Spotted vaccine to follow?

Spotted vaccine to follow?

Using cloning and recombinant DNA techniques, microbiologistsat the National Institute of Allergy and Infectious Diseases' Rocky Mountain Laboratories in Hamilton, Mont., have produced a possible vaccine against Rocky Mountain spotted fever. Caused by the bacterium Rickettsia rickettsii, the tick-borne disease destroys cells of the vascular system, leading to low blood volume and fluid-swollen tissues.

Members of the Hamilton team recently described protectionagainst the disease in mice, using antibodies against two surface antigens of R. rickettsii. Those antigens, however, are difficult to purify, and the bacteria are difficult to grow in culture. To optimize the system, DNA coding for the antigens has been introduced into Escherichia coli to create a recombinant E. coli capable of producing large quantities of the antigens, they report in the Jan. 2 SCIENCE. Preparations of the E. coli successfully protect mice against lethal doses of R. rickettsii, and experiments are being expanded to include guinea pigs. Preliminary results suggest that the cloned vaccine may also be effective in other species.

Between 700 and 800 cases of Rocky Mountain spotted feverare reported each year, with most of those (despite the disease's name) in the Southeast, according to the Centers for Disease Control in Atlanta. But it is likely the disease is more prevalent than these figures indicate, since spotted fever can mimic a wide variety of other disorders, such as pneumonia and measles. There is no satisfactory diagnostic test, yet early diagnosis and antibiotic treatment can save lives. The fatality rate is 4 percent with treatment, 7 percent without.