Effect of Calcıum Carbonate Encapsulatıon on the Oral Actıvıty of Cpg Olıgodeoxynucleotıdes and Assessment of the Response of Human Monocytes to Tlr Lıgands

Abstract

Toll-like receptor (TLR) ligands modulate immune responses and have been used in immunotherapy. Clinical trials designed to evaluate the utility of CpG ODN, a synthetic TLR9 ligand, relied on parenteral routes of administration. Therapy would be simplified if these ODN could be delivered orally. My thesis compared the activity of orally delivered free and calcium carbonate encapsulated CpG ODN in murine models of acute colitis, LPS-induced inflammation and L. monocytogenes infection in comparison with parenteral CpG ODN. Results indicate that orally delivered CpG ODN induce gastrointestinal rather than systemic immunity and that calcium carbonate encapsulation does not significantly alter this behavior. The TLR7/8 agonist R848 was identified as a more effective oral immune modifier for protection from enteric and systemic L. monocytogenes infection. The differential response of human monocytes to TLR7 and TLR8 agonists was investigated. While both agonists induced monocytes to differentiate into macrophages, their activity was somewhat different. TLR8 but not TLR7 stimulation led to the production of pro-inflammatory cytokines. TLR7 ligation blocked TLR8 but not TLR2 or 4 cytokine responses in a dose and time dependent manner. TLR2 and 4 ligations also blocked TLR8 dependent cytokine responses. The effects of complex TLR ligand stimulation on monocytes was investigated using heat-killed bacteria. L. monocytogenes and E. coli stimulation induced monocytes to differentiate into suppressive macrophages characterized by high IL-10 secretion that reduced pro-inflammatory cytokine induction by L. rhamnosus. Efforts are underway to identify the suppressive molecule(s) present in E. coli lipid and protein extracts that could be of therapeutic value.