Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Many koalas suffer from leukemia and from chlamydia infections. A koala retrovirus (KoRV) isolated from an animal in a German zoo was able to infect rat and human cells in vitro and rats in vivo. Virus infection modulates cytokine production in a way characteristic of immunosuppression, suggesting that virus-induced immunosuppression might contribute to common chlamydia infections of koalas. In addition, the transmembrane envelope protein of the KoRV can generate neutralizing antibodies that may be the basis of a successful vaccine. ((See related article in June 2006: vol. 80, issue 11, page 5651.))