Effect of Chicken AvBD11 on the Cytokines in the Erythrocytes of Chickens Infected with the Avian Influenza Virus of the Subtype H9N2

(1) The aim of this study was to elucidate the role of the <i>Gallus gallus</i> avian β-defensin 11 (AvBD11) in the immune response induced by the avian influenza virus H9N2. (2) AvBD11 was expressed using <i>E. coli</i>, and the effects of different concentrations of AvBD11 on cytokine expression in the ex vivo and in vivo erythrocytes of chickens infected with the avian influenza subtype H9N2 were detected by using fluorescence quantification. (3) The results showed that cytokine expression varied among the test groups compared to the control group in the in vitro assay at 2, 6, and 10 h. <i>Lipopolysaccharide induced TNF factor</i> (<i>LITAF</i>) and <i>Interferon-γ</i> (<i>IFN-γ</i>) were significantly increased in the AvBD11 group with the addition of the final concentration of 15 μg/mL at 6 h. At 10 h, <i>Interleukin-1β</i> (<i>IL-1β</i>) and <i>IFN-γ</i> were both more significantly increased in the 15 and 10 μg/mL groups than in the H9N2 group alone. In the in vivo test, <i>IFN-γ</i> and <i>Interleukin-10</i> (<i>IL-10</i>) were significantly increased in the high-dose group than in the H9N2 group at 3 d and 7 d. (4) In conclusion, the ability of AvBD11 to induce the expression of more cytokines by chicken erythrocytes in a short period of time suggests that it is not only an antimicrobial peptide but also a possible immunomodulator.