Cytokine and acute-phase proteins response following vaccination against infectious bronchitis in broilers

Infectious bronchitis (IB) is an important disease of poultry, and vaccination is the best method of preventing IB in the poultry industry worldwide.

This study was designed to evaluate cytokine and acute-phase protein (APP) responses and their correlations with antibody titres following vaccination regimes against IB in the broiler.

Broilers were vaccinated with H120 and 1/96 vaccine strains, and MIX (H120 + 1/96) vaccine strains on Days 0 and 14. Heterophils/lymphocyte (H/L) ratio, APPs including chicken serum amyloid A (SAA), chicken pentraxin 3 (chPTX3), chicken interleukin 1β (IL-1β), chicken interleukin 6 (IL-6) levels and antibody titres were measured.

An increase in the H/L ratio, SAA, chPTX3, IL-1β and IL-6 levels in vaccinated groups was observed 1 day after the first (highest rates) and second (lower levels) vaccination up to 3 days in three different patterns and then started to decrease. The results showed an immediate, short-lived response and moderate increases in all criteria. Changing patterns of APPs were different but in similar pattern after the first and second immunization in vaccinated groups. A positive correlation between all criteria values on Days 1 and 15 with antibody titres on Day 28 may indicate agonistic cross-regulation.

Different types of IB vaccines could induce different patterns of APPs responses, which can be used to evaluate immune response outcomes in vaccine design, development and administration. The IL-6 with the highest increase can be a sensitive parameter and chPTX3 with the high increase could be an important criterion.