UBC microbiologists have identified a key defence mechanism used by the immune system against Listeria, a finding with important implications for the development of vaccines. Listeria is the bacteria that causes listeriosis, the food-borne infection that caused 22 deaths in Canada in an August 2008 outbreak in meat products produced by Maple Leaf Foods.
The study, published in PLoS ONE, focuses on dendritic cells, which help activate the immune system. Dendritic cells collect pathogen materials and present them to other parts of the immune system (such as T-cells) in a process called cross-presentation. "Dendritic cells are gatekeepers--they are small in numbers but very active in patrolling tissues that are in contact with the external environment, such as the skin," says Wilfred Jefferies, a professor at UBC's Michael Smith Laboratories and Department of Microbiology and Immunology.
"Their job is to apprehend the pathogens while avoiding getting infected. We've found that they achieve this by sampling bits and pieces of the bacterial pathogens in the area surrounding infected cells, instead of directly approaching the bacteria."
The research also shows that when cross-presentation is deactivated, the host becomes severely compromised in its ability to generate the appropriate T-cells to fight the Listeria infection.
"We know a great deal about how our body’s adaptive immune system reacts to viruses but generally very little about immune response against bacterial infections," says Jefferies, also a member of the UBC Blood Research Centre, the Biomedical Research Centre, the Brain Research Centre and the Vancouver Coastal Health Research Institute.
"This study establishes the vital role of dendritic cell cross-presentation in fighting bacteria infections and sheds light on how we can manipulate and engage immune responses. This knowledge will ultimately aid in the design of vaccines against bacteria and other pathogens."
The UBC team also includes post-doctoral fellows Anna Reinicke and Genc Basha and graduate student Kyla Omilusik.
The study was supported by funding from the Canadian Institutes of Health Research (CIHR). "Better understanding of the body's immune system is the key to develop new strategies for treating bacterial infections and for creating new vaccines for Listeria", says Dr. Bhagirath Singh, Scientific Director at CIHR's Institute of Infection and Immunity.
"Dr. Jefferies's work advances our collective effort to prevent listerosis by focusing on the way our immune defences are wired and triggered upon initial infection by invading pathogens."
