Restoration of CD4 T-cell responses to cytomegalovirus is short-lived in severely immunodeficient HIV-infected patients responding to highly active antiretroviral therapy

OBJECTIVES: To define the level of pathogen-specific immune reconstitution persisting over 3 to 5 years of highly active antiretroviral therapy (HAART) in HIV-infected patients who began therapy with CD4 T-cell counts below 50 cells/microL. METHODS: Cytomegalovirus (CMV)-specific T-cell responses were analysed in adult HIV-1-infected patients with nadir CD4 T-cell counts below 50 cells/microL before HAART. CMV-specific CD4 T-cell responses were measured by interferon-gamma enzyme-linked immunospot assay (ELISpot assay), lymphoproliferation and interferon-gamma levels in cell culture supernatants. RESULTS: CD4 T-cell responses to CMV were low in untreated patients and remained low during the first year on HAART, but increased progressively to levels similar to those found in HIV-seronegative CMV-seropositive controls at 3 years. Responses then declined markedly and at 5 years were lower than controls. This could not be explained by changes in CD4 or CD8 T-cell counts or plasma HIV RNA levels. Interferon-gamma and interleukin-5 responses to a mitogen were maintained or elevated. CONCLUSIONS: CMV-specific CD4 T-cell responses were found to decline after 3-5 years on HAART and may provide inadequate long-term protection against CMV disease in patients who are severely immunodeficient prior to treatment.     

Nadir CD4+ T-cell count and numbers of CD28+ CD4+ T-cells predict functional responses to immunizations in chronic HIV-1 infection

OBJECTIVE: To ascertain whether delaying the initiation of highly active antiretroviral therapy (HAART) compromises functional immune reconstitution in HIV-1 infection in persons who regain 'normal' CD4 T-cell counts after suppressive antiretroviral therapies. DESIGN: Prospective open-label study carried out at two University-affiliated HIV-outpatient clinics in the USA. SUBJECTS AND METHODS: Response to immunization was used as a model for in vivo functional immune competence in 29 HIV-1 infected patients with CD4 T-cell counts > 450 x 106 cells/l and HIV-RNA < 400 copies/ml for > 12 months after HAART and nine HIV-1 seronegative controls. After immunization with tetanus toxoid, diphtheria-toxoid, and keyhole limpet hemocyanin, immune response scores (IRS) were calculated using postimmunization antibody concentrations, lymphocyte proliferation, and delayed-type hypersensitivity responses to vaccine antigens. RESULTS: Despite normal numbers of circulating CD4 T-cells, the CD4 T-cell nadir before HAART initiation predicted the immune response to immunization (rho = 0.5; P < 0.005) while current CD4 T-cell count did not. Likewise, CD4 T-lymphocyte expression of the co-stimulatory molecule CD28 was also an independent predictor of response to immunization (rho = 0.5; P < 0.005). CONCLUSIONS: Even among persons who controlled HIV replication and normalized CD4 T-cell counts with HAART, pretreatment CD4 T-cell count and numbers of circulating CD4+CD28+ T-cells at immunization, but not current CD4 T-cell count, predict the ability to respond to vaccination. Delaying the initiation of HAART in chronic HIV-1 infection results in impaired functional immune restoration despite normalization of circulating CD4 T-cell numbers.     

CD4 T-lymphocyte recovery in individuals with advanced HIV-1 infection receiving potent antiretroviral therapy for 4 years: the Swiss HIV Cohort Study

BACKGROUND: Highly active antiretroviral therapy (HAART) for human immunodeficiency virus (HIV)-1 infection allows recovery of CD4 T lymphocytes. Few studies have explored the long-term T-lymphocyte responses to HAART. METHODS: Plasma HIV-1 RNA levels and CD4 and CD8 T-lymphocyte counts were longitudinally analyzed over 4 years in 2235 participants of the Swiss HIV Cohort, commencing HAART between 1996 and 1997. The CD4 T-lymphocyte count increase, the percentage of individuals with a CD4 T-lymphocyte count of 500/microL or greater and less than 200/microL, and the determinants of CD4 T-lymphocyte recovery were evaluated in individuals treated with continuous (CONT; n = 985) and discontinuous (DISCONT; n = 1250) HAART. RESULTS: At 4 years, 69.5% of subjects (CONT, 84.5%; DISCONT, 53.6%; P<.001) showed HIV-1 RNA levels below 400 copies/mL, while the median CD4 T-lymphocyte count increased from 190/microL to 423/microL (CONT, 486/microL; DISCONT, 343/microL; P<.001). Of the 2235 participants, 38.8% (CONT, 47.7%; DISCONT, 29.4%; P<.001) reached a CD4 T-lymphocyte count of 500/microL or greater, but in 15.6%, CD4 T-lymphocyte count remained below 200/microL (CONT, 5.9%; DISCONT, 25.9%; P<.001). Larger increases in CD4 T-lymphocyte count were associated with higher baseline HIV-1 RNA, a larger percentage of undetectable HIV-1 RNA levels, lower baseline CD8 T-lymphocyte count, and younger age. Individuals reaching a CD4 T-lymphocyte count of 500/microL or greater at 4 years were characterized by higher nadir and baseline CD4 T-lymphocyte counts and a more sustained reduction of HIV-1 RNA levels. CONCLUSIONS: At 4 years, only 39% of individuals treated with HAART reached a CD4 T-lymphocyte count of 500/microL or greater, and 16% with CD4 T-lymphocyte counts less than 200/microL remained susceptible to opportunistic infections. Treatment interruptions, a poor virologic response, and older age were the major factors negatively affecting the recovery of CD4 T lymphocytes.     

Setting a minimum threshold CD4 count for initiation of highly active antiretroviral therapy in HIV-infected patients

The aim of our study was to determine a minimum threshold CD4 count for highly active antiretroviral therapy (HAART) initiation in HIV-infected patients. A schema using longitudinal data from a clinical cohort was designed. The presenting CD4 counts of asymptomatic HIV-infected patients in Hong Kong were evaluated in relation to their progression to AIDS within 1 year of diagnosis of HIV infection. A graph was generated to depict the changes in the percentage of cumulative AIDS diagnoses for every 10 cell/microL increase in presenting CD4 count. Of 181 patients, 24 had developed AIDS within 1 year of diagnosis of HIV infection. Setting the CD4 count threshold at 150 cells/microL gave a good balance between the number of preventable AIDS-defining events and the number of non-AIDS patients initiating HAART. No extra AIDS-defining events occurred when the CD4 count threshold was reduced from 200 to 150 cells/microL, despite the addition of 13 more patients. In multivariate Cox regression analysis, presenting CD4 count was a significant predictor for AIDS occurrence. The relative hazard for AIDS occurrence of patients with presenting CD4 counts 相似文献   

NK-associated receptors on CD8 T cells from treatment-naive HIV-infected individuals: defective expression of CD56.

OBJECTIVES: This study addresses the detailed expression of natural killer (NK)- associated receptors on CD8 T lymphocytes in treatment-naive HIV-infected individuals. DESIGN: Experimental study analysing the expression of NK-associated receptors on peripheral blood T lymphocytes from HIV-infected individuals compared with healthy controls. METHODS: Flow cytometry was used to analyse the expression of CD56, CD16, CD94, NKG2A, NKB1, CD161, CD244, and perforin, according to the CD28 phenotype, on CD8(bright) T cells obtained from treatment-naive HIV-infected individuals and from healthy controls. RESULTS: The results showed that CD8(bright) T cells from treatment-naive HIV-infected individuals had a decreased expression of CD56 and that CD8(bright)CD56 cell numbers correlated with CD4 cell counts. NK-associated markers were preferentially expressed on CD8(bright)CD28 negative T cells, both in healthy controls and HIV-infected individuals. An increased expression of CD94, CD244, and perforin, which was the consequence of the expansion of the CD8(bright)CD28 negative T-cell subset, was also observed in HIV infection. CONCLUSIONS: As the CD8(bright)CD56 T cells are the mature cytolytic effector cells, the defective expression of CD56 on CD8(bright) T cells shown in HIV-infected individuals could be involved in the decreased peripheral blood T-cell cytotoxicity found in HIV infection.     

Proportions of circulating T cells with a regulatory cell phenotype increase with HIV-associated immune activation and remain high on antiretroviral therapy

OBJECTIVE: To examine the relationships between blood CD4 natural regulatory T (Treg) cells, plasma HIV RNA level, CD4 T-cell count and immune activation in untreated HIV-infected patients and immunodeficient patients beginning antiretroviral therapy (ART), using a novel phenotype to define Treg cells (CD25CD127CD4). Data were compared with established Treg cell markers (FoxP3, CTLA-4 and GITR). METHODS: Twenty-nine untreated HIV-infected patients with CD4 T-cell counts of < 300 or > 400/microl were compared in a cross-sectional study and 12 patients beginning combination ART with < 100 CD4 T cells/mul were followed for 1 year on therapy. Three- and four-colour flow cytometry was used to quantitate proportions of Treg cells. RESULTS: In control donors and patients with high CD4 T-cell counts, 28-89% (median 60%) of CD25CD127CD4 cells were FoxP3, but < 10% expressed GITR or CTLA-4. Immunodeficient patients also had CD4-negative lymphocytes with the phenotype FoxP3CD127. Proportions of CD25CD127 cells and activated (HLA-DR) cells in the CD4 T-cell population were increased in patients with low CD4 T cell counts. The proportion of CD25CD127CD4 T cells correlated positively with plasma HIV RNA level and CD4 T-cell activation, but inversely with CD4 T-cell count. Longitudinal studies of 12 patients receiving ART in two distinct cohorts (Western Australia and Malaysia) showed that the proportion of CD25CD127CD4 cells decreased slightly over time, but remained above levels seen in non-HIV controls. CONCLUSIONS: Proportions of circulating T cells with a regulatory cell phenotype increase with HIV-associated immune activation and remain high after 1 year on ART.     

HAART in HIV-infected patients: restoration of antigen-specific CD4 T-cell responses in vitro is correlated with CD4 memory T-cell reconstitution, whereas improvement in delayed type hypersensitivity is related to a decrease in viraemia.

OBJECTIVE: To analyse prospectively the effect of highly active antiretroviral treatment (HAART) on CD4 T-cell responses in vitro and in vivo in HIV-infected patients. DESIGN: Prospective study with 49 protease inhibitor-naive adult patients. Data were collected at baseline and after 3 and 6 months of HAART. METHODS: In vitro CD4 T-cell reactivity was analysed by stimulation of peripheral blood mononuclear cells with several antigens. In vivo CD4 T-cell reactivity (delayed type hypersensitivity) was assessed by Multitest Merieux. Both measurements were correlated to CD4 (memory) T-cell count and HIV-1 viraemia. RESULTS: Restoration of specific CD4 T-cell proliferation was observed in most patients. The in vitro T-cell response was restored more frequently against antigens to which the immune system is constantly exposed (Candida albicans, Mycobacterium tuberculosis, M. avium) as compared with a low-exposure antigen (tetanus toxoid). Overall, delayed type hypersensitivity detection rate increased under HAART. Multivariate analysis showed improvement of antigen-specific T-cell proliferation to be significantly associated with an increase in memory CD4 T-cells, whereas improvement of the delayed type hypersensitivity response was associated with a decrease in plasma HIV-1 RNA. CONCLUSIONS: HAART for 6 months restored antigen-specific CD4 T-cell response to several antigens. In vitro immune reconstitution was closely correlated with an increase in memory CD4 cells. Restoration of delayed type hypersensitivity was associated with suppression of viraemia. It appears that in addition to expansion of memory CD4 cells, suppression of viraemia following HAART may allow an improved inflammatory reaction, thus providing even stronger immune reconstitution.     

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.     

Aberrant production of soluble costimulatory molecules CTLA-4, CD28, CD80 and CD86 in patients with systemic lupus erythematosus

OBJECTIVE: The costimulatory interactions of the B7 family molecules CD80 and CD86 on antigen-presenting cells with their T-cell counter-receptors CD28 and CTLA-4 modulate T lymphocyte-mediated immune responses in a reciprocal manner. We investigated the possible aberrant production of soluble (s) forms of the T-cell costimulatory molecules CD80, CD86, CD28 and CTLA-4 in plasma of patients with systemic lupus erythematosus (SLE), an autoimmune disease arising from T-lymphocyte dysregulation. METHODS: Plasma concentration and ex vivo production of soluble costimulatory molecules of 79 SLE patients with or without active disease and 40 sex- and age-matched healthy subjects were measured by enzyme-linked immunosorbent assay. RESULTS: Plasma sCTLA-4, sCD28, sCD80 and sCD86 concentrations of all SLE patients were significantly higher than concentrations in control subjects (all P<0.01). These increases were observed even in patients with inactive disease [SLE Disease Activity Index (SLEDAI) <3]. Plasma sCTLA-4 concentration in all SLE patients correlated significantly with SLEDAI score (r = 0.228, P = 0.043). Upon mitogen treatment of peripheral blood mononuclear cells, the percentage increases in ex vivo production of sCD28 and sCD80 and the percentage decrease in sCTLA-4 release were all significantly smaller in SLE patients with active disease than in healthy subjects (P<0.01, P<0.05 and P<0.0001, respectively). CONCLUSION: The aberrant production of soluble T-cell costimulatory molecules is important in the immunopathogenesis of SLE, which occurs by the dysregulation of T-lymphocyte costimulation. Plasma sCTLA concentration could potentially serve as a surrogate marker of SLE disease activity.     

Granule-dependent mechanisms of lysis are defective in CD8 T cells of HIV-infected, antiretroviral therapy-treated individuals

BACKGROUND: HIV-specific cytotoxic T-cell (CTL) responses are defective in HIV-infected patients undergoing antiretroviral therapy (ART). This defect has been attributed to the decreased antigenic burden secondary to ART-associated suppression of HIV-replication, and is responsible for the rebounds of viraemia that occur when patients interrupt therapy. CTL are stimulated by type 1 cytokines and can kill targets via granule-dependent (perforin and granzymes) and -independent (tumour necrosis factor-alpha, CD95) mechanisms. METHODS: Granule-dependent and granule-independent mechanisms of CTL killing, as well as type 1 cytokine production by CD4 T cells, were analysed in 57 chronically HIV-infected ART-treated or ART-untreated individuals. RESULTS: The results can be summarized as follows: the frequency of gp160 (env)-specific interferon-gamma-secreting CD8 T lymphocytes correlates positively with HIV viraemia in ART-treated and -untreated patients; Env-specific perforin- and granzymes-expressing CD8 T lymphocytes, and Env-stimulated perforin and granzymes mRNA, are reduced in ART-treated patients independently of HIV viral load and of type 1 cytokine production; tumour necrosis factor-alpha production is increased in ART-treated individuals; and Env-specific immature CD8+28+27+ cells are only marginally augmented in ART-treated patients, Similar results are observed in cytomegalovirus-specific CD8 T cells and peripheral blood mononuclear cells. CONCLUSIONS: A defect of CTL function that selectively affects the granule-dependent mechanisms of lysis is observed in ART-treated individuals. Because interferon-gamma production is higher in these patients, this could be a defect primarily involving CTL. These data suggest an independence of CD8 T-cell numbers and their lytic ability in HIV-infected, ART-receiving patients. Immunomodulants are needed to successfully treat HIV infection.     

HIV patients on antiretroviral therapy have high frequencies of CD8 T cells specific for Immediate Early protein-1 of cytomegalovirus

OBJECTIVE: To assess the frequency and phenotype of cytomegalovirus (CMV)-specific CD8 T cells in previously immunocompromised HIV patients with stable undetectable HIV viremia due to highly active antiretroviral therapy (HAART). METHODS: Twenty-one CMV-seropositive HIV patients with nadir CD4 T-cell counts < 50 x 10(6) cells/l, at least 4 years on HAART and 6 months of complete viral suppression (< 50 HIV RNA copies/ml) and 12 CMV-seropositive, HIV-seronegative age/sex-matched controls were studied. CD4 and CD8 T-cell responses to whole CMV and two HLA-A*02 restricted CMV peptides [NLV from pp65 and VLE from Immediate Early 1 (IE1)] were measured by interferon (IFN)gamma ELISpot. Phenotypes of peptide-specific CD8 T cells were determined by tetramer staining. RESULTS: In the ELISpot assay, HIV patients had significantly more CD8 T cells producing IFN gamma in response to VLE than controls, whereas numbers of NLV-specific and CMV-specific IFN gamma spots were similar. Four HIV patients and one control had large VLE and/or NLV-specific CD8 T-cell populations despite the absence of CMV-specific CD4 T cells. The majority of peptide-specific CD8 T cells from HIV patients and controls were CD28-, CD45RO+ and CD45RA-. However, a significantly higher proportion of VLE-specific CD8 T cells expressed perforin compared to NLV-specific CD8 T cells in HIV patients. CONCLUSIONS: HIV patients had elevated numbers of IE1-specific, IFNgamma-producing perforin-positive CD8 T cells compared to controls. As IE1 is expressed early during CMV reactivation, these cells may be important for preventing CMV replication to pathogenic levels. In addition, CMV-specific CD4 T cells are not essential for maintenance of large populations of CMV-specific CD8 T cells in aviremic HIV patients on HAART.     

Susceptibility to opportunistic infections in HIV-infected patients with increased CD4 T-cell counts on antiretroviral therapy may be predicted by markers of dysfunctional effector memory CD4 T cells and B cells

OBJECTIVES: HIV-infected patients responding to combination antiretroviral therapy (ART) after experiencing severe immunodeficiency may exhibit persistent immune defects and occasionally experience opportunistic infections (OIs) despite increased CD4 T-cell counts. The investigation of immune defects in such patients was examined in this study. METHODS: CD4 effector memory T-cell (T(em)-cell) function [assessed by blood cytomegalovirus (CMV) interferon-gamma (IFN-gamma) enzyme-linked immunosorbent spot-forming cell assay (ELISPOT) counts] and B-cell dysregulation [assessed by serum immunoglobulin A (IgA) and IgE levels] were examined in 27 patients with increased CD4 T-cell counts after receiving ART for over 2 years. Two of these patients and one other had developed OIs on ART and are described in detail. RESULTS: Serum levels of IgA and IgE were higher than reference intervals (P<0.001) and CMV IFN-gamma ELISPOT counts were lower than those in non-HIV-infected controls (P<0.001) in the HIV-infected patients. Low CMV IFN-gamma ELISPOT counts were associated with high IgA levels (r=-0.5, P=0.01, Spearman's correlation test) and segregated with high IgE levels (P=0.06, Fisher's test). CMV IFN-gamma ELISPOT counts and serum IgA and IgE levels did not change significantly over a median time of 35 (range 8-60) months after the first measurement, whereas CD4 T-cell counts increased. All three patients who experienced OIs had repeatedly low CMV IFN-gamma ELISPOT counts and increased serum levels of IgA and/or IgE. CONCLUSION: Low CD4 T(em)-cell function and B-cell dysregulation are immune defects that may persist independently of changes in the CD4 T-cell count in HIV-1-infected patients responding to ART and are associated with an increased risk of developing an OI.     

CD4+ Lymphocyte Depletion in HIV-Infected Patients is Associated with gp120-Immunoglobulin-Complement Attachment to CD4+ Cells

The mechanism of CD4+ lymphocyte depletion, which is the main immunological feature in HIV-infected patients, is unclear. We investigated whether gp120-immunoglobulin-complement complexes on the surface of CD4+ cells might be involved in the elimination of CD4+ lymphocytes. The results obtained in 63 HIV-infected patients show that gp120 is attached to a variable degree to CD4+ cells. Importantly, the percentage of CD4+gp120+ lymphocytes is inversely associated with CD4+ lymphocyte counts in the peripheral blood (p = 0.0004). CD4+gp120+ blood lymphocytes bind IgM (p = 0.0027) and IgG antibodies (p = 0.0001) and complement (p = 0.0005). These results suggest that immune complex-mediated cell elimination is an important mechanism of CD4+ cell depletion in patients with AIDS.     

HCV recovery from peripheral blood mononuclear cell culture supernatants derived from HCV–HIV co-infected haemophilic patients with undetectable HCV viraemia

Hepatitis C viraemia, in 38 human immunodeficiency virus positive (HIV+)/hepatitis C virus positive (HCV+) patients, was determined in haemophilic patients during the 4 years since initiation of highly active antiretroviral therapy (HAART). Six of 38 patients had persistently HCV-negative viraemia for more than 2 years. No correlation between HCV-negative viraemia and CD4+ T-cell counts, HIV viral load, age, type or severity of haemophilia could be established. Reduced levels of HIV viral load and the immune reconstitution that follows the initiation of HAART were not enough to explain the disappearance of HCV from plasma. Individuals who cleared plasma HCV had significantly higher CD8+ T-cell counts (P=0.0013) (mean +/- SE: 1153 +/- 117.8 cells microL(-1)) than those with HCV-positive viraemia (819.1 +/- 40.72 cells microL(-1)). Because HCV could maintain a low replication level in peripheral blood mononuclear cells (PBMC), we cultured PBMC of five of six patients with undetectable HCV viraemia. We found four of five HCV RNA-positive cultures. The presence of HCV RNA in our cultures proved that these cells may be an important viral reservoir that could contribute to HCV recurrence in plasma even after long periods of negative viraemia. In summary, our results indicate that in spite of prolonged HCV-negative plasma viraemia, HCV patients that are co-infected with HIV may harbour replication-competent HCV in their PBMC. Therefore, true clearance of HCV infection is difficult to achieve in these patients.     

Prolonged survival and tissue trafficking following adoptive transfer of CD4zeta gene-modified autologous CD4(+) and CD8(+) T cells in human immunodeficiency virus-infected subjects

We have genetically engineered CD4(+) and CD8(+) T cells with human immunodeficiency virus (HIV) specificity by inserting a gene, CD4zeta, containing the extracellular domain of human CD4 (which binds HIV env) linked to the zeta (zeta) chain of the T-cell receptor (which mediates T-cell activation). Twenty-four HIV-positive subjects received a single infusion of 2 to 3 x 10(10) autologous CD4zeta-modified CD4(+) and CD8(+) T cells administered with (n = 11) or without (n = 13) interleukin-2 (IL-2). Subjects had CD4 counts greater than 50/microL and viral loads of at least 1000 copies/mL at entry. T cells were costimulated ex vivo through CD3 and CD28 and expanded for approximately 2 weeks. CD4zeta was detected in 1% to 3% of blood mononuclear cells at 8 weeks and 0.1% at 1 year after infusion, and survival was not enhanced by IL-2. Trafficking of gene-modified T cells to bulk rectal tissue and/or isolated lamina propria lymphocytes was documented in a subset of 5 of 5 patients at 14 days and 2 of 3 at 1 year. A greater than 0.5 log mean decrease in rectal tissue-associated HIV RNA was observed for at least 14 days, suggesting compartmental antiviral activity of CD4zeta T cells. CD4(+) counts increased by 73/microL at 8 weeks in the group receiving IL-2. There was no significant mean change in plasma HIV RNA or blood proviral DNA in either treatment arm. This sustained, high-level persistence of gene-modified T cells demonstrates the feasibility of ex vivo T-cell gene therapy in HIV-infected adults and suggests the importance of providing HIV-specific T-helper function.     

Dysregulation of CD4+CD25+CD127lowFOXP3+ regulatory T cells in HIV-infected pregnant women

Pregnancy represents a major challenge to immunologic tolerance. How the fetal "semiallograft" evades maternal immune attack is unknown. Pregnancy success may involve alteration of both central (thymic) and peripheral tolerance mechanisms. HIV infection is characterized by CD4(+) T-cell depletion, chronic immune activation, and altered lymphocyte subsets. We studied immunologic consequences of pregnancy in 20 HIV-infected women receiving highly active antiretroviral therapy (HAART), and for comparison in 16 HIV-negative women. Lymphocyte subsets, thymic output, and cytokine profiles were measured prospectively during pregnancy and postpartum. A significant expansion of CD4(+)CD25(+)CD127(low)FoxP3(+) regulatory T cells indicating alteration of peripheral tolerance was seen during second trimester, but only in HIV-negative women. HIV-infected women had lower CD4 counts, lower thymic output and Th-2 cytokines, and more immune activation at all time points compared with controls. Immune activation was decreased in HIV-infected patients during pregnancy. In contrast, CD4 counts were increased in both groups. In conclusion, the study does not indicate that pregnancy adversely affects the immunologic course of HIV infection. However, despite HAART during pregnancy, HIV-infected women display different immunologic profiles from HIV-negative women, which may have importance for the induction of fetal-maternal tolerance and in part explain the increased risk of abortion in HIV-infected women.     

Impaired IFN-gamma-secreting capacity in mycobacterial antigen-specific CD4 T cells during chronic HIV-1 infection despite long-term HAART

OBJECTIVE: To determine whether long-term HAART in chronic HIV-1 infection restores fully functional Mycobacterium tuberculosis (MTB)-specific CD4 T-cell responses. DESIGN: A cross-sectional study of HIV-1-seropositive subjects on continuous HAART for over one year with CD4 cell counts greater than 300 cells/microl and undetectable viraemia, antiretroviral-naive individuals with primary HIV-1 infection (PHI), and healthy bacillus Calmette-Guérin-vaccinated low-risk controls. METHODS: Purified protein derivative (PPD)-specific cytokine-secreting CD4 T cells were quantified ex vivo by enzyme-linked immunospot assay and intracellular cytokine staining. Lymphoproliferation was detected by [3H]-thymidine incorporation. RESULTS: PPD-specific IFN-gamma-secreting CD4 T cells were markedly reduced in chronic HAART-treated HIV-1-positive and PHI subjects compared with healthy controls [medians 30, 155 and 582 spot-forming cells/million peripheral blood mononuclear cells (PBMC), respectively, P < 0.0001 and P < 0.002], but the frequency of these cells was, nonetheless, significantly greater in viraemic PHI subjects than in aviraemic chronic HIV-1-positive subjects (P < 0.01). In the latter, low frequencies of PPD-specific IL-2 and IL-4-secreting CD4 T cells were also observed. However, lymphoproliferation was evident after the in-vitro stimulation of PBMC with PPD, indicating that MTB-specific T cells were present. The defect in IFN-gamma secretion could be overcome by culture with IL-12. CONCLUSION: Despite an improvement in CD4 T-cell counts after HAART, MTB-specific CD4 T cells from chronically infected patients have impaired IFN-gamma-secreting capacity. The early initiation of HAART might preserve functional CD4 T-cell responses to MTB, and warrants evaluation in populations with a high risk of dual infection.     

Correlation of blood lymphocyte CTLA-4 (CD152) induction in Hodgkin's disease with proliferative activity,interleukin 2 and interferon-gamma production

Expression of the downregulatory CTLA-4 molecule was determined on unstimulated and anti-CD3 + recombinant interleukin 2 (rIL-2)-stimulated peripheral blood T cells in Hodgkin's disease (HD) and correlated with the T-cells' proliferative activity, IL-2 and interferon (IFN)-gamma production. There was a negligible percentage of CTLA-4+/CD3+ cells before culture. The mean percentage of CTLA-4+/CD3+ lymphocytes increased gradually, peaked after 72 h of stimulation and returned to basal values after 96 h of stimulation. The mean proportion of CTLA-4+/CD3+ cells from untreated patients was significantly higher after 24, 48 and 72 h of stimulation compared with controls. The mean percentage of CTLA-4+/CD3+ cells from patients in clinical remission (CR) was lower than that of untreated patients, but remained significantly higher compared with controls. Lymphocytes from untreated HD patients showed impaired proliferative activity, IL-2 and IFN-gamma production compared with controls. The proliferative activity of the lymphocytes, IL-2 and IFN-gamma production remained significantly lower in CR compared with controls. The proportion of CTLA-4+/CD3+ cells negatively correlated with proliferative activity, IL-2 and IFN-gamma production in HD patients and controls. However, some untreated patients as well as patients in CR with normal mean fluorescence intensity values of CTLA-4 showed unimpaired T-cell function tests. Our study provides the first evidence of an increased expression of downregulatory CTLA-4 molecule on stimulated T-cells in HD, which could be one of the mechanisms of immune deficiency in this disease.     

CTLA-4 upregulation during HIV infection: association with anergy and possible target for therapeutic intervention

OBJECTIVE: To study the role of cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4) during HIV infection. METHODS: Intracellular CTLA-4 expression, determined by flow-cytometry, and proliferative responses to HIV antigens, were studied in peripheral blood mononuclear cells (PBMC) from 93 HIV-1-infected [HIV(+)] patients and 40 HIV-1 seronegative controls. RESULTS: The proportions of CTLA-4 expressing CD4+ T cells were: (1) significantly higher in HIV(+) patients, 10.95 +/- 0.66%, than in controls, 6 +/- 0.45% (P < 0.0001); (2) inversely correlated to CD4+ counts (r = -0.67, P < 0.005, n = 16, drug-naive patients; r = -0.57, P < 0.0001, n = 77, HAART-treated patients); and (3) positively correlated to proportion of activated (HLA-DR+CD3+) (r = 0.53, P < 0.0001) and memory (CD45RO+CD4+) T cells (r = 0.46, P < 0.001). CD28 median fluorescence intensity in CTLA-4- cells was twice that in CTLA-4+ cells (140 +/- 5.3 versus 70 +/- 2.28, P < 0.00001), whereas cells low in CD28 and CD4, expressed more CTLA-4 (P < 0.0001). Higher proportion of CTLA-4+CD4+ cells expressed CCR5 and Ki-67, in comparison with CTLA-4-CD4+ cells, (65 +/- 11.9 and 25 +/- 7.5% versus 27 +/- 8.9 and 3.7 +/- 2%, P < 0.0001 and P < 0.01, respectively). Among HAART-treated patients, with viral load below detectable levels, CD4+ cells increase was inversely correlated to %CTLA-4+CD4+ cells (r = -0.5, P = 0.003, n = 39). Proliferation of PBMC to anti-CD3, gp-120 depleted HIV-1 antigen or HIV-1 p24 stimulation was inversely correlated with CTLA-4 levels (r = -0.68, P = 0.0035; r = -0.38,P = 0.04; and r = -0.43, P = 0.028, respectively). CONCLUSIONS: (1) CTLA-4 is upregulated during HIV infection and may therefore account for CD4 T-cell decline and anergy in HIV-1 infection. (2) Increased levels of CTLA-4 may undermine immune responses and in the HAART-treated patient-immune reconstitution. (3) Blocking of CTLA-4 may offer a novel approach for immune-based therapy in HIV infection.     

Impairment of CD4(+)CD25(+) regulatory T-cells in autoimmune liver disease

BACKGROUND/AIMS: CD4(+) lymphocytes constitutively expressing the IL-2-receptor alpha-chain (CD25) regulate the activation of CD4 and CD8 autoreactive T-cells by suppressing their proliferation and effector function. The aim of this study is to: (1) measure the percentage of CD4(+)CD25(+) T-cells (T-regs) in patients with autoimmune liver disease at presentation and during remission, (2) correlate their frequency with disease activity, (3) determine their ability to expand and (4) to inhibit interferon-gamma (IFNgamma) production by CD4(+)CD25- T-cells. METHODS: 41 patients were studied. Percentage of T-regs was determined on peripheral blood mononuclear cells (PBMCs) by triple-colour flow cytometry; their ability to expand by exposing PBMCs to a T-cell expander (CD3/CD28 Dynabeads); their immunoregulatory function by measuring their ability to suppress IFNgamma production by CD4(+)CD25(-) T-cells. RESULTS: T-regs were significantly less in patients than in controls, and at diagnosis than during remission. Their percentage was inversely correlated with titres of anti-liver kidney microsomal and soluble liver antigen autoantibodies. T-regs ability to expand was significantly lower in patients than in controls, but that to suppress IFNgamma production by CD4(+)CD25(-) T-cells was maintained. CONCLUSIONS: Decreased T-regs numbers and ability to expand may favour the emergence of liver-targeted autoimmunity, despite preserved suppressor function. Treatment should aim at increasing T-regs number.