While the middle years of the twentieth century saw the development of antibiotics, potent new weapons against bacterial diseases, no such chemical defenses against viral diseases had yet emerged other than a few anti-viral vaccines. This was and continues to be a significant gap, since more than half of the communicable diseases that affect human beings are caused by ribonucleic acid (RNA) viruses. The first step was to find out how the body protected itself against viruses; it was known that antibodies acted only against bacteria.That step was taken by Alick Isaacs, a Scottish virologist, in 1957.

Isaacs was born in Glasgow, Scotland, in 1921, to a Russian Jewish family. Hestudied medicine at Glasgow University but found he preferred research to the actual practice of medicine. Accordingly, he pursued graduate studies in bacteriology at Glasgow and secured fellowships to research influenza with eminent microbiologists Stuart Harris of England and Frank MacFarlane Burnet in Australia. Returning to England, Isaacs joined the World Influenza Centre at the National Institute for Medical Research in 1951. There, he carried out hiscontinuing studies of viral influenza until his untimely death in 1967.

Early in his studies of influenza, Isaacs became interested in the viral interference phenomenon--the fact that an RNA virus in a cell inhibits the growthof any other viruses in that cell. He found that this interference seemed tobe caused by something inside the cell. In 1957, while working with the visiting Swiss scientist Jean Lindenmann, Isaacs found that chick embryos injected with influenza virus released very small amounts of a protein that destroyed the virus and also inhibited the growth of any other viruses in the embryos. Isaacs and Lindenmann named the interfering protein interferon.

Further research showed that interferon was produced within hours of a viralinvasion (antibodies take several days to form), and that most living things,including plants, can make the protective protein. Interferon was seen as the cell's first line of defense against viral infections, and its discovery was expected to pave the way for successful treatment of viral diseases.

Because interferon was thought to be species-specific (meaning only human interferon will work in human beings) and the body produces it in only minute amounts, interferon research inched forward at a snail's pace.

Interest in interferon was revived in the late 1960s when Ion Gresser (1928-), an American researcher in Paris, discovered that the protein stopped or slowed the growth of tumors in mice and also stimulated the production of tumor-killing lymphocytes. Gresser and the Finnish virologist Kari Cantell then developed a way to make interferon in useful amounts from human blood cells. Monoclonal antibodies, first produced in 1975, made large-scale purification ofinterferon possible, and the mid-1980s saw the advent of genetically engineered interferon, the first example of which was produced from bacteria by Swissscientist Charles Weissmann in 1980. Scientists now know that there are three major types of interferon: alpha, beta, and gamma. They have also learned that interferons are not species specific but can have activity in other species.

Research of interferon's ability to kill cancer cells is active. It has beenused successfully against leukemia, osteogenic sarcoma (a bone cancer), and as a therapy for delaying disease recurrence and prolonging survival in patients with melanoma (skin cancer). Research also continueson the use of interferon to treat viral diseases like rabies, hepatitis, andherpes infections. In December 1997, researchers from the Duke University Medical Center also announced study results that indicate interferon may be a way to preserve donor livers longer prior to transplantation.

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