Nat. Biotechnol. 25, 1395–1402; published online December 7, 2007; corrected after print 8 April 2008.

In the version of this article initially published, the name of a person quoted on p. 1399 was incorrect. The CSO of Replicor of Laval, QC, Canada, given as “Andrew Toussaint” should be “Andrew Vaillant.” The error has been corrected in the HTML and PDF versions of the article.