Rubber trouble

By Matt Walker SURGICAL gloves and condoms pose a risk to millions of people who have a potentially fatal allergy to latex. Now researchers in California have come up with a virus-resistant, non-allergenic alternative extracted from an obscure Mexican plant. Ordinary latex—a milky fluid extracted from the Brazilian rubber tree, Hevea brasiliensis—contains a number of soluble proteins as well as the terpenoid compounds that form rubber. Until the 1980s, rubber manufacturers used to wash away most of these proteins before using the fluid. Then came AIDS, and manufacturing processes were changed to meet the huge new demand for barrier products, says Katrina Cornish of the US Department of Agriculture’s Western Regional Research Center in Albany, California. Since then, overexposure to these proteins has sparked a wave of allergic reactions to latex. These range from itchiness and flaking skin to asthma and anaphylactic shock—a condition that can kill unless the sufferer is quickly injected with adrenalin. Now more than 20 million people in the US alone are likely to be allergic to latex. Most rubber products are now being washed again, says Cornish, but the latex allergy remains. “You can’t turn the clock back,” she says. The hunt for a better alternative led Cornish and her colleagues to the guayule plant (Parthenium argentatum), a perennial shrub native to the deserts of Mexico and south-western Texas. They have already shown that latex from guayule is free from the allergenic proteins found in rubber latex and does not produce a reaction. “The bottom line is: would it be resistant to viruses?” says Cornish. So she and her colleague David Lytle tested the performance of a pair of guayule latex gloves by filling them with a solution containing a test virus called phi X174—smaller than bacteria and the HIV, hepatitis B and herpes simplex viruses. They then put the gloves in a centrifuge tube containing a virus-free solution. After an hour in the centrifuge, the virus had failed to pass through the glove into a buffer solution. Condoms made from guayule latex were similarly checked and passed standard tests with flying colours. Guayule latex also seems to have a longer shelf life than conventional rubber, and is harder to pierce,
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