependent, B cell extrinsic mechanism. This proposal aims to determine the therapeutic potential of CpG-B ODNs in the management of SLE. We propose to study these TLR9 agonists with MRL/lpr and humanized models, both in vitro and in vivo, to demonstrate the translatability of my work. We hypothesize that CpG-B ODNs can increase the number of Bregs and protect the host against SLE by acting through B cell intrinsic, TLR9 agonization. This application is broken down into two aims: Aim 1 is to delineate the cellular and molecular mechanisms by which CpG-B ODNs stimulate Breg differentiation in vitro. The first objective is to elucidate the mechanism of the B cell extrinsic pathway by using cell-specific Tlr9-/- co-culture experiments. By elucidating its mechanism, we can more effectively limit the B cell extrinsic pathway in the future. We will then analyze the pro- vs. anti-inflammatory profiles of the intrinsic and extrinsic mechanisms. Lastly, we propose to validate these findings in human PBMCs. Aim 2 is to determine the efficacy of using CpG-B ODNs in vivo. We aim to enhance the B cell intrinsic mechanism, while limiting the B cell extrinsic mechanism using Tlr9 conditional knockout mice. After determining that we can confer protection in MRL/lpr mice, we will demonstrate that we can protect mice with a human immune system. These experiments will demonstrate the potential efficacy of CpG-B ODNs in future human trials. We believe that CpG-B ODNs have the potential to be passive, yet effective treatments for lupus. This work will be the focus of the applicant’s Ph.D. candidacy and training plan. The applicant also plans to attend conferences, shadow physicians, and continue to practice the skills necessary to being a successful and productive physician-scientist.