NEXT GENERATION TOOLS FOR IMAGING BACTERIAL INFECTION AND ITS RELATIONSHIP TO THE IMMUNE SYSTEM

One of the great challenges of modern biomedical research is observing biologicphenomena in animals and people. An important example of this is our limited ability to monitorthe course of bacterial infection. An image-based readout of a bacterial infection would allowdifferentiation of infection from other etiologies, a tailored duration of antibiotic treatment, andidentification of antibiotic resistance suggesting an appropriate class of antibiotic. In addition to the clinical and population implications of improved monitoring of bacterialinfections, basic researchers do not have simple tools to measure the immune response to thesite of a bacterial infection. Again, imaging is suited to address this problem by facilitating in vivomonitoring over space and time. My work seeks to develop imaging-based chemical andsynthetic biology technologies that illuminate bacterial pathogenesis, response to antibiotics, thedevelopment of antibiotic resistance, and bacterial interactions with the immune system. Ipropose complementary approaches to accomplish these goals using immune cells deliveredinto the blood stream that track bacterial biomarkers ?including bacterial surface markers andbacterial enzymes? and using direct bacterial imaging with positron emission tomography(PET). These new approaches leverage concepts and techniques I have developed including?cell-cell proximity reporters?, protein destabilizing domains, and PET imaging based on theantibiotic trimethoprim (TMP). Advantages of using immune cells include the ability to generatemultiplexed sensors and reporter outputs, transcriptional and enzymatic signal amplification,and regional assessment of immune cell trafficking. An advantage of direct bacterial imaging isthe ability to image the bacterial load that does not depend on immune cell access to theinfection. The primary objectives of this proposal are 1) to develop new receptors that can reportthe severity and species of bacterial infection in vivo. 2) to develop new classes of caged smallmolecules for monitoring immune cell-bacterial cell interactions using synthetic biologyprinciples, and 3) to evaluate a new class of PET radiotracers I recently developed for imaginginfection in a rat model of cystic fibrosis (CF) and measure bacterial radiotracer uptake inpatients with CF before and after antibiotics. This work builds a foundation to monitor pathologic bacteria in vivo and spans frombench to bedside. I expect to provide sets of reagents to the scientific community includingplasmids encoding receptors for a variety of bacteria, enzyme activated small molecules, anduseful PET probes, all geared toward specific imaging of live bacteria.