Immune responses and interactions following simultaneous application of live Newcastle disease, infectious bronchitis and avian metapneumovirus vaccines in specific-pathogen-free chicks

• Simultaneous administration of live NDV, IBV and aMPV vaccines was studied in SPF chicks.
• The level of NDV antibodies were above the protective titre and were similar in single, dual or triple-vaccinated chicks.
• The level of aMPV antibody titres were suppressed but clinical protection against the disease was not affected.
• The levels of IBV ELISA antibodies were similar in all the IBV-vaccinated groups and all chicks protected against M41.
• At 21 days post vaccination, the tracheal CD4+, CD8+ and IgA-bearing B-cells readings were similar in all vaccinated groups.

Interactions between live Newcastle disease virus (NDV), avian metapneumovirus (aMPV) and infectious bronchitis virus (IBV) vaccines following simultaneous vaccination of day old specific pathogen free (SPF) chicks were evaluated. The chicks were divided into eight groups: seven vaccinated against NDV, aMPV and IBV (single, dual or triple) and one unvaccinated as control. Haemagglutination inhibition (HI) NDV antibody titres were similar across all groups but were above protective titres. aMPV vaccine when given with other live vaccines suppressed levels of aMPV enzyme-linked immunosorbent assay (ELISA) antibodies. Cellular and local immunity induced by administration of NDV, aMPV or IBV vaccines (individually or together) showed significant increase in CD4+, CD8+ and IgA bearing B-cells in the trachea compared to the unvaccinated group. Differences between the vaccinated groups were insignificant. Simultaneous vaccination with live NDV, aMPV and IBV did not affect the protection conferred against aMPV or IBV.