Unlike DNA viruses, which are known to encode virus-specific antiapoptosis genes, RSV -an RNA virus with a small (approximately 15.2 kb) viral genome -was shown to alter host cell expression of the apoptosis inhibitor IEX-1L. After demonstrating that IEX-1L mRNA was present at sevenfold higher concentrations in RSV-infected respiratory epithelial cells when compared with uninfected cells, we concluded that this cellular response protected against TNF-α-induced programmed cell death during viral infection. Further efforts to determine which of the 11 RSV proteins participate in the trans-activation of the IEX-1L gene (either directly or indirectly) are ongoing.