Cholesterol 25-Hydroxylase inhibits bovine parainfluenza virus type 3 replication through enzyme activity-dependent and -independent ways.

Bovine parainfluenza virus type 3 (BPIV3) is one of the most important pathogens associated with bovine respiratory diseases in both young and adult cattle widespreadly around the world. The host factors which participate in the infection of BPIV3 are poorly understood. Here, we found the bovine protein Cholesterol 25-hydroxylase (CH25 H) plays an important role in the infection of BPIV3. CH25H is a multi-transmembrane and endoplasmic reticulum-related enzyme that catalyzes oxidation reaction of cholesterol to production of 25-hydroxycholesterol (25HC) and significantly inhibits the replication of several viruses. In this study, we found that CH25H is an interferon-stimulated gene (ISG), which taken part in the antiviral innate immunity. In addition, the overexpression of CH25H could inhibit the replication of BPIV3, and 25HC significantly inhibited BPIV3 infection by preventing the synthesis of both virus antigenomic RNA (cRNA) and genomic RNA (gRNA) in MDBK cells. Interestingly, CH25H-M, a mutant lacking hydroxylase activity, still had an antiviral effect against BPIV3. Taken together, our findings highlight the antiviral function of CH25H during BPIV3 infection, and suggest that CH25H inhibits viral infection through both enzyme activity-dependent and -independent ways.

Deficiency of melanoma differentiation-associated protein 5 results in exacerbated chronic postviral lung inflammation.

RATIONALE: Respiratory viral infections can result in the establishment of chronic lung diseases. Understanding the early innate immune mechanisms that participate in the development of chronic postviral lung disease may reveal new targets for therapeutic intervention. The intracellular viral sensor protein melanoma differentiation-associated protein 5 (MDA5) sustains the acute immune response to Sendai virus, a mouse pathogen that causes chronic lung inflammation, but its role in the development of postviral chronic lung disease is unknown. OBJECTIVES: To establish the role of MDA5 in the development of chronic lung disease. METHODS: MDA5-deficient or control mice were infected with Sendai virus. The acute inflammatory response was evaluated by profiling chemokine and cytokine expression and by characterizing the composition of the cellular infiltrate. The impact of MDA5 on chronic lung pathology and function was evaluated through histological studies, degree of oxygen saturation, and responsiveness to carbachol. MEASUREMENTS AND MAIN RESULTS: MDA5 deficiency resulted in normal virus replication and in a distinct profile of chemokines and cytokines that associated with acute lung neutropenia and enhanced accumulation of alternatively activated macrophages. Diminished expression of neutrophil-recruiting chemokines was also observed in cells infected with influenza virus, suggesting a key role of MDA5 in driving the early accumulation of neutrophils at the infection site. The biased acute inflammatory response of MDA5-deficient mice led to an enhanced chronic lung inflammation, epithelial cell hyperplasia, airway hyperreactivity, and diminished blood oxygen saturation. CONCLUSIONS: MDA5 modulates the development of chronic lung inflammation by regulating the early inflammatory response in the lung.

Dipeptidyl peptidase I-dependent neutrophil recruitment modulates the inflammatory response to Sendai virus infection.

The role of innate immunity in the pathogenesis of asthma is unclear. Although increased presence of neutrophils is associated with persistent asthma and asthma exacerbations, how neutrophils participate in the pathogenesis of asthma remains controversial. In this study, we show that the absence of dipeptidyl peptidase I (DPPI), a lysosomal cysteine protease found in neutrophils, dampens the acute inflammatory response and the subsequent mucous cell metaplasia that accompanies the asthma phenotype induced by Sendai virus infection. This attenuated phenotype is accompanied by a significant decrease in the accumulation of neutrophils and the local production of CXCL2, TNF, IL-1beta, and IL-6 in the lung of infected DPPI-/- mice. Adoptive transfer of DPPI-sufficient neutrophils into DPPI-/- mice restored the levels of CXCL2 and enhanced cytokine production on day 4 postinfection and subsequent mucous cell metaplasia on day 21 postinfection. These results indicate that DPPI and neutrophils play a critical role in Sendai virus-induced asthma phenotype as a result of a DPPI-dependent neutrophil recruitment and cytokine response.

2-Deoxy-2,3-didehydro-N-acetylneuraminic acid analogues structurally modified at the C-4 position: synthesis and biological evaluation as inhibitors of human parainfluenza virus type 1.

To explore the influence of binding to human parainfluenza virus type 1 (hPIV-1), a series of 4-O-substituted Neu5Ac2en derivatives 6a-e was synthesized and tested for their ability to inhibit hPIV-1 sialidase. Among compounds 6a-e, the 4-O-ethyl-Neu5Ac2en derivative 6b showed the most potent inhibitory activity (IC50 6.3 microM) against hPIV-1 sialidase.

Molecular basis of proteolytic activation of Sendai virus infection and the defensive compounds for infection.

It has been proposed that the pathogenicity of Sendai virus is primarily determined by a host cellular protease(s) that activates viral infectivity by proteolytic cleavage of envelope fusion glycoproteins. We isolated a trypsin-like serine protease, tryptase Clara, localized in and secreted from Clara cells of the bronchial epithelium of rats. The enzyme specifically cleaved the precursor of fusion glycoprotein F0 of Sendai virus at residue Arg116 in the consensus cleavage motif, Gln(Glu)-X-Arg, resulting in the presentation of the membrane fusion domain in the amino-terminus of the F1 subunit. Administration of an antibody against tryptase Clara in the airway significantly inhibited the activation of progeny virus and multiple cycles of viral replication, thus reducing the mortality rate. These findings indicate that tryptase Clara in the airway is a primary determinant of Sendai virus infection and that proteolytic activation occurs extracellularly. We identified two cellular inhibitory compounds against tryptase Clara in bronchial lavage. One was a mucus protease inhibitor, a major serine protease inhibitor of granulocyte elastase in the lining fluids of the human respiratory tract, and the other was a pulmonary surfactant which may adsorb the enzyme, resulting in its inactivation. These compounds inhibited virus activation by tryptase Clara in vitro and in vivo, but did not themselves affect the hemagglutination and the infectivity of the virus. The functional domain of the mucus protease inhibitor against the enzyme, which is organized in two homologous N- and C-terminal domains, is located in the C-terminal. Administration of these compounds in the airway may be useful for preventing infection with Sendai virus.

Respiratory syncytial virus infection in lower respiratory tract and asthma attack in hospitalized children in North Hokkaido, Japan.

Respiratory syncytial virus (RSV) infection is severe and life-threatening in some infants. To investigate the epidemiology of RSV infection in hospitalized children in North Hokkaido, Japan, we tried to detect RSV antigen in nasopharyngeal aspirates (NPA) from those children with lower respiratory tract infection (LRTI) and asthma attack. From April 1991 to March 1992, 317 patients were hospitalized in our pediatric ward for the treatment of LRTI and asthma attack. The presence of RSV antigen in NPA taken from 283 patients (89.3%) were examined by enzyme immunoassay. RSV antigen was detected in 88 patients (31.1%). RSV LRTI were noted throughout the year, and the epidemic peak was observed in November and December. There was no significant correlation between the RSV antigen positive rate and mean temperature. RSV played an important role in LTRI in children in North Hokkaido, Japan. RSV LRTI in North Hokkaido was not rare in summer, indicating that RSV was transmitted commonly among children throughout the year.