Differential expression of nuclear factor-kappaB mediates increased pulmonary expression of tumor necrosis factor-alpha and virus-induced asthma

Small Animal Models of Respiratory Viral Infection Related to Asthma

Respiratory viral infections are strongly associated with asthma exacerbations. Rhinovirus is most frequently-detected pathogen; followed by respiratory syncytial virus; metapneumovirus; parainfluenza virus; enterovirus and coronavirus. In addition; viral infection; in combination with genetics; allergen exposure; microbiome and other pathogens; may play a role in asthma development. In particular; asthma development has been linked to wheezing-associated respiratory viral infections in early life. To understand underlying mechanisms of viral-induced airways disease; investigators have studied respiratory viral infections in small animals. This report reviews animal models of human respiratory viral infection employing mice; rats; guinea pigs; hamsters and ferrets. Investigators have modeled asthma exacerbations by infecting mice with allergic airways disease. Asthma development has been modeled by administration of virus to immature animals. Small animal models of respiratory viral infection will identify cell and molecular targets for the treatment of asthma.

Local cytokine response upon respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the leading cause of childhood hospitalization and respiratory distress and has been recognized for several decades as a major health and economic burden worldwide. This virus has developed several virulence mechanisms to impair the establishment of a protective immune response to re-infection. Accordingly, inefficient immunological memory is usually generated after exposure to this pathogen. Furthermore, it has been shown that RSV can actively promote the induction of an inadequate cellular immune response at the site of infection that causes exacerbated inflammation in the respiratory tract. Such an inflammatory response is both inefficient for clearing the virus and can be responsible for detrimental symptoms, such as asthma and wheezing. Recent data suggest that RSV possesses molecular mechanisms to induce the secretion of pro-inflammatory cytokines that modulate the immune response and impair viral clearance by reducing IFN-γ production. Here, we discuss recent research leading to the identification of RSV virulence factors that are responsible of promoting a pro-inflammatory environment at the airways and their implications on pathogenicity.

The infectious march: the complex interaction between microbes and the immune system in asthma

There has been significant progress in our knowledge about the relationship between infectious disease and the immune system in relation to asthma, but many unanswered questions still remain. Respiratory tract infections such as those caused by respiratory syncytial virus and rhinovirus during the first 2 years of life are still clearly associated with later wheezing and asthma, but the mechanism has not been completely worked out. Is there an "infectious march" triggered by infection in infancy that progresses to disease pathology or are infants who contract respiratory infections predisposed to developing asthma? This review focuses on the common themes in the interaction between microbes and the immune system, and presents a critical appraisal of the evidence to date. The various mechanisms whereby microbes alter the immune response and how this might influence asthma are discussed along with new and promising clinical practices for prevention and therapy. Recent advances in using sensitive polymerase chain reaction detection methods have allowed more rigorous testing of the causality hypothesis of virus infection leading to asthma, but the evidence is still equivocal. Various exceptions and inconsistencies in the clinical trials are discussed in light of new guidelines for subject inclusion/exclusion in hopes of providing some standardization. Despite past failures in vaccination and disappointing results of some clinical trials, the new strategies for prophylaxis including RNA interference and targeted delivery of microbicides offer a large dose of hope to a world suffering from an increasing incidence of asthma as well as a huge burden of health care cost and loss of quality of life.

Rats susceptible to virus-induced asthma have a persistent virus-induced change in the predominant pulmonary form of the NF-κB inhibitor IκBα

Weanling Brown Norway (BN) rats are susceptible to persistent steroid-responsive pulmonary abnormalities following resolution of an acute respiratory virus infection. In contrast, Fischer 344 (F344) rats recover without complications. Previous studies determined that NF-κB activation and subunit composition were markedly different between these 2 rat strains. This study examined whether viral infection also resulted in altered pulmonary expression of IκBα and IκBβ, 2 inhibitory regulators of NF-κB. Western blot analyses of total pulmonary protein extracted from BN and F344 rats at 7, 10, and 14 days after inoculation (n = 5 per group) did not reveal virus-induced differences in IκBβ expression. In contrast, a lower molecular weight form of IκBα appeared in the BN rats at 14 days postinfection, and it was still present at 21 days after infection (n = 5 per group). The change in IκBα expression observed in the susceptible BN but not the resistant F344 animals occurs when the epithelium is proliferating during the repair phase, and it correlates with the development of the persistent virus-induced airway inflammation and pulmonary functional abnormalities. These results further implicate differential regulation of NF-κB in the pathogenesis of virus-induced asthma.

Role of muscarinic receptor activation in regulating immune cell activity in nasal mucosa

BACKGROUND

The prevalence of airway inflammatory disorders keeps rising; its pathogenic mechanism is still not fully understood.

OBJECTIVE

The present study aimed to investigate the role of muscarinic receptor (M receptor) in regulating the immune cell activity in nasal mucosa by using surgical removed nasal mucosa from patients with nasal polyposis (NP) as a study platform.

METHODS

Human nasal mucosal sample was collected from inferior turbinectomy of 86 patients with NP or/and allergic rhinitis. Expression of tumor necrosis factor alpha (TNF-alpha), M receptor, OX40 ligand was measured in nasal mucosa by enzyme-linked immunosorbent assay, flow cytometry, and Western blotting assay.

RESULTS

When compared with non-NP (nNP) nasal mucosa, contents of TNF-alpha and TNF-alpha+ cells markedly increased in NP nasal mucosa; immune staining colocalized M3 receptor+ and TNF-alpha+ cells in NP nasal mucosa; exposure of isolated CD4+ T cells to methacholine induced the release of TNF-alpha. We also found CD11c+/M3 receptor+ cells in NP nasal mucosa. Methacholine increased the expression of OX40L in dendritic cells. Staphylococcal (S) aureus and S. enterotoxin B (SEB) were detected in NP nasal mucosa. Exposure of dendritic cells or naïve CD4+ T cells to SEB initiated the expression of M3 receptor at mRNA and protein levels.

CONCLUSIONS

The present data demonstrate that parasympathetic activity has the capacity to activate dendritic cells to release OX40 ligand, the latter induces CD4+ T cells to produce IL-4 and TNF-alpha that may further contribute to the pathogenesis of NP.