We designed siRNAs targeting ST6GAL1, in an attempt to inhibit pdmH1N1 and H3N2 virus infection in HEp-2, HBE, and A549 cells, which are representative of the upper, middle and lower respiratory tract epithelial cells, respectively, without inducing an interferon response. Treatment with siRNAs is not dependent upon a functional immune system. Therefore siRNA therapies could be as effective in

elderly or immunocompromised individuals as in immunocompetent individuals [23]. The siRNAs targeting ST6GAL1 that we used in this current study could be ideal in preventing influenza infection in patient groups with low immunity. find protocol Our results pertaining to virus binding indicate that ST6GAL1-specific siRNAs reduce the number of IAV virions that attach to epithelial cells, because of reduced expression of SAα 2,6Gal on the cell surface. Recent studies have suggested that

some siRNAs could have side effects [24] that adversely affect cell viability. We demonstrated that the effective dose (10 nM) of siRNAs, under the conditions tested, was not toxic to respiratory epithelial cells in vitro. However, we did notice that expression levels of receptors were substantially diminished as a result of siRNA targeting. Influenza viruses naturally infect epithelial cells in the upper respiratory tract and the lungs of humans. Thus, siRNAs can be administered by inhalation. This would result in much higher local siRNA concentrations than could be achieved by parenteral injection, without adversely affecting epithelial cells CT99021 manufacturer [23]. Studies focusing on these aspects are currently underway in our laboratories. In other studies, investigators found that human influenza viruses can still infect ST6GAL1 knock-out mice, achieving similar titers in the lung and trachea as compared with wild-type animals [25]. A

possible explanation for this is that there was greater efficiency of infection as a result of a deficient systemic influenza-specific humoral response in these ST6GAL1 knock-out mice [26]. There are two major types of SAα2,3Gal, which differ in their penultimate bond (Neu5Acα2-3Galβ1-3GalNAc or Neu5Acα2-3Galβ1-4GlcNAc) and these are synthesized by Selleckchem CHIR99021 different enzymes [27–29]. Some human influenza virus strains propagated in allantoic cavities are able to bind to both SAα2,6Gal and SAα2,3Gal [9, 25, 30]. When recombinant rat α2,3-sialyltransferase was used to reconstitute sialic acids, only one type of galactose was linked to other glycans through β-1,3 but not β-1,4 linkages [31–33]; however, it is possible that other strains maintain the ability to bind to Neu5Acα2-3Galβ1-4GlcNAc. Thus, SAα2,3Gal (Neu5Acα2-3Galβ1-4GlcNAc) present in these mice can compensate for the loss of SAα2,6Gal [34]. Monteerarat et al.