Lung Pathology in Fatal Novel Human Influenza A (H1N1) Infection

Department of Pathology, São Paulo University, Brazil.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 10/2009; 181(1):72-9. DOI: 10.1164/rccm.200909-1420OC
Source: PubMed


There are no reports of the systemic human pathology of the novel swine H1N1 influenza (S-OIV) infection.
The autopsy findings of 21 Brazilian patients with confirmed S-OIV infection are presented. These patients died in the winter of the southern hemisphere 2009 pandemic, with acute respiratory failure.
Lung tissue was submitted to virologic and bacteriologic analysis with real-time reverse transcriptase polymerase chain reaction and electron microscopy. Expression of toll-like receptor (TLR)-3, IFN-gamma, tumor necrosis factor-alpha, CD8(+) T cells and granzyme B(+) cells in the lungs was investigated by immunohistochemistry.
Patients were aged from 1 to 68 years (72% between 30 and 59 yr) and 12 were male. Sixteen patients had preexisting medical conditions. Diffuse alveolar damage was present in 20 individuals. In six patients, diffuse alveolar damage was associated with necrotizing bronchiolitis and in five with extensive hemorrhage. There was also a cytopathic effect in the bronchial and alveolar epithelial cells, as well as necrosis, epithelial hyperplasia, and squamous metaplasia of the large airways. There was marked expression of TLR-3 and IFN-gamma and a large number of CD8(+) T cells and granzyme B(+) cells within the lung tissue. Changes in other organs were mainly secondary to multiple organ failure.
Autopsies have shown that the main pathological changes associated with S-OIV infection are localized to the lungs, where three distinct histological patterns can be identified. We also show evidence of ongoing pulmonary aberrant immune response. Our results reinforce the usefulness of autopsy in increasing the understanding of the novel human influenza A (H1N1) infection.

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Available from: Stephania M. Bezerra, Oct 26, 2015
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    • "Early treatment with antiviral drugs may improve outcome of severe influenza [13], but no specific treatment for ARDS is available. Severe H1N1 infection is associated with hypercytokinemia [14,15] and a dysregulated immune response [16]. The increase in IL-6 has been found to correlate with respiratory involvement in adult [17] and paediatric [18] patients. "
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    ABSTRACT: Background Activin A and its binding protein follistatin (FS) are increased in inflammatory disorders and sepsis. Overexpression of activin A in the lung causes similar histopathological changes as acute respiratory distress syndrome (ARDS). ARDS and severe respiratory failure are complications of influenza A(H1N1) infection. Interleukin 6 (IL-6), which in experimental studies increases after activin A release, is known to be related to the severity of H1N1 infection. Our aim was to evaluate the levels of activin A, activin B, FS, IL-6 and IL-10 and their association with the severity of respiratory failure in critically ill H1N1 patients. Methods A substudy of a prospective, observational cohort of H1N1 patients in Finnish intensive care units (ICU). Clinical information was recorded during ICU treatment, and serum activin A, activin B, FS, IL-6 and IL-10 were measured at admission to ICU and on days 2 and 7. Results Blood samples from 29 patients were analysed. At the time of admission to intensive care unit, elevated serum levels above the normal range for respective age group and sex were observed in 44% for activin A, 57% for activin B, and 39% for FS. In 13 of the 29 patients, serial samples at all time points were available and in these the highest activin A, activin B and FS were above the normal range in 85%, 100% and 46% of the patients, respectively. No difference in baseline or highest activin A or activin B was found in patients with or without acute lung injury (ALI) or ARDS (P > 0.05 for all). Peak levels of IL-6 were significantly elevated in ALI/ARDS patients. Peak activin A and activin A/FS were associated with ventilatory support free-days, severity of acute illness and length of ICU stay (P < 0.05 for all). Conclusions Higher than normal values of these proteins were common in patients with H1N1 infection but we found no association with the severity of their respiratory failure.
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    • "However, inappropriate cell death can disrupt the architecture and integrity of the bronchoalveolar network, leading to barrier disruption and compromised arterial blood oxygenation following lethal influenza infection in the mouse model (Sanders et al., 2013). In humans, both necrosis and apoptosis of distal pulmonary epithelia were described as a classical feature of H5N1 or H1N1 influenza-induced acute respiratory distress syndrome (Korteweg and Gu, 2008; Mauad et al., 2010). Viruses can trigger not only apoptosis but also an alternative form of caspase-independent cell death called programmed necrosis (or necroptosis). "

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