技术资料

SAMHD1 restricts human immunodeficiency virus type 1 (HIV-1) replication in myeloid cells and CD4(+) T cells,while Vpx can mediate SAMHD1 degradation to promote HIV-1 replication. Although the restriction mechanisms of SAMHD1 have been well-described,SAMHD1 expression and Vpx-mediated SAMHD1 degradation during chronic HIV-1 infection were poorly understood. Flow cytometric analysis was used to directly visualize ex vivo,and after in vitro SIV-Vpx treatment,SAMHD1 expression in CD4(+) T cells and monocytes. Here we report activated CD4(+) T cells without SAMHD1 expression were severely reduced,and SAMHD1 in CD4(+) T cells became susceptible to SIV-Vpx mediated degradation during chronic HIV-1 infection,which was absent from uninfected donors. These alterations were irreversible,even after long-term fully suppressive antiretroviral treatment. Although SAMHD1 expression in CD4(+) T cells and monocytes was not found to correlate with plasma viral load,Vpx-mediated SAMHD1 degradation was associated with indicators of immune activation. In vitro assays further revealed that T-cell activation and an upregulated IFN-I pathway contributed to these altered SAMHD1 properties. These findings provide insight into how immune activation during HIV-1 infection leads to irreparable aberrations in restriction factors and in subsequent viral evasion from host antiviral defenses. View Publication

Rheumatoid arthritis (RA) is closely associated with HLA-DRB1 alleles that code a five-amino acid sequence motif in positions 70-74 of the HLA-DRbeta-chain,called the shared epitope (SE). The mechanistic basis of SE-RA association is unknown. We recently found that the SE functions as an allele-specific signal-transducing ligand that activates an NO-mediated pathway in other cells. To better understand the role of the SE in the immune system,we examined its effect on T cell polarization in mice. In CD11c(+)CD8(+) dendritic cells (DCs),the SE inhibited the enzymatic activity of indoleamine 2,3 dioxygenase,a key enzyme in immune tolerance and T cell regulation,whereas in CD11c(+)CD8(-) DCs,the ligand activated robust production of IL-6. When SE-activated DCs were cocultured with CD4(+) T cells,the differentiation of Foxp3(+) T regulatory cells was suppressed,whereas Th17 cells were expanded. The polarizing effects could be seen with SE(+) synthetic peptides,but even more so when the SE was in its natural tridimensional conformation as part of HLA-DR tetrameric proteins. In vivo administration of the SE ligand resulted in a greater abundance of Th17 cells in the draining lymph nodes and increased IL-17 production by splenocytes. Thus,we conclude that the SE acts as a potent immune-stimulatory ligand that can polarize T cell differentiation toward Th17 cells,a T cell subset that was recently implicated in the pathogenesis of autoimmune diseases,including RA. View Publication

Interleukin-10 (IL-10) has potent immunoregulatory effects on the maturation and the antigen-presenting cell (APC) function of dendritic cells (DCs). The molecular basis underlying these effects in DCs,however,is ill defined. It is well established that the transcription factor NF-kappaB is a key regulator of DC development,maturation,and APC function. This study was initiated to determine the effects of IL-10 on the NF-kappaB signaling pathway in immature DCs. IL-10 pretreatment of myeloid DCs cultured from bone marrow resulted in reduced DNA binding and nuclear translocation of NF-kappaB after anti-CD40 antibody or lipopolysaccharide (LPS) stimulation. Furthermore,inhibited NF-kappaB activation was characterized by reduced degradation,phosphorylation,or both of IkappaBalpha and IkappaBepsilon but not IkappaBbeta and by reduced phosphorylation of Ser536,located in the trans-activation domain of p65. Notably,IL-10-mediated inhibition of NF-kappaB coincided with suppressed IkappaB kinase (IKK) activity in vitro. Furthermore,IL-10 blocked inducible Akt phosphorylation,and inhibitors of phosphatidylinositol 3-kinase (PI3K) effectively suppressed the activation of Akt,IKK,and NF-kappaB. These findings demonstrate that IL-10 targets IKK activation in immature DCs and that suppressing the PI3K pathway in part mediates blockade of the pathway. View Publication