The induction of neutralizing antibodies and protective efficacy of rAPMV-3 or rNDV expressing HA protein against H5N1 HPAIV in SPF chickens (experiment 2). Day old SPF chicks were immunized with 106 PFU/bird of rNDV/HA or rAPMV-3/HA through oculonasal route. Three weeks after immunization, chickens were infected with 106 EID50 of H5N1 HPAIV. The infected birds were observed for 10 days post-challenge and the mortality rate for each group were recorded daily. (A) At day four post-challenge oropharyngeal swabs were taken from survived birds and each swab sample were inoculated in five 10-day-old embryonated eggs for re-isolation of challenge virus. The infected eggs were detected by HA assay. (B) Three weeks post-immunization the sera were collected from all chickens and the level of antibodies induced against the H5N2 LPAIV were detected by micro-virus neutralization assay (C) and HI assay. (D) The humoral antibody responses against NDV and APMV-3 also were detected by HI assay. (E) Serum titers are expressed as reciprocals Log2 dilution. Statistical significance among groups was: p < 0.01(**) and p < 0.0001 (***).