Preservation of intrahepatic hepatitis C virus (HCV)-specific CD4+ T cell responses despite global loss of CD4+ T cells in HCV/HIV coinfection

BACKGROUND: Human immunodeficiency virus (HIV) coinfection and low peripheral blood CD4(+) T cell counts are associated with increased hepatitis C liver disease. METHODS: Hepatitis C virus (HCV)-specific CD4(+) T cell responses were assessed using interferon (IFN)- gamma enzyme-linked immunospot assays on peripheral blood mononuclear cells and expanded liver lymphocytes from HCV-monoinfected and HCV/HIV-coinfected subjects. Cell frequencies were determined using flow cytometry. RESULTS: HIV coinfection was associated with decreased CD4(+) T cell percentages in both peripheral blood (21% vs. 48%; P<.0001) and liver (15% vs. 36%; P<.0001) and with reduced responsiveness of peripheral CD4(+) T cells to HCV antigens compared with HCV monoinfection (22% vs. 45%; P=.021). However, intrahepatic HCV-specific responses were maintained in HCV/HIV coinfection, compared with HCV monoinfection (38% vs. 32%; P=.7). Notably, the presence of HCV-specific responses was not related to the frequency of liver CD4(+) T cells (P=.4). Circulating and liver CD4(+) T cell percentages were correlated (r=0.58; P<.0001). Circulating percentages were also inversely associated with liver fibrosis stage among HCV/HIV-coinfected subjects (P=.029). Neither hepatic CD4(+) T cell percentages nor HCV-specific IFN- gamma responses in the liver or periphery predicted stage. CONCLUSIONS: Despite decreases in peripheral blood HCV-specific CD4(+) T cell responses and intrahepatic CD4(+) T cell percentages, intrahepatic HCV-specific CD4(+) IFN- gamma responses were preserved in HCV/HIV coinfection.     

Relationship of frequency of CD4+CD25+Foxp3+ regulatory T cells with disease progression in antiretroviral-naive HIV-1 infected Chinese

Forty-five antiretroviral-naive HIV-1 infected patients and 14 healthy controls in North China were enrolled in this study. The frequency of CD4+CD25+Foxp3+ regulatory T cells (Tregs) and levels of expression of CD95, HLA-DR and CD38 in T cells were detected by flow cytometry. We found that the frequency of Tregs was higher in AIDS patients than in asymptomatic HIV-1 infected patients (P=0.004). The frequency of Tregs was significantly correlated with absolute CD4 count, viral load, CD4+CD95+ T cells and CD8+CD95+ T cells (P<0.05). The relationship between the frequency of Tregs and immune activation was not found in HIV-infected patients. We concluded that the frequency of Tregs in HIV-infected Chinese patients was significantly correlated with disease progression.     

CD8+CD38+ T cells but not HIV type 1 RNA viral load predict CD4+ T cell loss in a predominantly minority female HIV+ adolescent population

The purpose of this study was to evaluate predictors of HIV-1 disease progression in a cohort of predominantly female and minority adolescents who had acquired their HIV-1 infections through sexual risk behaviors. Subjects were identified from the REACH cohort who were not on antiretroviral therapy for at least 1 year and whose baseline CD4(+) T cells were >300 cells/mm(3). Biomedical and demographic characteristics of the subjects at the start of the study period were evaluated as predictors of CD4(+) T cell loss in univariate and multivariate models. Two-thirds of the 99 subjects meeting the selection criteria were female and 87% were black or Hispanic similar to the REACH cohort as a whole. Higher absolute CD8(+) CD38(+) T cell counts at the start of the assessment period were associated with a greater rate of loss of CD4(+) T cells. HIV-1 RNA viral load was among other potential predictors of HIV-1 disease progression that had no association with the rate of CD4(+) T cell loss in this cohort. This study extends the observed association of higher CD8(+) CD38(+) T cells numbers being predictive of HIV-1 disease progression into predominantly female, minority youth.     

Comparison of HCV-specific intrahepatic CD4+ T cells in HIV/HCV versus HCV

Persons with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) coinfection are at increased risk for progression to cirrhosis compared with persons with HCV alone, but the reasons for this are unclear. In chronic HCV, the mechanism of liver injury is presumed to be due to HCV-specific T cell destruction of hepatocytes, so it is paradoxical that immunosuppressed hosts have higher rates of fibrosis progression. We examined intrahepatic cellular immune responses to HCV antigens to determine whether there were qualitative or quantitative differences in subjects with and without HIV. Expanded, CD4-enriched, liver-infiltrating lymphocytes from 18 subjects with chronic HCV and 12 subjects with HIV/HCV were cultured in the presence of HCV core protein, nonstructural proteins NS3 and NS5, and recall antigens tetanus toxoid and Candida. Secretion of interferon gamma (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and interleukin (IL) 10 was determined using enzyme-linked immunosorbent spot assay. There were no significant differences in liver biopsy grade or stage for HIV/HCV versus HCV groups. There were no significant differences between groups in the secretion of IFN-gamma or TNF-alpha in response to HCV or recall antigens. However, there was a significant increase in IL-10 secretion in response to NS3 and NS5 in subjects with HCV compared with HIV and HCV coinfection. In conclusion, subjects with coinfection have an alteration of intrahepatic HCV-specific IL-10 cytokine response that may have implications for HCV-related disease progression.     

CD4+ CD25+调节性T细胞在免疫性血小板减少性紫癜中的调节作用

目的检测免疫性血小板减少性紫癜(ITP)患者治疗前后CD4 CD2 5调节性T细胞(Treg)的比例以及变化规律,探讨Treg在ITP发病机制中的作用。方法收集42例ITP患者治疗前、后外周血标本,分离血单个核细胞,采用流式细胞术检测ITP患者治疗前后Treg的比例以及变化。结果ITP患者治疗前Treg比例明显低于正常对照组(P<0.01),治疗后Treg比例显著升高,明显高于治疗前,但仍低于正常对照组(P<0.01);治疗有效组ITP患者Treg比例显著高于治疗无效组(P<0.01),治疗显效组显著高于良效和进步组(P<0.01),良效和进步组与治疗无效组比较差别无显著性。(P>0.05)。结论ITP患者外周血Treg比例降低,提示Treg可能参与了ITP的发病机制。     

Exploring regulatory mechanisms of CD8+ T cell contraction

A small fraction of the CD8 T cell effector population that responds to an infection progresses through the contraction phase to the memory stage. The factors regulating the extent of contraction are poorly understood. Competition for limited resources has been widely postulated to be the cause of cell death during the contraction phase, but our data show that competition does not affect contraction kinetics. We go on to demonstrate that all effector cells present at the peak of the response have the potential to become bona fide memory cells, thus excluding selection on the basis of functionality. We propose that the fate of a CD8 effector cell is predetermined before the onset of contraction and discuss possible mechanisms of regulation.     

Relationship between the frequency of HIV-specific CD8+ T cells and the level of CD38+CD8+ T cells in untreated HIV-infected individuals

CD8+ T cells are critical for effective host defenses against viral infections. Studies addressing HIV-induced immune responses in infected individuals have suggested that CD8+ T cells play an important role in controlling viral replication. However, despite an abundance of HIV-specific CD8+ T cells, HIV is not contained in many untreated patients. Active HIV replication is associated with numerous immunologic changes, the most notable and consistent of which is an increase in CD8+ T cells expressing CD38. Previous studies have demonstrated that the expression of CD38 on CD8+ T cells is associated with poor prognostic outcome in infected individuals with detectable plasma viremia; however, the relationship between the expression of CD38 and the frequency of HIV-specific CD8+ T cells is unclear. We demonstrate a correlation between levels of HIV-specific CD8+ T cells and levels of CD8+ T cells expressing CD38 in untreated patients. The distribution of HIV-specific CD8+ T cells was heavily skewed toward CD38+CD8+ T cells in patients with a high percentage of CD38+CD8+ T cells. Spontaneous/Fas-mediated apoptosis in CD38+CD8+ T cells was significantly higher in patients with high percentages of CD38+CD8+ T cells. Our data suggest that a substantial proportion of the HIV-specific CD8+ T cells present in CD38+CD8+ T cells in patients with active viral replication arise by HIV-driven aberrant immune activation and may not manifest effective cytolytic activity against infected targets due to a high degree of susceptibility to apoptosis, thus providing an explanation of why HIV is not successfully contained by CD8+ T cells in such individuals.     

HIV-1感染者CD73~+CD8~+ T细胞减少与T细胞异常活化的相关性研究

目的探讨HIV-1感染者外周血CD8~+T细胞上CD73的表达特点及其与T细胞异常活化和疾病进展的关系。方法研究入选65例HIV-1感染者和27例健康对照。通过流式细胞术检测研究对象外周血CD73~+CD8~+T细胞的频率和绝对计数,并将患者CD73~+CD8~+T细胞绝对计数和频率与其CD4~+T细胞计数、HIV-1载量以及CD38~+CD8~+T细胞频率进行相关性分析。结果与健康对照相比,HIV-1感染者外周血CD73~+CD8~+T细胞绝对计数和频率均明显降低(P均0.05);HIV-1感染者外周血CD73~+CD8~+T细胞绝对计数和频率与CD4~+T细胞计数呈正相关(r=0.555,P=0.001;r=0.342,P=0.005),与CD38~+CD8~+T细胞频率呈负相关(r=-0.384,P=0.002;r=-0.387,P=0.001);HIV-1感染者CD73~+CD8~+T细胞的绝对计数与HIV-1载量呈弱负相关(r=-0.261,P=0.035)。结论 HIV-1感染者外周血CD73~+CD8~+T细胞的减少不但与患者T细胞的活化程度呈显著负相关,而且与AIDS疾病进展相关。     

Inverse correlation between NKG2D expression on CD8+ T cells and the frequency of CD4+CD25+ regulatory T cells in patients with esophageal cancer

Although malignant diseases are known to be associated with immune suppression, detailed mechanisms of this phenomenon are still unknown. NKG2D is an activating cell surface receptor expressed by natural killer (NK) cells and CD8+ T cells, and it has been reported that NKG2D engagement is extremely important for T cell activation. In the current study, NKG2D expression on CD8+ T cells and the frequency of CD4+ CD25+ regulatory T (Treg) cells were determined by multicolor flow cytometry to investigate one of the mechanisms responsible for immune evasion in esophageal cancer patients. NKG2D expression on CD8+ T lymphocytes in esophageal cancer patients was significantly lower than in those of normal controls. NKG2D expression in T3/T4 esophageal cancer was significantly lower than that in T1/T2 esophageal cancer. CD8+ T cells from patients with lymph node metastasis expressed significantly lower NKG2D than those without lymph node metastasis. Moreover, significantly lower NKG2D expression was observed in stage III/IV cancer in comparison with stage I/II. The frequency of CD4+CD25+ Treg cells in esophageal cancer patients was significantly higher than those in normal controls. NKG2D expression on CD8+ T cells was significantly inversely correlated with the frequency of CD4+CD25+ Treg cells in esophageal cancer patients. Our data indicates that decreased NKG2D expression on CD8+ T cells is correlated with disease severity. Decreased NKG2D expression and an increase in Treg cells may be one of the key mechanisms responsible for immune evasion in esophageal cancer.     

Evaluation of cellular immune responses in subjects chronically infected with HIV type 1

The importance of host cellular immune responses, particularly CD8(+) cytotoxic T-lymphocyte (CTL) responses, in control of human immunodeficiency virus type 1 (HIV-1) infection has been demonstrated in many clinical studies. These studies, along with vaccination challenge studies in rhesus macaques, indicate the importance of cellular immune responses against HIV-1. Toward this end, we evaluated anti-HIV-1 cellular immune responses in a cohort of 54 subjects who were chronically infected with HIV-1. By validation of IFN-gamma ELISpot assay, we established a dual cut-off criterion for scoring a positive response. The magnitude and frequency of cellular immune responses were measured against HIV-1 antigens (Gag, Pol, Nef, Rev, and Tat), using synthetic peptides as antigens in ELISpot assay. Here we showed that HIV-1 Gag, Pol, and Nef were frequent targets of T cell responses in these subjects, whereas Tat and Rev were less frequently recognized. We further evaluated the possible association between host cellular immune responses and corresponding plasma viral loads in this cohort. By performing ranking correlation analysis, we demonstrated a positive correlation between host viral loads and ELISpot responses of HIV Gag and Pol in untreated subjects. For the subjects under antiviral regimens, however, we did not find any significant association. Our findings suggest that the high levels of ELISpot responses in chronically infected subjects were reflective of their persistent viral infection.     

Association between HIV Type 1-specific T cell responses and CD4+ T cell counts or CD4+:CD8+ T cell ratios in HIV Type 1 subtype B infection in China

CD4+ T cell counts and CD4+:CD8+ T cell ratios represent key determinants of HIV disease progression and infectivity. However, the relationship between the HIV-1-specific cytotoxic T lymphocyte (CTL) response and these determinants has not been elucidated for all HIV-1B and HIV-1C proteins. In the present study, virusspecific T cell responses to HIV-1B and HIV-1C proteins were analyzed with interferon gamma (IFN-gamma) enzyme- linked immunospot (ELISpot) assays using synthetic overlapping peptides corresponding to naturally occurring HIV-1B and HIV-1C consensus sequences. For Gag/Gag p24/Gag p17, a correlation between T cell responses and CD4+ T cell count in HIV-1 clade B and clade C was seen: elevated T cell response resulted in higher CD4+ T cell production. A statistically significant correlation between the Pol-specific T cell response and CD4+ T cell counts was also found in HIV-1 subtype C. For all HIV-1B and HIV-1C proteins, a correlation between the HIV-1-specific T cell response and CD4+:CD8+ T cell ratios was found for Tat and Pol proteins. CD4+ T cell counts in patients with Tat and/or Rev T cell response were higher than in patients without Tat and/or Rev T cell response. We suggest that this correlation within HIV-1B and HIV-1C Gag p24/Gag p17 responses makes the Gag p24/Gag p17 region a potential vaccine candidate and that HIV-1-specific CTL epitopes toward Pol are important in controlling HIV-1 infection; we emphasize that future vaccination strategies should include these early antigens, Tat and Rev.     

CD4+CD25+调节性T细胞在肿瘤免疫逃逸机制中的作用研究进展

CD4+CD25+调节性T细胞是一类具有免疫抑制功能的T细胞亚群,能阻止肿瘤免疫和逃避肿瘤对抗原的有效识别.Foxp3是近年来发现的一种转录因子,是CD4+CD25+调节性T细胞表面特异性标志,检测其表达可以作为判定CD4+CD25+调节性T细胞的方法.最近,大量研究已经证实CD4+CD25+调节性T细胞与各种肿瘤生存期和不良预后密切相关.目前,CD4+CD25+调节性T细胞的靶向治疗和选择性清除成为新的免疫治疗方法.     

Propagation of CD4+ T cells specific for HIV type 1 envelope gp120 from chronically HIV type 1-infected subjects

HIV-specific CD4+ T cell responses, in particular to the HIV envelope antigen gp120, are often undetectable in the peripheral blood of HIV-infected individuals. The failure to detect these cells poses a significant impediment to studying the T cell populations that are considered to be essential for controlling HIV infection and has led to speculation that these cells are entirely depleted during HIV infection. This study was designed to test whether gp120-specific CD4+ T cells exist in HIV-infected subjects and can be expanded from peripheral blood mononuclear cells by in vitro stimulation with the gp120 antigen, allowing better characterization of these cells. Although gp120-specific T cell responses were barely observed in patient cells ex vivo before antigenic stimulation, CD4+ T cells specific for gp120 were successfully propagated from the blood of each asymptomatic chronically HIV-infected subject studied. The dominant epitopes recognized by gp120-specific CD4+ T cells from these HIV-infected subjects were mapped to well-conserved sites in the C1 and C2 domains of gp120. Two CD4+ T cell lines recognizing these two regions were subsequently established. The CD4+ T cell lines proliferated and produced interferon gamma in response to the specific epitopes, and the responses were MHC class II restricted. These T cell lines also exhibited cross-reactivity with gp120 from T cell line-adapted HIV-1 strains IIIB and MN, as well as with gp120 from primary isolates SF33 (subtype B), CA1 (subtype A), and CA10 (subtype A/E). The data demonstrate that CD4+ T cells specific for gp120 are not entirely depleted from the peripheral blood of chronically HIV-infected subjects; these cells are present in low numbers but can be expanded after antigenic stimulation in vitro.     

Relationship of CD4+CD25+ regulatory T cells to immune status in HIV-infected patients

OBJECTIVE: To determine whether the frequencies of CD4+CD25+ regulatory T cells (T Reg) were related to immune status in HIV-infected patients. METHODS: Peripheral blood CD4 T-cell populations were examined for T-helper 1 cells (Th1), T-helper 2 cells (Th2), and T Reg by intracellular staining for interferon (IFN)-gamma and interleukin (IL)-4, and surface staining for CD25, respectively. The immunoregulatory properties of T Reg were assessed by measurement of the inhibitory effects of isolated CD4+CD25+ T Reg on CD4+CD25- T-cell proliferation. RESULTS: Isolated CD4+CD25+ T Reg from both HIV-infected patients and healthy controls strongly expressed CD45RO, HLA-DR, and FoxP3. HIV-infected patients with detectable plasma HIV-1 RNA showed a statistically significant increase in CD4+CD25high T Reg frequencies (P < 0.05) compared to healthy controls, with T Reg frequency inversely proportional to CD4 T-cell count (P < 0.01). However, in HIV-infected patients with undetectable plasma HIV-1 RNA, CD4+CD25high T Reg frequencies were not increased and were not related to CD4 T-cell counts. In both HIV-infected patient groups, T Reg frequency was inversely related to Th1 frequency (detectable HIV-1 RNA: P < 0.05; undetectable: P < 0.001), but positively related to Th2 frequency (detectable HIV-1 RNA: P < 0.01; undetectable: P < 0.001). T Reg activity was lower in patients with detectable plasma HIV-1 RNA than in patients with undetectable plasma HIV-1 RNA. CONCLUSIONS: Increased T Reg frequencies in peripheral blood were related to low peripheral blood CD4 T-cell counts and polarization toward Th2 immune responses in HIV-infected patients.     

CD4+CD25+ T regulatory cells control anti-islet CD8+ T cells through TGF-beta-TGF-beta receptor interactions in type 1 diabetes

Pancreatic lymph node-derived CD4+CD25+ T regulatory (Treg) cells inhibit in situ differentiation of islet-reactive CD8+ T cells into cytotoxic T lymphocytes, thereby preventing diabetes progression. The mechanism by which these Treg cells suppress anti-islet CD8+ T cells is unknown. Here, we show by using a CD8+ T cell-mediated model of type 1 diabetes that transforming growth factor (TGF)-beta-TGF-beta receptor signals are critical for CD4+CD25+ Treg cell regulation of autoreactive islet-specific cytotoxic T lymphocytes. Transgenic expression of tumor necrosis factor alpha from birth to 25 days of age in the islets of B6 mice that constitutively express CD80 on their beta cells results in accumulation of CD4+CD25+TGF-beta+ cells exclusively in the islets and pancreatic lymph nodes, which delays diabetes progression. In contrast, expression of tumor necrosis factor alpha until 28 days of age prevents islet accumulation of CD4+CD25+TGF-beta+ Treg cells, resulting in acceleration to diabetes. Furthermore, adoptive transfer experiments demonstrated that CD4+CD25+ Treg cells could not control na?ve or activated islet-reactive CD8+ T cells bearing a dominant negative TGF-beta receptor type II. Our data demonstrate that, in vivo, TGF-beta signaling in CD8+ T cells is critical for CD4+CD25+ Treg cell suppression of islet-reactive CD8+ T cells in type 1 diabetes.