Steiner, Dr. Theodore

UBC Division Head

Dr. Theodore Steiner is a Professor of Medicine and Head of the Division of Infectious Diseases at the University of British Columbia, as well as an Investigator at BC Children’s Hospital. His research focuses on the intestinal immune system, particularly how immune responses to bacterial components such as flagellin contribute to conditions like C. difficile infection and inflammatory bowel disease. Dr. Steiner also leads clinical and basic science research programs that explore infectious diarrhea, tropical medicine, and adaptive immune responses to pathogens including SARS‑CoV‑2. His work aims to advance novel therapies that modulate gut inflammation and improve outcomes for patients with complex infectious and inflammatory diseases.

Research interests

Basic/translational science

1. Immune responses to C. difficile infection (CDI)  (Funded: Merck, CIHR) Our laboratory examines the role of T-cell immunity in CDI and how it correlates with initial infection, relapsing infection, and response to fecal microbial therapy (FMT or “stool transplant”). We are also examining the role of adaptive immunity and toxin neutralization in mouse models of CDI.
2. Development of cellular therapy for inflammatory bowel disease (IBD) (Funded: Crohn’s and Colitis Canada) Using a novel technology known as the chimeric antigen receptor (CAR), we are developing regulatory T cells specific to bacterial flagellin, a key antigen in IBD. The goal is to obtain regulatory T cells from patients with IBD, introduce the flagellin-CAR, and infuse them back into the patient, where they will home to the intestinal immune tissues and suppress inflammation. We are also examining the potential role of type-1 regulatory T cells (Tr1) in cellular therapy.
3. Role of stress signals in intestinal immunity We have shown that intestinal epithelial immune responses to bacterial products like flagellin are modulated by exposure to stress or danger signals. We are currently using human-derived intestinal organoids (enteroids) to model these responses, and understand the link between epithelial stress responses and development of abnormal anti-commensal adaptive immune responses to drive inflammation in IBD.
4. Modulation of TLR5 signalling in taxonomically diverse flagellins We are examining the molecular mechanisms of flagellin/TLR5 interaction and inflammatory signaling, based on the observation that some flagellins that are targets of robust antibody and T cell responses yet poor TLR5 agonists.
5. Measurement of T cell responses to antibiotics in patients with delayed-type hypersensitivity reactions Using a novel FACS-based T cell activation assay, we are measuring antibiotic-specific T cell responses in patients presenting with allergic reactions to antibiotics (rashes, kidney injury, etc.) to develop a clinically useful test that can determine safety to rechallenge in the future.

Clinical research and expertise

My main area of focus is intestinal infections, including CDI and travel-related diarrhea, particularly in difficult clinical situations, such as CDI in the setting of IBD. I am also certified in Tropical Medicine and see general infectious disease consultations in both inpatient and outpatient settings. As an immunology researcher, I am also very interested in infections complicating biologic therapies for autoimmune diseases.

• Fecal microbial therapy for recurrent CDI I participate in several studies examining the benefits of different routes and types of FMT material for the treatment of recurrent CDI. As the leading provider of FMT in BC, I have performed the procedure on over 150 patients as part of different clinical trials.
• Novel CDI prevention and treatment I have participated as a site investigator on trials of CDI vaccines and new therapeutic agents