title: Antigen-specific H1N1 influenza antibody responses in acute respiratory tract infections and their relation to influenza infection and disease course.
abstract: BACKGROUND
  Early antibody responses to influenza infection are important in both clearance of virus and fighting the disease. Acute influenza antibody titers directed toward H1-antigens and their relation to infection type and patient outcomes have not been well investigated.
  
  
  OBJECTIVE
  Using hemagglutination inhibition (HI) assays, we aimed to characterize the H1-specific antibody titers in patients with influenza infection or another respiratory infection before and after the H1N1-pandemic influenza outbreak. Among patients with acute influenza infection we related duration of illness, severity of symptoms, and need for hospitalization to antibody titers.
  
  
  METHODS
  There were 134 adult patients (average age 34.7) who presented to an urban academic emergency department (ED) from October through March during the 2008-2011 influenza seasons with symptoms of fever and a cough. Nasal aspirates were tested by viral culture, and peripheral blood serum was run in seven H1-subtype HI assays.
  
  
  RESULTS
  Acutely infected influenza patients had markedly lower antibody titers for six of the seven pseudotype viruses. For the average over the seven titers (log units, base 2) their mean was 7.24 (95% CI 6.88, 7.61) compared with 8.60 (95% CI 8.27, 8.92) among patients who had a non-influenza respiratory illness, p<0.0001. Among patients with seasonal influenza infection, titers of some antibodies correlated with severity of symptoms and with total duration of illness (p<0.02).
  
  
  CONCLUSIONS
  In patients with acute respiratory infections, lower concentrations of H1-influenza-specific antibodies were associated with influenza infection. Among influenza-infected patients, higher antibody titers were present in patients with a longer duration of illness and with higher severity-of-symptom scores.
authors.affiliation: Department of Emergency Medicine, University of Massachusetts Medical School, Worcester, MA, United States(1); Department of Emergency Medicine, Alpert Medical School of Brown University, Providence, RI, United States(2). Electronic address: johnpharan@gmail.com.
authors.forename: John Patrick
authors.initials: JP
authors.lastname: Haran
authors.affiliation: Division of Biostatistics and Health Services Research, Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA, United States.
authors.forename: David C
authors.initials: DC
authors.lastname: Hoaglin
authors.affiliation: Laboratory of Nucleic Acid Vaccines, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, United States.
authors.forename: Huaiqing
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Emergency Medicine, University of Massachusetts Medical School, Worcester, MA, United States(1).
authors.forename: Edward W
authors.initials: EW
authors.lastname: Boyer
authors.affiliation: Laboratory of Nucleic Acid Vaccines, Department of Medicine, University of Massachusetts Medical School, Worcester, MA, United States.
authors.forename: Shan
authors.initials: S
authors.lastname: Lu
mesh_terms: D000328:Adult; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral / Q000097:blood*; D000917:Antibody Formation; D018450:Disease Progression; D005260:Female; D006385:Hemagglutination Inhibition Tests; D006389:Hemagglutinins, Viral / Q000276:immunology*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D007251:Influenza, Human / Q000175:diagnosis* / Q000276:immunology* / Q000821:virology; D008297:Male; D012141:Respiratory Tract Infections / Q000150:complications / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D006389:Hemagglutinins, Viral
keywords: Antibodies; Bacterial pneumonia; H1N1 influenza; Seasonal influenza