BCG impact on Innate Lymphoid Cells: Determining the Site of Proliferation
Tuberculosis (TB) is an infectious lung disease that is a major cause of mortality, causing an estimated 1.7 million deaths globally per year. The current prophylactic vaccine used against TB, bacille Calmette Guérin (BCG), fails to reliably protect against pulmonary TB in adults. A more efficacious vaccine to protect against TB is urgently required. The recent discovery of a new immune cell subset, the innate lymphoid cells (ILCs) have provided a potential target for vaccine development. Previous work by the Kirman lab revealed an increase in the number of ILCs in murine lungs at 4 weeks post-vaccination with intranasal (i.n.) BCG. My project used a mouse model to determine how early after BCG vaccination ILCs proliferate, and whether ILCs proliferate within the lungs or traffic to the lungs after expanding elsewhere. Understanding the anatomical site of ILC proliferation following BCG vaccination will provide insight into the role of ILCs in the immune response to the BCG vaccine, and will help inform the best route of vaccine delivery. It was hypothesised that ILCs would divide within the lung, as lung-resident ILC populations have been documented. Two experimental approaches were used to test the hypothesis that ILCs proliferate in the lungs following BCG vaccination. The first method was an in-vivo dual labelling system which used i.n. administration of the fluorescent dye carboxyfluorescein diacetate succinimidyl ester (CFSE) to label cells of the lungs, and the thymidine analogue bromodeoxyuridine (BrdU) to label all proliferating cells in the mouse. Using flow cytometry, ILC subsets were then analysed for the presence of CFSE and BrdU, indicating whether proliferation had occurred within the lungs. The second method utilised the immunomodulatory drug FTY720 to block lymphocyte egress from secondary lymphoid tissue to see if this altered the numbers of proliferating ILCs in the lungs, thereby indicating whether or not ILCs proliferate locally within the lungs. Both approaches showed BCG vaccination induced ILC proliferation within the lungs, which was consistently elevated between 1.5 and 4 weeks post-vaccination. These important findings have laid the foundation for further research into the role of ILCs in anti-mycobacterial immunity, and potentially into the manipulation of these cells for vaccine development.
Advisor: Kirman, Jo
Degree Name: Bachelor of Biomedical Sciences with Honours
Degree Discipline: Microbiology and Immunology
Publisher: University of Otago
Keywords: Innate; Lymphoid; BCG; Tuberculosis
Research Type: Thesis