Targeting Borrelia burgdorferi's Heat Shock Protein for the Diagnosis and Treatment of Lyme Disease

Infections are most commonly identified by microscopy, culturing the organism, or testing the patients blood for antigens or antibodies. These methods are unreliable in bacteria that persist in a non-dividing, metabolically inactive dormant state, leading to treatment delays and an increased risk of developing chronic morbidities. Borrelia burgdorferi (B. burgdorferi), the causative spirochete in Lyme Borreliosis, is an example of a stealth pathogen difficult to culture from blood, capable of evading the host immune system, and under adverse growth conditions in host tissue, can survive in a dormant state. Despite early diagnosis and treatment, 20-35% of patients with Lyme Borreliosis experience chronic symptoms, the etiology of which remains unknown due to the lack of accurate diagnostics to demonstrate the presence of a persistent infection. In vivo diagnostic imaging of bacterial infections is currently reliant on targeting their metabolic pathways, an ineffective method to identify microbial species with low metabolic activity. Here we characterize HS-198 as a small molecule-fluorescent conjugate that selectively targets the highly conserved bacterial protein, HtpG (High temperature protein G) within B. burgdorferi, the bacteria responsible for Lyme Disease. We describe the use of HS-198 to target morphologic forms of B. burgdorferi in both the logarithmic growth phase and the metabolically dormant stationary phase. Furthermore, in a murine infection model, systemically injected HS-198 identified B. burgdorferi as revealed by imaging in post necropsy tissue sections. These findings demonstrate how small molecule probes directed at conserved bacterial protein targets can function to identify the microbe using non-invasive imaging and potentially as scaffolds to deliver antimicrobial agents to the pathogen, potentially solving both the problem of diagnosis and treatment.