Antigenically Modified Red Cells in Chickens Infected with Newcastle Disease

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Abstract
Antigenically modified erythrocytes were detected by the use of antiserum to Newcastle disease virus (NDV) modified erythrocytes. Antisera were prepared by immunization of rabbits with chicken red cells previously treated in vitro with NDV. Specific NDV treated cell agglutinin was obtained by proper agglutinin adsorption with normal and influenza virus treated red cells. Groups of 4- to 6-week-old chickens were infected by various routes and blood samples were collected at intervals for testing. Antigenically modified red cells were detected as early as 4 hours after intravenous inoculation of the virus and such cells were demonstrable for at leasty, 2 weeks in the surviving animals. The initial symptoms were evident as early as 48 hours after intravenous inoculation and death occurred usually in 72 to 96 hours in fatal infections. Comparable results were obtained by other routes of inoculation. Simultaneous studies indicated that the presence of modified cells was independent of the persistence of the viremic stage of infection. Agglutinins for modified cells were present in all animals infected by the different routes, although variations in titers were noted. Maximum titers were obtained between the 5th and 6th days of infection and agglutinins were still present as long as 37 days after the initial infection. Hemagglutinin inhibiting antibody was present on the 5th day after infection and reached a maximum in approximately 3 weeks, after which it gradually decreased in titer but was still present at the end of the test period. Modified cell antibody was shown to be distinct from the virus inhibiting antibody and produced at a rate different from antibody to the virus.