HSP70 induced by Hantavirus infection interacts with viral nucleocapsid protein and its overexpression suppresses virus infection in Vero E6 cells.

Hantavirus (HTV) infection is known to induce innate cellular response, a more specified cellular response in the host cells. However, whether it stimulates synthesis of stress proteins, particularly associations of viral proteins, is entirely unknown. The primary focus of this research is using Vero E6 cells infected with Hantaan 76-118 (HTNV) as an in vitro infection model to examine the individual contribution of HTV infection to heat shock response. This study shows that HTNV infection rapidly induced HSP70 expression in Vero E6 cells, which underwent a nucleo-cytoplasmic shuttle that lasted for more than 3 d. The increased HSP70 was preceded by induction of HSP70 mRNA. The physical association of HSP70 with viral nucleocapsid protein (NP) in infected cells was demonstrated by co-localization and immunoprecipation. Vero E6 cells that constitutively overexpress HSP70 after stable transfection with HSP70 gene, when infected with HTNV, showed selectively reduced NP synthesis. These findings suggest HSP70 is actively involved in the control of the expression level of viral structural proteins and possibly involved in virus assembly by binding of NP to HSP70. Overexpression of HSP70 does not favor viral propagation.