The role of cytokines in relation to clinical manifestations, disease severity, and outcome of children with H1N1 virus infection remains thus far unclear. The aim of this study was to evaluate interleukin IL-1
In the last years the world has been facing a new pandemia caused by an H1N1 influenza virus, the so-called H1N1/09 virus, which contains a unique combination of gene segments that has never been identified in humans or animals [
The novel influenza H1N1 virus was identified as a cause of febrile respiratory infections ranging from self-limited to severe illness both in adults and children. Recent data reported that most cases of H1N1 infection with high rate of hospitalizations occurred in children who aged 5–14 years. A small percentage of these patients can develop more complicated and severe symptoms, such as elevated fever, violent dry cough, pneumonia, and acute respiratory distress syndrome (ARDS) [
Several hypotheses to explain this particular virulence of H1N1 in children were advocated, including downregulation of type 1 interferon expression, apoptosis, and hyperinduction of proinflammatory cytokines [
We conducted a prospective observational clinical study among children admitted from October 2009 to December 2010 with the diagnosis of influenza H1N1 virus infection and LRTI to the Pediatric Intensive Care Unit (PICU) and Pediatric Infectious Disease Unit (PIDU) of the “Agostino Gemelli” Hospital, Catholic University Medical School, Rome, Italy. Patients with H1N1 influenza virus infection were grouped according to age, etiology of virus infection, findings of chest radiograph, clinical and laboratory characteristics, respiratory care, and final outcome (Table
Clinical and radiological findings, respiratory assessment, and complications of H1N1 infected children. In bold the more severe H1N1 patients.
Patients | Fever at first day of admission | Duration of cough (days) | SpO2 at admission in room air | Chest X-ray | Respiratory care | Antimicrobial therapy | Complications | Length of stay in hospital (days) | Outcome (GOS) |
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10 |
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7 | 90 | Interstitial pneumonia | O2 supplementation | Klaritromicin, Oseltamivir | None | 7 | 5 |
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11 |
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4 | 92 | Normal | O2 supplementation | Oseltamivir | None | 4 | 5 |
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12 |
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5 | 94 | Normal | None | Oseltamivir | None | 3 | 5 |
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13 |
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5 | 95 | Normal | None | Oseltamivir | None | 3 | 5 |
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14 |
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6 | 91 | Hyperinflated lung | O2 supplementation | Oseltamivir | None | 6 | 5 |
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15 |
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6 | 93 | Normal | None | Oseltamivir | None | 3 | 5 |
CPAP: continuous positive airway pressure; EI: endotracheal intubation; MV: mechanical ventilation.
Clinical and radiological findings, respiratory assessment, and complications of LRTI children. In bold the more severe LRTI patients.
Patients | Fever at first day of admission | Duration of cough (days) | SpO2 at admission in room air | Chest X-ray | Respiratory care | Antimicrobial therapy | Complications | Length of stay in hospital (days) | Outcome (GOS) |
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9 |
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4 | 93% | Segmental pulmonary atelectasia | O2 supplementation | Amoxicillin | None | 5 | 5 |
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10 |
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3 | 91% | Interstitial pneumonia | O2 supplementation | Claritromicina | None | 5 | 5 |
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11 |
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4 | 88% | Normal | O2 supplementation | Amoxicillin | None | 4 | 5 |
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12 |
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3 | 93% | Normal | None | Amoxicillin | None | 2 | 5 |
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13 |
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3 | 91% | Normal | O2 supplementation | Amoxicillin | None | 3 | 5 |
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14 |
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3 | 86% | Hyperinflated lung | O2 supplementation | Amoxicillin | None | 3 | 5 |
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15 |
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4 | 90% | Normal | O2 supplementation | Amoxicillin | None | 3 | 5 |
CPAP: continuous positive airway pressure; EI: endotracheal intubation; MV: mechanical ventilation.
Oral Oseltamivir (60 mg twice daily for 5 days) was administered to all 15 patients with the diagnosis of influenza H1N1 virus infection, and supportive therapy for ARDS was started based on the severity of respiratory failure (Table
The outcome of patients was assessed upon discharge from the hospital using the Glasgow Outcome Score (GOS), which assigns a score of 1 to children who died, 2 to persistent vegetative state, 3 to severe neurologic deficits, 4 to mild neurologic deficits, and 5 to completely healthy children [
In H1N1 patients we collected blood samples using indwelling radial artery catheters in children admitted to the PICU or arterial puncture in children admitted to the PIDU after local painful treatment. All samples were obtained in the acute phase of the illness, at the moment of the admission of the patients, and before starting any treatment. The plasma samples were submitted for microbiological and biochemical analysis (leukocyte and platelet counts, serum C-reactive protein concentration, procalcitonin, glucose-protein concentration, electrolytes, acid-base study, BUN, etc.).
To measure interleukin levels all blood samples were centrifuged for 10 min at 5,000 rpm, and the supernatants were immediately stored at −70°C until analysis.
As controls, we used blood radial artery samples collected from children with the diagnosis of LRTI who had undergone blood sample analysis at the moment of their admission to the PICU or PIDU.
The study was approved by the Institutional Review Board, and the parents of participating children were informed about study and provided written informed consent.
IL-1
The nonparametric Mann-Whitney test and
We include in this study 15 patients with H1N1 virus infection and 15 children with LRTI. Patients with H1N1 infection aged 2.8 years to 17.3 years, with a mean age of 7.9 years, while children with LRTI aged 1.1 years to 6.3 years, with a mean age of 3.7 years. Nine children with severe H1N1 virus infection were admitted to our PICU due to the severity of their respiratory compromise, while the other 6 patients to the PIDU. Among children with LRTI, 8 out of 15 were admitted to the PICU with the diagnosis of severe RSV bronchiolitis, while the other 7 were admitted to the PIDU (4 with diagnosis of non-RSV bronchiolitis and 3 with diagnosis of influenza A (H2N3) virus infection). Regarding clinical differences between the two groups, H1N1 patients experienced higher median fever (39.2°C) compared to controls (37.7°C) (
In H1N1 patients we detected different plasma levels of interleukins. In these patients we found significantly (
Levels of IL-1
Levels of IL-1
Significantly higher levels of interleukin IL-6 and IL-1
Box plot representation was used. H1N1 patients had significantly higher levels of IL-1
To elucidate the association between interleukin expression and disease severity, we analyzed their plasma levels both in patients with severe (9 patients) and mild symptoms (6 patients) of H1N1 influenza virus infection. Compared to the mild patients, severe H1N1 patients produced significant higher levels of IL-1
Box plot representation was used. H1N1 patients with severe disease had significantly higher levels of IL-1
Moreover, to verify whether there was a correlation between interleukin up-regulation and clinical manifestations in H1N1 patients, we compared the plasma levels of these cytokines with some clinical symptoms referred to the patients. In particular, we detected a positive correlation between plasma level of IL-6 and fever with a coefficient of determination of 0
A scatter plot shows the relationship between fever and IL-6 plasma levels. The line represents the regression line (linear regression equation: fever = 0.02
A scatter plot show the relationship between SpO2 at admission in room air and IL-6 plasma level. The line represents the regression line (linear regression equation:
Our study, despite the limited patient sample so far evaluated, provides evidence that H1N1 virus infection induces an early and significant up-regulation of interleukin IL-1
To date it is difficult to explain the exact role of ILs in the mechanisms of virus host response, because both pro-inflammatory and immunoprotective actions have been reported in previous researches. H1N1 virus infection causes the activation of the host macrophages and lymphocytes determining the release of pro-inflammatory cytokines. The increased expression of pro-inflammatory cytokines into the lung tissue may lead to higher blood vessel permeability, phagocytic cell recruitment, apoptosis of lung epithelial cells, and release of neutrophil-derived enzymes, such as myeloperoxidase and elastase, responsible of severity of acute lung injury [
Up to now it is difficult to explain if the observed ILs up-regulation in H1N1 patients can represent a protective mechanisms for respiratory cell survival or it is secondary to a loss of physiological control of ILs biosynthesis. Available clinical and experimental data does not permit a definitive clarification of these findings. ILs plasma levels increase in several inflammatory diseases, such as allergen provocation and asthma. Recently, lymphocytes and in particular activated T cells were revealed to express ILs receptors in the experimental animal model of pulmonary sarcoidosis and chemical lung injury [
Previous studies, in fact, reported that different viral lung infections are associated with early up-regulation of cytokine biosynthesis suggesting that the changes of ILs release may contribute to the development of airway inflammation and bronchial hyperreactivity [
In conclusion, our observations provide new evidence that an immune response is activated at the early stage of pandemic H1N1 influenza virus infection with up-regulated production of plasma interleukins IL-1