Graphical Abstract.

In vivo experiment, H1N1 virus infection caused recruitment and M1 polarization of macrophages in the lung, accompanied by the increasement of LC3 and CD63 expression, as autophagy and exosome markers. In vitro experiment, H1N1 virus also promoted the formation of autophagosomes and exosomes in macrophages and epithelial cells. Based on the assumption that autophagosomes could fuse with multivesicular bodies (MVBs) to formulate amphisomes, to induce colocalization of LC3 and CD63 in virus-infected cells. Besides, secreted exosomes were found to induce M1 polarization and recruitment of adjacent macrophages. Moreover, LY294002 and GW4869 inhibited recruitment of macrophages via inhibiting formation/maturation of autophagosomes and exosomes in virus-infected cells.