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The small band of interferon researchers were able to produce or get their hands on enough interferon to analyze its nature, but the stuff was far too scarce or any significant tests on humans. Most of the credit for relieving that acute shortage goes to a stubborn Finnish virologist, Kari Cantell, who proudly admits that "interferon has been my hobby and main scientific interest for over 20 years." Cantell began his career by studying the role of leukocytes, or white blood cells, in fighting infection. He became intrigued when he learned from other researchers in 1961 that these cells could produce IF. By 1963 he had concluded that they might yield enough of the elusive substance to get research efforts off the ground. For the next ten years, he devoted all his time to developing the method that today supplies most of the world's leukocyte IF.
Cantell's manufacturing facility is unimposing, at best. It consists of a suite of labs in Helsinki's Central Public Health Laboratory. There, Cantell works with white cells derived from the 500 to 800 pints of blood donated daily to the Finnish Red Cross by citizens in and near the nation's capital. The Red Cross spins the whole blood in a centrifuge to separate its elements; the heavy red blood cells sink to the bottom, white cells settle just above, and the liquid plasma rises to the top. The Red Cross keeps the plasma and red cells for transfusions and turns the white cells over to Cantell. He infects the leukocytes with Sendai virus, an influenza-like virus harmless to humans, and incubates them at 37.5? C (99.5? F) for 24 hours. The resultant IF solution is centrifuged to separate out the white cells and partly purified to destroy the virus. What remains is a highly impure IF preparation; even after it is partly purified it consists of only one part IF for every 999 parts of other substances. To purify it totally is both impractical (99% of the interferon is destroyed) and prohibitively expensive. By last year Cantell and a small staff were turning out 400 billion units annually (one unit is the amount of IF that protects half of a cell culture in a laboratory plate from being destroyed by a test virus). That may sound like a lot, but daily doses of millions of units are needed for each patient being tested, and in the early 1970s Cantell's impure product did not go very far.
Still, researchers now had enough interferon to move studies out of the laboratory and into the clinic. In 1972 Virologist Thomas Merigan, of Stanford University, and a group of British researchers began studying IF's effect on the common cold. Soviet doctors were claiming success in warding off respiratory infections with weak sprays of IF made in a Moscow laboratory. Merigan and his colleagues gave 16 volunteers a nasal spray of interferon one day before and three days after they were exposed to common cold viruses. Another 16 volunteers were subjected to the same viruses without any protection. The results seemed miraculous. None of the 16 sprayed subjects developed cold symptoms, but 13 of the unsprayed did. There was one catch: at the IF strengths that Merigan used, each spray cost $700.