Burden of Human Metapneumovirus and Respiratory Syncytial Virus Infections in Asthmatic Children.

BACKGROUND: Human metapneumovirus (hMPV) and respiratory syncytial virus (RSV) are the leading causes of acute respiratory illness in children. Clinical burden of each infection on the respiratory distress in asthmatic patients remains unclear. The purpose of the study was to clarify the effect of these infections on the severity of asthmatic children in the seasonal outbreaks. METHODS: A total of 1,217 pediatric inpatients with hMPV (n = 114) or RSV (n = 1,103) infection in Yamaguchi prefecture, Japan, between 2011 and 2014 were enrolled. Bronchial asthma was defined as having more than 3 episodes of wheezing illness over 1 year of age. Infection was determined by the positive antigen test for each virus in the nasal specimens. RESULTS: The number of patients peaked at age 12-15 months in hMPV infection and at age 0-3 months in RSV infection. The proportion of hypoxic patients (40-50%) did not differ at any age between hMPV-infected and RSV-infected children. In the analysis of date from > 1 year old patients with hypoxia, hMPV-infection group was older (P = 0.036), and more frequently had history of asthma (P = 0.015) or abnormal chest roentgenogram (P < 0.001) than RSV-infection group. Multivariate analysis indicated that the hypoxia-associated factors were history of asthma in both hMPV (odds ratio [OR]: 15.8; P < 0.001) and RSV infections (OR, 2.2; P = 0.005), higher body temperature in hMPV infection (OR, 2.2; P = 0.009), and younger age in RSV infection (OR, 1.4; P = 0.004). CONCLUSIONS: Outbreaks of hMPV, rather than, RSV infection may have a greater impact on the development of hypoxic respiratory illness in asthmatic children.

Serum levels of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinases-1 in human herpesvirus-6-infected infants with or without febrile seizures.

Human herpesvirus-6 (HHV-6) is a cause of exanthema subitum and, sometimes, of febrile seizures. However, the pathogenesis of febrile seizures associated with HHV-6 infection remains unclear. We investigated serum matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinases-1 (TIMP-1) levels in infants with HHV-6 infection. Serum levels of both MMP-9 and TIMP-1 were significantly higher in infants with HHV-6 infection than in controls. Serum TIMP-1 levels were significantly higher in infants with febrile seizures than in infants without febrile seizures. Serum MMP-9/TIMP-1 ratios were significantly lower in infants with febrile seizures than in infants without febrile seizures. In infants with HHV-6 infection, positive correlations were found between serum MMP-9 concentrations and the white blood cells (WBC) count, and between serum TIMP-1 concentrations and the WBC count. Positive correlations were also found between the amounts of HHV-6 DNA and the ratios of MMP-9/TIMP-1 in infants with HHV-6 infection. In conclusion, we suggest that high serum levels of MMP-9 and TIMP-1 in infants with HHV-6 infection may induce dysfunction of the blood-brain barrier, eventually causing febrile seizures.