Reactivation of Newcastle Disease Virus Neutralized by Antibody

In an effort to improve current technology for detection of Newcastle disease virus in convalescent birds, a procedure has been developed for efficient reactivation of virus that has been neutralized by antibody. The reactivation capabilities of fluorocarbon treatment, ultrasonic treatment, pH extremes, and proteolytic digestion were evaluated using the LaSota strain of virus. Reactivation was maximum after proteolytic digestion with either trypsin or papain, and reactivation effciency was up to 100%, depending on the enzyme used for digestion and the amount of antibody in the neutralization mixture. Reactivation at pH extremes was considerably less efficient than reactiviation by proteolytic digestion, and neither fluorocarbon nor ultrasonic treatments effectively recovered antibody-neutralized Newcastle disease virus.