Muscovy duck reovirus enters susceptible cells via a caveolae-mediated endocytosis-like pathway

Muscovy duck reovirus (MDRV) causes immunosuppression and results in high mortality among Muscovy ducklings. Cell entry is the first step of virus infection and represents a potential therapeutic target. However, very little is known about the mechanism by which MDRV penetrates the cells. The aim of this study was to explore the mechanism of MDRV cell entry and subsequent infection. DF-1 and Vero cells were pretreated with the inhibitors chlorpromazine (CPZ), cytochalasin D, methyl-beta-cyclodextrin (M-beta-CD), genistein, dynasore, nocodazole, or NH4Cl, and then infected with MDRV. The copy number of the MDRV p10.8 gene and the expression of viral sigma A protein were determined by RT-PCR and western blot, respectively. Both sigma A expression and p10.8 gene copy number were decreased by treatment with M-beta-CD, genistein, dynasore, nocodazole, and NH4Cl. In contrast, no effects on virus infection were detected when inhibitors of clathrin-mediated endocytosis or macropinocytosis were used. In addition, the colocalization between MDRV sigma A protein and caveolin-1 was evaluated by double-label immunofluorescence. Collectively, our data revealed that MDRV can enter susceptible cells through caveolin-dependent endocytosis involving dynamin and microtubules. Moreover, the acidic environment of the endosomes was found to be critical for efficient infection. Our findings provide new insights into the infection process of MDRV.