Suppressive effect of Newcastle disease virus on the primary and secondary immune responses of hamsters.

The effect of Newcastle disease virus (NDV) on the formation of 19 S haemolytic plaque-forming cells (HPFC) in the secondary immune response and on the formation of 7 S HPFC in both primary and secondary immune responses of hamsters to sheep red blood cells (SRBC) was studied. The 19 S and the 7 S HPFC in the spleens of hamsters injected with SRBC were demonstrated by the direct and indirect Jerne's method, repectively. A single intraperitoneal injection of NDV 5 days prior to primary immunization markedly depressed the number of 7 S HPFC. NDV administered 5 days prior to the second injection of SRBC resulted in a significant decrease in the number of both 19 S and 7 S HPFC. It is asssumed that interferon induced by NDV is responsible for the suppressive effect of the virus on both the primary and secondary immune responses of hamsters to SRBC.