Effect of Passively Transferred Immunoglobulins on Marek's Disease

Early events in the pathogenesis of Marek's disease (MD) were studied in chicks with no passive MD antibodies, with congenitally derived parental antibodies, and with injected antibodies (immunoglobulins). MD responses in chicks inoculated with immunoglobulins at hatching were virtually identical to responses in chicks with parental antibodies. In vivo neutralization indices of 1.0 log1l lesionproducing-50% dose (LPD50) were obtained for cell-associated MD virus inocula in chicks with passive antibodies directed against either MD virus or an antigenically related herpesvirus of turkeys (HVT). Parallel studies with cell-free MD virus gave neutralization indices of 2.1 log1o LPD50. Latent periods (50% response times) for both lympholiferative lesions and for degenerative skin and bursal lesions were approximately 50-70% greater in antibody-free chicks. Also noted in MD-infected chicks with passive antibody were absence of bursal atrophy, delayed latent periods for precipitin antigen and cell-free virus production in the skin, and lower frequency of virus isolation from buffy coat cells. These data suggest possible mechanisms for the inhibitory role of passive antibody on the in vivo dissemination and primary oncogenic functions of MD virus.