In this issue of Nature Structural Biology (on page 765), Tate and coworkers present the structure of the cricket paralysis virus — the first structure of an insect picornavirus. An accompanying News and Views report (on page 717) notes that the study of insect viruses, and indeed of insect pathogens in general, has been rather limited in comparison to the study of mammalian pathogens. Thus, it is ironic to note that some of the first characterized pathogenic diseases were those of insects, specifically silkworm caterpillars and moths.
In the mid 1800s, a pervasive disease decimated silkworm agriculture in France. In an effort to save the silk-production industry, the French government persuaded Louis Pasteur, well-respected for his work on fermentation, to study the problem — despite the fact that he had no experience with silkworms, or even with animals in general. A recent biography of Pasteur (shown to the right) outlines his contributions to understanding and preventing insect disease. His efforts from 1865 to 1870 led to the discovery that the disease affecting the silkworms was really two separate parasitic infections — known as pébrine and flacherie. The agents causing pébrine and flacherie were later identified as microsporidia and bacteria, respectively (and it was later shown that flacherie also has an important viral component). Pasteur's results suggested that certain procedures — which may seem obvious today but were not well established at the time — should allow silkworm breeders to restore their stocks and revive silk production. These included identification and isolation of uninfected silkworms, selective breeding, and increased cleanliness of silkworm colonies. The silkworm infection experiments, and his success in reviving the silkworm colonies, undoubtedly left Pasteur better prepared to analyze the roles of microbes and hygiene in human disease.
Pasteur began his career in science as a crystallographer, and his early work made significant contributions to basic chemistry. For example, he laid the foundation for understanding stereochemistry by showing that crystals of two compounds that had the same molecular composition, tartaric acid and paratartaric acid, diffracted light in opposite directions. Given Pasteur's work in the disparate fields of crystallography and insect disease, one can imagine that he would take great pleasure in seeing the two disciplines come together now to yield the high resolution X-ray crystal structure of the cricket paralysis virus.