Immunology of avian influenza virus: a review

Avian influenza virus can cause serious disease in a wide variety of birds and mammals, but its natural host range is in wild ducks, gulls, and shoreb irds. Infections in poultry can be inapparent or cause respiratory disease, decreases in production, or a rapidly fatal systemic disease known as high ly pathogenic avian influenza (HPAI). For the protection of poultry, neutra lizing antibody to the hemagglutinin and neuraminidase proteins provide the primary protection against disease. A variety of vaccines elicit neutraliz ing antibody, including killed whole virus vaccines and fowl-pox recombinan t vaccines. Antigenic drift of influenza viruses appears to be less importa nt in causing vaccine failures in poultry as compared to humans. The cytoto xic T lymphocyte response can reduce viral shedding in mildly pathogenic av ian influenza viruses, but provides questionable protection against HPAI. I nfluenza viruses can directly affect the immune response of infected birds, and the role of the Mr gene, interferons, and other cytokines in protectio n from disease remains unknown. Published by Elsevier Science Ltd.