PLASMINOGEN IS REQUIRED FOR EFFICIENT DISSEMINATION OF BORRELIA-BURGDORFERI IN TICKS AND FOR ENHANCEMENT OF SPIROCHETEMIA IN MICE

The role of the host plasminogen activation system in transmission of and invasion by Borrelia burgdorferi, the tick-borne spirochetal agent of Lyme disease, was investigated using plasminogen (Plg)-knockout mi ce. PLG was not detected in spirochetes from unfed ticks, but binding occurred as ticks fed on the host's blood. Plasminogen activators were derived from the host blood meal. PLG was required for efficient diss emination of B. burgdorferi within the tick and for enhancement of spi rochetemia in mice but was not critical for transmission and infection . These results provide evidence for a bacterium using a vertebrate pr otease to disseminate in an invertebrate vector and underscores the in terplay among vector, pathogen, and host in promoting the life cycle a nd disease.