Abstract
BACKGROUND: Infectious bronchitis (IB) is an important disease of poultry, and vaccination is the best method of preventing IB in the poultry industry worldwide. OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.