Role of IgE immune complexes in the regulation of HIV-1 replication and increased cell death of infected U1 monocytes: involvement of CD23/Fc epsilon RII-mediated nitric oxide and cyclic AMP pathways.
BACKGROUND
IgE/anti-IgE immune complexes (IgE-IC) induce the release of multiple mediators from monocytes/macrophages and the monocytic cell line U937 following the ligation of the low-affinity Fc epsilon receptors (Fc epsilon RII/CD23). These effects are mediated through an accumulation of cAMP and the generation of L-arginine-dependent nitric oxide (NO). Since high IgE levels predict more rapid progression to acquired immunodeficiency syndrome, we attempted to define the effects of IgE-IC on human immunodeficiency virus (HIV) production in monocytes.


METHODS
Two variants of HIV-1 chronically infected monocytic U1 cells were stimulated with IgE-IC and virus replication was quantified. NO and cAMP involvement was tested through the use of agonistic and antagonistic chemicals of these two pathways.


RESULTS
IgE-IC induced p24 production by U1 cells with low-level constitutive expression of HIV-1 mRNAs and extracellular HIV capsid protein p24 levels (U1low), upon their pretreatment with interleukin 4 (IL-4) or IL-13. This effect was due to the crosslinking of CD23, as it was reversed by blocking the IgE binding site on CD23. The IgE-IC effect could also be mimicked by crosslinking of CD23 by a specific monoclonal antibody. p24 induction by IgE-IC was then shown to be due to CD23-mediated stimulation of cAMP, NO, and tumor necrosis factor alpha (TNF alpha) generation. In another variant of U1 cells with > 1 log higher constitutive production of p24 levels (U1high), IgE-IC addition dramatically decreased all cell functions tested and accelerated cell death. This phenomenon was reversed by blocking the nitric oxide generation.


CONCLUSIONS
These data point out a regulatory role of IgE-IC on HIV-1 production in monocytic cells, through CD23-mediated stimulation of cAMP and NO pathways. IgE-IC can also stimulate increased cell death in high HIV producing cells through the NO pathway.
Ouaaz
F
F
Molecular Immuno-hematology Group, CNRS URA625, Pitié-Salpêtrière Hospital, Paris, France.
Ruscetti
F W
FW
Dugas
B
B
Mikovits
J
J
Agut
H
H
Debré
P
P
Mossalayi
M D
MD
D000936:Antigen-Antibody Complex / Q000276:immunology* / Q000494:pharmacology; D016923:Cell Death / Q000235:genetics*; D000242:Cyclic AMP / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000235:genetics; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007073:Immunoglobulin E / Q000276:immunology* / Q000378:metabolism; D009000:Monocytes / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D017455:Receptors, IgE / Q000378:metabolism; D015398:Signal Transduction; D014779:Virus Replication / Q000235:genetics
D000936:Antigen-Antibody Complex; D012333:RNA, Messenger; D017455:Receptors, IgE; D009569:Nitric Oxide; D007073:Immunoglobulin E; D000242:Cyclic AMP