The DNA Bomb

Modified Crops are In the Crosshairs Now. You May Be Next.

This is the doomsday scenario: Assassins seek to take down a world leader, but they won't need to risk using bullets or bombs. Instead, they stand on a receiving line and shake the leader's hand, coming away with a genetic sample—a fleck of skin, a stray hair—that reveals his secret vulnerabilities. Then they engineer a pathogen that will attack only the dignitary. The next time he addresses a crowd, one terrorist simply coughs, releasing the pathogen-loaded virus into the air. It circulates silently, a contagion harmless to all but its target. Within hours, the leader is dead.

Perhaps less frightening, though all the more likely, is the threat of attacks against agriculture. Because DNA varies little from person to person, picking out an individual is extraordinarily hard; an entire species of plant, though, is a barn-side target. Ecoterrorists have already begun building arsenals of weeds designed to choke out genetically modified (GM) crops, which are by definition distinct. Scientists have so far laughed these predators off, but the time is coming when an entire variety of corn or rice could be quietly and efficiently destroyed.

Last week, the Bush administration rolled out its initiative against domestic terrorism, but efforts today may prove worthless tomorrow. Though this year's triumphal publication of the human genome in draft form is expected to catapult medicine to a level that would have seemed miraculous a generation ago, it has also raised questions about whether this plowshare might be beaten into a sword.

"We mapped the human genome for goodness—for medical advances and for saving lives, not for nefarious acts. But anything you do always has a dark side," notes a Bush administration official who requested that she not be identified. "I'm with a community that sees the bad things in this world; I see all of the intelligence reports produced. Sometimes I think, 'My God, how could that be used by this adversary or a second nation working with a terrorist organization?' "

Departments once thought of as soft, like Agriculture and Health and Human Services, have become vanguard agencies for domestic defense consulted by the National Security Council because of their expertise with food and emerging diseases, she says. The White House official says she'd like to see scientists police themselves better regarding what they publish and with whom they share data. She predicts President Bush will repeat Clinton's pooh-poohed attempt to include controls and security demands on biological agents in an omnibus crime package.

For now, crafting a genetic bullet that could be carried by many but kill only one isn't within reach, but neither is it beyond imagining. "I see that prospect as an easy fix for biologicals . . . one that would require money and time, but seems rather doable," one researcher with an intelligence agency writes to the Voice. A Secret Service spokesman says the agency is aware of the issue, but can't comment on it for fear of tipping its hand.

Targeting a person with a custom-tailored pathogen would be difficult and expensive, emphasizes Dr. William Nierman, director for research at the Institute for Genomic Research, a central player in the Human Genome Project. But asked by the Voice, Nierman, who was a Navy researcher, explains how it might be done.

First, fish out the target from a sea of human genes, using the handful of DNA markers that "give essentially unique identification to an individual or his/her identical twin," he writes, in an e-mail interview.

Then seek that person's weaknesses—tiny details in DNA that make a particular person sensitive to drugs or disease. Little is known about this kind of variation, but it "undoubtedly does exist," Nierman says. "It is well established for some drugs, and genetic susceptibility to infectious agents is widely believed to be true. . . . Once these differential sensitivities are characterized, they potentially can be used for single-person targeting."

Now fire. Precursors to the futuristic technology an assassin might employ are being developed today as tools to fight cancer or deliver gene therapy, Nierman says. Load a common virus with a destructive gene, then release the bug into the wild. Designed to activate only in the presence of a single host, the pathogen could flit unnoticed through an entire city of unwitting carriers, a "harmless propagation," as Nierman terms it, before reaching its target. Every cabbie, waiter, doctor, elevator passenger, and family member would be a Typhoid Mary. Imagine Kennedy's "Magic Bullet" benignly ricocheting through generations.

No one interviewed by the Voice could theorize a direct defense against such a pathogen, but several expressed skepticism that such a weapon could even be created. For starters, the cost and level of expertise needed would be prohibitive. "To do this now for an individual is almost beyond the pale," says Dr. John Aach, with Harvard Medical School's Lipper Center for Computational Genetics. "The future is weird, period, but I don't see anything like this happening."

Dr. Temple Smith, a founder of bioinformatics and currently director of the BioMolecular Engineering Research Center at Boston University, flamed the concept. Smith says serious agents of biological warfare target basic—and therefore common—genetic receptors. Going after one person would therefore be unfeasible. "There is no kiss of death," he writes. "Hey, there are a lot of dumb ideas out there!"

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