Animals

Approximately 4–6 week-old female Balb/c mice were purchased from The Charles River Laboratory (Wilmington, MA). Cramp^−/− (Cnlp^−/−) mice were bred from Cramp^−/− knockout Balb/c breeding pairs at the Johns Hopkins animal facility [31, 32]. Mice were backcrossed at least 70 times. Infected mice were maintained in an animal biosafety level 3 laboratory at all times. This study was carried out in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The animal protocol was approved by the Institutional Animal Care and Use Committee of the Johns Hopkins University, and covers all animal procedures.