Influence of host resistance on viral adaptation: hepatitis C virus as a case study Anne Plauzolles,1 Michaela Lucas,2,3 Silvana Gaudieri41Centre for Forensic Science, 2School of Medicine and Pharmacology, Harry Perkins Institute, 3School of Pathology and Laboratory Medicine, 4School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, WA, AustraliaAbstract: Genetic and cellular studies have shown that the host's innate and adaptive immune responses are an important correlate of viral infection outcome. The features of the host's immune response (host resistance) reflect the coevolution between hosts and pathogens that has occurred over millennia, and that has also resulted in a number of strategies developed by viruses to improve fitness and survival within the host (viral adaptation). In this review, we discuss viral adaptation to host immune pressure via protein–protein interactions and sequence-specific mutations. Specifically, we will present the “state of play” on viral escape mutations to host T-cell responses in the context of the hepatitis C virus, and their influence on infection outcome.Keywords: hepatitis C virus, viral adaptation, immune escape, adaptive immune response