John Dunn, a member of the research team from Brookhaven, explains that the structure of OspC is predominantly helical, and very different from OspA, which is flat. Also, a region on the surface of OspC has a strong negative charge. Dunn says the negatively charged region may be attracted to a positively charged site on the surface of human cells, helping the bacterium to cause infection. This feature is only found in the OspC protein derived from bacterial strains that cause human disease.
The scientists believe that a vaccine based on OspC will be more effective than the current OspA-based vaccine because the OspA protein is only present in the bacteria while they are in the cold-blooded deer ticks stomach, and not in the host. After the tick bites the warm-blooded mammalian host, the injected bacteria produce OspC in the hosts bloodstream.
When the host is vaccinated solely with OspA, antibodies to this protein can only kill the bacterium inside the tick if it ingests these antibodies with its blood-meal. If the bacterium finds its way into the host, it changes into several other forms for which the vaccine offers no protection.
In contrast, an OspC-based vaccine would enable the host to make antibodies to kill the Lyme disease bacteria within the hosts body.
Another member of the Brookhaven team, Subramanyam Swaminathan, added, In order to develop an effective OspC-based vaccine, well have to know the three-dimensional structures of at least a few variants of OspC, especially those from invasive strains. Since weve solved the structure of OspC based on two infectious strains of the Lyme disease bacterium, we now have a prototype for determining the structure of OspC from other strains.