Correction

MEDICAL SCIENCES. For the article “IL-18 binding and inhibition of interferon γ induction by human poxvirus-encoded proteins” by Yan Xiang and Bernard Moss, which appeared in number 20, September 28, 1999, of Proc. Natl. Acad. Sci. USA (96, 11537–11542), the authors wish to make the following correction. Because of unrecognized contamination during large-scale propagation of a recombinant virus expression vector, the preparation of MC53L protein contained human IL-18 binding protein. This contamination affected the MC53L protein results only. Subsequent experiments with six-histidine-tagged recombinant proteins expressed in transfected cells confirmed that the human IL-18 binding protein and the MC54L protein bound IL-18 with the reported affinities, whereas the MC53L protein did not bind IL-18. We apologize for any inconvenience caused by our error regarding the binding properties of the MC53L protein.