Letters.

One killer of a cold?

The article on the Ebola virus' deadly glycoprotein ("Ebola protein explains deadly mystery," SN: 8/5/00, p. 85) was frightening enough, but even more terrifying to me was the fact that the researchers had genetically engineered a cold virus, one of the most easily transmitted and successful viruses on the planet, to carry the Ebola glycoprotein. I hope that modified virus never escapes the laboratory, and I hope the germ warfare laboratories and terrorists of the world don't read NATURE MEDICINE or SCIENCE NEWS. Couldn't a safer, less easily transmitted virus have been employed?

Vic Walker El Dorado Hills, Calif.

Several of our readers have questioned the wisdom of endowing a seemingly highly contagious cold virus with a gene that gives the Ebola virus its lethality. The scientists stress that their experiments were carried out in a biocontainment laboratory especially designed to prevent accidental release of dangerous microbes. Equally important, the adenovirus used had been genetically engineered so that it can no longer replicate. In essence, it was simply used to ferry the Ebola gene into human cells. A cell infected with this adenovirus doesn't produce new copies of the virus.

--J. Travis

Dirty story

The article titled "Do more infections mean less asthma?" (SN: 8/26/00, p. 134) suggests that exposure to microbes in early life helps develop a child's immune system. Speaking of dietary habits among 18th-century "Scotch-Irish" immigrants to the back-country regions of colonial America, David Hackett Fischer notes in Albion's Seed (1989, Oxford University Press): "The quality of butter was believed to be improved in proportion to the number of human hairs embedded in it. "The mair dirt the less hurt,' Appalachian housewives liked to say." Perhaps they were on to something.

John Derbyshire Huntington, N.Y.

We originally reviewed the inverse relationship of febrile infections and asthma nearly 40 years ago. However, it's not possible to explain the current increase in the prevalence and the morbidity of asthma simply on the basis of "more infections . . . less asthma." Infantile atopic eczema often precedes the onset of the respiratory problems. Neither genetic nor environmental-dietary factors can adequately account for that or the fact that childhood allergy, almost nonexistent one or two generations ago, has become such a universal problem. The question has been raised whether health-care practices (such as immunizations and overzealous administration of antihistamines, antibiotics, and antipyretics) play a role in this respect. Are we practicing physicians, like the ancient Theban king Oedipus, responsible for the plague we're trying to resolve?

Constantine J. Falliers Denver, Colo.

Who's placenta is it?

The first sentence in "DNA vaccine immunizes fetal lambs" (SN: 8/19/00, p. 116) is incorrect when it refers to "a woman's placenta." A woman doesn't have a placenta, nor does any other mammalian mother. The placenta is an organ of the fetus. The mother's tissue ends at the uterus lining.

Bruce S. Sibbett San Bernardino, Calif.