Developments to Watch
A NEW GAUGE FOR AIDS TREATMENTS
THE EVALUATION OF AIDS therapies is a tricky business. Waiting until a drug regimen shows a clear-cut effect in extending life or reducing secondary infections may take years. And measures of a treatment's effectiveness now in use are less predictive than doctors would like. For example, it's clear that a big drop in the numbers of an immune system cell called CD4 is a bad sign. But a small, drug-induced rise in CD4 counts doesn't necessarily help. Doctors and AIDS activists think there may be a better gauge of a patient's progress: directly measuring the amount of virus--the viral load--in the body.
Now there's firm proof that it works. To evaluate a new AIDS drug, Pharmacia & Upjohn Co. is using a sensitive test, polymerase chain reaction (PCR), to measure viral load. The preliminary results, announced on Jan. 17, are striking. Subjects who started the trial with less virus took longer to get sick than those harboring more HIV. And those in whom the drug cut viral levels 90% were five times less likely to die or progress to more serious stages of the disease. That means the amount of virus is "a very powerful predictor," says AIDS activist Ben Cheng of Project Inform. Clinicians and activists are now pressuring insurers and HMOs to pay for PCR viral load tests, which cost between $125 and $250 each, as part of normal patient care.Edited by Neil GrossReturn to top
`CHIRPING' LASERS THAT CAN SMASH ATOMS
EVEN BEFORE THE GIANT, $11 billion Superconducting Super Collider (SSC) was scrubbed in 1993, an international band of scientists was chasing a much cheaper alternative: an atom-smasher small enough to sit on a laboratory table and allow any university lab to probe the frontiers of subatomic physics.
Well, splitting atoms on a table is no longer the stuff of distant dreams. Gerard A. Mourou, director of the University of Michigan's Ultrafast Optical Science Center, is convinced that semiconductor lasers can match the SSC's power--or even top it. The key is using one laser pulse to drill a hole through a gas, creating a plasma tunnel that serves to guide subsequent laser pulses. A following pulse can then snare electrons in its energy field and push them to atom-smashing speeds.
Accelerating an electron to speeds fast enough to split an atom is a function of distance. In normal accelerators, it takes miles of electromagnets to get up the necessary speed and energy. But with so-called "chirping" lasers that Mourou helped pioneer, "we could achieve SSC energies in just a few meters," he says. Chirping involves stretching a laser pulse so its energy can be amplified many times, then compressing it into an ultrashort, ultrapotent blast. Before the plasma tunnel, there was no way to prevent these pulses from rapidly diffusing. Optical fibers wouldn't work because chirped pulses would vaporize the glass.
In the current setup, the pulses travel only a centimeter. By yearend, Mourou hopes to extend the distance to several centimeters. And scientists are already working on plasma tunnels many meters long (photo).Edited by Neil GrossReturn to top
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BEULAH, PEEL ME A VACCINE
IT MAY NOT BE LONG BEFORE GETTING vaccinated against a disease is as easy as eating a banana. British researchers say they've found a commercially viable way of growing medicines from plants--an advance over the slow and costly fermentation techniques used to produce most vaccines today. Axis Genetics, a small Cambridge biotechoutfit, first infects the plants with genetically engineered viruses. These in turn produce structures in the plant leaves that contain biologically active proteins and protein fragments, called peptides, that can be used as vaccines.
The first peptides produced this way were small and of limited usefulness. Help came last July from scientists at the Scottish Crop Research Institute (SCRI) who were experimenting with the same technique. They altered the shape of the virus particles using an animal protein "overcoating." The plants then began producing proteins 10 times the size of earlier peptides. That increase makes them suitable for a variety of medicines, says Mike Smith, a professor at SCRI.Edited by Neil GrossReturn to top