title: Serological response of patients with influenza A (H1N1) pdm09-associated pneumonia: an observational study.
abstract: BACKGROUND
  Little is known about the dynamics or magnitude of antibody response in patients with influenza A (H1N1) pdm09-associated pneumonia. We described and compared the antibody response to influenza A (H1N1) pdm09 in patients with and without pneumonia.
  
  
  METHODS
  We collected serum samples and determined antibody titers by the hemagglutination inhibition (HI) and microneutralization (mNT) assays from patients with RT-PCR confirmed influenza A (H1N1) pdm09 virus at baseline, 1, 2 and 6 months after onset of illness.
  
  
  RESULTS
  Fifty-nine patients were enrolled, 45 (76.3%) were between 15 and 60 years of age, 49 (83.1%) were hospitalized and 25 (42.4%) had complications with pneumonia. Ninety-four percent of patients had HI titers ≥ 1: 40 and 90% had mNT titers ≥ 1: 160 at 2 months after illness. Geometric mean titers (GMT) of HI and mNT increased significantly (p<0.001) between baseline and months 1 or 2, then declined significantly (p<0.001) at month 6 by the HI assay, but dropped to an insignificant level (p=0.24) by the mNT assay. The mNT-GMT was at least twice as high as corresponding HI antibodies over a 6 month period. The GMT of HI and mNT in those with pneumonia (1 mo) peaked earlier than that of those without pneumonia (2 mo). When adjusted by age and gender, those with pneumonia had a higher HI-GMT than those without pneumonia at 1 month (264 vs. 117, p=0.007), 2 months (212 vs. 159, p=0.013), and 6 months (160 vs. 82, p=0.018).
  
  
  CONCLUSIONS
  The patients recovered from influenza A (H1N1) pdm09-associated pneumonia, clearly developed an earlier and more robust antibody response until 6 months after onset of illness. The results in our study are useful to determine an appropriate donor and timing to obtain convalescent plasma for adjunctive treatment of seriously ill patients with pandemic H1N1 influenza.
authors: Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
authors: Nasikarn
authors: N
authors: Angkasekwinai
authors: Bualan
authors: B
authors: Kaewnapha
authors: Duangdao
authors: D
authors: Waywa
authors: Peerawong
authors: P
authors: Werarak
authors: Sasima
authors: S
authors: Tongsai
authors: Kulkanya
authors: K
authors: Chokephaibulkit
authors: Visanu
authors: V
authors: Thamlikitkul
authors: Sontana
authors: S
authors: Siritantikorn
mesh_terms: D000293:Adolescent; D000328:Adult; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology*; D007251:Influenza, Human / Q000097:blood / Q000150:complications* / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000150:complications*; D011247:Pregnancy; D012698:Serologic Tests; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral