To determine the role of human metapneumovirus (HMPV) in respiratory tract infections (RTIs) of lung transplant recipients, 60 patients were prospectively enrolled in this study spanning from September 2005 to November 2007. Community-acquired respiratory viruses (CARVs) were identified by polymerase chain reaction and tissue culture in respiratory secretions. Of 112 RTIs, 51 were associated with > or =1 CARV, including 7 HMPV, 13 respiratory syncytial virus (RSV), 19 parainfluenza virus 1, 2, or 3 (PIV), 16 influenza A or B (FLU), and 3 human rhinoviruses (HRV). Sixteen CARV-RTIs had multiple pathogens. While the standard protocol was to admit all paramyxoviral RTIs for inhaled ribavirin, 16% CARV-RTIs required hospitalization because of the severity of their respiratory compromise, including 25% of HPMV-single-agent RTI, 38% of RSV single-agent RTI, 10% of PIV-single-agent RTI, and 19% of multiple-agent RTIs. None of those with non-CARV RTIs required hospitalization. The incidence of clinically diagnosed acute graft rejection in the first 2 months after an RTI varied from 0 for single-agent HRV to 88% for single-agent RSV (25% for single-agent HMPV). A new diagnosis of chronic graft rejection in the first year after an RTI was made in approximately 25% of the RTIs and did not significantly vary with the etiologic agent. No deaths occurred during this study. In conclusion, HMPV was associated with 6% of the RTIs in lung transplant recipients and its morbidity was similar to the average moribidity of CARVs.

Calcific aortic valve disease is a chronic inflammatory process, and aortic valve interstitial cells (AVICs) from diseased aortic valves express greater levels of osteogenic factors in response to proinflammatory stimulation. Here, we report that lower cellular levels of IL-37 in AVICs of diseased human aortic valves likely account for augmented expression of bone morphogenetic protein-2 (BMP-2) and alkaline phosphatase (ALP) following stimulation of Toll-like receptor (TLR) 2 or 4. Treatment of diseased AVICs with recombinant human IL-37 suppresses the levels of BMP-2 and ALP as well as calcium deposit formation. In mice, aortic valve thickening is observed when exposed to a TLR4 agonist or a high fat diet for a prolonged period; however, mice expressing human IL-37 exhibit significantly lower BMP-2 levels and less aortic valve thickening when subjected to the same regimens. A high fat diet in mice results in oxidized low-density lipoprotein (oxLDL) deposition in aortic valve leaflets. Moreover, the osteogenic responses in human AVICs induced by oxLDL are suppressed by recombinant IL-37. Mechanistically, reduced osteogenic responses to oxLDL in human AVICs are associated with the ability of IL-37 to inhibit NF-κB and ERK1/2. These findings suggest that augmented expression of osteogenic factors in AVICs of diseased aortic valves from humans is at least partly due to a relative IL-37 deficiency. Because recombinant IL-37 suppresses the osteogenic responses in human AVICs and alleviates aortic valve lesions in mice exposed to high fat diet or a proinflammatory stimulus, IL-37 has therapeutic potential for progressive calcific aortic valve disease.Toll-like receptors | inflammation | oxidized low-density lipoprotein | calcification | signal transduction