Seneca Valley virus (SVV, also known as Senecavirus A), an oncolytic virus, is a nonenveloped, positive-strand RNA virus and the sole member of the genus Senecavirus within the family Picornaviridae. The mechanisms of SVV entry into cells are currently almost unknown. In the present study, we found that SVV entry into HEK293T cells is acidic pH-dependent by using ammonium chloride (NH4Cl) and chloroquine, both of which could inhibit SVV infection. We confirmed that dynamin II is required for SVV entry by using dynasore, silencing the dynamin II protein, or expressing the dominant-negative (DN) K44A mutant of dynamin II. Then, we discovered that chlorpromazine (CPZ) treatment or knockdown of the clathrin heavy chain (CLTC) protein significantly inhibited SVV infection. In addition, overexpression of CLTC promoted SVV infection. Caveolin-1 and membrane cholesterol were also required for SVV endocytosis. Notably, utilizing genistein, EIPA or nocodazole, we observed that macropinocytosis and microtubules are not involved in SVV entry. Furthermore, overexpression of the Rab7 and Rab9 proteins but not the Rab5 or Rab11 proteins promoted SVV infection. The findings were further validated by the knockdown of four Rabs and Lamp1 proteins, indicating that after internalization, SVV is transported from late endosomes to the trans-Golgi network (TGN) or lysosomes, respectively, eventually releasing its RNA into the cytosol from the lysosomes. Our findings concretely revealed SVV endocytosis mechanisms in HEK293T cells and provided an insightful theoretical foundation for further research into SVV oncolytic mechanisms.
Keywords: Rab GTPases; Seneca Valley Virus; acidic pH; endocytic pathway; endolysosomal pathway.