Poor functional immune recovery in aged HIV-1-infected patients following successfully treatment with antiretroviral therapy

Aging is now a well-recognized characteristic of the HIV-infected population and both AIDS and aging are characterized by a deficiency of the T-cell compartment. The objective of the present study was to evaluate the impact of antiretroviral (ARV) therapy in recovering functional response of T cells to both HIV-1-specific ENV peptides (ENV) and tetanus toxoid (TT), in young and aged AIDS patients who responded to ARV therapy by controlling virus replication and elevating CD4⁺ T cell counts. Here, we observed that proliferative response of T-cells to either HIV-1-specific Env peptides or tetanus toxoid (TT) was significantly lower in older antiretroviral (ARV)-treated patients. With regard to cytokine profile, lower levels of IFN-γ, IL-17 and IL-21, associated with elevated IL-10 release, were produced by Env- or TT-stimulated T-cells from older patients. The IL-10 neutralization by anti-IL-10 mAb did not elevate IFN-γ and IL-21 release in older patients. Finally, even after a booster dose of TT, reduced anti-TT IgG titers were quantified in older AIDS patients and it was related to both lower IL-21 and IFN-γ production and reduced frequency of central memory T-cells. Our results reveal that ARV therapy, despite the adequate recovery of CD4⁺ T cell counts and suppression of viremia, was less efficient in recovering adequate immune response in older AIDS patients.     

Interleukin-21 and cellular activation concurrently induce potent cytotoxic function and promote antiviral activity in human CD8 T cells

Infection with human immunodeficiency virus (HIV)-1 induces a progressive deterioration of the immune system that ultimately leads to acquired immune deficiency syndrome (AIDS). Murine models indicate that the common γ-chain (γ(c))-sharing cytokine interleukin (IL)-21 and its receptor (IL-21R) play a crucial role in maintaining polyfunctional T cell responses during chronic viral infections. Therefore, we analyzed the ability of this cytokine to modulate the properties of human CD8 T cells in comparison with other γ(c)-sharing cytokines (IL-2, IL-7, and IL-15). CD8 T cells from healthy volunteers were stimulated in vitro via T cell receptor signals to mimic the heightened status of immune activation of HIV-infected patients. The administration of IL-21 upregulated cytotoxic effector function and the expression of the costimulatory molecule CD28. Notably, this outcome was not accompanied by increased cellular proliferation or activation. Moreover, IL-21 promoted antiviral activity while not inducing HIV-1 replication in vitro. Thus, IL-21 may be a favorable molecule for immunotherapy and a suitable vaccine adjuvant in HIV-infected individuals.     

Determinants of HIV-specific CD8 T-cell responses in HIV-infected pediatric patients and enhancement of HIV-gag-specific responses with exogenous IL-15

Cellular immune responses play a central role in controlling HIV-1 infection. HIV-specific IFN-gamma production by CD8 T cells was evaluated in 17 HLA-A2+ HIV-infected pediatric patients (age range 1 month to 16 years) in an ELISPOT assay. Most patients (15/17) exhibited responses to HIV-gag, followed by responses to envelope gp120, gp41, and V3 loop. Only 7 patients responded to all four antigenic peptides. Treatment-related immune reconstitution of CD4 T cells was associated with increase in gag-specific responses, but these declined with prolonged viral suppression. Exogenous IL-15 resulted in augmentation of HIV-gag-specific response in 71% of patients, while IL-2 and IL-7 had variable effects, augmenting responses in 25% patients. Thus, HIV-specific CD8 T-cell responses are dependent on both CD4 T-cell help and antigenic stimulation. The cytokine IL-15 may be a useful modality as adjunctive therapy to augment HIV-specific memory CD8 T cells.     

Decreased CD127 expression on T Cells in HIV-1-infected adults receiving antiretroviral therapy with or without intermittent IL-2 therapy

BACKGROUND: The interleukin-7 (IL-7)/IL-7 receptor alpha (IL-7Ralpha) system is an important regulator of T-cell homeostasis. We evaluated the IL-7/IL-7Ralpha system in a large cohort of HIV-infected patients, including a subset treated with intermittent IL-2. METHODS: IL-7 serum levels and CD127 (IL-7Ralpha) expression on T cells were evaluated in a cross-sectional study of 36 healthy volunteers, 151 HIV-infected patients, and 83 HIV-infected patients who had received IL-2 therapy. Multivariate regression models were used to determine predictors of CD127 expression. RESULTS: HIV-infected patients had higher IL-7 levels compared with healthy volunteers (P = 0.022) and IL-2-treated patients (P = 0.012). CD127 expression was significantly lower on CD4 and CD8 T cells of HIV-infected patients compared with healthy volunteers (P = 0.008 and P < 0.001, respectively), and CD127 median fluorescence intensity was lowest on CD4 T cells in IL-2-treated patients (P < 0.001 compared with HIV-infected patients). The proportion of naive and effector memory/effector T cells were significant predictors of CD127 expression on T cells. IL-2 immunotherapy led to the expansion of a CD25/CD127-low subset of CD4 T cells. CONCLUSIONS: CD127 expression on T cells remains low in HIV-infected patients despite antiretroviral therapy, reflecting persistent aberration in the subset composition of the T-cell pool.     

CD127 expression and regulation are altered in the memory CD8 T cells of HIV-infected patients--reversal by highly active anti-retroviral therapy (HAART)

HIV infection activates abnormally the immune system and the chronic phase is accompanied by marked alterations in the CD8 compartment. The expression of CD127 (IL-7R alpha chain) by memory CD8 T lymphocytes in HIV-infected patients is analysed and reported. The memory CD8 T cell subset was characterized by expression of CD45RA and CD27 markers, and CD127 cell surface expression was measured ex vivo by four-colour flow cytometry. HIV infection was associated with a fall in the proportion of CD127(+) cells among memory CD8 lymphocytes that resulted in a higher CD127(-) CD45RA(-)CD27(+) CD8 T cell count in HIV-infected patients. Diminished CD127 cell surface expression [mean fluorescence intensity (MFI)] by positive cells was also observed in this subset. The data suggest that these defects were reversed by highly active anti-retroviral therapy (HAART). The regulation of CD127 expression was also studied in vitro. Down-regulation of CD127 by interleukin (IL)-7 was observed in memory CD8 lymphocytes from healthy donors and HAART patients. Expression of CD127 by memory CD8 lymphocytes cultured in the absence of IL-7 confirmed that IL-7R regulation is altered in viraemic patients. Under the same experimental conditions, memory CD8 lymphocytes from HAART patients were shown to express CD127 at levels comparable to cells from healthy individuals. Altered CD127 cell surface expression and defective CD127 regulation in the memory CD8 T lymphocytes of HIV-infected patients are potential mechanisms by which these cells may be impeded in their physiological response to endogenous IL-7 stimulatory signals. Our data suggest that these defects are reversed during the immune reconstitution that follows HAART.     

The role of cytokines in T-cell memory in health and disease

Upon stimulation with their cognate antigen, naive T cells undergo proliferation and differentiation into effector cells, followed by apoptosis or survival as precursors of long-lived memory cells. These phases of a T-cell response and the ensuing maintenance of memory T cells are shaped by cytokines, most notably interleukin-2 (IL-2), IL-7, and IL-15 that share the common γ chain (γ_c) cytokine receptor. Steady-state production of IL-7 and IL-15 is necessary for background proliferation and homeostatic survival of CD4⁺ and CD8⁺ memory T cells. During immune responses, augmented levels of IL-2, IL-15, IL-21, IL-12, IL-18, and type-I interferons determine the memory potential of antigen-specific effector CD8⁺ cells, while increased IL-2 and IL-15 cause bystander proliferation of heterologous CD4⁺ and CD8⁺ memory T cells. Limiting availability of γ_c cytokines, reduction in regulatory T cells or IL-10, and persistence of inflammation or cognate antigen can result in memory T cells, which fail to become cytokine-dependent long-lived cells. Conversely, increased IL-7 and IL-15 can expand memory T cells, including pathogenic tissue-resident memory T cells, as seen in lymphopenia and certain chronic-inflammatory disorders and malignancies. These abovementioned factors impact immunotherapy and vaccines directed at memory T cells in cancer and chronic infection.     

白细胞介素-21的免疫调节机制

白细胞介素-21（IL-21）是由激活的CD4^＋T细胞产生的细胞因子.IL-21受体（IL-21R）与IL-2R、IL-4R、IL-7R、ID9R、IL-15R等受体享有共同的受体γ链,广泛表达于免疫细胞上,介导各种免疫效应.IL-21能够增强免疫效应细胞增殖、抗原诱导的激活、克隆扩增,IFN-γ产生,以及NK细胞和T细胞的细胞毒效应.IL-21在被发现之初是作为抗肿瘤因子,最近发现IL-21与自身免疫和炎症性疾病具有相关性.     

Cytokine profile of a long-term pediatric HIV survivor with hyper-IgE syndrome and a normal CD4 T-cell count.

BACKGROUND: An elevated IgE level and increased production of T(H2) cytokines are factors associated with poor prognosis in HIV infection. We report a pediatric long-term survivor of vertically acquired HIV infection with a normal CD4 count and a low viral burden despite the lack of antiretroviral therapy and a phenotype resembling hyper-IgE syndrome. OBJECTIVE: We sought to characterize the patient's T(H1) versus T(H2) cytokine profile and anti-HIV-specific immune responses. METHODS: Supernatants collected from cultures of peripheral blood T cells stimulated with phorbol myristate acetate plus ionomycin were assayed for T(H1) and T(H2) cytokines by means of ELISA. Specific IgE antibodies were determined by immunoblot. HIV-specific cytotoxic T-lymphocyte responses were measured from cell lysis by fresh T cells of autologous B-lymphoblastoid cells expressing recombinant HIV proteins. RESULTS: Patient CD4(+) T cells secreted significantly more T(H2) cytokines, IL-4 (P <.003) and IL-5 (P <.03), than HIV-infected and seronegative control cells. No difference was noted in T(H1) cytokine production. IgE specific for HIV gp160, p24, p17, and p66 proteins and Aspergillus fumigatus was detected in patient sera. Despite predominance of T(H2) cytokines, HIV-specific cytotoxic T-lymphocyte activity was vigorous. CONCLUSIONS: The patient demonstrated predominantly T(H2) cytokine production in vitro. Unlike other patients with HIV who have hyper-IgE and increased T(H2) cytokine production, our patient has maintained HIV-specific immune responses, a low viral load, and a normal CD4 count without antiretroviral therapy. These findings support a diagnosis of primary hyper-IgE syndrome. Presence of anti-HIV-specific IgE may represent a protective mechanism against HIV replication in our patient.     

Effects of cryopreservation on lymphocyte immunophenotype and function

Cryopreservation of isolated peripheral blood mononuclear cells (PBMCs) for phenotypic and functional analyses is considered a standard procedure in order to minimize operator-dependent inter-assay variability and to optimize the use of available resources. However, only few and somewhat conflicting data are presently available on the effects of cryopreservation on PBMCs, especially in samples from HIV-infected patients in which assessment of lymphocyte phenotype and function is of the outmost importance. In this study, we compared fresh versus frozen/thawed (F/T) samples isolated from 19 healthy individuals and 21 HIV-infected patients, showing that cryopreservation induces: (i) a profound decrease of CD62L expression, with a consequent significant decline of the calculated proportions of "na?ve" (CD45RA+CD62L+) and "central memory" (CD45RO+CD62L+) T cells; (ii) an increase of the calculated proportions of "effector" CD8+ T cells (CD45RA+CD62L- and CD45RO+CD62L-) in the healthy subjects, while no changes were observed in the HIV-infected group; (iii) a significant decline of CC chemokine receptor 5 (CCR5) expression; (iv) a loss of proliferative responses to some HIV antigens (i.e. p24) and recall antigens [cytomegalovirus (CMV) and Influenza] in HIV-infected patients. We thus conclude that cryopreservation induces a consistent set of changes in PBMCs from both healthy and HIV-infected individuals, and that certain immunological studies of HIV-infected patients (i.e. studies of immune reconstitution following antiretroviral therapy in HIV-infected patients or studies of HIV-infectivity in vitro using CCR5-tropic strains) should be performed on fresh samples.     

Dissociation of CD154 and cytokine expression patterns in CD38+ CD4+ memory T cells in chronic HIV-1 infection

Expression of the activation antigen CD38 on T cells is a strong predictor of the risk of HIV disease progression, but it is not known whether CD38 is a marker or mediator of dysfunction. We examined the relationship between CD38 expression and responses to T-cell receptor stimulation in central memory and effector memory CD4 T cells in HIV-infected persons and in healthy controls. Basal CD38 expression was preserved by blocking golgi transport with brefeldin A. Intracellular expression of interleukin 2, interferon γ, and CD154 was measured after stimulating peripheral blood mononuclear cells with the superantigen staphylococcal enterotoxin B with or without anti-CD28 costimulation. Interferon-γ responses were comparable or increased in stimulated CD38 memory cells, and the interleukin 2 responses of costimulated CD38 central memory cells were decreased in HIV infection. In CD38 cells and especially in CD38 cells of HIV-infected persons, stimulated memory cells more often failed to express CD154 (CD40 ligand) when induced to express cytokine. A dissociated cytokine and CD154 expression by memory CD4 T cells may impair interactions between T cells and antigen-presenting cells, contribute to impaired immunity and help explain the relationship between CD38 expression and disease progression in chronic HIV infection.     

Central memory CD4 cells are an early indicator of immune reconstitution in HIV/AIDS patients with anti-retroviral treatment

The number of central memory cells among the CD4+ T cells and the of activation of CD8+ T cells is believed to be a better indicator of immune restoration in patients on antiretroviral therapy (ART) than the absolute numbers of CD4(+) and CD8+ T cells alone. In the current study, we investigated the changes in the CD4(+) T cell subsets and their association with immune reconstitution and immune activation at early stages of ART. A prospective study was performed in 21 asymptomatic treatment-naive HIV-infected patients with CD4(+) T cells less than 350 cells/μl. Blood samples were evaluated at base line, and at 2, 4, 8 and 12 weeks' post antiretroviral therapy (ART). A biphasic increase of CD4(+) T cells, central memory CD4 cells (CD4 CM) and CD4 na?ve cells were observed after ART, with a rapid increase before week 4. Change in CD4 CM at week 4 positively correlated with the change in CD4(+) T cells at weeks 12 post ART, and negatively correlated with the change in CD8(+)CD38(+) T cells at weeks 12 post ART. We conclude that CD4 CM cells are a major contributor to early immune reconstitution in treatment-naive HIV-infected patients with delayed ART, and might be an early indicator for immune reconstitution.     

Attenuation of cytokine responsiveness during T cell development and differentiation.

Cytokines play critical roles during T cell development; however, it is unclear to what extent development is altered by the high levels of cytokines produced during immune responses. A potential mechanism to shield developing cells from cytokine influence is attenuation of cytokine signaling. Using intracellular staining and flow cytometry to detect cytokine-induced Stat phosphorylation, we analyzed the cytokine responsiveness of developmentally defined mouse T cells. We assessed CD4(-)CD8(-) (DN), CD4(+)CD8(+) (DP), CD4(+)CD8(-) (SP4), and CD4(-)CD8(+) (SP8) in the thymus, and CD4(+)CD44(lo) (naive), CD4(+)CD44(hi) (memory), CD8(+)CD44(lo) (naive), and CD8(+)CD44(hi) (memory) in the periphery for responsiveness to interleukin-2 (IL-2), IL-4, IL-6, IL-7, IL- 10, IL-15, interferon-alpha (IFN-alpha), and IFN-gamma. SP thymocytes responded to a wider range of cytokines than did the less mature DN and DP subpopulations. DP thymocytes were nonresponsive to all cytokines tested except for modest responses to IL-4 and IFN-alpha. Peripheral naive and memory T cells also displayed differential cytokine sensitivity. Memory T cells were less responsive to the proinflammatory cytokines IL-6 and IFN-gamma when compared with naive T cells, and the memory CD4(+) subset was less responsive to IL-4. In summary, developing thymocytes and memory T cells appear to be resistant to the influences of numerous cytokines produced during immune responses.     

Impeded Th1 CD4 memory T cell generation in chronic-persisting liver infection with Echinococcus multilocularis

Memory T cells of the CD4 lineage coordinate immune responses against pathogens via the antigen-induced secretion of potent effector cytokines. The efficacy of these responses is thought to depend on both the overall number of pathogen-specific memory T cells and the particular array of cytokines that these cells are programmed to secrete. It is unknown to what extent cellular immunity can be induced by Echinococcus multilocularis infection. To examine the immunological memory provided by the adaptive cellular immune system in control of the chronic-persisting infection, peripheral lymphocytes of patients with alveolar echinococcosis (AE) were studied ex vivo. Stimulation of memory cells was performed with E. multilocularis vesicular fluid, purified protein derivative as recall antigen and phytohemagglutinin. Cytomegalovirus latency served as disease control. Frequencies of circulating CD4(+) T cells secreting IFN-gamma, IL-2, tumor necrosis factor-alpha, IL-4, IL-5 and IL-10 were determined by both cytokine flow cytometry and ELISPOT assays. Most strikingly, in chronic AE the frequencies of E. multilocularis antigen-specific cells committed to T(h)1-cytokine production were low (mean 0.5% of CD4(+) T cells). However, an E. multilocularis-specific response of CD4(+) T cells at frequencies of >/=0.1% was detected in the majority of AE patients (68%). Low numbers of cells committed to T(h)1 cytokine secretion were invariably seen in patients with active and inactive disease. Interestingly, the number of specific CD4(+) memory T cells was not increased in cured AE patients after complete surgical removal of the metacestode. Hyporesponsiveness during the chronic helminth infection was E. multilocularis specific. Thus, our results demonstrate that antigen-specific memory function against E. multilocularis is markedly different from that against viral or bacterial pathogens. Whether the antigen-specific cellular hyporesponsiveness with impeded T(h)1 CD4(+) memory T cell generation is a cause or a result of the progressive metacestode activity remains to be determined.     

Temporary restoration of immune response against Toxoplasma gondii in HIV-infected individuals after HAART,as studied in the hu-PBMC-SCID mouse model

We studied immune reconstitution against the parasite T. gondii in HIV-infected patients treated for 1 years with highly active antiretroviral therapy (HAART). We used SCID mice, humanized with peripheral blood mononuclear cells (PBMC) from patients, which were then infected with T. gondii cysts. Mice humanized with PBMC from patients before the start of HAART were highly susceptible to infection. In contrast, mice humanized with PBMC from patients who had received HAART for 6 months displayed higher survival rates, correlating with lower intracerebral parasite loads. However, this resistance was lost during follow up because mice humanized with PBMC from patients treated with HAART for 12 months survived for no longer than mice that had not been humanized. Specific lymphocyte proliferation assays showed that the increase in proliferative response depended on treatment duration and that HAART induced changes in IFN-gamma secretion in the presence of Toxoplasma antigens. Thus, our results indicate partial immune reconstitution against T. gondii in HIV-infected patients following HAART, possibly due to changes in the patterns of specific IFN-gamma production and redistribution of functional memory CD4+ cells.     

Distributional characteristics of CD25 and CD127 on CD4+ T cell subsets in chronic HCV infection

Attenuated CD4+ T-cell-mediated immune responses are involved in persistence of HCV infection, but the mechanism remains undefined. In this study, the proportions of CD4+ T cell subsets, naïve, central memory, effector memory and effector cells, along with CD25 (IL-2Rα) and CD127 (IL-7Rα) expression on different CD4+ T cell subsets, were measured by polychromatic flow cytometry in 24 chronic HCV-infected individuals and 21 healthy controls. A significant decrease in naïve CD4+ T cells and an increase of central memory and effector memory CD4+ T cells were found in HCV-infected patients compared with healthy controls. HCV-infected patients showed a lower level of CD127 expression in all CD4+ T cells subsets, especially in central memory and effector CD4+ T cells. In terms of total CD4+ T cells, an increase in CD25+ regular T cells (CD4+ CD25+ CD127lo) was found in HCV-infected patients. Interestingly, naïve CD4+ T cells showed increased CD25 expression, while effector memory and effector CD4+ T cells had lower CD25 expression. These data indicated that variations in different fractions of CD4+ T cells, including the phenotypic profile and expression level of CD25 and CD127, may be associated with low efficiency of immune response in chronic HCV infection. These results will strengthen the understanding of pathogenesis and dysfunction of CD4+ T cell immunity during long-term HCV persistence.     

Interleukin-7 receptor expression on CD8(+) T cells is reduced in HIV infection and partially restored with effective antiretroviral therapy.

Interleukin (IL)-7 enhances CD8 T-cell proliferation and cytolytic activity. The expression of its receptor, CD127 (IL-7R alpha), may therefore be important in the immunopathogenesis of HIV disease. CD127 expression on CD8(+) T cells from HIV seronegative controls, untreated HIV-seropositive patients, and HIV-positive patients receiving antiretroviral therapy with sustained viral suppression was analyzed by flow cytometry in a cross-sectional study. Among healthy controls, 65% of CD8 cells expressed CD127 ( n = 7). This dropped to 21.6% among untreated HIV-positive patients ( n = 16), and approached normal levels (47.7%) in HIV-positive individuals on effective therapy ( n = 20). The same pattern was observed for na?ve (CD45RA(+) ) and memory (CD45RO(+) ) CD8(+) T cells but changes were more extreme within the memory cell population. Duration of viral suppression was the only parameter evaluated that correlated with extent of CD127 expression in treated patients. Impairment of CTL activity in HIV disease may be caused, in part, by downregulation of IL-7 receptor expression. Improved immune function with effective antiretroviral therapy is associated with recovery of this molecule. The correlation between virologic suppression and apparent CD127 recovery suggests that essential cytokine signaling pathways may be restored with sustained inhibition of viral replication.     

Differential expression of Ly6C and T-bet distinguish effector and memory Th1 CD4(+) cell properties during viral infection

CD4(+) T?cells differentiate into multiple effector types, but it is unclear how they form memory T?cells during infection in?vivo. Profiling virus-specific CD4(+) T?cells revealed that effector cells with T helper 1 (Th1) or T follicular helper (Tfh) cell characteristics differentiated into memory cells, although expression of Tfh cell markers declined over time. In contrast to virus-specific effector CD8(+) T?cells, increased IL-7R expression was not a reliable marker of CD4(+) memory precursor cells. However, decreased Ly6C and T-bet (Tbx21) expression distinguished a subset of Th1 cells that displayed greater longevity and proliferative responses to secondary infection. Moreover, the gene expression profile of Ly6C(lo)T-bet(int) Th1 effector cells was virtually identical to mature memory CD4(+) T?cells, indicating early maturation of memory CD4(+) T?cell features in this subset during acute viral infection. This study provides a framework for memory CD4(+) T?cell development after acute viral infection.     

Generation and maintenance of memory T cells

Typical immune responses lead to the prominent clonal expansion of antigen-specific T cells followed by their differentiation into effector cells. Most effector cells die at the end of the immune response but some of the responding cells survive and form long-lived memory cells. The factors controlling the formation and survival of memory T cells are discussed. Recent evidence suggests that T memory cells arise from a subset of effector cells. The longevity of T memory cells may require continuous contact with cytokines, notably IL-15 for CD8(+) cells.