Abstract
Although infectious bronchitis virus (IBV) is the first coronavirus identified, little is known about which membrane protein of host cells could interact with IBV spike protein and facilitate the infection by the virus. In this study, by using a monoclonal antibody to the S1 protein of IBV M41 strain, we found that heat shock protein member 8 (HSPA8) could interact with spike protein of IBV. HSPA8 was found to be present on the cell membrane and chicken tissues, with highest expression level in the kidney. Results of co-IP and GST-pull-down assays indicated that the receptor binding domain (RBD) of IBV M41 could interact with HSPA8. The results of binding blocking assay and infection inhibition assay showed that recombinant protein HSPA8 and antibody to HSPA8 could inhibit IBV M41 infection of chicken embryonic kidney (CEK) cells. Further, we found that HSPA8 interacted with the N-terminal 19–272 amino acids of S1 of IBV Beaudette, H120 and QX strains and HSPA8 from human and pig also interacted with IBV M41-RBD. Finally the results of binding blocking assay and infection inhibition assay showed that recombinant HSPA8 protein and antibody to HSPA8 could inhibit IBV Beaudette strain infection of Vero cells that were treated with heparanase to remove heparan sulfate from the cell surface. Taken together, our results indicate that HSPA8 is a novel host factor involved in IBV infection.
Highlights
Infectious bronchitis virus (IBV) is a member of genus gamma-coronavirus in the family Coronaviridae, causing serious economic losses to the poultry industry (Cavanagh, 2007)
We performed immunoprecipitation assay with membrane proteins from infectious bronchitis virus (IBV) M41 infected chicken embryonic kidney (CEK) cells and found that HSPA8 was involved in the interaction of host cell membrane and IBV spike protein (Figure 1)
These results suggest that HSPA8 might be involved in tissue tropism of IBV infection in chicken, considering that IBV infection usually causes respiratory distress and kidney damage
Summary
Infectious bronchitis virus (IBV) is a member of genus gamma-coronavirus in the family Coronaviridae, causing serious economic losses to the poultry industry (Cavanagh, 2007). IBV has many genotypes and serotypes circulating in poultry farms leading to continuous outbreaks of infectious bronchitis (IB) disease (Bijlenga et al, 2004). IBV is an enveloped virus with a single stranded unsegmented positive sense RNA genome of about 27 kb size. The IBV virion is made up of spike protein (S), membrane protein (M), nucleoprotein (N), envelope protein (E), and genomic RNA (Lai and Cavanagh, 1997). Spike protein determines the IBV tropism and can be cleaved into the two subunits: S1 and S2 by host furin protein (Cavanagh et al, 1992; Casais et al, 2003). The S1 subunit is responsible for binding to the cell surface receptor, while S2 is responsible for fusion of viral envelope and cellular membrane (Luo and Weiss, 1998; Belouzard et al, 2012)
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