LA JOLLA — Eva Engvall is a scientist who breeds Abyssinian cats as an avocation and is reluctant to name the kittens lest it become harder to part with them.
That was not a problem with something as distant from cats as enzyme-linked immunosorbent assay, a diagnostic test that she helped pioneer while a young graduate student at the University of Stockholm and which she gave the melodious name of ELISA.
Since then, someone else patented the test and another company trademarked the name. She is resigned about the legal title, but appropriation of the name bothered her. "I thought that was really tacky," she said.
Almost every year brings new applications of ELISA, a simple, accurate method of testing for abnormal cells, and it is becoming one of the most widely used diagnostic tests in the world.
It is employed to detect antibodies to the AIDS virus in blood, to chase down viruses in dolphins and poinsettias and parasitic diseases in humans in Africa, to monitor the effect of antibiotic therapy, to detect disease in Oregon cherry trees so they can be destroyed before infecting the whole orchard. It is also the process that makes home pregnancy tests work.
The procedure uses antibodies, those immune molecules that the body manufactures to neutralize viruses and other invaders that it recognizes as foreign. An enzyme is attached to the antibody as a flag, and a chemical is then added that the enzyme breaks down, producing a color that shows the presence of telltale substances, like hormones in the pregnancy test or antibodies in the AIDS test.
And there is something for cats in ELISA too. Veterinarians use it in their offices to test for feline leukemia.
Engvall, 46, divorced mother of two grown children, won two awards for her work on ELISA, although the patent went to a Dutch company that had also worked on it. The test grew out of an older procedure that used a radioactive tag instead of the enzyme, with radioactivity the measure.
That, however, entailed problems in the disposal of radioactive materials and the short shelf life of testing ingredients.
'The Most Versatile'
"ELISA is the most versatile immuno assay there is," Engvall said. "It can be done very inexpensively and applied to almost anything you can think of."
She began her work in her native Sweden,. where she studied for her doctorate in immunology. Her professor, Peter Perlmann, was interested in substituting enzymes for radioactive markers.
She produced an assay following Perlmann's idea in 1970. "It turned out to be a great thing, but we really didn't think about it while we were working on it," Engvall said. "It took 10 years before anyone in the United States paid any attention."
Early interest in ELISA focused on it as a research tool and as a way to monitor therapy by measuring the level of infection in the body.
"I don't think my professor thought of it as a poor man's assay," Engvall said. "I thought it could be developed into an assay that anybody could afford. . . . Some of the modifications I did early on stressed that part of it."
Her current research is far removed from ELISA. At the La Jolla Cancer Research Foundation, she is looking for clues to the ability of tumor cells to travel through the body. And allied with researchers at the University of California, San Diego, she is looking for ways to regenerate severed nerves, perhaps even to restore the capacity for memory.
She started with basement protein, a thin, mysterious layer of sturdy protein that underlies the cells that line blood vessels and other bodily organs.
"If you cut yourself and the cut is deep enough to go through the basement membrane, then you get a scar," Engvall said. "You can bang yourself and get a terrible bruise. Everything else can be destroyed, but if the basement membrane is intact, everything will heal perfectly. Nobody really understands why."
What intrigues the researchers is the failure of basement membranes to inhibit the movement of tumor cells, which, unlike normal cells, can migrate through their own basement membranes and other basement member barriers in the blood system.
She also works with a collagen from basement membrane called laminin, so rare that only three-thousandths of a gram can be extracted from 500 grams of placenta.
Laminin, the researchers found, makes nerves regenerate. Now they are looking for ways to reproduce the substance in quantity in the lab.
The adult central nervous system lacks a basement membrane and therefore laminin. "That's why you can do nothing about brain damage," Engvall said. "The idea is to put some basement membrane components wherever they are needed and get healing that way."
University researchers are trying to use basement membrane components to restore memory.
They cut connections in the brains of laboratory rats. "The animals are healthy to all appearances. . . . But they can't learn."