Antihemagglutinating and Neutralizing Factors Against Newcastle Disease Virus (NDV) Occurring in Sera of Patients Convalescent from Mumps

Abstract
When sera of 22 mumps patients were tested against Newcastle disease virus (NDV), 13 gave significant responses by neutralization test and 11 by inhibition of hemagglutination. Of 23 control patients, with undiagnosed diseases of the central nervous system, 3 gave responses by neutralization test but none by anti-hemagglutination test against NDV. The neutralizing capacity of mumps sera against NDV was impaired or destroyed by heat, whereas the antihemagglutinating factor was relatively heat-stable. Hypotheses are advanced regarding the nature and significance of serologic reactions obtained between mumps sera and NDV. It is suggested that the serologic diagnosis of Newcastle disease in man be made with caution in the absence of virus isolation.