Study Sheds New Light on Disease Transmission, Implications for Vaccine Development.(Brief Article)

2001 JAN 24 - (NewsRx.com & NewsRx.net) -- New research on the tick-borne bacteria responsible for Lyme disease likely will make scientists think differently about how to develop a more effective vaccine.

The findings clearly demonstrate that as a tick feeds on its host, molecular changes occur on the outer surface of the Lyme bacteria Borrelia burgdorferi that are more complex than previously known. During the tick's blood meal, its saliva transmits the bacteria to the host.

In terms of Lyme disease immunization, this is important because any truly effective vaccine must prime the immune system to mount an antibody attack against foreign antigens-the invader's outer surface proteins.

"Previous research showed there were certain surface proteins that were expressed in the tick gut and others that were expressed in the host, and that a switch occurred en route from the tick to the host. This paper shows us that things are a lot more complicated," said Aravinda M. de Silva, PhD, assistant professor of microbiology and immunology at the University of North Carolina at Chapel Hill School of Medicine.

The new findings are reported in the January 16, 2001, issue of the Proceedings of the National Academy of Sciences. Along with de Silva, co-authors are Jun Ohnishi, PhD, UNC postdoctoral researcher in microbiology and immunology, and Joseph Piesman, PhD, division of vector-borne diseases at the U.S. Centers for Disease Control and Prevention.

In their study, the researchers focused on two (OspA and OspC ) of the more than 150 membrane proteins known to be associated with B. burgdorferi.

"We wanted to see how these two proteins changed as the bacteria moved from the tick gut to the host," de Silva said. "And to our surprise, what we observed was not simply a matter of one protein being expressed in the gut and another being expressed in the host, as had been previously thought. During transmission, what the tick actually spits into the host is a bacteria population that is highly variable, compared to the fairly homogeneous population found in the tick before the blood meal."