title: Histopathological and immunohistochemical findings of 20 autopsy cases with 2009 H1N1 virus infection.
abstract: Twenty autopsy cases with 2009 pandemic influenza A (2009 H1N1) virus infection, performed between August 2009 and February 2010, were histopathologically analyzed. Hematoxylin-eosin staining, immunohistochemistry for type A influenza nucleoprotein antigen, and real-time reverse transcription-PCR assay for viral RNA were performed on formalin-fixed and paraffin-embedded specimens. In addition, the D222G amino acid substitution in influenza virus hemagglutinin, which binds to specific cell receptors, was analyzed in formalin-fixed and paraffin-embedded trachea and lung sections by direct sequencing of PCR-amplified products. There were several histopathological patterns in the lung according to the most remarkable findings in each case: acute diffuse alveolar damage (DAD) with a hyaline membrane (four cases), organized DAD (one case), acute massive intra-alveolar edema with variable degrees of hemorrhage (three cases), neutrophilic bronchopneumonia (five cases) and tracheobronchitis with limited histopathological changes in alveoli (four cases). In two cases, the main findings were due to preexisting disease. Influenza virus antigen was only detected in the respiratory tract in 10 cases by immunohistochemistry. The antigen was detected in type II pneumocytes (three cases) in the epithelial cells of the trachea, bronchi and glands (six cases), and in the epithelial cells in both of the above (one case). The four cases with acute DAD presented with antigen-positive type II pneumocytes. In one case, the D222G substitution was detected in the lung as a major sequence, although 222D was prominent in the trachea, suggesting that selection of the viral clones occurred in the respiratory tract. In five cases, the pathogenesis of 2009 H1N1 was confirmed to be viral infection in pneumocytes, which caused severe alveolar damage and fatal viral pneumonia. Further studies on both host and viral factors in autopsy or biopsy materials will be essential to elucidate the other pathogenic factors involved in influenza virus infection.
authors.affiliation: Department of Pathology, National Institute of Infectious Diseases, Tokyo, Japan. tenko@nih.go.jp
authors.forename: Noriko
authors.initials: N
authors.lastname: Nakajima
authors.forename: Yuko
authors.initials: Y
authors.lastname: Sato
authors.forename: Harutaka
authors.initials: H
authors.lastname: Katano
authors.forename: Hideki
authors.initials: H
authors.lastname: Hasegawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Kumasaka
authors.forename: Satoru
authors.initials: S
authors.lastname: Hata
authors.forename: Shinya
authors.initials: S
authors.lastname: Tanaka
authors.forename: Tomonori
authors.initials: T
authors.lastname: Amano
authors.forename: Takahiko
authors.initials: T
authors.lastname: Kasai
authors.forename: Ja-Mun
authors.initials: JM
authors.lastname: Chong
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Iizuka
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Iiduka
authors.forename: Iwao
authors.initials: I
authors.lastname: Nakazato
authors.forename: Yohko
authors.initials: Y
authors.lastname: Hino
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hamamatsu
authors.forename: Hisashi
authors.initials: H
authors.lastname: Horiguchi
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Akio
authors.initials: A
authors.lastname: Hasegawa
authors.forename: Akio
authors.initials: A
authors.lastname: Hasagawa
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Kanaya
authors.forename: Reiko
authors.initials: R
authors.lastname: Oku
authors.forename: Takeshi
authors.initials: T
authors.lastname: Oya
authors.forename: Tetsutaro
authors.initials: T
authors.lastname: Sata
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000956:Antigens, Viral / Q000302:isolation & purification; D001344:Autopsy; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D005260:Female; D005404:Fixatives; D005557:Formaldehyde; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D053118:Influenza A Virus, H1N1 Subtype / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D007251:Influenza, Human / Q000401:mortality / Q000473:pathology* / Q000821:virology*; D007564:Japan / Q000453:epidemiology; D008168:Lung / Q000473:pathology* / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D058873:Pandemics; D016612:Paraffin Embedding; D012367:RNA, Viral / Q000302:isolation & purification; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D016707:Tissue Fixation; D055815:Young Adult
chemical_list: D000956:Antigens, Viral; D005404:Fixatives; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D012367:RNA, Viral; D005557:Formaldehyde