Characterization and mode of action of Cochlin LCCL domain as a new host-targeted immunostimulating therapy against bacterial infections – COCH

Resistance to antibiotics is a major worldwide challenge in the treatment against bacterial infections. There is an urgent need for the development of novel therapeutics, and boosting the host immune system represents a promising alternative to antibiotics in the fight against infections in order to lower antibioresistance. Endogenous mechanisms controlling anti-bacterial immunity remain insufficiently understood, in part because proteins potentially involved in such regulation remain understudied – one example is the extracellular matrix protein cochlin. We recently described that endogenous circulating cochlin LCCL protein (encoded by COCH / Coch) enhances host innate response against Pseudomonas aeruginosa Gram-negative and Staphylococcus aureus Gram-positive bacterial infections, through the increased levels of early pro-inflammatory cytokines TNF, IL-6 and IL-1b and chemokines MCP-1 and KC at the infection site, as well as increased recruitment of neutrophils and macrophages. Consistently, Coch-deficiency results in defect in controlling bacterial growth and spread, and overall decrease in survival to infections. In addition, administration of recombinant cochlin LCCL abolishes bacterial colonization in a rapid and sustained manner. Thus, utilizing the innate immune regulating cochlin axis for therapeutic purposes appears a novel and attractive therapeutic target to activate for increased protection and clearance of bacterial challenges. Nevertheless, toward its practical application new mechanistic and pharmacological knowledge is needed. Our project aims to gain such knowledge and leverage this into the proof-of-concept that targeting host cochlin LCCL-dependent anti-bacterial response can be used as an innovative antibacterial approach. Specifically, in this proposal, we will investigate in vitro at the cell level the surface receptor(s) of cochlin LCCL and its downstream signalling cascade. These can by themselves represent subsequent pharmaceutical targets. Next, recombinant cochlin LCCL anti-bacterial potency, toxicity, distribution through the body, and stability following administration of recombinant cochlin LCCL by different routes will be assessed in pre-clinical studies. These studies will also allow us to identify which branch(es) of the immune response is (are) modified in vivo by cochlin LCCL by assessing cytokines and chemokines secretion and phenotyping the immune cells at the infection site using unbiased approaches. Together, these studies will provide essential information toward development of a novel class of antibacterial therapies based on boosting the host response rather than directly targeting bacteria, thus eliminating the concerns of bacterial resistance. It is also expected that our proposal will have significant spin-off effects for the general understanding of innate immunity which can be applicable to many other diseases.