Thymus activity measured by T-cell receptor excision circles in patients with different severities of respiratory syncytial virus infection.

BACKGROUND: Respiratory syncytial virus (RSV) infection is an important cause of hospitalization in previously healthy infants. Immunological mechanisms predisposing infants to severe disease are poorly understood. Early biomarkers for disease severity may assist clinical decisions. We investigated T-cell receptor excision circles (TREC), episomal DNA made during thymic T-cell receptor rearrangement, and a marker for thymus activity, both during disease and in neonatal screening cards as a risk factor for RSV disease severity. METHODS: One hundred thirteen patients hospitalized with RSV infection <12 months of age, grouped by disease severity, were available for this investigation, in which we conducted both a prospective and a case-control study. The prospective study included 47 RSV positive infants (mild n = 13, moderate n = 10, severe n = 24). TREC counts were determined by PCR of DNA extracted from EDTA-blood collected on hospitalization, and corrected for lymphocytes using ANCOVA. The case-control study included 85 newborns who later in infancy became RSV positive (mild n = 32, moderate n = 24, severe n = 29) and 47 newborns who never developed RSV disease as healthy controls included from health centres in the same catchment area. TRECs were measured using DNA extracted from dry blood spots from stored neonatal screening cards, followed by PCR. Student's T-test compared patients with controls, ANOVA compared disease severity groups. RESULTS: During RSV infection patients in the severe disease group had significantly lower (p = 0.017) TREC/200 µL blood compared to the other two disease groups, after correction for lymphocyte count. Newborn TREC levels, were significantly higher in RSV patients compared to controls (p < 0.0001). No significant differences in TREC copies at birth were found between disease severities. CONCLUSION: During acute RSV infection a lower number of TREC is found in the severe disease group. TREC has potential as an immunological marker for severe RSV infection. Higher neonatal TREC counts indicate that infants later presenting with severe RSV do not have reduced thymic activity at birth and probably no congenital T-cell defect.

The role of microRNAs in respiratory viral infection: friend or foe?

MicroRNAs (miRNAs) have emerged as a class of regulatory RNAs in host-pathogen interactions. Aberrant miRNA expression seems to play a central role in the pathology of several respiratory viruses, promoting development and progression of infection. miRNAs may thus serve as therapeutic and prognostic factors for respiratory viral infectious disease caused by a variety of agents. We present a comprehensive review of recent findings related to the role of miRNAs in different respiratory viral infections and discuss possible therapeutic opportunities aiming to attenuate the burden of viral infections. Our review supports the emerging concept that cellular and viral-encoded miRNAs might be broadly implicated in human respiratory viral infections, with either positive or negative effects on virus life cycle. Copyright © 2016 John Wiley & Sons, Ltd.

Nasal mucosal microRNA expression in children with respiratory syncytial virus infection.

BACKGROUND: Respiratory syncytial virus (RSV) infection is a common cause of pediatric hospitalization. microRNA, key regulators of the immune system, have not previously been investigated in respiratory specimens during viral infection. We investigated microRNA expression in the nasal mucosa of 42 RSV-positive infants, also comparing microRNA expression between disease severity subgroups. METHODS: Nasal mucosa cytology specimens were collected from RSV-positive infants and healthy controls. 32 microRNA were selected by microarray for qPCR verification in 19 control, 16 mild, 7 moderate and 19 severe disease samples. RESULTS: Compared to healthy controls, RSV-positive infants downregulated miR-34b, miR-34c, miR-125b, miR-29c, mir125a, miR-429 and miR-27b and upregulated miR-155, miR-31, miR-203a, miR-16 and let-7d. On disease subgroups analysis, miR-125a and miR-429 were downregulated in mild disease (p=0.03 and 0.02, respectively), but not in severe disease (p=0.3 and 0.3). CONCLUSION: microRNA expression in nasal epithelium cytology brushings of RSV-positive infants shows a distinct profile of immune-associated miRNA. miR-125a has important functions within NF-κB signaling and macrophage function. The lack of downregulation of miR-125a and miR-429 in severe disease may help explain differences in disease manifestations on infection with RSV.

Downregulation of IL7R, CCR7, and TLR4 in the cord blood of children with respiratory syncytial virus disease.

The association between gene expression at birth of 11 candidate genes with important innate and adaptive immune functions and later respiratory syncytial virus (RSV) disease was investigated. Cord blood was collected from 2108 newborns. Forty-seven were subsequently RSV positive. Gene expression analysis by quantitative reverse transcription-polymerase chain reaction was compared to 17 controls. There was downregulation of interleukin 7 receptor (IL7R) (P = .0001) and chemokine receptor 7 (CCR7) (P = .002), and in the severe disease subcategory, downregulation of Toll-like receptor 4 (TLR4) (P = .003). IL7R and CCR7 facilitate communication between adaptive and innate immune systems. TLR4 activates the innate immune system on RSV exposure. Delayed innate and adaptive immune activation may predispose children to more severe RSV disease.

Reduced Dicer expression in the cord blood of infants admitted with severe respiratory syncytial virus disease.

BACKGROUND: Respiratory syncytial virus (RSV) is one of the most important causes of pediatric hospital admissions in the developed world. The ribonuclease Dicer is an important regulator of gene expression and cellular function via RNA interference, and may also have anti-viral functions. A previous microarray analysis of the cord blood of 5 patients with RSV disease suggested downregulation of Dicer. In order to further investigate whether reduced Dicer expression can predispose newborns to RSV disease, we have analyzed the gene expression of Dicer in the cord blood of 37 infants with confirmed RSV disease. METHODS: The cord blood of 2108 newborns was collected. 51 had a positive nasopharyngeal aspirate for RSV <1 year, and were grouped according to disease severity. 37 had sufficient cord blood RNA of good quality. Dicer gene expression was assessed by qPCR analysis of cord blood using a TaqMan low-density array and compared to control infants who did not present with RSV disease using the Mann-Whitney test. RESULTS: There was significant downregulation of Dicer in the severe disease group: relative quantity 0.69 (95% CI: 0.56 - 0.87), p = 0.002. There was no significant downregulation in the mild disease group. CONCLUSIONS: We demonstrate reduced Dicer expression in the cord blood of infants with severe RSV disease, prior to RSV exposure. We theorize that this may predispose to RSV disease by disruption of leukocyte gene regulation or direct anti-viral RNA interference mechanisms.