| 摘要 |
<p>Marek's disease virus which causes a serious infection in poultry may be attenuated by serial passage in tissue culture. Passaging causes the loss of the A antigen after a certain number of passes while important protective antigens are retained. The virus may be attenuated in avian cells particularly those of the chick and duck, kidney cells and embryo fibroblasts being especially preferred. Usually about 20 to 40 passes are required. The live protective virus so obtained is cultivated further into a vaccine for parenteral administration.</p> |
