ukb.uni-bonn.de

Research Overview

Molecular Immunology 

The innate immune system uses a comprehensive set of sensors and receptors to survey the extracellular and intracellular space for signs of infection or cell damage. We are interested in the cell biology that underlies pathogen and danger detection and the appropriate response. To specifically interfere with and visualize molecular processes in the cell, we generate and use alpaca single domain antibodies (nanobodies or VHHs) targeting the individual components. These will allow us to dissect the complex biological pathways and extract mechanistic information in an unprecedented way.

 

Inflammasome activation

To integrate information and initiate a rapid inflammatory response, specialized sentinel cells can assemble large macromolecular signaling complexes called inflammasomes. These coordinate the recruitment and autocatalytic activation of caspase-1 to mature pro-inflammatory cytokines and/or induce pyroptotic cell death. While we have learned fundamental lessons on the nature of inflammasome activation in the last years, many molecular details remain poorly understood. These including the identity of ligands/signals and sensors, the conformational changes involved in activation, the ultrastructure and regulation of ‘foci’ of the adaptor molecule ASC, and the fine-tuning of caspase-1 activity towards the desired outcome.

In line with the mechanistic studies, we will also investigate inflammasome assembly in response to virus infections using a representative panel of DNA and RNA viruses expressing a novel inflammasome sensor.

 

 

Nanobodies

In addition to conventional antibodies, alpacas and other camelids produce heavy chain-only antibodies that are composed of two identical heavy chains. They recognize their targets by means of a single variable domain and achieve affinities comparable to conventional antibodies. Importantly, antigen binding is retained when the variable domain (VHH or nanobody) is expressed on its own. The nanobody repertoire from an immunized alpaca can be transferred to a plasmid library, from which desirable nanobodies can be identified by well-established screening techniques such as phage display. Unlike antibodies, nanobodies are small (about 15 kDa) and mostly stable in the absence of disulfide bonds and glycosylation. This allows us to express nanobodies in the cytosol of cells to specifically perturb protein function by masking protein-protein interaction interfaces, stabilizing or inducing distinct protein conformations, or reaching into the catalytic center of enzymes. This allows us to – in principle – interfere with any biological process at high precision. To facilitate the identification of nanobodies with desired properties in the cell, we have established a novel functional screening approach based on lentiviral VHH libraries. Nanobodies can moreover be easily produced in bacteria and functionalized for the use in advanced and conventional microscopy, non-invasive imaging techniques, flow cytometry, mass cytometry, and biochemistry.

PRESS