There are many different strains of the bacterium that can cause Lyme disease in people following transmission from feeding ticks. Scientists know that reinfection by the same strain is rare – some diseases can create lasting immunity – but they did not realize that host protection takes place within the feeding ticks.
In a new study published in PLoS Pathogens, scientists at NIAID’s Rocky Mountain Laboratories studied the impact of the infection history of the mammalian host upon Lyme disease spirochetes within a feeding tick. They learned that if the host, such as a mouse, already had been infected with the same strain of Borrelia burgdorferi that the tick carries, antibodies from the host would bind to and neutralize the bacterium within the tick midgut without killing them. Previously, scientists had presumed the neutralization took place within the host after the tick transmitted its bacterium.
They also observed that if the tick carried a different strain of B. burgdorferi than the host was infected with, then the host would become “super-infected” with both strains when the tick transmitted the new strain of bacterium into the host.
The finding demonstrates that an effective vaccine targeting strain-specific components of the Lyme disease spirochete can neutralize bacteria within the tick but would need to be specifically designed to protect against multiple strains.
Reference: B Bhatia, et al. Infection history of the blood-meal host dictates pathogenic potential of the Lyme disease spirochete within the feeding tick vector. PLoS Pathogens. DOI: 10.1371/journal.ppat.1006959 (2018).