Some viruses envelop their genetic material within a protein-coated capsid in a further lipid membrane layout, for example, influenza virus, baculovirus, hepatitis-C, HIV, and Herpes virus. These enveloped particles require successive steps to successfully entry and infect host cells. They usually first attach onto host receptors (and attachment factors), and their membranes fuse to interact with endosome vesicles that traffic the virus toward the endoplasmic reticulum, where it is uncoated. The proteins are finally transported to the cytosol and nucleus [64] (Figure 2 ). There is convincing evidence showing that most viral infections are strongly influenced by changes in the redox environment and that host PDI mediates infection of enveloped viruses [65] [66] [67] [68] [69] [70] .