Structural and functional analysis of myeloid molecules involved in pathogen recognition
Myeloid cells express numerous cell surface molecules involved in the recognition of the so-called Pathogen-Associated Molecular patterns (PAMPs). Receptors for PAMPs include the members of the TLR family as well as several lectins and lectin-like molecules. Our laboratory is actively working on thefunctional dissection oflectins which participate in the binding, uptake and capture of pathogens by dendritic cells and macrophages. Specifically we are characterizing relevant functionalregions of DC-SIGN, which contribute to its multimerization state on the cell surface as well as on its ability to recognize pathogens such as HIV, Ebola virus, Leishmania, Aspergillus, Candida and Mycobacterium. In addition we are interested in the intracellular signalsand transcriptional activities modulatedupon engagement of TLR and lectins by these and other pathogens.
Regulation of macrophage and dendritic cells gene expression
Macrophages are the terminally differentiated derivative of the peripheral blood monocyte. Together these two cell types play a major role in regulation of both humoral and cellular immune responses and as the primary line of defence against a number of microorganisms. During an inflammatory response, induced by infection or tissue injury, macrophages produce a variety of soluble mediators (cytokines) which impact on the functioning of a large number of cell types. The main interest of my lab is in studying the molecular mechanisms which are responsible for the regulation of cytokine genes in monocytes, macrophages and dendritic cells. The research is divided into two interrelated areas, transcriptional regulation and signal transduction. The overall goal is to understand how signals initiated at the cell surface by macrophage activating agents, such as LPS from gram negative bacteria, are communicated to the nucleus and induce cytokine gene expression.
C-type lectin receptors in cattle
Additionally, in collaboration with Tracey Coffey (Institute for Animal Health, Compton) we are also examining the role of C-type lectin receptors in the control of innate immune cell response to mycobacterial pathogens. The virulent species M. tuberculosis and M. bovis, as well as the attenuated vaccine strain M. bovis BCG, are all members of the M. tuberculosis complex, along with M. microti, M. africanum, and M. canettii. All the members are closely related, sharing >99% identity at the nucleotide level and identical 16sRNA sequence. Despite this they differ significantly in morphology, biochemistry, host range, virulence and disease patterns. For example, the only natural host for M. tuberculosis is humans, where it can cause tuberculosis (TB). The zoonotic pathogen M. bovis however, has a broad host range, causing infections in several mammals, including humans and cattle. The mechanisms by which bacterial and/or host factors cause persistent infection are still not completely understood. M. tuberculosis has been demonstrated to activate a wide range of signaling pathways and transcription factors, including NF-kB, AP-1, and MAPK in macrophages. Until now, the identity of the cell surface signaling molecule(s) responsible for these responses is still unclear. We have recently determined that bovine macrophages respond different to different mycobacterial strains. Using HEK cells transfected with the recently bovine TLRs and C-type lectin receptors (bovine DC-SIGN, bovine dectin-1), we now intend to elucidate the role of these receptors in NF-ÎºB and chemokine gene expression.