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| Mammalian hormones help bacteria spread Lyme disease |
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20 April 2007, for Nature Network Boston Some microbes are adept at making themselves at home in various host species—and spreading disease from one species to another—despite the hosts’ different physiological environments. According to Tufts researchers, mammals harboring the Lyme disease-causing bacteria unwittingly provide hormone signals that tell the microbe when to prepare to transfer into another host. The team, led by Linden Hu, studied the bacterium Borrelia burgdorferi, which resides in various mammals like mice and dogs and causes Lyme disease when transmitted to humans. The bacteria move from one animal to another by hitching a ride in the blood meal of a biting tick. They colonize the tick’s gut, producing high levels of a protein called OspA on their outer surface, which helps them attach to the gut lining. The bacteria produce very little OspA when in mammals, so researchers wondered whether the microbes prepare for the transfer to ticks by ramping up the production of the protein and, if this is the case, what causes them to do so. They found that the bacteria are able to sense and react when a tick bites their host. When bitten, mammals release hormones that trigger inflammation, such as epinephrine. The Tufts researchers showed that these hormones bind to the bacteria, increasing the production of OspA and effectively telling the microbe that it’s time to move into a tick. In mouse studies, the team found that blocking these hormones reduced by half the chances of the bacteria moving from the mice to uninfected ticks. The research appeared online this week in the Proceedings of the National Academy of Sciences. |