Abstract L22 is a 14.8-kDa protein constituent of the large ribosomal subunit, which is not conserved in prokaryotes and does not share RNA binding motifs with any other known protein such as PKR and RIG-I/Mda5. L22 associates with human telomerase, the small viral RNA HVP-1 in Herpesvirus papio–infected baboon cells, the 39X region within the 39-untranslated region (UTR) of the human Hepatitis C virus (HCV) genomic RNA, poly (ADPribose) polymerase in Drosophila melanogaster, and the Herpes simplex–infected cell proteins (ICP) 4 and ICP 22 in human cells. In uninfected human B cells, L22 is located in the nucleoli and cytoplasm, whereas following EBV infection, L22 is found in the nucleoplasm. In transformed B cells, EBER 1 is quantitatively bound by L22 (>95%), whereas only 30%–50% of the L22 protein associates with this RNA and inhibits regulation of cellular activities by the Epstein-Barr virus small RNA EBER-1. However, the function of L22 both in the ribosome and in these several RNP complexes remains unknown. Here we investigated whether L22 has an effect on antiviral response; the replication of VSV and activation of eIF2. First, the replication of VSV was evaluated after transfection of L22 in A549 cells. When the cells were infected with VSV (MOI =1), a significant enhancement of replication of virus was detected. The phosphorylation of the α subunit of eIF2 complex was inhibited by transfection of L22, which is usually followed by VSV infection through PKR activation. Our data also showed L22 inhibited phosphorylation of IRF3 and STAT1. Therefore, we suggest that ribosomal protein L22 negatively regulates type I IFN response in VSV infection model, which facilitates the replication of VSV. This study was supported by Brain Korea 21 Project for Medical Science, Yonsei University.