Kartik Chandran studies the process by which the highly pathogenic Ebola and Marburg filoviruses gain entry into the cytoplasm of host cells. The filovirus entry mechanism is unusually complex. It consists of multiple steps in which the virus interacts with and co-opts distinct host cell molecules, and is itself structurally transformed as a result. His research has identified endosomal host factors that are critical for filovirus entry, such as the Niemann-Pick C1 protein, and may serve as potential targets for antiviral therapy. His work has also identified endosomal cysteine proteases that are required for viral entry and act by cleaving the viral glycoprotein.