title: Interleukin-10-induced HIV-1 expression is mediated by induction of both membrane-bound tumour necrosis factor (TNF)-alpha and TNF receptor type 1 in a promonocytic cell line.
abstract: OBJECTIVE
  To investigate whether the upregulatory effect of interleukin (IL)-10 on HIV expression in a model of latent HIV infection is mediated by induction of endogenous tumour necrosis factor (TNF)-alpha and TNF receptors (TNFR).
  
  
  METHODS
  The latently HIV-infected promonocytic cell line U1 was examined, because in this in vitro model IL-10 has been shown to synergize with multiple cytokines, including TNF-alpha, in enhancing HIV production.
  
  
  METHODS
  Membrane-bound TNF-alpha, TNFR-1 and TNFR-2 surface expression were determined by flow cytometry. TNF-alpha mRNA was estimated by competitive polymerase chain reaction (PCR), and TNF-alpha, soluble TNFR-1 and soluble TNFR-2 supernatant content by enzyme-linked immunosorbent assay. HIV-1 expression was quantitated by reverse transcriptase assay and p24 antigen release.
  
  
  RESULTS
  We demonstrated that IL-10 induces a time and cell-concentration dependent upregulation of HIV expression in U1 cells. This effect is mediated through the endogenous production of TNF-alpha as demonstrated by blocking experiments with anti-TNF-alpha antibodies and by detection of IL-10-induced increase of TNF-alpha mRNA by competitive PCR. More importantly, IL-10 is able to upregulate membrane-bound TNF-alpha and TNFR-1, along with a consistent increase in the shedding of soluble TNFR-1 without inducing detectable TNF-alpha secretion.
  
  
  CONCLUSIONS
  IL-10 activates HIV expression through the membrane-bound TNF-alpha/TNFR-1 pathway, suggesting an amplification mechanism of HIV expression that might occur during cell-to-cell interaction. This positive regulatory effect of IL-10 in an in vitro model of chronic HIV infection is consistent with the inexorable progression of disease seen in advanced patients when both IL-10 and TNF-alpha are elevated.
authors.affiliation: Institute of Internal Medicine, Infectious Diseases and Immunopathology, University of Milan, Italy.
authors.forename: W
authors.initials: W
authors.lastname: Barcellini
authors.forename: G P
authors.initials: GP
authors.lastname: Rizzardi
authors.forename: J B
authors.initials: JB
authors.lastname: Marriott
authors.forename: C
authors.initials: C
authors.lastname: Fain
authors.forename: R J
authors.initials: RJ
authors.lastname: Shattock
authors.forename: P L
authors.initials: PL
authors.lastname: Meroni
authors.forename: G
authors.initials: G
authors.lastname: Poli
authors.forename: A G
authors.initials: AG
authors.lastname: Dalgleish
mesh_terms: D015703:Antigens, CD / Q000096:biosynthesis*; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry; D005786:Gene Expression Regulation / Q000187:drug effects; D015497:HIV-1 / Q000254:growth & development*; D006801:Humans; D016753:Interleukin-10 / Q000494:pharmacology*; D009000:Monocytes; D010431:Pentoxifylline / Q000494:pharmacology; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D018124:Receptors, Tumor Necrosis Factor / Q000096:biosynthesis*; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D014775:Virus Activation / Q000187:drug effects*; D017735:Virus Latency
chemical_list: D015703:Antigens, CD; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D013755:Tetradecanoylphorbol Acetate; D010431:Pentoxifylline