Antiviral Immunity and Prophylaxis

This chapter argues that antiviral immunity in animals is mediated by both cellular and humoral factors, and the nature of the immune response generated by different individuals infected with the same virus can be different, depending on the individual's genetic constitution, environmental influences, and other factors that can determine the course and pathogenesis of the infection. Innate immune defenses exhibit neither antigen specificity nor memory, but they provide a critical line of first defense against viral infections because they are constantly present and are operational immediately after viral infection. Innate immunity is often considered separate from acquired immune responses, but they are inextricably linked, and innate responses modulate subsequent acquired responses in many ways. Viruses that are transmitted horizontally between individuals must first breach the barriers at their portal of entry before they can cause infection in their respective hosts. In the ongoing war and détente between virus and host, viruses have developed remarkably sophisticated mechanisms to avoid the various host protective responses. Vaccination is the most effective way of preventing viral diseases. There are some important differences between vaccination practices in humans and animals. The immunogenicity of inactivated vaccines, especially that of purified protein vaccines and synthetic peptides, usually needs to be enhanced; this may be achieved by mixing the antigen with an adjuvant, incorporation of the antigen in liposomes, or incorporation of the antigen in an immunostimulating complex.