siRNA against the G gene of human metapneumovirus

We designed and validated two siRNA molecules against the G gene using A549 cells and demonstrated consistent 88-92% knock-down for one siRNA molecule, which was used in subsequent experiments. Significant reduction of G mRNA in A549 cells infected with hMPV did not result in a reduction in viral growth, nor did it significantly increase the production of type I interferon (α/β) in response to infection. However, there was a moderate increase in IFN-β mRNA expression in response to infection in siG-transfected cells compared to untransfected and si-mismatch-transfected cells. Expression of G by recombinant adenovirus did not affect type I IFN expression.G has been previously described as a type I interferon antagonist, although our findings suggest it may not be a significant antagonist.Human metapneumovirus (hMPV) is a member of the Pneumoviridae subfamily of the Paramyxoviridae[1]. hMPV infects half of all infants under the age of 1？year and almost all children have been infected by the age of 10？years [2,3]. hMPV causes acute respiratory disease in children worldwide [4-6]. Currently, there are no vaccines or targeted therapies for hMPV infection. RNA interference (RNAi) is a mechanism of post-transcriptional gene silencing found in almost all eukaryotes and is triggered by endogenous small non-coding microRNAs (miRNAs) or small interfering RNAs (siRNAs) [7]. The recently development of synthetic sequence-specific siRNAs has allowed a variety of host and pathogen genes to be targeted for mRNA cleavage, effectively silencing or significantly reducing gene expression [7]. Reports for RSV and hMPV suggest that RNAi can inhibit viral mRNA expression, and is a potentially effective therapy for respiratory infections [8-13].siRNA molecules targeting the nucleoprotein (N) and phosphoprotein (P) mRNA of hMPV have been found effective at inhibiting the hMPV genome [13]. Here we have designed and validated a siRNA molecule against the G gene, which encodes a principal atta