Based on all these critical functions of N in the virus life cycle, it is not surprising that siS knockdown of the S segment readily decreased virus replication. Another Atropine sulfate protein important for virus replication is the L protein. L mRNA is the least abundant during infection, so we anticipated that it could be more efficiently suppressed by siRNA, leading to a significant decrease of ANDV replication. To our surprise, siL had minimal effects on viral protein synthesis and virus Ipratropium Bromide release in VeroE6 cells. Similar to siL, siM only modestly reduced protein levels in Vero-E6 cells. This weak inhibition by siM was not the result of designing ineffective siRNAs, since siM completely suppressed Gc protein when Gc was expressed from an ANDV GPC plasmid. Surprisingly, co-transfection of siS and siM, or siS and siL, did not suppress viral protein expression and virus production any more than did siS alone. Overall, the results reported here for ANDV infection of a continuous cell lineare similar to previous findings that siRNAs targeting the L and M segments of other bunyaviruses are weaker inhibitors than those targeting the S segment. Vascular endothelial cells are the main target cells of ANDV infection in humans. To our surprise, the pattern of viral replication inhibition observed using the 3 siRNAs pools in primary human lung cells was different from that observed in Vero-E6 cells. While siM minimally affected ANDV growth in Vero-E6 cells, it very efficiently inhibited virus protein expression, and, more importantly, infectious virus releasein HMVEC-L. This reduction of virus replication was not due to the induction of IFN-b by the siM. The differing abilities of the siRNAs to inhibit ANDV replication in Vero-E6 cells compared with HMVEC-L are likely related to differences in virus replication dynamics and protein pools in these different cells. Unlike in Vero-E6 cells, ANDV titers in endothelial cells are relatively low despite considerable accumulation of intracellular viral proteins. In addition, unlike in Vero-E6 cells, viral glycoproteins are detected mainly in the lysosome rather than at the cell surface in endothelial cells. It is plausible that in endothelial cells, viral glycoproteins are a limiting factor for virus production, and reducing the glycoprotein levels with siM has greater impact on virus replication and release. Such significantly different siRNA inhibitory profiles between a continuous cell line that supports ANDV growth and primary lung endothelial cellsstress the importance of testing siRNAs in a variety of infection settings. While the delivery of siRNA is still a challenge to their actual clinical use, the ability of siRNAs to efficiently block ANDV replication up to 24 h post-infection is very encouraging. Although suggesting the use of siRNA as a treatment for HPS based on the in vitro results presented here is quite premature, our study can be considered as proof of principle that siRNAs directed against ANDV genome can effectively lower virus replication and infectious virus release. As ANDV viremia levels correlate with HPS severity, and ANDV RNA peaks at the time of pulmonary edema, siRNA suppression has potential as a therapeutic HPS treatment. The cytotoxic effects of virus core proteins, chronic inflammation, and recurrent/ prolonged immune responses have all been suggested as cofactors responsible for liver damage. A central hypothesis for disease pathogenesis is associated with excess iron load.