Lung pathology in fatal novel human influenza A (H1N1) infection.
BACKGROUND
There are no reports of the systemic human pathology of the novel swine H1N1 influenza (S-OIV) infection.


OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Mauad
Thais
T
Department of Pathology, São Paulo University, Brazil. tmauad@usp.br
Hajjar
Ludhmila A
LA
Callegari
Giovanna D
GD
da Silva
Luiz F F
LF
Schout
Denise
D
Galas
Filomena R B G
FR
Alves
Venancio A F
VA
Malheiros
Denise M A C
DM
Auler
Jose O C
JO
Ferreira
Aurea F
AF
Borsato
Marcela R L
MR
Bezerra
Stephania M
SM
Gutierrez
Paulo S
PS
Caldini
Elia T E G
ET
Pasqualucci
Carlos A
CA
Dolhnikoff
Marisa
M
Saldiva
Paulo H N
PH
D000293:Adolescent; D000368:Aged; D001344:Autopsy; D001990:Bronchiolitis, Viral / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D007251:Influenza, Human / Q000276:immunology / Q000473:pathology*; D016676:Macrophages, Alveolar / Q000276:immunology; D008297:Male; D008875:Middle Aged; D011650:Pulmonary Alveoli / Q000276:immunology / Q000473:pathology*; D055815:Young Adult