The last decade of intensive research in the field of infectious diseases has resulted in a better conceptual understanding of the molecular mechanisms behind the host-parasite interactions that lead to establishment and progression of the disease. However, with the discovery of an increasing number of species-specific virulence mechanisms and novel host defense strategies, the picture is becoming more and more complex. This volume of the book series Contributions to Microbiology presents a number of selected articles dealing with bacterial and viral pathogens and the resulting host response to infection with these microorganisms. As novel therapeutic anti-bacterial and anti-viral strategies are primarily focused on significant pathophysiological mechanisms, this publication will not only attract the interest of scientific and medical professionals, but will also be of importance for students in the field of microbiology, infectious diseases, cell biology and immunology.