NLRC5 Induction During Respiratory Syncytial Virus Infection Of Airway Epithelial Cells

Respiratory syncytial virus (RS V) is the leading cause of acute respiratory tract viral infection in infants, causing bronchiolitis and pneumonia. RSV infection is widespread among children. It was estimated that 60% of infants are infected during their first RSV season and all children by the age of 2-3 years old will have been infected with the virus. RSV infection is recognized as the "most common cause of bronchiolitis and pneumonia in children under 1 year of age in the United States" by the CDC of USA. And RSV infection in early life is also a risk factor for childhood asthma.It is known that RSV infection leads to increased expression of class I MHC molecules in epithelial cells, the primary target of RSV infection. NLRC5, a NOD-like, CARD domain-containing intracellular protein was recently identified as a transcriptional regulator of MHC I expression. To further study the function of NLRC5, which may related for RSV disease, we attempted to generate an antibody for the detection of endogenous NLRC5 since several commercial antibodies failed to cleanly detect NLRC5 expression. To this end, we used a recombinant protein corresponding to the C-terminal 258 aa residues of human NLRC5 as immunogen and got the monoclonal antibody and antiserum against human NLRC5.We found that these antibodies could specifically recognized the overexpressed NLRC5 and endogenous NLRC5 induced by IFN-y. We show here that RSV infection upregulated the level of NLRC5. And NLRC5 is required for the expression of MHC I molecules during RSV infection of A549 human airway epithelial cells. Inhibition of NLRC5 expression by siRNA reduced MHCI expression during RSV infection, while overexpression of NLRC5 resulted in increased expression of MHC I molecules. It is well recognized that airway epithelial cells possess innate immune function that has a critical role in control of infection as well as activation of immune cells. Increased expression of MHC I molecules of infected epithelial cells may lead to recruitment of cytotoxic T lymphocytes for viral clearance of infected cells and possible immunopathological damage of surrounding cells with MHC I upregulation. This study therefore understates the importance of T cell-mediated immunity in RSV disease.