Bhattacharya Group: Developing novel therapeutics for inflammatory diseases

Developing new therapeutics that target the chemokine network in inflammation is the major focus of our laboratory, which is based at the Wellcome Centre for Human Genetics.

Although inflammation is a fundamental host-defence response that serves to rid the body of the causes and consequences of infection and tissue injury, it is also a pathologic mechanism that can adversely affect organ function. Inflammation contributes to a variety of cardiovascular, pulmonary neurological, gastrointestinal, musculoskeletal, cutaneous, renal and hepatic disorders, creating substantial disease burden. Inflammation is driven by a network including secreted cytokines and chemokines, cellular receptors and leucocytes. The leucocytes include neutrophils, eosinophils, basophils, monocytes, macrophages, T and B-lymphocytes and dendritic cells. Cytokines and chemokines are secreted proteins, and are produced by damaged tissues in response to damage-associated molecular patterns (DAMPs) or pathogen-associated molecular patterns (PAMPs) which signal through pattern-recognition receptors to activate gene transcription. Chemokines cause directed leucocyte migration to sites of inflammation by signalling through cellular G-protein coupled receptors (GPCRs).

Despite having a well-documented mechanistic role in this process, and despite being supported by substantial target validation, no successful anti-chemokine therapeutic to treat inflammatory disease has yet been developed. We believe that the reason for this lies in the inherent robustness of the chemokine network. The robustness arises from the structure of the chemokine network. This includes large numbers of components (>40 chemokine, 19 GPCRs, multiple leucocyte subclasses), promiscuous interactions between chemokines and receptors, and promiscuous expression of GPCRs, which creates multiple synergistically acting pathways between chemokine and leucocytes. Leucocytes themselves are secrete multiple chemokines creating feedforward amplification, which also contributes to network robustness.

Ticks are blood-feeding parasites that parasitise mammals, birds, reptiles, and amphibians. They have adapted through evolution and natural selection for over 250 million years to evade the host's defence mechanisms, allowing them to feed for days to weeks. One class of proteins found in their saliva are called evasins. These bind and neutralise multiple chemokines, overcoming the robustness of the chemokine network, and inhibiting inflammation. Evasins have been shown to be potently active in several preclinical inflammatory disease models. 

Using a biotechnology platform – Bug-to-Drug – that uses yeast surface display, we have identified and characterised over 40 evasins that have broad and promiscuous chemokine binding properties. As a result, they are predicted to be potently active in inflammatory diseases and have potential as biological therapeutics. Their clinical development has not progressed due to concerns regarding potential immunogenicity, parenteral delivery and cost. Peptides mimicking protein activity can overcome the perceived limitations of therapeutic proteins. We have now established that peptides possessing multiple-chemokine-binding and anti- inflammatory activities can be developed from the chemokine-binding site of an evasin. This provides a clear line-of-sight to the clinical development of new therapeutics with applications in inflammation. 

A key question we seek to address is how tick evasins achieve their remarkable promiscuity for binding and neutralising chemokines. Promiscuity may result from multiple binding sites or a single but flexible binding site, or some combination of the two mechanisms. Evasin binding may directly or allosterically interfere with chemokine functions, effecting neutralisation. Our approach is to identify evasin sequence elements that are responsible for chemokine binding, and conversely, identify chemokine sequence elements responsible for evasin binding and for other chemokine functions. We have developed a high-throughput phage-display approach combined with NextGen sequencing technology to identify these elements. In addition to answering a fundamental scientific question, this has translational potential. Synthetic peptides derived from such sequence elements can have therapeutic application as anti-inflammatory agents, and application as diagnostics, as molecular probes to identify activated endothelium and inflammation in vivo.