title: HIV-1 Tat mutants in the cysteine-rich region downregulate HLA class II expression in T lymphocytic and macrophage cell lines.
abstract: Human macrophage and T cell lines were stably transfected with HIV-1 wild-type Tat or Tat mutants in the cysteine-rich region displaying trans-dominant negative effects on HIV-1 life cycle. The expression of HLA class I and class II molecules was not affected by wild-type Tat. Tat mutants, instead, profoundly down-regulated in a dose-dependent fashion the expression of class II, but not of class I, in both cell types by acting at the transcriptional level. Down-regulation was manifested on constitutive and IFN-gamma-induced class II gene expression and did not correlate with reduced transcription of the AIR-1 gene product CIITA, the major transcriptional activator of class II genes, indicating that Tat mutants did not act by inhibiting AIR-1 gene expression. Class II down-modulation had important functional implications in macrophages, as both antigen processing and presenting capacity were inhibited. These results represent the first evidence that a modified HIV-1 Tat product can act as a potent immunosuppressor by inhibiting the HLA class II expression necessary for triggering both cellular and humoral responses against pathogens. The use of these HIV-1 Tat mutants also discloses new opportunities to investigate the molecular mechanisms underlying the coordinate HLA class II gene transcription.
authors.affiliation: Department of Clinical and Biological Sciences School of Medicine, University of Insubria, Varese, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Tosi
authors.forename: A
authors.initials: A
authors.lastname: De Lerma Barbaro
authors.forename: A
authors.initials: A
authors.lastname: D'Agostino
authors.forename: M T
authors.initials: MT
authors.lastname: Valle
authors.forename: A M
authors.initials: AM
authors.lastname: Megiovanni
authors.forename: F
authors.initials: F
authors.lastname: Manca
authors.forename: A
authors.initials: A
authors.lastname: Caputo
authors.forename: G
authors.initials: G
authors.lastname: Barbanti-Brodano
authors.forename: R S
authors.initials: RS
authors.lastname: Accolla
mesh_terms: D017951:Antigen Presentation; D002460:Cell Line; D003545:Cysteine; D015536:Down-Regulation; D005786:Gene Expression Regulation; D015696:Gene Products, tat / Q000502:physiology*; D015497:HIV-1 / Q000502:physiology*; D015395:Histocompatibility Antigens Class I / Q000096:biosynthesis; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D008264:Macrophages / Q000378:metabolism*; D009687:Nuclear Proteins; D012333:RNA, Messenger / Q000032:analysis; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics; D054322:tat Gene Products, Human Immunodeficiency Virus
chemical_list: D015696:Gene Products, tat; D015395:Histocompatibility Antigens Class I; D000949:Histocompatibility Antigens Class II; C083728:MHC class II transactivator protein; D009687:Nuclear Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D054322:tat Gene Products, Human Immunodeficiency Virus; D007371:Interferon-gamma; D003545:Cysteine