Scientists Say Rare Vine Offers Hope For AIDS Cure
Apr. 06, 1993
KORUP, Cameroon (AP) _ Leaves of a previously unknown vine in a Cameroon rain forest contain a chemical that blocks reproduction of the AIDS virus in the test tube, researchers say.
Though hopes are high, all involved realize any cure or treatment based on the chemical is years away.
''It is, at present, in preclinical development,'' said Gordon Cragg, chief of the U.S. National Cancer Institute's natural products branch. ''Some limited testing is being done in animals (mice and dogs) to see if the concentrations required for activity against the virus can be attained without it being too toxic.''
Leaves of the vine have yielded an alkaloid called Michellamine B during laboratory tests at the National Cancer Institute in Frederick, Md., the U.S. government's premier cancer research facility. Researchers there say Michellamine B inhibits replication of the AIDS virus.
''We're excited about something showing this spectrum of activity against AIDS,'' said Dr. Johnson Jato, vice dean of the University of Yaounde Center for Health Services and the Cameroon liaison for the American researchers.
The vine was discovered by Duncan Thomas, a British botanist, in Cameroon's remote Korup National Park.
The vine, which Thomas has tentatively named ancistrocladus korupensis after the rain forest, is one of the National Cancer Institute's best leads from an extensive plant-collecting program.
Some 20,000 samples from 25 countries have been tested since 1986. So far, only two other plants, from Samoa and Sarawak in Malaysia, have shown some activity against the acquired immune deficiency syndrome virus. Both are in earlier stages of research than korupensis, said Cragg.
A more immediate problem is getting enough vine leaves.
Researchers still do not know how much of the vine exists, over how big an area it grows and how best to cultivate it. Finding the answers brought Thomas, 43, back to Cameroon and Korup last month.
''The local people don't have a use for it. They don't even have a name for it,'' he said as he walked through the forest, scanning the canopy for the distinctive broad-leaved vine.
It has only been found in a small section of the 740,000-acre rain forest, an area roughly the size of Rhode Island along Cameroon's northern border with Nigeria. It is bound south and east by a palm oil plantation that abruptly ends at the protected forest.
An offshoot of a family of vines also found in the Congo, korupensis likes the sandy soils and flat terrain near the Ndian River.
Thomas first discovered the vine in 1987 during a plant collecting trip for the Missouri Botanical Gardens in St. Louis. It is one of several institutions that supplies the National Cancer Institute with plant specimens for testing against cancer cells and the AIDS virus.
It was during one of these routine tests in late 1990 that researchers discovered Michellamine B and its effect on the AIDS virus.
They wanted more leaves, but by that time Thomas had left Cameroon for Corvallis, Ore., where he works as an environmental consultant. Missouri sent other botanists, but they could not locate the vine. So Thomas was asked to return.
''I remembered exactly where I found it,'' Thomas said. ''I don't always know what day it is or remember people's names, but I'm a botantist, I can remember where I've found every plant I've collected.''
He showed the vine and its habitat to researchers from the institute, the Missouri Botanical Gardens, the Smithsonian Tropical Research Institute in Washington, D.C., and the University of Yaounde.
With Missouri botanist Roy Gereau, Thomas trained some local men to identify the vine and its leaves.
Gereau said the discovery and its promise against the deadly AIDS virus provides ''the dream argument'' for environmentalists who have been fighting for conservation of rain forests as reservoirs of unknown resources.