Human metapneumovirus small hydrophobic protein inhibits NF-κB transcriptional activity

Human metapneumovirus, a leading cause of respiratory tract infections in infants, encodes a small hydrophobic (SH) protein of unknown function. In this study, we showed that infection of airway epithelial cells or mice with recombinant human metapneumovirus lacking SH expression (rhMPV-Delta SH) enhanced secretion of proinflammatory mediators, including interleukin 6 (IL-6) and IL-8, encoded by two NF-kappa B-dependent genes, compared to infection with wild-type rhMPV. RhMPV-Delta SH infection resulted in enhanced NF-kappa B-dependent gene transcription and in increased levels of phosphorylated and acetylated NF-kB without affecting its nuclear translocation, identifying a possible novel mechanism by which paramyxovirus SH proteins modulate NF-kB activation.