The antibody responses and the protective efficacy rAPMV-3 or rNDV expressing HA against NDV strain GB Texas in immunized SPF chickens. Four-day-old SPF chickens were immunized with 106.5 TCID50/ml of rAPMV-3/HA or rNDV/HA through oculonasal route. Three weeks after immunization, chickens were infected with 100 CLD50 of NDV strain GB Texas. The infected birds were observed for 10 days post-challenge and the mortality rate clinical signs of NDV were recorded daily. (A) Three weeks post-immunization the sera were collected from all chickens and the level of antibodies induced against APMV-3 and NDV were detected by HI assay. (B) Serum titers are expressed as reciprocals Log2 dilution. Statistical significance among groups was: P < 0.05 (*) and p < 0.0001 (***).