Exosomes derived from avian influenza virus-infected chickens modulate host immune responses.

Exosomes are emerging as key mediators of host-pathogen interactions, particularly as carriers of viral components during infection. This study aims to examine the immunomodulatory effects of serum-derived exosomes from Brown Leghorn chickens infected with low pathogenic avian influenza virus (LPAIV) or highly pathogenic avian influenza virus (HPAIV). These exosomes (CTRL-EXO [noninfected], LPAIV-EXO, and HPAIV-EXO) were intramuscularly injected into naïve chickens, after which tissues and serum were collected. Cytokine gene expression in immune-related tissues (lung, spleen, and trachea) was quantified through reverse transcription-quantitative polymerase chain reaction to evaluate the immune response. Unlike the lung and trachea, the spleen showed the strongest immune response following exosome injection, associated with elevated antiviral cytokines and interferons in the AIV-exosome group. In parallel, these exosomes were applied to chicken macrophage HD11 cells to determine cellular uptake and cytokine expression using reverse transcription-quantitative polymerase chain reaction. Furthermore, immunocytochemistry was performed to detect exosome-delivered viral nucleoprotein and nonstructural protein 1 proteins in HD11 cells. LPAIV-EXO induced the strongest immune activation, evidenced by increased cytokine expression and immunochemical detection of viral proteins. Collectively, these findings indicate that AIV-derived exosomes modulate host immune responses in vivo and in vitro, underscoring their potential in immune regulation and vaccine development.