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


RESULTS
Blood 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
Infection 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.
Giamarellos-Bourboulis
Evangelos J
EJ
4th Department of Internal Medicine, University of Athens, Medical School, Greece, Athens, Greece. giamarel@ath.forthnet.gr
Raftogiannis
Maria
M
Antonopoulou
Anastasia
A
Baziaka
Fotini
F
Koutoukas
Pantelis
P
Savva
Athina
A
Kanni
Theodora
T
Georgitsi
Marianna
M
Pistiki
Aikaterini
A
Tsaganos
Thomas
T
Pelekanos
Nikolaos
N
Athanassia
Sofia
S
Galani
Labrini
L
Giannitsioti
Efthymia
E
Kavatha
Dimitra
D
Kontopidou
Flora
F
Mouktaroudi
Maria
M
Poulakou
Garyfallia
G
Sakka
Vissaria
V
Panagopoulos
Periklis
P
Papadopoulos
Antonios
A
Kanellakopoulou
Kyriaki
K
Giamarellou
Helen
H
D056704:Adaptive Immunity / Q000276:immunology; D000328:Adult; D001772:Blood Cell Count; D016207:Cytokines / Q000097:blood; D003710:Demography; D005260:Female; D006801:Humans; D007107:Immune System / Q000821:virology*; D007113:Immunity, Innate / Q000276:immunology; D053118:Influenza A Virus, H1N1 Subtype / Q000502:physiology*; D007251:Influenza, Human / Q000097:blood / Q000150:complications / Q000821:virology; D008297:Male; D011014:Pneumonia / Q000097:blood / Q000150:complications / Q000821:virology; D013997:Time Factors
D016207:Cytokines