Altered eosinophil levels as a result of viral infection in asthma exacerbation in childhood

Abstract

Respiratory viral infection is known to be a significant cause of asthma exacerbation. Eosinophils have been considered to play an important role in the pathogenesis of virus-induced asthma exacerbations. To determine how often asthma exacerbation is caused by virus infections and to examine the relationship between eosinophilia and asthma episode, we investigated 64 children who experienced asthma attacks between October 1999 and March 2000. We used rapid enzyme immunoassays to detect antigens of respiratory syncytial virus (RSV), influenza A virus, and adenovirus in nasopharyngeal secretions (NPS) of these children, and enumerated eosinophils in the blood and NPS. We detected RSV in 27% and influenza A virus in 17% of the patients. No adenovirus infection or RSV/influenza A co-infection was detected. RSV-infected children were younger (3.85 +/- 0.83 years old) than influenza A virus-infected patients (5.23 +/- 1.34 years old). Eighty-two per cent of patients in the RSV group and 36% of patients in the influenza A virus group had moderate-to-severe asthma episodes (p < 0.05). In RSV-infected children, the eosinophil counts in NPS were higher in the 'severe' group, and younger patients had a greater number of eosinophils in their NPS than older patients (p < 0.05). These trends were not found in influenza A virus patients. In conclusion, our results indicate that, compared with influenza A virus-induced asthma attacks, RSV infection had a higher probability of being associated with asthma exacerbation in infants and younger children and induced attacks of greater severity. The increase in the number of eosinophils in the NPS of RSV-infected children may be responsible, in part, for these differences.

Rhinovirus Induces Airway Epithelial Gene Expression through Double-Stranded RNA and IFN-Dependent Pathways

“…RV is a very simple plus-stranded virus with only viral genomic RNA in the virion. Previous report has suggested that dsRNA, generated from viral replication, can induce robust cellular responses (34). Here, we found that RV replication generated an enormous amount of RNA in the infected cells ( Figure 1A).…”

“…This supports the notion that very few copies of dsRNA are actually required to initiate PKR signaling. It is interesting to note that all the asthma-exacerbating viruses (such as RV, respiratory syncytial virus (34), and influenza) generate dsRNA in their life cycles. Therefore, it would be fruitful to continue the study of the role of dsRNA in airway inflammatory responses and asthma exacerbations.…”

Some Epidemiological Aspects of Bronchial Asthma in Children in Qena Governorate, Egypt

“…We found that 80% of asthmatic episodes in children were attributed to viral infections. This data are close to those reported by other researchers [40,41] who reported that respiratory viral infections precipitated acute exacerbations of asthma and were the most common reason for hospital admissions. Additionally, an Egyptian study by ElGamal et al [42] revealed that 71% of asthmatic episodes in children were attributed to viral infections.…”

Eosinophil Granular Proteins Damage Bronchial Epithelial Cells Infected with Respiratory Syncytial Virus

“…MBP deposition has been observed in the bronchial tissue of patients with asthma [19], chronic urticaria, atopic dermatitis and immunoglobulin E-mediated cutaneous late phase reactions [20]. Furthermore, in the patients with bronchiolitis and bronchial asthma caused by RS virus infection, eosinophils and ECP were increased in the bronchoalveolar lavage fluids [21] and nasopharyngeal secretions [22,23,24]. Collectively, these in vitro and in vivo studies indicate that toxic eosinophil granule proteins, specifically MBP, may play an important role in the pathophysiology of asthma.…”