ABSTRACT
Objective:To analyze the expression of human leukocyte antigen G (HLA-G) in human T-cell leukemia virus type 1 (HTLV-1)-positive T cells, and to investigate its role in the occurrence and development of HTLV-1 infection.Methods:The expression of HLA-G in HTLV-1-positive T cell lines (MT2 and MT4) was detected by Western blot and real-time PCR. HLA-G gene in MT2 and MT4 cells was knocked down by siRNA, and the effects of HLA-G on the expression of HTLV-1 Tax and P19 at mRNA and protein levels were detected by Western blot and real-time PCR. Moreover, the changes in cytokine expression in MT2 and MT4 cells were monitored at RNA level after HLA-G gene silencing. The proliferation ability of MT2 and MT4 cells was analyzed by CCK8. Signal transducer and activator of transcription 3 (STAT3) pathway-related proteins were detected by Western blot.Results:Compared with HTLV-1-negative T cells (Jurkat and MOLT4), the expression of HLA-G increased significantly in MT2 and MT4 cells. After knocking down the HLA-G gene with siRNA in MT2 and MT4 cells, the expression of HTLV-1 Tax and P19 at mRNA and protein levels was decreased, and the expression of antiviral cytokines IFN-γ and TNF-α was increased. The proliferation of MT2 and MT4 cells and STAT3 phosphorylation in these cells were decreased.Conclusions:HTLV-1 could induce T cells to overexpress the immune tolerance molecule HLA-G. Silencing HLA-G gene in HTLV-1-positive T cells could promote the production of antiviral cytokines and reduce IL-6 expression and STAT3 phosphorylation, thereby effectively inhibiting the replication of HTLV-1.
ABSTRACT
Objective To investigate whether cyclic GMP-AMP synthase ( cGAS ) , a cytosolic DNA sensor, could recognize the reverse transcription intermediate and induce the subsequent signaling path-way during the infection of human T cell leukemia virus type 1 ( HTLV-1 ) . Methods Biotin-labeled ssDNA90, a reverse transcription intermediate of HTLV-1, was transfected into HeLa cells and the interac-tion between it and cGAS was detected by co-immunoprecipitation experiments. HeLa cells were co-cultured with HTLV-1-positive MT2 cells and the interaction between cGAS and stimulator of interferon genes ( STING) was analyzed by co-immunoprecipitation experiments. The expression of STING in HeLa cells was silenced by siRNA. cGAS was transfected into the HeLa cells 24 h after the silencing and after 24 h, these cells were co-cultured with MT2 cells for another 24 h. Real-time PCR assay was used to measure the ex-pression of IFN-β, RANTES ( regulated upon activation, normal T-cell expressed, and secreted) , TNF-α, HTLV-1 protein Tax, p19 and HBZ. Immunoblot assay was performed to evaluate the phosphorylation of IRF3 and p65 in HeLa cells. Results cGAS interacted with ssDNA90. cGAS interacted with STING in the cytoplasm. In STING-silenced HeLa cells, cGAS transfection had no influence on the expression of IFN-β, RANTES , TNF-α, Tax , p19 or HBZ , nor did it affect the phosphorylation of IRF3 or p65 . Conclusions cGAS interacted with HTLV-1 RTI ssDNA90 and activated STING-dependent innate immune responses.
ABSTRACT
Objective To investigate the influence of early growth response gene-1 (EGR1) on the autophagy of host cells following infection with human T cell leukemia virus type 1 (HTLV-1).MethodsA HTLV-1-positive cell line MT2 was co-cultured with HeLa cells for 24 h to construct the virus early infection model.Immunoblotting assay was used to detect the expression of HTLV-1 core protein p19 and EGR1.Luciferase reporter gene analysis was used to detect the transcriptional activity of 5′-regulatory sequence of EGR1 at different time points after co-culturing.An effective small interfering RNA (siRNA) targeting EGR1 was screened out and transfected into HeLa cells by Lipofectamine 2000.Then the transfected HeLa cells were co-cultured with the HTLV-1-positive cell line MT2 for 24 h.Immunoblotting assay was used to detect HTLV-1 core protein p19, EGR1 and autophagy-related protein LC3.Real-time PCR was performed to detect viral load.Autophagosome was analyzed by immunofluorescence after co-culturing.Results The expression of EGR1 and the transcriptional activity of pEGR1-luc gradually increased after co-culturing HeLa cells with MT2 cells for 8 h (P<0.01).The expression of EGR1 was positively correlated with host cell autophagy following HTLV-1 infection.The effective siRNA for silencing the expression of EGR1 was obtained and named as siE2.The viral load, the expression of HTLV-1 core protein p19 and the proportion of LC3B/LC3A in the co-culture model were markedly down-regulated by RNA interference with siE2, which was concomitant with a persistent decrease of intracellular autophagosome (P<0.01).Conclusion EGR1 is associated with host cell autophagy and viral replication in HTLV-1 infection.
ABSTRACT
Objective To investigate the function and the possible mechanism of cyclic GMP-AMP synthase (cGAS), a DNA sensor, in HeLa cells during human T cell leukemia virus type 1 (HTLV-1) in-fection.Methods HeLa cells were co-cultured with MT2 cells (HTLV-1-positive T cells) and then detec-ted by immunoblot assay to analyze the changes in the expression of cGAS .A hemagglutinin ( HA)-tagged cGAS plasmid was constructed and transfected into HeLa cells .Twenty-four hours after transfection , these cells were co-cultured with MT2 cells for another 24 hours.Immunoblot assay was used to detect the expres-sion of HTLV-1 proteins Tax and p19.Real-time PCR was performed to measure the expression of HTLV-1 Tax, p19, Env, HBZ and px at mRNA level .Immunoblot assay was also used to analyze the phosphorylation of interferon regulatory factor 3 (IRF3) and p65.Expression of interferon (IFN)-β, IFN-gamma-inducible protein 10 ( IP-10 ) , RANTES ( regulated on activation , normal T cell expressed and secreted ) and tumor necrosis factor (TNF)-αwas detected by real-time PCR assay.Results Expression of cGAS was enhanced in HeLa cells after co-cultured with MT2 cells.Compared with control cells , the HeLa cells that were trans-fected with cGAS plasmid showed lower levels of Tax and p 19 proteins, suppressed expression of HTLV-1 Tax, p19, Env, HBZ and px at mRNA level , enhanced phosphorylation of IRF 3 and p65, and higher levels of IFN-β, IP-10, RANTES and TNF-αafter co-cultured with MT2 cells.Conclusion cGAS might promote the innate immune response and inhibit HTLV-1 replication in HTLV-1-infected HeLa cells .
ABSTRACT
Objective To explore the expression of early growth response gene-1 (EGR-1) in T cells that were positive for Tax protein of human T-cell leukemia virus type 1 (HTLV-1) and its possible reg-ulatory mechanism .Methods A series of expression structures carrying the regulatory elements of EGR-1 in different length and luciferase reporter genes were constructed .TaxP cells were transfected with the con-structs containing reporter genes and cultured with 5μmol/L of NF-κB inhibitor BAY 11-7082 or equal vol-ume of DMSO.After cultured for 24 hours the cells were collected to test the luciferase activity .BAY 11-7082 or equal volume of DMSO was added into the supernatant of TaxP cell culture to test the expression of EGR-1 protein by Western blot after 24 hours of culture .Tax and its mutants M22 and M47 were transfected into 293 T cells respectively to test the expression of EGR-1 protein by Western blot after 24 hours of culture . Results The expression structures carrying the regulatory elements of EGR-1 in different length and their mutants followed by luciferase reporter genes were successfully constructed .The luciferase activity in the cells transfected with the constructs containing the elements E 1 and E2 were higher than that transfected with E3, DelE and MutE, but the reporter gene expressions were decreased with the interference of BAY 11-7082 (P<0.01).However, there were no significant changes with the luciferase activity in the cells transfected by elements E3, DelE and MutE.Western blot analysis indicated that the expression of EGR-1 protein was significantly decreased with the interference of BAY 10-7082 .The expression of EGR-1 protein in M22 mu-tants-transfected 293 T cells were decreased significantly in comparison with those by wild type tax-and M47-transfected cells .Conclusion NF-κB was the key nuclear factor in regulating the expression of EGR-1 pro-tein in Tax-positive T cells .
ABSTRACT
Objective To explore the regulatory effects of HTLV-1 ( human T-cell leukemia virus type 1 ) Tax protein on the expression of HMGB 1 ( high mobility group box 1 ) gene in T cells .Methods Total RNA and protein were extracted from Tax +-T cells ( TaxP ) , Tax--T cells ( TaxN ) and Jurkat cells which were stably transfected with pCMV-Tax and pCMV-Neo, respectively.Then, the expression levels of HMGB1 mRNA and protein in different CD 4+T cells were analyzed by real-time PCR and Western blot (WB).By using liposome-mediated method, pGL3-HMGB1-luc reporter genes and pGL3-neo-luc were tran-siently transfected into TaxP and TaxN cells and the basal transcriptional activity was observed in different T cells.Additionally, pCMV-Tax and pGL3-HMGB1-luc reporter genes were also co-transfected into Jurkat cells and the regulatory effects of Tax protein on HMGB 1 gene was detected .The chromatin immunoprecipi-tation (ChIP) assay was used to identify HMGB1 genomic sites directly targeted by Tax .Results The ex-pression levels of HMGB1 mRNA and protein in Tax+-T cells ( TaxP) were higher than those in Tax--T cells (TaxN).The transcription regulation trends for HMGB1 gene in TaxN and TaxP cells were similar but not identical in diverse T cells.pHLuc3 (containing -504-+83 HMGB1) showed the highest transcriptional ac-tivity of HMGB1 gene in both TaxP and TaxN cells , but HMGB1 transcriptional activity of pHLuc 6 in TaxP cells was significantly stronger than that in TaxN cells .Luciferase assays also showed that Tax protein promo-ted the transcription of HMGB1 gene in a dose-dependent manner .The ChIP assay further confirmed that Tax protein enriched at the HMGB1 region of -1163--1043.Conclusion The region of nt -504--383 is essen-tial for the basal promoter activity of -1163-+83 HMGB1 gene originated from pHLuc 6 reporter plasmid , and Tax protein enriched probably at the HMGB 1 site of -1163--1043 enhances HMGB1 transcription.
ABSTRACT
Objective To investigate the influence of extracellular high mobility group box 1 (HMGB1) on viral replication in HTLV-1 infected T cells.Methods HMGB1 in culture supernatants of adult T-cell leukemia virus 1 (HTLV-1) virus-negative cell:Jurkat,MOLT4 cells and HTLV-1 virus-positive cells:MT2,MT4,was detected by ELISA;The HTLV-1 long terminal repeat reporter gene (pHTLV-1-LTR-luc) was transfected into MT2 cells by Tfx-50-mediated transfection,and 0.25,0.50,0.75 μg/ml of HMGB1 polyclonal antibody(HMGB1 PcAb) and its isotype control rabbit IgG antibodies,0.03,0.1,0.3 μg/ml rhHMGB1 and its control PBS,were added into culture supernatant respectively,then luciferase activity was detected after 48 h;Similarly,0.25 μg/ml HMGB1 PcAb and the isotype control antibody,0.3 μg/ml rhH-MGB1 and the control PBS were added to the culture supernatant of MT2 cell,the viral gene,pol1,pol2,gag,env,etc,were performed by real-time PCR.Results Culture supernatant HMGB1 levels has no significant difference between HTLV-1 positive cells MT2 and MT4 and the other two virus-negative T cell lines;Compared with isotype control antibody group,the culture supernatant,to which is added 0.25 μg/ml HMGB1 PcAb,can significantly inhibit the HTLV-1-LTR transcriptional activity and suppress the expressions of the viral gene pol1,pol2,gag,env.Compared with the control PBS,0.3 μg/ml rhHMGB1 significantly promotes the transcriptional activity of the HTLV-1-LTR and the expressions of the viral gene pol1,pol2,gag,env.Conclusion The extracellular HMGB1 can promote viral replication of HTLV-1 infected T cells.
ABSTRACT
Objective To explore the effect of HTLV-1 (human T-cell leukemia virus type 1 ) Tax protein on the DcR3 gene expression in T cells.Methods The construction of DcR3 (-1010 bp to +114 bp) luciferase reporter gene; MT2,TaxP,and Jurkat E6-1 cells were transfected with DcR3 luciferase reporter gene (pGL3-DcR3-1uc) using liposomes according to the manufacturer's instructions.For the control group,pGL3-basic replaced it respectively.At 48 h after incubation,luciferase activity was measured with a luciferase assay system; Jurkat cells were transfected with pCMV-Tax-Bam using liposomes,and total RNA was extracted from the cells at 48 h after incubation.Reverse transcription was performed using standard protocols.Then real time PCR with primers DcR3 and 3-actin was conducted;The expression of DcR3 protein was detected by flow cytometry in MT2,TaxP,and Jurkat cells.Results The construction of DcR3 luciferase reporter gene is identified correctly; The detection of luciferase activity showed that the luciferase activity of experimental group in MT2 cells was increased by (32.07±12.43)-fold,of which in TaxP cells was increased by ( 13.27±4.04)-fold,and the luciferase activity of experimental group in Jurkat cells was increased by ( 1.26±0.49 ) -fold.And there is statistic significance about the relative luciferase activity of experimental group in MT2 cells and TaxP cells compared to the relative lueiferase activity of experimental group in Jurkat cells respectively ( P＜0.01 ) ; The result of real-time PCR showed that the level of DcR3 mRNA in the experimental group was higher compared with the control group(P＜0.05) ; The result of FCM shows the expression of DcR3 protein in MT2,TaxP cells is higher than that in Jurkat cells( P＜0.05 ).Conclusion Tax protein can promote the expression of DcR3 gene in T cells.