Science: Door Ajar

At the Virus Laboratory of the University of California, two researchers announced this week that they have taken an infectious virus apart and reduced it to a mixture of utterly dead chemicals, then put it together and made it infectious again. Drs. H. Fraenkel-Conrat and Robley C. Williams do not want it said that they have “created life”; a simple virus is alive in a special sense only. But they do believe that they have come closer to one of science’s major aims—knowing the nature of life. Says Dr. Williams: “We have no doubt that eventually we will be able to build the viruses we want, at least the simpler ones, by taking the component parts out of laboratory bottles.”

Degraded Virus. The two researchers worked with the simple and well-known virus that causes mosaic disease in tobacco plants and is called TMV for short. Its particles are rod-shaped, and are known to consist of central cores of nucleic acid with protein molecules strung around them. Drs. Fraenkel-Conrat and Williams prepared pure solutions of the submicroscopic rods, mixed them with dilute alkaline chemicals and held them close to the freezing point for two to three days. This treatment “degraded” some of the virus, separating the rods into nucleic acid and protein molecules. Undegraded rods were taken out of the solution with an ultracentrifuge, and the protein fraction was precipitated by chemical treatment. The nucleic acid part of the virus was isolated by a slightly different method. Now neither part contained any complete virus particles. Both parts were inert chemicals, and thus had no power to infect a tobacco plant.

Drs. Fraenkel-Conrat and Williams then mixed the two parts of the virus together, made the solution slightly acid and held it just above freezing point for 24 hours. At the end of this period, the protein molecules had rearranged themselves on the nucleic acid cores. When tested on tobacco plants, the virus proved infectious. It grew and multiplied in the green leaves, producing the characteristic spots of tobacco mosaic disease.

Practical Possibility. The technique of degrading and reconstituting viruses may make it possible to create safe and effective vaccines against diseases, e.g., polio, that are caused by simple viruses. Only about 1% of the TMV particles that were reconstituted during the experiment proved fully infectious. The rest were imperfect in some way. Apparently their protein molecules had not arranged themselves properly. When scientists learn to control this rebuilding process, they may be able to produce slightly imperfect viruses that can stimulate the defensive forces of the human body, but cannot start a real infection. Says Dr. Williams: “This is the work we want to get into, and we feel that the door, if not completely open, is now well ajar.”