The chicken TH1 response: potential therapeutic applications of ChIFN-γ.

•Emergence of increasingly virulent viruses requires new anti-viral strategies.•One approach may be the therapeutic in ovo administration of cytokines.•This review describes the role of TH-1 cytokines in immune responses to viruses.•We focuses on the use of interferon-γ to treat CAV infection in chickens.•In ovo administration of ChIFN-γ prevents depletion of T-cells during CAV infection.