A STUDY ON THE LONG-TERM IMMUNITY INDUCED BY LA-SOTA-STRAIN OF NEWCASTLE-DISEASE-VIRUS GROWN IN A BS BEK CELL-LINE OF BOVINE EMBRYO KIDNEY ORIGIN/

Twenty-day-old susceptible chickens were divided into three groups; tw o were vaccinated with inactivated, water in oil emulsified La Sota st rain of Newcastle disease virus (NDV) obtained from a bovine embryo ki dney (BS/BEK) cell line and from chicken embryos, respectively. The th ird unvaccinated group represented the control. At 30-day intervals su bgroups were exposed to the Herts 33 virulent NDV strain. Serological and clinical findings showed no appreciable difference in the immunoge nicity of the antigen from either culture systems and no significant d ifferences could be observed in its ability to protect against ND chal lenge.