RESUMO
HIV Nef-mediated up-regulation of invariant chain (Ii chain, also CD74) is presumed to play an active role in HIV immunopathogenesis. However, this has not been definitely ascertained. In order to help elucidate this hypothesis, Ii chain, CD4, HLA-DR and HLA-ABC expression was analyzed ex vivo in monocyte-derived macrophages (MDMs) from HIV(+) subjects. Viral load, CD4(+) T cell count and immune activation were also determined in enrolled subjects. Correlations between these parameters and the modulation of cell surface molecules in infected cells were studied. Ii chain expression was found to be up-regulated in infected MDMs derived from all patients but one (median fold up-regulation 2.47±1.82 (range 0.87-7.36)). Moreover, the magnitude of Ii chain up-regulation significantly correlated with higher activation of B and CD4(+) T cells (studied by HLA-DR and CD38 expression). On the other hand, lower HLA-ABC (i.e. stronger down-regulation) in infected MDMs was associated with higher CD4 counts. No correlation was observed between the magnitude of Ii chain up-regulation and the other Nef functions studied here. This is the first study reporting that Ii chain up-regulation occurs on naturally infected antigen presenting cells obtained directly from HIV(+) subjects. Moreover, it is also shown that the magnitude of this up-regulation correlates with immune activation. This allows postulating an alternative hypothesis regarding the contribution of Ii chain up-regulation to HIV-mediated immune damage.
Assuntos
Síndrome da Imunodeficiência Adquirida/imunologia , Síndrome da Imunodeficiência Adquirida/patologia , Antígenos de Diferenciação de Linfócitos B/biossíntese , HIV/imunologia , HIV/patogenicidade , Antígenos de Histocompatibilidade Classe II/biossíntese , ADP-Ribosil Ciclase 1/análise , Síndrome da Imunodeficiência Adquirida/virologia , Linfócitos B/química , Linfócitos B/imunologia , Contagem de Linfócito CD4 , Linfócitos T CD4-Positivos/química , Linfócitos T CD4-Positivos/imunologia , Células Cultivadas , Perfilação da Expressão Gênica , Antígenos HLA-DR/análise , Humanos , Macrófagos/imunologia , Macrófagos/virologia , Glicoproteínas de Membrana/análise , Regulação para Cima , Carga ViralRESUMO
HIV-1 Nef protein plays a major role in viral immunopathogenesis, modulating surface expression of several immune receptors, altering signal transduction pathways, and enhancing viral infectivity, among other activities. Nef also exhibits great intersubtype diversity, but most studies have been focused only on Nef proteins from subtype B. Thus, little is known about the functional capacities of nonsubtype B Nef proteins in host cells. Here, we investigated cell surface regulation of MHC-I, MHC-II, the MHC-II-associated chaperone invariant chain (Ii), CD4, CD3, and CD28 in cells transfected or infected with five different Nef alleles including one HIV-1 subtype C and F allele. No significant difference among the Nef proteins regarding CD3, CD28, and MHC-II downregulation was observed. The NefC showed a slightly, yet significant, diminished capacity to downregulate MHC-I in all cells, as well as to downregulate CD4 in Jurkat cells and PBMCs. Strikingly, the two alleles from NefC and NefF were unable to upregulate the Ii chain both in transfected and infected cells. Moreover, the internalization rate of the surface Ii chain was only slightly affected by NefC and NefF, whereas it was drastically reduced by NefB. Nef domains known to be involved in Ii chain upregulation were conserved among the five alleles analyzed here. In summary, we identified two primary HIV-1 NefC and NefF alleles that are selectively impaired for Ii upregulation and that may help to elucidate the mechanism of this Nef function in the future. It will be important to determine whether the observed differences are HIV-1 subtype dependent and influence viral immunopathogenesis.
Assuntos
Antígenos de Diferenciação de Linfócitos B/biossíntese , HIV-1/fisiologia , Antígenos de Histocompatibilidade Classe II/biossíntese , Receptores Imunológicos/biossíntese , Produtos do Gene nef do Vírus da Imunodeficiência Humana/fisiologia , Sequência de Aminoácidos , Células Cultivadas , Regulação da Expressão Gênica , Genótipo , HIV-1/classificação , HIV-1/imunologia , Células HeLa , Humanos , Células Jurkat , Leucócitos Mononucleares/imunologia , Leucócitos Mononucleares/virologia , Dados de Sequência Molecular , Filogenia , Alinhamento de Sequência , Produtos do Gene nef do Vírus da Imunodeficiência Humana/genéticaRESUMO
Interleukin-4 (IL-4) is known to be involved in both the in vivo IgE response and the elevated B cell IgE Fc receptor (Fc epsilon R11) expression seen after a parasite infection. To further analyze the relationship between Fc epsilon R11 expression and IL-4 production, purified B cells from uninfected, Nippostrongylus brasiliensis (Nbr) infected and from goat anti-mouse IgD (GaM delta) injected mice were isolated on various days post-treatment. The Fc episolon R11 levels on purified B cells from normal mice decreased after an overnight culture in media alone and addition of IL-4 to these cultures resulted in a 4 to 13-fold enhancement of Fc epsilon R11 levels. In contrast, the Fc epsilon R11 levels on B cells from Nbr infected mice were elevated after an overnight culture in media alone and addition of IL-4 did not further enhance the already upregulated Fc epsilon R11 levels. Overnight culture of purified B cell blasts from Nbr infected mice in the presence of an anti-IL-4 monoclonal antibody (11B11) caused the elevated Fc epsilon R11 levels to return to levels seen in normal mice, without affecting the Fc epsilon R11 levels on purified Go or B cell blasts from uninfected mice or Go B cells from Nbr infected mice. 11B11 also inhibited the elevated Fc epsilon R11 levels on highly purified B cells obtained by FACS sorting the non-adherent spleen cell population for class II+ cells. In contrast to Nbr infection, the Fc epsilon R11 levels on B cells were downregulated in the GaM delta injected mice. However, analogous to the Nbr system, the Fc epsilon R11 levels were unresponsive to the addition of exogenous IL-4. This study indicates that IL-4 production is seen in T depleted splenocytes and that this alternate source of IL-4 serves to maintain the elevated Fc epsilon R11 levels on B cells.