An in vivo and in vitro study of infectious laryngotracheitis virus in chicken leukocytes.

Infectious laryngotracheitis (ILT) virus, an avian herpesvirus, caused an infection in chickens that was followed by leukopenia due to a decrease in the number of circulating lymphocytes. Viral synthesis in leukocytes in cell cultures was evident by specific and progressive viral antigens in the nuclei of infected leukocytes as shown by fluorescent-antibody technique and by the formation of multinucleated giant cells, typical of the herpesviruses. In addition, viral multiplication was observed in the leukocyte cell cultures as shown by viral assay. It is suggested that the leukocytes in chicken are participating in the production of ILT virus by serving as host cells for viral multiplication. This is followed by a cytopathogenic effect, with the production of multinucleated giant cells. That may result in the destruction of cells, causing a leukopenia.