Thursday 22 March 2018

Stephen Crohn

'Man who couldn't catch Aids' was key to developing drug to treat the disease

STEPHEN Crohn, who has died aged 66, was known as "the man who can't catch Aids" despite being a homosexual with a high-risk lifestyle in LA; as a result he was able to make a huge contribution to scientific understanding of the disease.

In March 1982, Crohn's partner, Jerry Green, with whom he ran a restaurant, became one of the first people to die of Aids, though the disease only acquired its name six months later. In the years that followed, Crohn lost, by his own estimation, more than 70 friends to the disease. Yet even though he had taken no special precautions and remained sexually active, every time he went to be tested, the results were negative.

In the early Nineties, his case came to the attention of Bill Paxton, a scientist at the Aaron Diamond Aids Research Centre in New York, who had been looking for gay men who seemed resistant to infection. With a colleague, David Ho, Paxton exposed Crohn's blood cells, and those of another volunteer, to HIV.

HIV causes infection by penetrating a type of white blood cell known as CD4, locking into two receptors on the outside of the cell. But the scientists found that the HIV, even at concentrations thousands of times higher than those that occur outside the laboratory, could not penetrate Crohn's CD4 cells. The reason, they discovered, was that one of the cell receptors, known as CCR5, was genetically flawed, preventing HIV from getting through. The variation, which appears to have no other effect on health, positive or negative, is known as the "delta 32 mutation" and occurs in less than one per cent of the population.

The research into Crohn's immune system led to the development of maraviroc, a drug that blocks the CCR5 receptor and is used to prevent infection spreading in patients who have contracted the virus. In 2006, an Aids patient in Germany was pronounced cured after receiving bone marrow transplants from a donor who had the mutation.

But despite his contribution to scientific knowledge about Aids, according to his family, Crohn suffered from an all-consuming sadness about friends who had died. "What's hard is living with the continuous grief," Crohn explained in a documentary in 1999. "You keep losing people every year – six people, seven people . . . and it goes on for such a long period of time. And the only thing you could compare it to would be being in a war."

On August 24, he took his own life.

Stephen Lyon Crohn was born on September 5, 1946 in Manhattan, inheriting his mutated gene from his father. After training as an artist and social worker, he worked as a painter and sculptor and as a freelance editor for Fodor's Travel. In later life, he ran support groups for Aids patients and made sure that the lives of all his friends who had died of the disease were commemorated with a square on the huge Aids Memorial Quilt, which now consists of more than 48,000 hand-sewn panels.

Crohn was the great-nephew of Burrill Crohn, a gastroenterologist who first described the inflammatory bowel disease that carries his name. Crohn himself felt that by helping scientists he was carrying on the family tradition.

Sunday Independent

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