Immunotherapeutic applications of nucleic acid based tlr agonists and antagonists

Abstract

Recent evidence suggests that genetic material is not just the blueprint of life. Depending on the type of the source that genomic material is extracted or the type of motif that DNA harbors DNA could be immunostimulatory or immunosuppressive to innate immune system cells. Unmethylated CpG motifs, from bacterial genome is recognized by TLR9 expressing cells as “non-self” and initiates an orchestrated immune activation characteristics of Th1-biased immunity. Conversely, mammalian genome rich in G-runs motifs, such as telomeric ends expressing TTAGGG repeats downregulate Th1-biased immune responses and contributes to restore over exuberant immune response. Several TLR agonists/antagonists candidates are currently under preclinical/clinical trials to prevent or treat cancer, infectious disease, allergic disorders and autoimmune or autoinflammatory diseases. In this thesis, we attempted to broaden the application of nucleic acid based TLR therapy by investigating their beneficial effects either as vaccine adjuvants against Foot and Mouse Disease or to test as immunosuppressive agents that may control autoimmune uveitis. We showed that an immunosuppressive ODN namely A151 downregulated severity of an established animal model of uveitis, endotoxin induced uveitis (EIU), up to more than 60% histologically, or more than 80% based on cytokine production such as MIP3α, IL6, IFNγ from uveitic animals. In order to compare effects of this biological immunosuppressive agent, next we studied effects of a broad-spectrum immunosuppressive drug, namely cyclosporine A in an emulsion form, commercially known as Restasis™. Our results indicated that Restasis™ had significantly lower capacity to reduce disease severity and downregulate in vivo chemokine or cytokine levels compared to A151. The second theme of this thesis was to demonstrate effective utilization of CpG ODN as an immunostimulatory agent. The adjuvant effect of CpG ODN 1555-PS in Foot and Mouth Disease (FMD) vaccine formulations were tested. In this study, CpG ODNs were formulated either with commercially used monovalent vaccine or mixed with free Serotype-O Ag. Data suggested that, in mice, inclusion of CpG ODN as an adjuvant, spared the Ag by 6 fold and the vaccine dependent virus neutralization titers were not only higher but also long lasting compared to commercial monovalent vaccine. CpG inclusion in the FMD vaccine helped to generate 1.5-2 fold more cell mediated immunity 24 h after booster injection. Implicating that virus infection could be more effectively controlled by the novel approach. In the last part of this thesis, effects of CpG ODNs as prophylactic agents for newborn broiler chicken were tested in vivo. Our results suggested that CpG ODN pretreatment not only significantly reduced mortality rates (> 2.0 %) but also contributed to growth performance of these industrially important animals. We demonstrated that nucleic acid based agonists and antagonists might be of great potential to be developed as therapeutic agents either in the clinic or forcontrolling health of industrially important animals.