慢性HIV/AIDS患者T淋巴细胞凋亡与疾病进展关系的研究

目的 探讨慢性未经抗病毒治疗的HIV/AIDS患者T淋巴细胞及各亚群凋亡与疾病进展的相关性.方法 以36例慢性未经抗病毒治疗的HIV/AIDS患者为研究对象,根据CD4细胞计数分为3组:<200个/μl组,200～350个/μl组,>350个/μl组,同时选取16例健康志愿者作对照,分离外周血单核细胞(PBMC)后,采用CD45RO及CD27标记T细胞亚群,Annexin V标记细胞凋亡,用流式细胞仪检测各项指标.其中4例患者及4例健康志愿者的PBMC在体外培养,比较分析体外培养0、3、6、12、24 h不同时间点T细胞凋亡的变化情况.结果 (1)HIV/AIDS患者CD4~+、CD8~+T细胞及各亚群上Annexin V表达百分比均显著高于健康人(P<0.05),但3组患者之间比较差异无统计学意义(P>0.05);(2)HIV/AIDS患者CD4~+、CD8~+T细胞及各业群上Annexin V表达百分比与CD4~+T细胞计数及病毒载显均无显著相关性(P>0.05);(3)随着体外细胞培养时间的延长,HIV/AIDS患者CD4~+T细胞的凋亡及死亡细胞百分比均显著高于健康人(P<0.05),并且HIV/AIDS患者CD4~+T细胞较CD8~+T细胞更易发生凋亡和死亡.结论 HIV/AIDS患者的T细胞凋亡水平显著高于健康人,并且CD4~+T细胞较CD8~+T细胞更易发生凋亡和死亡,但是T细胞凋亡水平与HIV的疾病进展程度并没有相关性.     

T-CELL AND NEURONAL APOPTOSIS IN HIV INFECTION: IMPLICATIONS FOR THERAPEUTIC INTERVENTION

The pathogenesis of HIV infection involves the selective loss of CD4 + T cells contributing to immune deficiency. Although loss of T cells leading to immune dysfunction in HIV infection is mediated in part by viral infection, there is a much larger effect on noninfected T cells undergoing apoptosis in response to activation stimuli. In the subset of patients with HIV dementia complex, neuronal injury, loss, and apoptosis are observed. Viral proteins, gp120 and Tat, exhibit proapoptotic activities when applied to T cell and neuronal cultures by direct and indirect mechanisms. The pathways leading to cell death involve the activation of one or more death receptor pathways (i.e., TNF-α, Fas, and TRAIL receptors), chemokine receptor signaling, cytokine dysregulation, caspase activation, calcium mobilization, and loss of mitochondrial membrane potential. In this review, the mechanisms involved in T-cell and neuronal apoptosis, as well as antiapoptotic pathways potentially amenable to therapeutic application, are discussed.     

Proliferating γδ T cells manifest high and spatially confined caspase-3 activity

Caspase-8 serves two paradoxical roles in T lymphocytes: it initiates apoptosis following death receptor engagement, and is also indispensible for proliferation following T-cell antigen receptor (TCR) signalling. These opposing processes appear to be controlled by both spatial and quantitative differences in caspase-8 activation. Given differences in the turnover of T-cell subsets, we compared caspase activity and susceptibility to cell death following TCR restimulation in murine CD4(+) and CD8(+) αβ T cells and γδ T cells. We observed a spectrum of caspase activity in non-dying effector T cells in which CD4(+) T cells manifested the lowest levels of active caspases whereas γδ T cells manifested the highest levels. Further analysis revealed that most of the difference in T-cell subsets was the result of high levels of active caspase-3 in non-dying effector γδ T cells. Despite this, γδ T cells manifested little spontaneous or CD3 restimulation-induced cell death as the result of confinement of active caspases to the cell membrane. By contrast, CD4(+) T cells were highly sensitive to CD3-induced cell death, associated with the appearance of active caspases in the cytoplasm and cleavage of the caspase substrates Bid and ICAD. Hence, the location and amount of active caspases distinguishes effector T-cell subsets and profoundly influences the fate of the T-cell response.     

T-cell and neuronal apoptosis in HIV infection: implications for therapeutic intervention

The pathogenesis of HIV infection involves the selective loss of CD4+ T cells contributing to immune deficiency. Although loss of T cells leading to immune dysfunction in HIV infection is mediated in part by viral infection, there is a much larger effect on noninfected T cells undergoing apoptosis in response to activation stimuli. In the subset of patients with HIV dementia complex, neuronal injury, loss, and apoptosis are observed. Viral proteins, gp120 and Tat, exhibit proapoptotic activities when applied to T cell and neuronal cultures by direct and indirect mechanisms. The pathways leading to cell death involve the activation of one or more death receptor pathways (i.e., TNF-alpha, Fas, and TRAIL receptors), chemokine receptor signaling, cytokine dysregulation, caspase activation, calcium mobilization, and loss of mitochondrial membrane potential. In this review, the mechanisms involved in T-cell and neuronal apoptosis, as well as antiapoptotic pathways potentially amenable to therapeutic application, are discussed.     

HIV病发病学新概念：肠淋巴组织主要病灶论

艾滋病 (acquiredimmunodeficiencysyndrome ,AIDS)无疑是人类空前严重的疾病 ,这不仅仅因为它是一种流行范围最广的传染病 ,而且它还是一种死亡率几乎高达 10 0 %的疾病。人免疫缺陷病毒病(humanimmunodeficiencyvirusdisease ,HIVdisease)指从HIV感染到AIDS发病整个病程 ,HIV     

Dynamics of fine T-cell subsets during HIV disease and after thymic ablation by mediastinal irradiation

The T-cell compartment is considerably more complex than just CD4 and CD8 T cells. Indeed, we can identify dozens of functionally and phenotypically distinct subsets within the peripheral blood of humans. These subsets are differentially affected in diseases which may underly some of the functional defects attributable to the disease. In HIV disease, all thymic-derived T-cell populations are gradually lost at identical rates during late-stage disease progression, while unusual, perhaps extrathymically-derived T cells expand. This expansion may reflect an attempt on the part of the immune system to compensate for the significant insult of HIV infection to the host: the abrogation of normal thymopoiesis and T-cell homeostasis.     

Progressive CD127 down‐regulation correlates with increased apoptosis of CD8 T cells during chronic HIV‐1 infection

Chronic HIV‐1 infection can induce a significant decrease in CD127 expression on CD8 T cells, but the underlying mechanisms and immunological consequences are unclear. In this study, we investigated CD127 expression on CD8 T cells from a total of 51 HIV‐1‐infected subjects and 16 healthy individuals and analyzed the association between CD127 expression and CD8 T‐cell apoptosis in these HIV‐1‐infected subjects. We found that CD127 expression on total CD8 T cells was significantly down‐regulated, which was correlated with the increased CD8 T‐cell apoptosis and disease progression of chronic HIV‐1 infection. The in vitro addition of IL‐7 efficiently rescued the spontaneous apoptosis of CD8 T cells from HIV‐1‐infected individuals. IL‐7 stimulation also transiently down‐regulated CD127 expression, whereas some of the CD127^? CD8 T cells regained CD127 expression soon after IL‐7 was retracted from the incubation medium. Thus, IL‐7 stimulation reduced apoptosis of both CD127⁺ and CD127^?CD8 T cells to some degree. These data indicate that CD127 loss might impair IL‐7 signaling and increase CD8 T‐cell apoptosis during HIV‐1 infection. This study, therefore, will extend the notion that IL‐7 could be a good candidate for immunotherapy in HIV‐1‐infected patients.     

Incomplete CD4 T cell recovery in HIV-1 infection after 12 months of highly active antiretroviral therapy is associated with ongoing increased CD4 T cell activation and turnover

To evaluate the relationship between T cell turnover, immune activation, and CD4 recovery in HIV infection, 32 antiretroviral-naive HIV-1-infected patients were studied before and after initiation of highly active antiretroviral therapy (HAART). Elevated CD4 and CD8 T cell turnover (measured by Ki67) in HIV infection decreased with HAART in blood and lymphoid tissue. Increased peripheral CD4 T cell turnover was strongly associated with immune activation even after viral suppression to less than 50 copies/mL (R = 0.8; p <.001). Increased CD4 T cell turnover correlated strongly with CD4 cell counts both before (R = -0.6; p <.001) and after (R = -0.4; p =.05) HAART. In patients with baseline CD4 cell counts of less than 350/microL, decreases in CD4 T cell turnover with HAART significantly correlated with increases in CD4 cell counts. In addition, persistently elevated levels of CD4 T cell turnover after HAART were associated with incomplete CD4 T cell recovery despite HIV RNA levels of less than 50 copies/mL. These data suggest that immune activation is central to CD4 cell depletion in HIV infection and immune reconstitution with HAART.     

Chagasic Patients Lack CD28 Expression on Many of Their Circulating T Lymphocytes

A balanced host-parasite interaction during Trypanosoma cruzi infection allows for the establishment of a chronic infection that can last for many years. T cells are a major element responsible for parasite specific and non-specific immunityduring the complex immune response of the host. However, the sub-populations of T cells involved in the response, as well as the exact mechanisms through which those cells are activated or rendered unresponsive, are not well defined. It is known thatco-stimulatory signals, some of which are mediated via CD28, are of critical importance in the triggering of appropriate T cell responses. In this study the authors performed double-labelling studies to determine the frequency of expression of CD28 byCD4⁺ and CD8⁺ T lymphocytes in the peripheral blood of patients with Chagas' disease. The results show that chagasic patients throughout the spectrum of chronic clinical forms of the infection have significantly higher meanfrequencies of CD4⁺CD28^– and CD8⁺CD28^– T cells, as compared with non-chagasic individuals. Considering the importance of CD28 for T-cell activation, the observed down-regulation or loss of CD28during infection may indicate a possible basis for observed immunoregulatory events or distinct stages of T-cell activation in this infection. Recent evidence from patients with HIV/AIDS indicates that CD28^– cell populations are morelikely to undergo apoptosis, and increased apoptosis has been observed in experimental Chagas disease.     

Decimated or missing in action: CD4+ T cells as targets and effectors in the pathogenesis of primary HIV infection

HIV infection provides a unique challenge to the immune system. CD4+ T cells are targets of infection, whereas effective anti-HIV CD4+ T-cell responses are essential for sustained viral control. There is increasing evidence of preferential depletion of certain subsets of CD4+ T cells. Studies of tissues have demonstrated preferential depletion of CD4+ T cells from gastrointestinal lymphoid tissue (GALT). Simian immunodeficiency virus infection of macaques results in extensive depletion of CD4+ memory T cells from GALT within weeks of infection. Other macaque studies suggest this rapid, profound depletion is generalized across all lymphoid tissue. Although these models provide insight into possible pathogenic processes, these results cannot be directly extrapolated to HIV infection in humans. Although there is depletion of CD4+ T cell memory cells early in HIV infection, the mechanism of this depletion appears to be related to increased cell turnover, chronicity of antigen exposure, and ineffective production of central memory CD4+ T cells rather than only direct cell depletion.     

T-cell homeostasis in HIV-1 infection

Failure of T-cell homeostasis is an important feature of HIV-1 infection. Substantial evidence indicates that T-cell homeostasis is independent of CD4⁺and CD8⁺subsets, and this may contribute to the decline of CD4⁺T cells to low levels in this disease. Moreover, failure of T-cell homeostasis appears to precede the development of clinically-defined AIDS by approximately 1.5 to 2 years and is thus an important milestone in HIV-1 disease progression. We argue that T-cell turnover and depletion of memory cells in HIV-1 infection can be viewed as the reverse of the process by which immune reconstitution occurs after stem cell transplantation, and that changes in the functional level of T-cell memory may be critical to both processes. An understanding of the relationship between T-cell memory and regeneration of lost T cells may help preserve and/or reconstitute immune system homeostasis in HIV-1-infected individuals.     

Phenotypic distribution of T cells of patients who have subsequently developed AIDS

In a previous study of asymptomatic homosexual men, we found that CD8+ T-cell levels were higher in homosexual men infected with the human immunodeficiency virus (HIV) than in uninfected homosexual men because of higher numbers of CD8+ T cells that do not express the Leu15 marker, a phenotype associated with cytotoxic function. Among infected men, there was a positive correlation between the number of CD8+Leu15- T cells and the number of CD4+ T cells. If CD4+ T-cell levels are taken as a measure of severity of HIV infection and immunodeficiency, these results suggested that higher CD8+Leu15- cells may represent a phenotypic profile associated with less severe infection or better control of infection. In the present study, we extend the analysis to include a group of men who progressed to AIDS but were studied well before the onset of AIDS, and we compare results of CD8 subset analyses with results of infected men who have not progressed to AIDS. Phenotypic subsets associated with helper, suppressor, cytotoxic, and natural killer cell function were determined by two-color immunofluorescence. The only phenotypic subset that distinguished men who progressed to AIDS from those who have not was lower numbers of CD4+ T cells in the former group. If CD8+Leu15- cell numbers (or other phenotypic subsets examined) reflect effective control of HIV infection, the relationship is not strong enough to be of prognostic or predictive value with respect to outcome of infection.     

Frequencies of FoxP3+ naive T cells are related to both viral load and naive T cell proliferation responses in HIV disease

HIV infection results in depletion and dysfunction of na?ve CD4(+) T cells. The mechanisms underlying these deficiencies are not understood. We investigated the frequencies of CD4(+) na?ve subsets in HIV disease as defined by expression of CD25 and/or FoxP3 and the relationship of these frequencies to na?ve T cell proliferation function. We observed increased proportions of CD25(+)FoxP3(+) and CD25(+)FoxP3(-) cells and decreased proportions of CD25(-)FoxP3(-) cells within the na?ve CD4(+) cell compartment from HIV-infected persons compared with findings in healthy donors. These perturbations were related to higher plasma HIV RNA levels but not with higher immune activation, as measured by the proportions of CD38(+) memory CD4(+) T cells. Na?ve T cell proliferation responses to mitogen stimulation were inversely related to the frequencies and absolute numbers of FoxP3(+) na?ve T cells. MDA, a marker of oxidative stress, and sCD14, a marker of monocyte activation and a surrogate for microbial translocation, were increased in serum samples from HIV(+) donors; however, neither marker was related to na?ve T cell function in HIV(+) donors. These observations suggest that alterations in na?ve T cell subset frequencies could contribute to na?ve T cell dysfunction in HIV disease, but these alterations are not necessarily the result of chronic immune activation.     

Into the wild: simian immunodeficiency virus (SIV) infection in natural hosts

Identifying distinctions between pathogenic HIV and simian immunodeficiency virus (SIV) infections and nonprogressive SIV in natural African primate hosts might provide key insights into HIV pathogenesis. Similar to pathogenic HIV infection in humans, natural SIV infections result in high viral replication and massive acute depletion of mucosal CD4(+) T cells. A key distinction of natural SIV infections is a rapidly developing anti-inflammatory milieu that prevents chronic activation, apoptosis and proliferation of T cells and preserves the function of other immune cell subsets, thus contributing to the integrity of the mucosal barrier and the lack of microbial translocation from the gut to the peritoneum. Immunologic features observed during natural SIV infections suggest approaches for designing new strategies for producing novel second-generation vaccines and therapeutic approaches to inhibit disease progression in HIV-infected humans.     

The CD28/HLA-DR expressions on CD4+T but not CD8+T cells are significant predictors for progression to AIDS

To investigate the changes of CD28 and HLA-DR molecules on CD4+ and CD8+ T cells during HIV infection, we classified 130 HIV-infected Koreans into four groups by the CD4 level as follows: group I (> or = 500 cells/mm3), group II (201-499 cells/mm3), group III (51-200 cells/mm3), and group IV (< or = 50 cells/mm3). In CD4+ T cells, the proportion of CD28 expression decreased significantly with the CD4 level while the proportion of HLA-DR expression increased gradually. In particular, the changes of HLA-DR expressions on CD4+ T cells were parallel to the loss of CD28 molecules from stage III to IV. However, the CD28 expression on CD8+ T cells decreased dramatically in the early stage of HIV infection, and the sum and pattern of CD28 and HLA-DR expressions on CD8+ T cells was stable after the first stage. Even though CD28 down-regulation on CD8+ T cells was very severe from the early stage of HIV infection, it might not influence the survival time of HIV-infected Koreans. The sum of the CD28+ subsets and HLA-DR subsets in each T cell was stable in all stages of disease progression. The sums of the CD28+ subsets and HLA-DR+ subsets in CD4+ T and CD8+ T cells were constant as approximately 100% and 55-60% of each T cell. These results suggested that the changes of CD28/HLA-DR expressions on CD4+ T cells were more predictable than those on CD8+ T cells in the evaluation of the disease progression during HIV-infected periods. However, we need further studies to understand why the sum of two molecules in each T cell are constant.     

IL-7Ralpha expression on CD4+ T lymphocytes decreases with HIV disease progression and inversely correlates with immune activation

Many factors can influence the rate of HIV disease progression, including those that maintain T cell homeostasis. One key homeostatic regulator is the IL‐7 receptor (IL‐7R). Previous studies have shown IL‐7R expression levels decrease in HIV infection, but effects on memory subtypes, CD4⁺ T cells, and cell function have not been explored. The present study examined the expression of the IL‐7Rα chain on naïve and memory T lymphocyte subsets of both HIV‐positive and HIV‐negative individuals from Nairobi, Kenya to assess the role of IL‐7Rα in HIV disease. Expression of IL‐7Rα was significantly reduced in all CD4⁺ and CD8⁺ T cell subsets in HIV‐positive individuals. This reduction was further enhanced in those with advanced HIV progression. Expression of IL‐7Rα was inversely correlated to immune activation, and apoptosis, and was positively correlated with CD4 count in both bivariate and multivariate analysis. Expression of IL‐7Rα did not correlate with HIV viral loads, indicating the elevated immune activation seen in HIV‐infected individuals may be impacting expression of IL‐7Rα, independent of viral loads. Signaling via the IL‐7R is essential for T cell homeostasis and maintenance of T cell memory. Reduction of this receptor may contribute to the homeostatic disruption seen in HIV.     

Differential upregulation of CD38 on different T-cell subsets may influence the ability to reconstitute CD4+ T cells under successful highly active antiretroviral therapy

BACKGROUND: Immune activation is an independent surrogate marker of CD4 T-cell depletion in HIV-infected patients. Highly active antiretroviral therapy (HAART) reduces disease progression as a direct consequence of suppressing HIV replication. Immune function does not normalize completely in most subjects on HAART, however, perhaps reflecting residual HIV replication. So far, it is unclear to what extent immune activation may influence the evolution of CD4 T-cell counts in patients on HAART. PATIENTS AND METHODS: The expression of CD38 on naive and memory subsets of CD4+ and CD8+ T cells was measured quantitatively by flow cytometry in 62 drug-naive HIV-positive and 30 HIV-uninfected controls. In addition, the evolution of this marker as well as that of some virologic parameters (plasma viremia and proviral load) and CD4 counts were assessed in 25 HIV-infected individuals who initiated HAART and were followed for 12 months. RESULTS: The mean level of CD38 on memory CD4+ and CD8+ T cells as well as in naive CD8+ cells was significantly higher in drug-naive HIV-positive subjects than in HIV-negative controls. Moreover, it was highly correlated with viral load titers. In patients on successful HAART, immune activation declined in all T-cell subsets, particularly among memory CD8+ cells. It remained elevated with respect to HIV-negative controls, however, even after 12 months of HAART. There was a significant correlation between the CD8+ T-cell activation decay and the increase of CD4+ T cells on HAART. Patients with the highest decline in CD8 activation were those showing the highest CD4 T-cell gains after 12 months of therapy. CONCLUSIONS: The level of CD38 expression on different T-cell subsets is differentially upregulated in drug-naive HIV-infected patients. After successful HAART, immune activation decreases in all T-cell subsets, although it still remains elevated in most cases after 12 months of HAART. The extent of immune deactivation under successful HAART correlates with the ability to reconstitute CD4 counts.     

Substance P primes lipoteichoic acid- and Pam3CysSerLys4-mediated activation of human mast cells by up-regulating Toll-like receptor 2

We investigated the distribution of natural killer (NK) cell subsets, their activating and inhibitory receptors, and their cytolytic potential, in primary human immunodeficiency virus (HIV)-infected (PHI) individuals at baseline and during 1 year of follow-up with or without antiretroviral therapy, and compared the results with those obtained in treatment-naïve, chronically HIV-infected (CHI) individuals, and HIV-seronegative (HN) healthy individuals. The proportion of the CD56^dim and CD56^bright subsets decreased with disease progression, whereas that of the CD56⁻ CD16⁺ subset increased. In the CD56^dim subset, the proportion of cells with natural cytotoxicity receptors (NCRs) decreased with disease progression, and their cytolytic potential was reduced. Conversely, the CD56^bright subset was characterized by a high proportion of NCR-positive, killer cell immunoglobulin-like receptor (KIR)-positive NKG2A⁺ cells in both CHI and PHI individuals, which was associated with an increase in their cytolytic potential. During the 1 year of follow-up, the PHI individuals with high viraemia levels and low CD4⁺ T-cell counts who received highly active antiretroviral therapy (HAART) had a similar proportion of NK subsets to CHI individuals, while patients with low viraemia levels and high CD4⁺ T-cell counts who remained untreated had values similar to those of the HN individuals. Our results indicate a marked perturbation of the NK cell compartment during HIV-1 infection that is multifaceted, starts early and is progressive, primarily involves the CD56^bright subset, and is partially corrected by effective HAART.     

Phenotypical and functional profiles of natural killer cells exhibiting matrix metalloproteinase-mediated CD16 cleavage after anti-HIV antibody-dependent activation

Natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) has been linked to protection from HIV infection and slower progression towards AIDS. However, antibody-dependent activation of NK cells results in phenotypical alterations similar to those observed on NK cells from individuals with progressive HIV infection. Activation of NK cells induces matrix metalloproteinase (MMP)-mediated cleavage of cell surface CD16. In the present study we assessed the phenotype and functional profile of NK cells exhibiting post-activation MMP-mediated CD16 cleavage. We found that NK cells achieving the highest levels of activation during stimulation exhibit the most profound decreases in CD16 expression. Further, we observed that educated KIR3DL1⁺ NK cells from human leucocyte antigen (HLA)-Bw4-carrying donors exhibit larger decreases in CD16 expression post-activation than the KIR3DL1⁻ NK cell subset containing cells educated via other inhibitory receptor/ligand combinations and non-educated NK cells. Lastly, we assessed the ex-vivo expression of CD16 on educated KIR3DL1⁺ NK cells and the KIR3DL1⁻ NK cell subset from HLA-Bw4-carrying HIV-uninfected and HIV-infected donors. Suggestive of in-vivo activation of KIR3DL1⁺ NK cells during HIV infection, CD16 expression was higher on KIR3DL1⁺ than KIR3DL1⁻ NK cells in uninfected donors but similar on both subsets in HIV-infected donors. These results are discussed in the context of how they may assist with understanding HIV disease progression and the design of immunotherapies that utilize antibody-dependent NK cell responses.     

CD4+ t-cell depletion in hiv infection: Killed by friendly fire?

Recent studies have emphasized the role of a chronic, generalized activation of the immune system as a prominent cause of CD4+ T-cell depletion in HIV-infected patients. The HIV-induced immune activation is a strong predictor of disease progression in humans, and lack of immune activation is a key feature of nonpathogenic simian immunodeficiency virus (SIV) infection of natural hosts. The mechanisms by which immune activation induces CD4+ T-cell depletion are still incompletely understood, but likely involve changes in the complex dynamics of the naive, memory, and effector subsets of T cells. A better understanding of how HIV-induced immune activation leads to CD4+ T-cell depletion may provide new targets for immune-based interventions that could be used, in addition to standard antiretroviral therapy, to slow disease progression in HIV-infected individuals.