B. burgdorferi destroys the distinct architecture of the lymph node that would enable it to function normally
Groundbreaking research by immunologists at University of California Davis has uncovered a key to Borrelia burgdorferi’s ability to elude the body’s immune defense system.
As they report in the June issue of PLoS Pathogens, the findings of their study in mice “suggest for the first time that B. burgdorferi, the bacteria that cause Lyme disease in people, dogs and wildlife, have developed a novel strategy for subverting the immune response of the animals they infect.”
Swollen lymph nodes, or lymphadenopathy, is one of the hallmarks of Lyme disease, although it has been unclear why this occurs or how it affects the course of the disease, according to lead author Nicole Baumgarth, DVM, PhD, an authority on immune responses at the UC Davis Center for Comparative Medicine.
So the team set out to explore in mice the mechanisms that cause the enlarged lymph nodes and to determine the nature of the resulting immune response. This is what they found:
• When mice were infected with B. burgdorferi, the live spirochetes accumulated in the animals’ lymph nodes.
• The lymph nodes responded with a strong, rapid accumulation of B cells - white blood cells that produce antibodies to fight infections.
• But at the same time, the presence of B. burgdorferi caused the destruction of the distinct architecture of the lymph node that usually helps it to function normally.
• Therefore, while B cells accumulated in large numbers and made some specific antibodies against B. burgdorferi, they did not form “germinal centers” - structures that are needed for the generation of highly functional and long-lived antibody responses.
“Overall, these findings suggest that B. burgdorferi hinder the immune system from generating a response that is fully functional and that can persist and protect after repeat infections,” Dr. Baumgarth said.
“Thus, the study might explain why people living in endemic areas can be repeatedly infected with these disease-causing spirochetes.”
(And perhaps will lead to an understanding of so-called “persistent Lyme disease” or “post-treatment Lyme syndrome,” and improved strategies for combating these problems.)
While Lyme disease occurs mainly in the Northeast and Upper Midwest/Great Lakes area, it is present on the West Coast as well, and the western black-legged tick, the main carrier of Lyme disease in the western US, has been found in 56 of California's 58 counties, according to the California Department of Public Health.
Sources: University of California Davis news release, June 8, 2011, and cited article, “Lymphoadenopathy during Lyme Borreliosis Is Caused by Spirochete Migration-Induced Specific B Cell Activation.”