(McClatchy-Tribune Information Services) -- The latest target in the search for a vaccine against Lyme disease? Tick spit.

Yale researchers have discovered a protein in tick saliva that helps protect mice from developing Lyme disease. The findings are published in today's issue of Cell Host & Microbe, according to a press release from Yale University.

Rather than using the bacterium that causes disease to produce a vaccine, the traditional method, researchers are investigating antibodies in the protein of the tick's saliva, which has been shown to give immunity to the disease.

"The interaction between the Lyme disease agent and ticks is very complex, and the bacteria uses a tick salivary protein to facilitate infection of the mammalian host," said the lead author, Dr. Erol Fikrig of the Yale School of Medicine and Howard Hughes Medical Institute. "By interfering with this important interaction, we can influence infection by the Lyme disease agent."

The Lyme bacterium, Borrelia burgdorferi, is transmitted by tick bite and is coated with a salivary protein known as Salp15. When the Yale researchers injected the protein into healthy mice, it helped protect them from Lyme disease. When combined with outer surface proteins of the bacterium, the protection increased, the authors said.

Several years ago, a vaccine was marketed that used just the surface proteins; it was taken off the market in 2002.

The authors said using the saliva of the insect may be a way to fight other insect-borne illnesses.

"Currently, we are working to determine if this strategy is likely to be important for West Nile virus infection, dengue fever and malaria, among other diseases," Fikrig said.

Other researchers were Jianfeng Dai, Penghua Wang, Sarojini Adusumilli, Carmen J. Booth and Sukanya Narasimhan of Yale School of Medicine, and Juan Anguita of the University of Massachusetts.

Copyright (C) 2009, New Haven Register, Conn.