PLoS ONE (Dec 2009)

Effect of the novel influenza A (H1N1) virus in the human immune system.

  • Evangelos J Giamarellos-Bourboulis,
  • Maria Raftogiannis,
  • Anastasia Antonopoulou,
  • Fotini Baziaka,
  • Pantelis Koutoukas,
  • Athina Savva,
  • Theodora Kanni,
  • Marianna Georgitsi,
  • Aikaterini Pistiki,
  • Thomas Tsaganos,
  • Nikolaos Pelekanos,
  • Sofia Athanassia,
  • Labrini Galani,
  • Efthymia Giannitsioti,
  • Dimitra Kavatha,
  • Flora Kontopidou,
  • Maria Mouktaroudi,
  • Garyfallia Poulakou,
  • Vissaria Sakka,
  • Periklis Panagopoulos,
  • Antonios Papadopoulos,
  • Kyriaki Kanellakopoulou,
  • Helen Giamarellou

DOI
https://doi.org/10.1371/journal.pone.0008393
Journal volume & issue
Vol. 4, no. 12
p. e8393

Abstract

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BackgroundThe pandemic by the novel H1N1 virus has created the need to study any probable effects of that infection in the immune system of the host.Methodology/principal findingsBlood was sampled within the first two days of the presentation of signs of infection from 10 healthy volunteers; from 18 cases of flu-like syndrome; and from 31 cases of infection by H1N1 confirmed by reverse RT-PCR. Absolute counts of subtypes of monocytes and of lymphocytes were determined after staining with monoclonal antibodies and analysis by flow cytometry. Peripheral blood mononuclear cells (PBMCs) were isolated from patients and stimulated with various bacterial stimuli. Concentrations of tumour necrosis factor-alpha, interleukin (IL)-1beta, IL-6, IL-18, interferon (FN)-alpha and of IFN-gamma were estimated in supernatants by an enzyme immunoassay. Infection by H1N1 was accompanied by an increase of monocytes. PBMCs of patients evoked strong cytokine production after stimulation with most of bacterial stimuli. Defective cytokine responses were shown in response to stimulation with phytohemagglutin and with heat-killed Streptococcus pneumoniae. Adaptive immune responses of H1N1-infected patients were characterized by decreases of CD4-lymphocytes and of B-lymphocytes and by increase of T-regulatory lymphocytes (Tregs).Conclusions/significanceInfection by the H1N1 virus is accompanied by a characteristic impairment of the innate immune responses characterized by defective cytokine responses to S.pneumoniae. Alterations of the adaptive immune responses are predominated by increase of Tregs. These findings signify a predisposition for pneumococcal infections after infection by H1N1 influenza.