Humoral And Cellular Immune Responses Following Simultaneous Application Of Live Newcastle Disease, Avian Metapneumovirus And Infectious Bronchitis Vaccines

A. Faez, A. Forrester, M. Baylis, S. Lemiere  and K. Ganapathy

 

We report the results of protection studies and humoral and cellular immune responses in specific-pathogen-free (SPF) chicks that received live Newcsatle disease virus (NDV), avian metapneumovirus (aMPV) or infectious bronchitis virus (IBV) vaccines in single, dual or triple combinations. Following the vaccination of day-old chicks, blood and trachea were collected at 21 days post vaccination (dpv). The blood was used for the detection of serum antibodies against NDV, aMPV and IBV. The trachea was examined for CD4+, CD8+ and lgA-bearing B-cells by immunohistochemistry (IHC). Between the NDV-vaccinated groups, there were no significant differences in the mean titres of the NDV haemagglutination inhibition (Hl) titres and they remained above the protective titre. For antibodies against aMPV, the mean titres were suppressed when aMPV vaccine was given with other live vaccines but the aMPV-vaccinated groups were fully protected when challenged with virulent aMPV. For IBV,  the mean levels of enzyme-linked immunosorbent assay (ELISA) antibodies were similar in the IBV-vaccinated groups and ali IBV-vaccinated groups were almost 100% protected against M41 challenge. Between the vaccinated groups, there were no significant differences in the mean numbers of CD4+, CD8+ and lgA-bearing B-cells, reflecting similar levels of tracheal cellular and lgA responses irrespective of single, dual or triple vaccine applications. Despite the aMPV humoral antibody suppression, the efficacy of none of the live vaccines was compromised when they were given simultaneously to young SPF chicks.

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