Predominant involvement of CD8+CD28- lymphocytes in human immunodeficiency virus-specific cytotoxic activity

The relationships of CD8+ T cell subsets in RA patients with disease activity and clinical parameters

BACKGROUND

CD8+ T cells are plentiful in rheumatoid arthritis (RA) and have a important role in it's pathogenesis. Many subsets have been identified in CD8+ T cells, however, the relationship between CD8+ T subpopulations and disease activity of RA is poorly defined. Here we detected different CD8+ T cell subsets in peripheral blood and examined their relationships with clinical features and serological parameters in RA.

METHODS

CD8+ T cell phenotypes and percentages in peripheral blood were determined by flow cytometry in 39 patients with RA. The clinical characteristics and serological parameters of RA patients were collected and DAS28-ESR was measured as indicator of disease activity. Linear regression was performed to assess the correlation of CD8+ T cell subsets with RA clinical variables.

RESULTS

Naive CD8+ T cells were significantly and negatively correlated with RA disease activity indicator DAS28-ESR(r² = 0.1027, p = 0.0468), erythrocyte sedimentation rate (ESR)(r² = 0.1891, p = 0.0057), clinical disease activity index(CDAI)(r² = 0.1474, p = 0.0158), simplified disease activity index(SDAI)(r² = 0.1465, p = 0.0255), and duration(r² = 0.1247, p = 0.0274). And the percent of naive CD8+ T cells were obviously decreased in RA with high disease activity when compared with RA in low disease activity(p < 0.01). In addition, Our results indicated significant positive correlations between CD8+ CD28- T cells and DAS28-ESR(r² = 0.1881, p = 0.0058), ESR(r² = 0.2279, p = 0.0021), c reaction protein (CRP)(r² = 0.2203, p = 0.0051), CDAI (r² = 0.1778, p = 0.0075), SDAI (r² = 0.2618, p = 0.0020), rheumatoid factor(RF)(r² = 0.1823, p = 0.0067), age(r² = 0.1968, p = 0.0047), as well as similar positive correlations between CD8+ CD27- T cells and DAS28-ESR(r² = 0.1661, p = 0.01), ESR(r² = 0.1586, p = 0.012), CRP(r² = 0.1778, p = 0.013), CDAI (r² = 0.1622, p = 0.0110), SDAI(r² = 0.2316, p = 0.0040), RF(r² = 0.2097, p = 0.0034), age(r² = 0.1932, p = 0.0051). Furthermore, interesting results showed observable positive correlations between activated CD8+ T cells and total cholesterol(TC)(r² = 0.2757, p = 0.0007), triglyceride(TG)(r² = 0.2886, p = 0.0005), low density lipoprotein(LDL-C)(r² = 0.09643, p = 0.0264) and Krebs yon denlungen-6(KL-6)(r² = 0.4171, p = 0.0002). And TCRγδ + CD8+ T cells were also found positively related with total cholesterol(TC)(r² = 0.5015, p < 0.0001), triglyceride(TG)(r² = 0.2031, p = 0.0045), and KL-6(r² = 0.2122, p = 0.0136).

CONCLUSIONS

Our results suggest that naive CD8+ T cells, CD8+ CD28- T cells, and CD8+ CD27- T cells are obviously correlated with inflammation and disease activity of RA. While activated CD8+ T cells and TCRγδ + CD8+ T cells may involve in lipidmetabolism and lung fibrosis of RA. These CD8+ T cell subsets may be new biomarkers and targets for RA disease evaluation, therapeutic target-selecting, curative effects and prognoses assessment.

Cytolytic CD4+ and CD8+ Regulatory T-Cells and Implications for Developing Immunotherapies to Combat Graft-Versus-Host Disease

Regulatory T-cells (Treg) are critical for the maintenance of immune homeostasis and tolerance induction. While the immunosuppressive mechanisms of Treg have been extensively investigated for decades, the mechanisms responsible for Treg cytotoxicity and their therapeutic potential in regulating immune responses have been incompletely explored and exploited. Conventional cytotoxic T effector cells (Teffs) are known to be important for adaptive immune responses, particularly in the settings of viral infections and cancer. CD4+ and CD8+ Treg subsets may also share similar cytotoxic properties with conventional Teffs. Cytotoxic effector Treg (cyTreg) are a heterogeneous population in the periphery that retain the capacity to suppress T-cell proliferation and activation, induce cellular apoptosis, and migrate to tissues to ensure immune homeostasis. The latter can occur through several cytolytic mechanisms, including the Granzyme/Perforin and Fas/FasL signaling pathways. This review focuses on the current knowledge and recent advances in our understanding of cyTreg and their potential application in the treatment of human disease, particularly Graft-versus-Host Disease (GVHD).

CD28 and CD57 define four populations with distinct phenotypic properties within human CD8+ T cells

After repeated antigen exposure, both memory and terminally differentiated cells can be generated within CD8⁺ T cells. Although, during their differentiation, activated CD8⁺ T cells may first lose CD28, and CD28^- cells may eventually express CD57 as a subsequent step, a population of CD28⁺ CD57⁺ (DP) CD8⁺ T cells can be identified in the peripheral blood. How this population is distinct from CD28^- CD57^- (DN) CD8⁺ T cells, and from the better characterized non-activated/early-activated CD28⁺ CD57^- and senescent-like CD28^- CD57⁺ CD8⁺ T cell subsets is currently unknown. Here, RNA expression of the four CD8⁺ T cell subsets isolated from human PBMCs was analyzed using microarrays. DN cells were more similar to "early" highly differentiated cells, with decreased TNF and IFN-γ production, impaired DNA damage response and apoptosis. Conversely, increased apoptosis and expression of cytokines, co-inhibitory, and chemokine receptors were found in DP cells. Higher levels of DP CD8⁺ T cells were observed 7 days after Hepatitis B vaccination, and decreased levels of DP cells were found in rheumatoid arthritis patients. More DP and DN CD8⁺ T cells were present in the bone marrow, in comparison with PBMCs. In summary, our results indicate that DP and DN cells are distinct CD8⁺ T cell subsets displaying defined properties.

Senescent T Cells Predict the Development of Hyperglycemia in Humans

Senescent T cells have been implicated in chronic inflammatory and cardiovascular diseases. In this study, we explored the relationship between senescent T cells and glycemic status in a cohort of 805 participants by investigating the frequency of CD57⁺ or CD28^null senescent T cells in peripheral blood. Participants with normal glucose tolerance (NGT) with follow-up data (N = 149) were included to determine whether hyperglycemia (prediabetes or type 2 diabetes) developed during follow-up (mean 2.3 years). CD8⁺CD57⁺ and CD8⁺CD28^null T-cell frequencies were significantly higher in prediabetes and type 2 diabetes compared with NGT. Increased CD57⁺ or CD28^null cells in the CD8⁺ T-cell subset were independently associated with hyperglycemia. Furthermore, among participants with baseline NGT, the frequency of CD8⁺CD57⁺ T cells was an independent predictor of hyperglycemia development. Immunofluorescent analyses confirmed that CD8⁺CD57⁺ T-cell infiltration was increased in visceral adipose tissue of patients with prediabetes or type 2 diabetes compared with those with NGT. Our data suggest that increased frequency of senescent CD8⁺ T cells in the peripheral blood is associated with development of hyperglycemia.

Human CD8+ T Cells in Asthma: Possible Pathways and Roles for NK-Like Subtypes

Asthma affects approximately 300 million people worldwide and is the most common chronic lung disease, which usually is associated with bronchial inflammation. Most research has focused upon the role of CD4+ T cells, and relatively few studies have addressed the phenotypic and functional roles of CD8+ T cell types and subtypes. Human NK-like CD8+ T cells may involve cells that have been described as CD8+CD28−, CD8+CD28−CD57+, CD8+CD27−, or CD8+ effector memory (TEM) cells, among other. However, most of the data that are available regarding these various cell types were obtained in murine models did not thoroughly characterize these cells with phenotypically or functionally or did not involve asthma-related settings. Nevertheless, one may conceptualize three principal roles for human NK-like CD8+ T cells in asthma: disease-promoting, regulatory, and/or tissue repair. Although evidence for some of these roles is scarce, it is possible to extrapolate some data from overlapping or related CD8+ T cell phenotypes, with caution. Clearly, further research is warranted, namely in terms of thorough functional and phenotypic characterization of human NK-like CD8+ T cells in human asthma of varying severity.

Mesenchymal stem cells control alloreactive CD8(+) CD28(-) T cells

CD28/B7 co-stimulation blockade with belatacept prevents alloreactivity in kidney transplant patients. However, cells lacking CD28 are not susceptible to belatacept treatment. As CD8(+) CD28(-) T-cells have cytotoxic and pathogenic properties, we investigated whether mesenchymal stem cells (MSC) are effective in controlling these cells. In mixed lymphocyte reactions (MLR), MSC and belatacept inhibited peripheral blood mononuclear cell (PBMC) proliferation in a dose-dependent manner. MSC at MSC/effector cell ratios of 1:160 and 1:2·5 reduced proliferation by 38·8 and 92·2%, respectively. Belatacept concentrations of 0·1 μg/ml and 10 μg/ml suppressed proliferation by 20·7 and 80·6%, respectively. Both treatments in combination did not inhibit each other's function. Allostimulated CD8(+) CD28(-) T cells were able to proliferate and expressed the cytolytic and cytotoxic effector molecules granzyme B, interferon (IFN)-γ and tumour necrosis factor (TNF)-α. While belatacept did not affect the proliferation of CD8(+) CD28(-) T cells, MSC reduced the percentage of CD28(-) T cells in the proliferating CD8(+) T cell fraction by 45·9% (P = 0·009). CD8(+) CD28(-) T cells as effector cells in MLR in the presence of CD4(+) T cell help gained CD28 expression, an effect independent of MSC. In contrast, allostimulated CD28(+) T cells did not lose CD28 expression in MLR-MSC co-culture, suggesting that MSC control pre-existing CD28(-) T cells and not newly induced CD28(-) T cells. In conclusion, alloreactive CD8(+) CD28(-) T cells that remain unaffected by belatacept treatment are inhibited by MSC. This study indicates the potential of an MSC-belatacept combination therapy to control alloreactivity.

Reduced regulatory T cells are associated with higher levels of Th1/TH17 cytokines and activated MAPK in type 1 bipolar disorder

Bipolar disorder (BD) has been associated with an immunologic imbalance shown by increased peripheral inflammatory markers. The underlying mechanisms of this phenomenon may include changes in circulating cells and differential activation of mitogen-activated protein kinases (MAPKs). Twenty-seven euthymic female subjects with BD type I (all medicated) and 24 age- and sex-matched controls were recruited in this study. Lymphocytes were isolated and stimulated in vitro to assess Th1/Th17/Th2 cytokines (IL-2, IL-4, IL-6, IL-10, IL-17, IFN-γ and TNF-α) and MAPK phosphorylation. The expression of phospho-MAPKs, a large panel of lymphocyte subsets and cytokines were assessed by multi-color flow cytometry. BD patients had reduced proportions of natural T regulatory cells (CD4+ CD25+ FoxP3+) (p<0.01) in parallel to higher cytokine production (all p<0.01) than healthy controls. In particular, BD was associated with a strong bias to Th1 rather than Th2 profile. There was an expansion of senescence-associated cells (CD8+ CD28-) in BD (p<0.0001). T cells of BD patients had an increased p-ERK signaling (p<0.0001), indicating lymphocyte activation. Our data suggest that multiple molecular and cellular mechanisms may contribute to the immunologic imbalance observed in BD. In addition, our data concur to an early senescence process in these patients.

CD8+ CD28- and CD8+ CD57+ T cells and their role in health and disease

Chronic antigenic stimulation leads to gradual accumulation of late-differentiated, antigen-specific, oligoclonal T cells, particularly within the CD8(+) T-cell compartment. They are characterized by critically shortened telomeres, loss of CD28 and/or gain of CD57 expression and are defined as either CD8(+) CD28(-) or CD8(+) CD57(+) T lymphocytes. There is growing evidence that the CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population plays a significant role in various diseases or conditions, associated with chronic immune activation such as cancer, chronic intracellular infections, chronic alcoholism, some chronic pulmonary diseases, autoimmune diseases, allogeneic transplantation, as well as has a great influence on age-related changes in the immune system status. CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population is heterogeneous and composed of various functionally competing (cytotoxic and immunosuppressive) subsets thus the overall effect of CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell-mediated immunity depends on the predominance of a particular subset. Many articles claim that CD8(+) CD28(-) (CD8(+) CD57(+)) T cells have lost their proliferative capacity during process of replicative senescence triggered by repeated antigenic stimulation. However recent data indicate that CD8(+) CD28(-) (CD8(+) CD57(+)) T cells can transiently up-regulate telomerase activity and proliferate under certain stimulation conditions. Similarly, conflicting data is provided regarding CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell sensitivity to apoptosis, finally leading to the conclusion that this T-cell population is also heterogeneous in terms of its apoptotic potential. This review provides a comprehensive approach to the CD8(+) CD28(-) (CD8(+) CD57(+)) T-cell population: we describe in detail its origins, molecular and functional characteristics, subsets, role in various diseases or conditions, associated with persistent antigenic stimulation.

Changes in T cell phenotype and activated MAPKs are correlated to impaired cellular responses to antigens and glucocorticoids during HTLV-I infection

Lymphocytes of human T-lymphotropic virus type-I (HTLV-I) infected patients were previously found tolerant to mitogenic stimuli as well as glucocorticoid treatment. These data suggest that common signaling events are impaired during this infection. The underlying mechanisms of these phenomena may include changes in cellular composition, cytokine milieu and the differential activation of mitogen-activated protein kinases (MAPKs). We investigated the role of (i) p38 and ERK MAPKs, (ii) lymphocyte subpopulations, (iii) and cytokines implicated in antigen or glucocorticoid-induced immunomodulation. Twenty-one asymptomatic carriers (AC), 19 patients with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and 21 healthy subjects took part in this study. Lymphocytes were isolated and cultured in vitro to assess lymphocyte proliferation and sensitivity to dexamethasone. The expression of phospho-MAPKs, lymphocyte subsets and cytokines were assessed by flow cytometry. Patients with HAM/TSP had a higher p38/ERK ratio (p<0.05) associated with a reduced response to mitogens (phytohaemagglutinin or PMA+ionomycin) (p<0.001) and higher sensitivity to dexamethasone (p<0.05). HAM/TSP patients presented increased frequency of activated T cells and CD8(+)CD28(-) regulatory T cells, being negatively related to the mitogenic response. These data suggest that multiple underlying mechanisms could be involved with HTLV-related changes in cellular response to mitogens and glucocorticoids.

Dynamics of T cell memory in human cytomegalovirus infection

Primary human cytomegalovirus (HCMV) infection of an immunocompetent individual leads to the generation of a robust CD4+ and CD8+ T cell response which subsequently controls viral replication. HCMV is never cleared from the host and enters into latency with periodic reactivation and viral replication, which is controlled by reactivation of the memory T cells. In this article, we discuss the magnitude, phenotype and clonality of the T cell response following primary HCMV infection, the selection of responding T cells into the long-term memory pool and maintenance of this memory T cell population in the face of a latent/persistent infection. The article also considers the effect that this long-term surveillance of HCMV has on the T cell memory phenotype, their differentiation, function and the associated concepts of T cell memory inflation and immunosenescence.

Analysis of CD28 and bcl-2 Expression on Peripheral Blood and Liver-Infiltrating Mononuclear Cells in Patients with Autoimmune Hepatitis

Because the underlying mechanism of hepatocellular damages in autoimmune hepatitis (AIH) still remains unclear, analysis of CD28 and bcl-2 molecules, which are critical for T cell activation and survival, was performed in patients with AIH. The number of CD28(+)CD4(+) peripheral blood mononuclear cells (PBMC) in corticosteroid (CS)-treated patients was comparable to normal control individuals but decreased in untreated AIH patients. In contrast, the number of CD28(+)CD8(+) PBMC was decreased in both CS-treated and untreated AIH patients. Analysis of liver-infiltrating mononuclear cells (LIMC) showed that the number of CD28(+)CD4(+) and CD28(-)CD8(+) LIMC were positively correlated with the histology activity index score. Bcl-2(+)CD4(+) LIMC were observed in the portal area of the liver and the numbers fluctuated with disease activity during the time course after CS administration. By contrast, CD8(+) LIMC were shown not to express bcl-2. Taken collectively, these results suggest that bcl-2(+)CD28(+)CD4(+) and bcl-2(-)CD28(-)CD8(+) cells may play critical and distinct roles in hepatocellular damage in AIH.

Inflammatory process of CD8+ CD28- T cells in induced sputum from asthmatic patients

Previously unreported CD8⁺CD28⁻ and CD8⁺CD28⁺ T-cell subsets occur in healthy individuals and expand in patients suffering from autoimmune disease. Here we studied, for the first time, the expression of CD8⁺CD28⁺, CD8⁺CD28⁻, and CD8⁺CD56⁺ subpopulations in induced sputum from asthmatics. Using sputum samples, purified CD8⁺ T cells were stained for surface antigen CD28, CD56, FITC-conjugated anti-perforin, and anti-IFN-γ. Cytotoxic activity was evaluated in a chromium releasing test. Induced sputum CD8⁺CD28⁻ T cells were found to be more expanded and expressed low levels of IFN-γ in severe asthmatics than mild asthma and age-matched healthy controls. The predominance of CD8⁺CD28⁻ T cells can be in part explained by the expansion of CD8⁺CD56⁺. CD8⁺CD28⁻ T cells from severe asthmatics produced high intracytoplasmic perforin and exerted a potent cytotoxic activity. Considering their phenotyping and functional properties, the CD8⁺CD28⁻ T-cell subset may constitute an intermediate phenotype in the process of CD8⁺ T-cell differentiation of effector-type cells in severe asthmatics. Functional studies showed that CD8⁺CD28⁻ T cells had cytotoxic function.

Phenotyping of lymphocytes expressing regulatory and effector markers in infiltrating ductal carcinoma of the breast

Dysfunction of the host immune system in cancer patients can be due to a number of reasons including suppression of tumour associated antigen reactive lymphocytes by regulatory T (Treg) cells. In this study, we used flow cytometry to determine the phenotype and relative abundance of the tumour infiltrating lymphocytes (TILs) from 47 enzymatically dissociated tumour specimens from patients with infiltrating ductal carcinoma (IDC) of the breast. The expression of both effector and regulatory markers on the TILs were determined by using a panel of monoclonal antibodies. Analysis revealed CD8(+) T cells (23.4+/-2.1%) were predominant in TILs, followed by CD4(+) T cells (12.6+/-1.7%) and CD56(+) natural killer cells (6.4+/-0.7%). The CD4(+)/CD8(+) ratio was 0.8+/-0.9%. Of the CD8(+) cells, there was a higher number (68.4+/-3.5%) that expressed the effector phenotype, namely, CD8(+)CD28(+) and about 46% of this subset expressed the activation marker, CD25. Thus, a lower number of infiltrating CD8(+) T cells (31.6+/-2.8%) expressed the marker for the suppressor phenotype, CD8(+)CD28(-). Of the CD4(+) T cells, 59.6+/-3.9% expressed the marker for the regulatory phenotype, CD4(+)CD25(+). About 43.6+/-3.8% CD4(+)CD25(+) subset co-expressed both the CD152 and FOXP3, the Treg-associated molecules. A positive correlation was found between the presence of CD4(+)CD25(+) subset and age (> or =50 years old) (r=0.51; p=0.045). However, no significant correlation between tumour stage and CD4(+)CD25(+) T cells was found. In addition, we also found that the CD4(+)CD25(-) subset correlated with the expression of the nuclear oestrogen receptor (ER)-alpha in the tumour cells (r=0.45; p=0.040). In conclusion, we detected the presence of cells expressing the markers for Tregs (CD4(+)CD25(+)) and suppressor (CD8(+)CD28(-)) in the tumour microenvironment. This is the first report of the relative abundance of Treg co-expressing CD152 and FOXP3 in breast carcinoma.

[Changes in CD4+ and CD8+ T-cell subsets in HIV-infected children differently correlate with viral replication and thymic function]

BACKGROUND AND OBJECTIVE

We intended to study the relationship between T-cell subsets with plasmatic detectable viral load (VL) and T-receptor excision circles (TREC).

PATIENTS AND METHOD

Twenty HIV-infected children on highly active antiretroviral therapy (HAART) were recruited in a 1-year longitudinal retrospective study. We analyzed the relationship between changes in peripheral blood T-cell subsets, VL and TREC markers by lineal regression.

RESULTS

Memory and activated CD4+ T-cells increases had a negative association with log10 TRECs increases. However, naive CD4+ T-cells increases had a positive association with log10 TRECs increases. In contrast, memory, activated and effector CD8+ T-cells increases positively correlated with log10 VL increases. On the other hand, naive CD8+ T-cells increases had a negative association with log10 VL increases.

CONCLUSIONS

CD4+ and CD8+ T-cells subsets change in a different way as a response to the changes produced by HAART in HIV vertically infected children. CD4+ T-cells are more dependent on thymic function and CD8+ T-cells are more dependent on viral replication. Thus, the decline in cellular activation would allow the production of more naive T-cells by the thymus.

HIV infection and aging: enhanced Interferon- and Tumor Necrosis Factor-alpha production by the CD8+ CD28- T subset

BACKGROUND

T cells from HIV+ and aged individuals show parallels in terms of suppressed proliferative activity and interleukin-2 (I1-2) production and an increased number of CD8+ CD28- T cells. In order to compare cytokine production from T cells from these two states, CD4+ and CD8+ T cells from HIV+ aged, and normal young donors (controls) were monitored for cytokine production by flow cytometry, quantitative PCR and ELISA upon activation by PMA and anti-CD3. In addition, the CD8+ T cell subsets CD28+ and CD28- from the HIV+ and the aged groups were evaluated for cytokine production by flow cytometry, and compared with those from young controls.

RESULTS

Flow cytometric analysis indicated that CD8+ T cells from both HIV+ and aged donors showed an increase of approximately 2-3 fold over controls in percentage of cells producing inflammatory cytokines IFN-gamma and TNF-alpha. Similar analysis also revealed that the production of interleukins-4,6 and 10, production was very low (1-2% of cells) and unchanged in these cells. Quantitative PCR also showed a substantial increase (4-5 fold) in IFN-gamma and TNF-alpha mRNA from HIV+ and aged CD8+ T cells, as did ELISA for secreted IFN-gamma and TNF-alpha (2.3-4 fold). Flow cytometric analysis showed that the CD8+ CD28- T cell subset accounts for approximately 80-86% of the IFN-gamma and TNF-alpha production from the CD8+ subset in the aged and HIV+ states. The CD4+ T cell, while not significantly changed in the HIV+ or aged states in terms of IFN-gamma production, showed a small but significant increase in TNF-alpha production in both states.

CONCLUSIONS

Our data appear compatible with physiologic conditions existing in HIV+ and aged individuals, i.e. elevated serum levels and elevated CD8+ T cell production of IFN-gamma and TNF-alpha. Thus, the capacity for increased production of cytokines IFN-gamma and TNF-alpha in the aged individual by the dominant CD8+ CD28- subset may have a profound influence on the clinical state by aggravating inflammatory pathologies such as rheumatoid arthritis, and possibly Alzheimer's disease and Crohn's disease. In AIDS, these cytokines may contribute to wasting and cachexia. We theorize that the predominant phenotypic change to the cytotoxic CD8+ CD28- T cell subsets in both the HIV+ and the aged states may reflect a natural "endpoint" in CD8+ T cell differentiation induced after a lifetime of immune activity (toward viruses, etc) in the aged, and after a massive accelerated response to HIV in the HIV-positive individual.

CD8beta/CD28 expression defines functionally distinct populations of peripheral blood T lymphocytes

Peripheral blood CD8+ T lymphocytes generally express the CD8 coreceptor as an alphabeta heterodimer. On these cells, the CD8beta chain is present either at high (CD8betahigh) or low density (CD8betalow). CD8betahigh cells are CD28+, whereas CD8betalow cells are CD28+ or CD28-. Therefore, three subpopulations of CD8+ T cells can be described: (i) CD8betahighCD28+ (ii) CD8betalowCD28+, and (iii) CD8betalowCD28- cells. Phenotypic and functional characterization of these CD8+ T cell subsets revealed significant differences. CD8betahighCD28+ cells predominantly express CD45RA. In contrast, CD8betalowCD28+ cells frequently express CD45R0 and the activating NK receptor CD161. CD8betalowCD28- cells frequently revert to the CD45RA phenotype. In addition, these cells express CD16, CD56, CD94, and the killer-inhibitory receptors NKB1 and CD158a. Intracellular IL-2 was frequently detected in CD8betahighCD28+ cells and CD8betalowCD28+ cells, but not CD8betalowCD28- cells. CD8betalowCD28+ cells and CD8betalowCD28- cells frequently stained positive for IFN-gamma. In addition, these cells contain intracellular perforin and granzyme A. Expression of Fas (CD95) as well as susceptibility to apoptosis is markedly increased in CD8betalowCD28+ and CD8betalowCD28- cells as compared to CD8betahighCD28+ cells. In vitro activation of peripheral blood lymphocytes triggered expansion of CD8betahighCD28+ cells as well as a development into CD8betalowCD28+ and CD8betalowCD28- cells. Similarly, activation of CD8betahighCD28+ cord blood cells resulted in the appearance of CD8betalowCD28+ and CD8betalowCD28- cells. These data suggest that CD8betahighCD28+ cells can differentiate into CD8betalowCD28+ and CD8betalowCD28- cells upon TCR stimulation. Therefore, the CD8beta/CD28 subsets in peripheral blood may reflect distinct stages of post-thymic CD8+T cell development.

Correlates of immune activation marker changes in human immunodeficiency virus (HIV)-seropositive and high-risk HIV-seronegative women who use illicit drugs

The majority of natural history studies of human immunodeficiency virus (HIV) infection have immune and viral parameters in men. Data demonstrating that women have lower HIV-1 RNA levels than men at the same CD4 cell counts have raised the question of immunologic differences in HIV-seropositive women. This study describes levels and changes in phenotypic markers of immune maturity, function, and activation in the CD4 and CD8 cell subsets in HIV-seropositive and high-risk HIV-seronegative women. Our primary hypothesis was that activation levels would be significantly higher among illicit drug users. However, results showed that HIV-1 RNA level was the strongest predictor of marker level and that both HIV-1 RNA level and CD4 cell count were independently associated with CD4 activation, but illicit drug use was not. In summary, this study demonstrated that immune activation was a significant pathogenic feature in women and that activation was driven by HIV infection and not illicit drug use.

Production of CD8+ T cell nonlytic suppressive factors by CD28, CD38, and HLA-DR subpopulations

HIV infection may be modified by CD8(+) T cells by the production of nonlytic antiviral factors. To determine subpopulations that mediate nonlytic, antiviral activity, we examined the production of beta chemokines and of CD8 antiviral factor (CAF) by different subsets, using CD8(+) cells derived from 24 HIV-1-infected and 25 uninfected individuals. Subjects with CD8(+) cell counts greater than 200/microl produced increased levels of MIP-1alpha by CD8(+)CD28(+), CD8(+)CD38(-), and CD8(+)HLA-DR(+) subsets as compared with uninfected controls. CD8(+)CD38(-) cells produced higher levels of MIP-1beta and RANTES. CAF production was increased by CD8(+)CD38(+) and CD8(+)HLA-DR(+) cells of HIV-infected individuals as compared with uninfected controls. Chemokine production was increased by cells that do not express activation markers, whereas CAF activity was increased by cells expressing CD38 or HLA-DR. These findings shed light on CD8(+) T cell noncytotoxic antiviral factor production during HIV infection.

Comprehensive analyses of a unique HIV-1-infected nonprogressor reveal a complex association of immunobiological mechanisms in the context of replication-incompetent infection

We recently demonstrated that a unique HIV-1-infected nonprogressor was infected with a nonevolving replication-incompetent HIV-1 strain, showing a total absence of viral evolution in vivo. Potent immune responses against HIV-1 were observed in his PBMC, despite an apparent lack of viral replication for at least 8 years. His PBMC resisted superinfection with CCR5, CXCR4, and dual-tropic HIV-1 strains, although highly purified CD4+ T cells supported infection, but without any visible cytopathic effect. Potent noncytolytic CD8+ T cell antiviral activity was shown to protect his PBMC from productive infection. This activity was not mediated by several known chemokines or IFN-gamma, which were produced at high levels after PHA activation of his CD8+ T cells, indicating the action of other CAF-like CD8 factors. This antiviral activity was a memory response, induced by HIV-specific stimulation to similar levels observed by PHA stimulation, but absent in ex vivo resting T cells. Immunological mechanisms associated with this antiviral suppressive activity included vigorous Gag-specific helper T cell proliferative responses and high-level IFN-gamma release by both CD4 and CD8 T cells. These responses were broadly directed against multiple Gag epitopes, both previously reported and some novel epitopes. Strong HIV-specific helper T cell function was also associated with strong neutralizing antibodies. Understanding how to induce these protective immune responses in other individuals could provide a major step forward in the design of effective immunotherapies or vaccines against HIV infection.

Role of 4-1BB (CD137) in the functional activation of cord blood CD28(-)CD8(+) T cells

The CD28(-) subset of CD8(+) T cells is associated with cytotoxic T lymphocyte (CTL) effector function. We investigated a potential role for 4-1BB, a costimulatory molecule structurally related to members of the tumor necrosis factor (TNF) receptor family, in the generation and functional activation of CD28(-) CTLs by using human cord blood (CB) cells composed exclusively of naive CD8(+) T cells with few or no CD28(-) CTLs. The 4-1BB was induced preferentially on the CB CD28(-)CD8(+) T cells when CD28 down-regulation was induced by interleukin 15 (IL-15) and IL-12 stimulation. Anti-4-1BB costimulation induced dramatic phenotypic changes in the CD28(-) CTLs, including restoration of CD28 expression as well as that of memory markers such as CD45RO and CC chemokine receptor 6 (CCR6). Anti-4-1BB costimulation also promoted long-term survival of CD28(-) CTLs, which were sensitive to activation-induced cell death upon anti-CD3 stimulation. The memory-type CD28(+) CTLs induced by anti-4-1BB costimulation acquired a greatly enhanced content of granzyme B, a cytolytic mediator, and enhanced cytotoxic activity as compared with CD28(-) CTLs. Strong cytotoxicity of memory-type CTLs to a 4-1BB ligand-expressing Epstein-Barr virus (EBV)-transformed B-cell line was almost completely abrogated by 4-1BB-Fc, a soluble form of 4-1BB, suggesting involvement of 4-1BB in cytolytic processes. Taken all together, our results suggest that 4-1BB plays a role in the differentiation of effector memory CTLs.

A subset of CD8 memory T cells from old mice have high levels of CD28 and produce IFN-gamma

Using carboxyfluorescein diacetate succinimidyl ester (CFSE)-tagged cells to measure proliferation in vivo, we found that only memory CD8(+) cells from mice older than 18 months gave measurable levels of proliferation and that the proportion of memory CD8(+) T cells able to proliferate in a nonirradiated recipient increased with age. CD8 cells that had proliferated in vivo contained higher levels of CD28 when compared to CD8 cells that had not divided. Cells with high levels of CD28 were preferentially able to divide in nonirradiated recipients. Using ex vivo intracellular staining analysis, we determined that most of the CD8(+) T cells that were capable of dividing in vivo produced IFN-gamma after isolation from recipient mice or their original host. These studies thus document the presence in aged mice of a population of CD28(hi) CD8(+) cells whose ability to proliferate in vivo without antigenic stimulation and to produce IFN-gamma may be involved in immune regulation.

T-cell dynamics after high-dose chemotherapy in adults: elucidation of the elusive CD8+ subset reveals multiple homeostatic T-cell compartments with distinct implications for immune competence

Recovery of total T cell numbers after in vivo T-cell depletion in humans is accompanied by complex perturbation within the CD8+ subset. We aimed to elucidate the reconstitution of CD8+ T cells by separate analysis of putative naïve CD95- CD28+, memory CD95+ CD28+ and CD28- T cell compartments after acute maximal depletion by high-dose chemotherapy (HD-ChT) in women with high-risk breast cancer. We found that recovery of putative naïve CD8+ CD95- CD28+ and CD4+ CD95- CD28+ T cells, was compatible with a thymus-dependent regenerative pathway since their recovery was slow and time-dependent, their values were tightly related to each other, and their reconstitution patterns were inversely related to age. By analysing non-naïve T cells, a striking diversion between putative memory T cells and CD28- T cells was found. These latter increased early well beyond normal values, thus playing a pivotal role in total T-cell homeostasis, and contributed to reduce the CD4 : CD8 ratio. In contrast, putative memory T cells returned to values not significantly different from those seen in patients at diagnosis, indicating that this compartment may recover after HD-ChT. At 3-5 years after treatment, naïve T cells persisted at low levels, with expansion of CD28- T cells, suggesting that such alterations may extend further. These findings indicate that CD28- T cells were responsible for 'blind' T-cell homeostasis, but support the notion that memory and naïve T cells are regulated separately. Given their distinct dynamics, quantitative evaluation of T-cell pools in patients undergoing chemotherapy should take into account separate analysis of naïve, memory and CD28- T cells.

Immunological changes in simian immunodeficiency virus (SIV(agm))-infected African green monkeys (AGM): expanded cytotoxic T lymphocyte, natural killer and B cell subsets in the natural host of SIV(agm)

The African green monkey (AGM) model system for simian immunodeficiency virus (SIV(agm)) has been used to examine why prolonged infection with the relevant virus does not result in the development of immunodeficiency in its natural host. Blood lymphocyte subset values were determined in uninfected (n=88) and naturally SIV(agm)-infected AGMs (n=74). A number of blood cell subsets, such as CD8alpha(+)CD3(+)CD28(neg), CD8alpha(+)CD3(neg) and CD20(+) cells, were expanded significantly in clinically asymptomatic animals carrying a relatively high plasma load of viral RNA (10(4)-10(7) RNA copies/ml plasma). The expanded CD8alpha(+)CD3(+)CD28(neg) subpopulation (1094 +/- 986 cells/microl blood in infected animals versus 402 +/- 364 cells/microl blood, P=0.03) comprised cells that resembled terminally differentiated effector CD8 T cells (CD27(neg) and CD11a(+)). In SIV(agm)-infected animals, the expanded CD8alpha(+)CD3(neg) cell subset shared identity with the CD16(+) population (natural killer cells). These results demonstrate for the first time that apathogenic SIV(agm) infection causes significant changes in the immune system of its natural host. Although previous studies had indicated that noncytotoxic mechanisms might play an important role in the suppression of virus replication in the natural host of SIV(agm), this study sheds new light on the possible role of cytotoxic T lymphocytes, the innate immune system and double-positive T helper cells (CD4(+)CD8alpha(+)CD3(+)) in suppressing virus replication in this animal model of AIDS.

CD8+CD28- T cells: certainties and uncertainties of a prevalent human T-cell subset

Human peripheral blood CD8+ T cells comprise cells that are in different states of differentiation and under the control of complex homeostatic processes. In a number of situations ranging from chronic inflammatory conditions and infectious diseases to ageing, immunodeficiency, iron overload and heavy alcohol intake, major phenotypic changes, usually associated with an increase in CD8+ T cells lacking CD28 expression, take place. CD8+CD28- T cells are characterized by a low proliferative capacity to conventional stimulation in vitro and by morphological and functional features of activated/memory T cells. Although the nature of the signals that give origin to this T-cell subset is uncertain, growing evidence argues for the existence of an interplay between epithelial cells, molecules with the MHC-class I fold and CD8+ T cells. The possibility that the generation of CD8+CD28- T cells is the combination of TCR/CD3zeta- and regulatory factor-mediated signals as a result of the sensing of modifications of the internal environment is discussed.

Highly activated CD8(+) T cells in the brain correlate with early central nervous system dysfunction in simian immunodeficiency virus infection

One of the consequences of HIV infection is damage to the CNS. To characterize the virologic, immunologic, and functional factors involved in HIV-induced CNS disease, we analyzed the viral loads and T cell infiltrates in the brains of SIV-infected rhesus monkeys whose CNS function (sensory evoked potential) was impaired. Following infection, CNS evoked potentials were abnormal, indicating early CNS disease. Upon autopsy at 11 wk post-SIV inoculation, the brains of infected animals contained over 5-fold more CD8(+) T cells than did uninfected controls. In both infected and uninfected groups, these CD8(+) T cells presented distinct levels of activation markers (CD11a and CD95) at different sites: brain > CSF > spleen = blood > lymph nodes. The CD8(+) cells obtained from the brains of infected monkeys expressed mRNA for cytolytic and proinflammatory molecules, such as granzymes A and B, perforin, and IFN-gamma. Therefore, the neurological dysfunctions correlated with increased numbers of CD8(+) T cells of an activated phenotype in the brain, suggesting that virus-host interactions contributed to the related CNS functional defects.

Markers of cell death-activation in lymphocytes of vertically HIV-infected children naive to highly active antiretroviral therapy: the role of age

BACKGROUND

Apoptosis plays a major role in depleting CD4(+) lymphocytes during infection with HIV-1. Few data exist on its role during HIV infection of children. Sensitivity of peripheral blood lymphocytes (PBLs) to apoptotic stimuli and the importance of the patient's age remain unclear.

OBJECTIVES

We sought to analyze the following: (1) markers of cell death-activation (CD95, CD45 isoforms, and CD28) in PBLs from vertically HIV-infected children of different ages before highly active antiretroviral therapy; (2) changes in other PBL populations; (3) PBL sensitivity to cell death and mitochondrial damages; and (4) role of age during progression of infection.

METHODS

Cell culture techniques and flow cytometry were used to analyze surface antigens, PBL susceptibility to apoptosis, or PBL susceptibility to change of mitochondrial membrane potential.

RESULTS

Donor age had a strong negative correlation with numbers of CD4(+) and CD8(+) T cells. Virgin T lymphocyte (CD45RA(+), CD95(-)) levels and those of CD95(+) cells showed no correlation with the children's clinical status but did show a correlation with patient age. CD28(-) T lymphocytes were markedly augmented in HIV-infected children but were unrelated to stage of infection or age. A relevant decrease in B lymphocytes and an increase in natural killer cells were also found. Finally, PBLs from HIV-positive children had a marked tendency to undergo apoptosis and mitochondrial damage.

CONCLUSION

Changes in PBL phenotype, increased expression of CD95, and high sensitivity to apoptosis suggest that a precocious aging of the immune system occurs in HIV-infected children.

[Relationship between T-cells subsets and prognostic markers in HIV-1-infected children]

BACKGROUND

To investigate the relationship between peripheral blood T-cell subsets and both CD4+ T-cell percentage and viral load (VL) in HIV-1-infected children.

PATIENTS AND METHOD

We studied 50 HIV-1-infected children on antiretroviral therapy. T-cell subsets were determined by flow cytometry. The VL was quantified using standardized molecular methods.

RESULTS

Memory (CD45RO+), activated memory (CD45RO+HLA-DR+) and CD45RA-CD62L+ (memory cells expressing L-selectin) CD4+ and CD8+ T-cells correlated positively with the VL and negatively with the percentage of CD4+ T-cells. Inversely, naive CD4+ and CD8+ T-cells (CD45RA+CD62L+) correlated positively with the percentage of CD4+ T-cells and negatively with the VL. HLA-DR+, CD38+ or HLA-DR+CD38+CD4+ and CD8+ T-cells correlated also positively with the VL and negatively with the percentage of CD4+ T-cells (with the exception of CD4+CD38+ which did not show any association with the VL). CD8+CD28+ T-cells correlated positively with the percentage of CD4+ T-cells and negatively with the VL, whereas CD8+ CD57+ and CD8+CD28-CD57+ exhibited an opposite association.

CONCLUSIONS

Our data suggest a relationship between the different lymphocyte subsets (memory, naïve, activated and effector T-cells) and the most commonly used markers in clinical practice, namely the viral load and the CD4+ T-cell percentage. Some of these subsets may be useful to determine the virologic and immunologic status in HIV-1-infected children.

Association of CD8+ T lymphocyte subsets with the most commonly used markers to monitor HIV type 1 infection in children treated with highly active antiretroviral therapy

In contrast to adults, there is no information about children concerning the effects of the new antiretroviral therapy on the chronic activation and expansion of CD8+ T cells. We have investigated the relationship between blood CD8(+) T cell subsets, with percent CD4+ cells (%CD4), percent CD8+ cells (%CD8), and plasma viral load (VL), in 39 vertically HIV-1-infected children receiving highly active antiretroviral therapy (HAART) (mean age, 7.6 years; range, 2-15.6 years). CD8+ subsets were examined by three-color multiparametric flow cytometry, and VL was quantified by standard assays. There was a strong positive correlation between activated CD8+ T cells and VL. An increase in memory and memory-activated CD8+ T cells correlated with increased VL, whereas nonactivated memory cells and CD28+ CD8+ T cells correlated negatively with VL. Naive and effector cells did not correlate with VL, although the CD8+ CD45RA -CD62L- subset correlated with increased VL. Activated CD8(+) T cells did not correlate with %CD4, but an increase in memory-activated and effector CD8+ T cells was associated with lower %CD4. Increased naive CD8+ and CD28 +CD8+ T cells showed a positive correlation with %CD4 and a negative correlation with %CD8. In conclusion, in HIV-1-infected children receiving HAART, the activation of CD8+ T cells is associated with high VL, whereas CD8 +CD28+ and nonactivated CD8+ memory cells are associated with lower viral load. Naive CD8+ and CD28 +CD8+ T cells are associated with an improved immunological status.

Enhanced interferon-gamma by CD8+ CD28- lymphocytes from HIV+ patients

Flow cytometric analysis of T cells from HIV+ and normal individuals activated for 15 hr showed that the percentage of cells producing interferon-gamma (INFgamma) was enhanced approximately threefold (39 compared to 14%) in the HIV+ CD8+ population. Activation modes, other than anti-CD3 with PMA, were ineffective, and in no case did the percentage of HIV+ CD4+ T cells show increased INFgamma production over controls. Enhanced INFgamma production was not induced by either anti-CD3 or PMA alone, or anti-CD3 or ConA with anti-CD28, or enhanced by N-acetylcysteine. In contrast to INFgamma production, the percentage of CD4+ T cells producing interleukin-2 (Il-2) greatly exceeded that of the CD8+ T cells. The results from flow cytometry analyses of HIV+ CD8+ T cells was supported by quantitative analysis of INFgamma mRNA (by PCR) and INFgamma secretion by ELISA. These methods showed a sixfold and three- to fivefold increase, respectively, on a per cell basis. As HIV infection progresses, as shown by loss of CD4+ T cells, the proportion of CD8+ CD28- T cells increases, and it is this T cell subset that is responsible for 80% or more of the enhanced INFgamma production. The enhanced INFgamma in HIV+ patients derives from two factors: the increase in CD8+ CD28- cells to 70% and the percentage producing INFgamma (60%, compared to 21% for CD8+ CD28+ cells). Our findings of a substantial increase in INFgamma production in HIV infection arising from the increased number of CD8+ CD28- T cells are compatible with clinical studies which show elevated INFgamma in HIV+ serum and INFgamma producing CD8+ T cells dominating HIV+ lymph nodes. We also found a significantly decreased proliferative response of the HIV+-derived CD8+ T cell fraction with coactivator anti-CD-28, in contrast to PMA (with anti-CD3), which is probably a reflection of the diminished population of CD8+ CD28+ T cells in HIV+ donors compared to normal donors (30.7 compared to 67.9%).

Longitudinal analysis of CD8+ T-cell phenotype and IL-7, IL-15 and IL-16 mRNA expressionin different tissues during primary simian immunodeficiency virus infection

Infection of macaques with pathogenic isolates of simian immunodeficiency virus (SIV) represents a useful model of HIV infection that offers the unique opportunity to investigate the very early modifications that affect CD8(+) T-lymphocyte subsets and related cytokines during lentiviral infection. Herein, three cynomolgus macaques were inoculated intravenously with a pathogenic isolate of SIVmac 251. In fresh isolated mononuclear cells from blood, lymph node and bronchoalveolar lavage, we analyzed changes in the phenotype of CD8(+) T cells and we used reverse transcription-PCR to monitor the expression of IL-7, IL-15 and IL-16 mRNA. We demonstrated that an expansion of CD8(+)CD28(-) T cells occurs from the third week of infection on in the peripheral blood and in the lung, whereas CD8(+)CD28(+) T cells expand in the lymph nodes. Concomitantly, we evidenced mRNA modulations in IL-16, IL-15 and IL-7 expression in the three compartments studied. The containment of systemic viral replication was associated with an overexpression of IL-16 mRNA in the lung and in the peripheral blood. Given the immunomodulatory properties of IL-15 and IL-7 and the potential antiviral ability of IL-16, these perturbations could have important implications in early viral dissemination and HIV immunopathogenesis.

CD11b expression identifies CD8+CD28+ T lymphocytes with phenotype and function of both naive/memory and effector cells

A previously unreported CD8(+)CD28(+)CD11b(+) T cell subset occurs in healthy individuals and expands in patients suffering from primary viral infections. In functional terms, these cells share the features of naive/memory CD8(+)CD28(+)CD11b(-) and terminally differentiated effector CD8(+)CD28(-)CD11b(+) subpopulations. Like CD28(-) cells, CD28(+)CD11b(+) lymphocytes have the ability to produce IFN-gamma, to express perforin granules in vivo, and to exert a potent cytolytic activity. Moreover, these cells can respond to chemotactic stimuli and can efficiently cross the endothelial barrier. In contrast, like their CD11b(-) counterpart, they still produce IL-2 and retain the ability to proliferate following mitogenic stimuli. The same CD28(+)CD11b(+) subpopulation detected in vivo could be generated by culturing naive CD28(+)CD11b(-) cells in the presence of mitogenic stimuli following the acquisition of a CD45RO(+) memory phenotype. Considering both phenotypic and functional properties, we argue that this subset may therefore constitute an intermediate phenotype in the process of CD8(+) T cell differentiation and that the CD11b marker expression can distinguish between memory- and effector-type T cells in the human CD8(+)CD28(+) T cell subset.

Comparison of T-cell subsets' reconstitution after 12 months of highly active antiretroviral therapy initiated during early versus advanced states of HIV disease

This research comprised a pilot open prospective clinical study comparing T-cell subset reconstitution in antiretroviral-naive patients, after 12 months of HAART when treatment was initiated in early stages (ES; n = 18) of infection versus advanced stages (AS; n = 20).

CONTROL GROUP

10 healthy HIV-negative individuals. Immunophenotypic markers were evaluated before and after 6-and 12-months' therapy. Functional assays were performed in one subset.

RESULTS

Viral load (VL) was < 200 copies/ml in all patients. Median percentages of CD4+ pretherapy were 33% and 6%, respectively, in the ES and AS groups, increment after 12 months of therapy was +15% and +13% respectively. Only the ES group achieved normal values. Declines of CD8+ percentage were significantly higher in the ES (-18%) than in the AS group (-2%). CD4+ memory and naive cells in the ES group were similar to those of controls before treatment and did not change after therapy. In contrast, CD4+ memory and naive cells in the AS group did not reach normal levels despite treatment. In the ES group, there was a significant increment in CD8+ naive cells (+8%) and a decrement in CD8+CD38+ cells (-17%), both populations reached values close to normal, whereas these subsets remained far from normal in the AS group. Improvement of lymphoproliferative response after therapy was observed in both groups. One patient in the ES group showed positive LPR against p24 after treatment. After 12 months' highly active antiretroviral therapy, only those who began such therapy in ES disease reached values within the range of healthy controls. To achieve a more complete immunologic reconstitution, early initiation of potent antiretroviral therapy should be recommended.

Human immunodeficiency virus type 1 induces apoptosis in CD4(+) but not in CD8(+) T cells in ex vivo-infected human lymphoid tissue

Progression of human immunodeficiency virus (HIV) disease is associated with massive death of CD4(+) T cells along with death and/or dysfunction of CD8(+) T cells. In vivo, both HIV infection per se and host factors may contribute to the death and/or dysfunction of CD4(+) and CD8(+) T cells. Progression of HIV disease is often characterized by a switch from R5 to X4 HIV type 1 (HIV-1) variants. In human lymphoid tissues ex vivo, it was shown that HIV infection is sufficient for CD4(+) T-cell depletion. Here we address the question of whether infection of human lymphoid tissue ex vivo with prototypic R5 or X4 HIV variants also depletes or impairs CD8(+) T cells. We report that whereas productive infection of lymphoid tissue ex vivo with R5 and X4 HIV-1 isolates induced apoptosis in CD4(+) T cells, neither viral isolate induced apoptosis in CD8(+) T cells. Moreover, in both infected and control tissues we found similar numbers of CD8(+) T cells and similar production of cytokines by these cells in response to phorbol myristate acetate or anti-CD3-anti-CD28 stimulation. Thus, whereas HIV-1 infection per se in human lymphoid tissue is sufficient to trigger apoptosis in CD4(+) T cells, the death of CD8(+) T cells apparently requires additional factors.

Expansion of rare CD8+ CD28- CD11b- T cells with impaired effector functions in HIV-1-infected patients

The decline in the number of CD4+ T cells in HIV-1-infected patients is known to be related to the increased number of CD8+CD28- T cells. In this paper, we show that CD8+CD28- T cells from HIV-positive patients have an impaired capability to interact with human endothelial cells. This is due to the dramatic expansion, within this subset, of rare CD11b- cells lacking cell-cell adhesion functions. In 50 HIV-positive patients, 19.5% +/- 6.5% of all T cells were CD8+CD28-CD11b-, whereas only 0.8% +/- 0.4% of all T cells from healthy donors showed this uncommon phenotype. The percentage of circulating CD8+CD28-CD11b- T cells was strongly related to the percentage of CD4+ T cells (r = -0.82). This population is peculiar in terms of HIV infection and was found to possess some characteristics associated with effector functions but its cytotoxic properties were impaired. The percentage of target cells lysed by CD8+CD28-CD11b- was significantly lower than that of cells lysed by its CD11b- counterpart (p <.05) both at low (5:1) or at relatively high (20:1) effector/target ratios. CD8+CD28-CD11b- T cells, which lack the ability to interact with endothelial cells, are likely to accumulate and persist in circulation. The biologic properties of CD8+CD28-CD11b- T cells suggest that these cells might be endstage or aberrant differentiated effector cells. Lack of cell-cell adhesion and impaired cytolytic functions favor the hypothesis of a role for CD8+CD28-CD11b- T cells in the development of immunodeficiency.

Loss of CD28 expression on CD8(+) T cells is induced by IL-2 receptor gamma chain signalling cytokines and type I IFN, and increases susceptibility to activation-induced apoptosis

CD8(+)CD28(-) T cells are selectively expanded during viral infections, indicating their importance in anti-viral immune responses. Since little is known about the differentiation of CD8(+)CD28(-) cells, we investigated the generation, function and survival characteristics of this subset. In healthy individuals CD8(+)CD28(-) T cells contained more elevated levels of perforin and IFN-gamma than the CD8(+)CD28(+) subset, indicating that they can have an effector function. CD8(+)CD28(-) cells were selectively expanded when activated CD8(+)CD28(+) T cells were cultured in IL-2, IL-7 or IL-15. Moreover, the generation of CD8(+)CD28(-) cells was accelerated by type I IFN suggesting that these cytokines which are released during viral infections influence CD8(+) T cell differentiation. We did not observe re-expression of CD28 by CD8(+)CD28(-) T cells in any of the experiments performed. Activated T cells are susceptible to activation-induced cell death (AICD) if re-stimulated in the absence of co-stimuli. AICD was induced in both CD28(+) and CD28(-) subsets of activated T cells when stimulated with anti-CD3 antibody in the absence of co-stimuli but the magnitude of death was greater in the CD28(-) subset. While co-stimulation through LFA-1 (CD11a and CD18) significantly reduced AICD in the CD8(+)CD28(+) subset, death was not prevented in CD8(+)CD28(-) cells. These results suggest that CD8(+)CD28(-) T cells are more functionally differentiated than the CD8(+)CD28(+) subset and indicate they may represent a terminally differentiated effector population which is destined for clearance by apoptosis at the end of the immune response.

Anti-human immunodeficiency virus type 1 (HIV-1) CD8(+) T-lymphocyte reactivity during combination antiretroviral therapy in HIV-1-infected patients with advanced immunodeficiency

The long-term efficacy of combination antiretroviral therapy may relate to augmentation of anti-human immunodeficiency virus type 1 (HIV-1) CD8(+) T-cell responses. We found that prolonged treatment of late-stage HIV-1-infected patients with a protease inhibitor and two nucleoside reverse transcriptase inhibitors failed to restore sustained, high levels of HIV-1-specific, HLA class I-restricted, cytotoxic-T-lymphocyte precursors and gamma interferon (IFN-gamma) production by CD8(+) T cells. In some patients, particularly those initiating three-drug combination therapy simultaneously rather than sequentially, there were early, transient increases in the frequency of anti-HIV-1 CD8(+) T cells that correlated with decreases in HIV-1 RNA and increases in T-cell counts. In the other patients, HIV-1-specific T-cell functions either failed to increase or declined from baseline during triple-drug therapy, even though some of these patients showed suppression of plasma HIV-1 RNA. These effects of combination therapy were not unique to HIV-1 specific T-cell responses, since similar effects were noted for CD8(+) T cells specific for the cytomegalovirus pp65 matrix protein. The level and breadth of CD8(+) cell reactivity to HLA A*02 HIV-1 epitopes, as determined by IFN-gamma production and HLA tetramer staining after combination therapy, were related to the corresponding responses prior to treatment. There was, however, a stable, residual population of potentially immunocompetent HIV-1-specific T cells remaining after therapy, as shown by tetramer staining of CD8(+) CD45RO(+) cells. These results indicate that new strategies will be needed to target residual, immunocompetent HIV-1-specific CD8(+) T cells to enhance the effectiveness of antiretroviral therapy in patients with advanced immunodeficiency.

Treatment-resistant expansion of CD8+CD28-cells in pediatric HIV infection

There is a disease stage-dependent loss of CD28 expression on T cells in HIV-infected children. In this study, T cell recovery, in particular CD28 expression on T cells, was analyzed after initiation of highly active antiretroviral therapy in a group of eight mostly treatment-naive HIV-infected children. Plasma HIV-RNA levels were recorded, and numbers of CD4, CD8, CD4+CD28+, and CD8+CD28+ cells were determined by two-color flow cytometry. Values after 12 mo of therapy were compared with age-matched, seronegative control subjects. CD4 recovery to subnormal values was observed in all children. CD8+CD28+ cells recovered and were within the normal range after 12 mo of therapy (patients, 703 +/- 250 cells/microL; controls, 789 +/- 269 cells/microL), whereas CD8+CD28- cells (546 +/- 269 cells/microL) remained significantly expanded compared with age-matched controls (140 +/- 35 cells/microL). Expansions of CD8+CD28- cells persisted even in cases with long-term suppression of viral replication. Highly active antiretroviral therapy in HIV-infected children induces substantial but incomplete T cell recovery.

Effect of long-term infection with nef-defective attenuated HIV type 1 on CD4+ and CD8+ T lymphocytes: increased CD45RO+CD4+ T lymphocytes and limited activation of CD8+ T lymphocytes

Members of the Sydney Blood Bank Cohort (SBBC) have been infected with an attenuated strain of HIV-1 with a natural nef/LTR mutation and have maintained relatively stable CD4+ T lymphocyte counts for 14-18 years. Flow cytometric analysis was used to examine the phenotype of CD4+ and CD8+ T lymphocytes in these subjects, including the immunologically important naive (CD45RA+CD62L+), primed (CD45RO+), and activated (CD38+HLA-DR+ and CD28-) subsets. The median values were compared between the SBBC and control groups, comprising age-, sex-, and transfusion-matched HIV-1-uninfected subjects; transfusion-acquired HIV-1-positive LTNPs; and sexually acquired HIV-1-positive LTNPs. Members of the SBBC not only had normal levels of naive CD4+ and CD8+ T lymphocytes, but had primed CD45RO+ CD4+ T lymphocytes at or above normal levels. Furthermore, these primed cells expressed markers suggesting recent exposure to specific antigen. SBBC members exhibited variable activation of CD8+ T lymphocytes. In particular, SBBC members with undetectable plasma HIV-1 RNA had normal levels of activated CD8+ T lymphocytes. Therefore, the result of long-term infection with natural nef/LTR mutant HIV-1 in these subjects suggests a decreased cytopathic effect of attenuated HIV-1 on susceptible activated CD4+ T lymphocyte subsets in vivo, and minimal activation of CD8+ T lymphocytes.

Weak anti-HIV CD8(+) T-cell effector activity in HIV primary infection

HIV-specific CD8(+) T cells play a major role in the control of virus during HIV primary infection (PI) but do not completely prevent viral replication. We used IFN-gamma enzyme-linked immunospot assay and intracellular staining to characterize the ex vivo CD8(+) T-cell responses to a large variety of HIV epitopic peptides in 24 subjects with early HIV PI. We observed HIV-specific responses in 71% of subjects. Gag and Nef peptides were more frequently recognized than Env and Pol peptides. The number of peptides recognized was low (median 2, range 0-6). In contrast, a much broader response was observed in 30 asymptomatic subjects with chronic infection: all were responders with a median of 5 peptides recognized (range 1-13). The frequency of HIV-specific CD8(+) T cells among PBMC for a given peptide was of the same order of magnitude in both groups. The proportion of HIV-specific CD8(+)CD28(-) terminally differentiated T cells was much lower in PI than at the chronic stage of infection. The weakness of the immune response during HIV PI could partially account for the failure to control HIV. These findings have potential importance for defining immunotherapeutic strategies and establishing the goals for effective vaccination.

Cutaneous CD8 T cell infiltrates in advanced HIV infection

BACKGROUND

Aggressive non-Hodgkin's lymphomas are common among patients infected with HIV. Although such lymphomas are mostly of the B-cell type, various cases of cutaneous T-cell lymphoma (CTCL) have also been reported. Recent reports suggest that some HIV-related lymphoproliferative conditions may not be clonal processes, but polyclonal lymphoid proliferations.

OBJECTIVE

We reviewed our experience with HIV patients seen at the dermatology clinics for possible CTCL.

METHODS

A retrospective study was performed to evaluate clinical, laboratory, and histologic findings of HIV-infected patients with atypical T-cell cutaneous infiltrates.

RESULTS

We observed 9 patients with advanced HIV infection and a cutaneous eruption characterized by a dense infiltrate of lymphocytes resembling mycosis fungoides histopathologically, but composed of CD8(+) cells. Although clonality was not identified in any of the 6 cases tested, 3 patients had similar CD8(+) infiltrates involving lymph nodes or bone marrow. Of the 9 patients, 8 died of AIDS wasting syndrome or infections in less than 1 year.

CONCLUSION

Cutaneous and systemic infiltrates with polyclonal CD8 T lymphocytes can be seen in patients with advanced HIV infection and profound CD4 lymphopenia. The clinical presentation may resemble CTCL and is associated with a poor outcome.

Peripheral human CD8(+)CD28(+)T lymphocytes give rise to CD28(-)progeny, but IL-4 prevents loss of CD28 expression

At birth, virtually all peripheral CD8(+) T cells express the CD28 co-stimulatory molecule, but healthy human adults accumulate CD28(-)CD8(+) T cells that often express the CD57 marker. While these CD28(-) subpopulations are known to exert effector-type functions, the generation, maintenance and regulation of CD28(-) (CD57(+) or CD57(-)) subpopulations remain unresolved. Here, we compared the differentiation of CD8(+)CD28(bright)CD57(-) T cells purified from healthy adults or neonates and propagated in IL-2, alone or with IL-4. With IL-2 alone, CD8(+)CD28(bright)CD57(-) T cell cultures yielded a prevailing CD28(-) subpopulation. The few persisting CD28(dim) and the major CD28(-) cells were characterized by similar telomere shortening at the plateau phase of cell growth. Cultures from adults donors generated four final CD8(+) phenotypes: a major CD28(-)CD57(+), and three minor CD28(-)CD57(-), CD28(dim)CD57(-) and CD28(dim)CD57(dim). These four end-stage CD8(+) subpopulations displayed a fairly similar representation of TCR V(beta) genes. In cultures initiated with umbilical cord blood, virtually all the original CD8(+)CD28(bright) T cells lost expression of CD28, but none acquired CD57 with IL-2 alone. IL-4 impacted on the differentiation pathways of the CD8(+)CD28(bright)CD57(-) T cells: the addition of IL-4 led both the neonatal and the adult lymphocytes to keep their expression of CD28. Thus, CD8(+)CD28(bright)CD57(-) T cells can give rise to four end-stage subpopulations, the balance of which is controlled by both the cytokine environment, IL-4 in particular, and the proportions of naive and memory CD8(+)CD28(+) T cells.

Enhanced IFN-gamma production in vitro by CD8+ T cells in hemophiliacs with AIDS as demonstrated on the single-cell level

We examined T cells from HIV-infected hemophiliacs under antiviral therapy, on the single-cell level, for cytokine production in vitro in response to stimulation. The percentage of IL-2-producing cells was markedly decreased among both CD3+CD8- and CD3+CD8+ cells, while the proportion of IFN-gamma-producing cells was preserved among CD3+CD8- cells and increased among CD3+CD8+ cells in HIV+ subjects, compared with HIV-uninfected controls. The increase in IFN-gamma-producing CD8+ cells was accounted for by the expansion of CD8+CD28- cells among total CD8+ T cells and by the higher percentage of IFN-gamma-expressing cells among both CD8+CD28+ and CD8+CD28- cells in HIV+ individuals, compared with controls. The enhanced IFN-gamma production in CD8+ cells from individuals in the advanced phase of HIV infection might implicate the host's response to chronic viral infection or senescence of host CD8+ cells.

HIV-specific cytotoxic T lymphocyte precursors exist in a CD28-CD8+ T cell subset and increase with loss of CD4 T cells

OBJECTIVES

To determine whether the CD28-CD8+ T cells that develop during HIV infection contain HIV-specific cytotoxic precursor cells.

DESIGN

CD8 subpopulations from six asymptomatic HIV-positive adults, with varying degrees of CD4 T cell loss, were sorted by flow cytometry and HIV-specific precursor cytotoxic T lymphocyte frequencies were measured. Three populations of CD8 T cells were tested: CD28+CD5-- T cells, CD28-CD57+ T cells (thought to be memory cells) and CD28-CD57- T cells (function unknown).

METHODS

Sorted CD8 subsets were stimulated with antigen presenting cells expressing HIV-1 Gag/Pol molecules. Cytotoxic T cell assays on Gag/Pol expressing 51Cr-labeled Epstein-Barr virus transformed autologous B cells lines or control targets were performed after 2 weeks. Specific lysis and precursor frequencies were calculated.

RESULTS

Both CD28 positive and CD28-CD57+ populations contained appreciable numbers of precursors (9-1720 per 10(6) CD8+ T cells). However, the CD28-CD57- population had fewer precursors in five out of six people studied. More CD28 positive HIV-specific cytotoxic T lymphocyte precursors were found in patients with CD4:CD8 ratios > 1, whereas more CD28-CD57+ precursors were found in patients whose CD4:CD8 ratios were < 1 (r2, 0.68).

CONCLUSIONS

Memory HIV-specific precursor cytotoxic T lymphocytes are found in both CD28 positive and CD28-CD8+ cells, however, a CD28-CD57- subpopulation had fewer. Because CD28-CD57+ cells are antigen-driven with limited diversity, the loss of CD28 on CD8 T cells during disease progression may reduce the response to new HIV mutations; this requires further testing.

C1.7 Antigen Expression on CD8+ T Cells Is Activation Dependent: Increased Proportion of C1.7+CD8+ T Cells in HIV-1-Infected Patients with Progressing Disease

The C1.7 Ag is a surface marker previously shown to be expressed on all NK cells and on a subset of CD8+ T cells. We report in this study that C1.7 Ag expression on peripheral blood-derived CD8+ T cells overlaps with activation markers S6F1high and CD29high and is reciprocally expressed with CD62L. C1.7 Ag expression can be induced in vitro on CD8+ T cells by anti-CD3 cross-linking, suggesting that C1.7 Ag is activation dependent. In contrast to NK cells, C1.7 Ag does not signal on CD8+ T cells, nor does it induce redirected lysis upon ligation. The proportion of C1.7 Ag+CD8+ T cells is increased in HIV-infected patients compared with healthy donors. In 69 HIV-infected patients, we observed a significant inverse correlation between the percentage of C1.7 Ag-expressing CD8+ T cells and the absolute CD4+ T cell count. Two-year clinical follow-up of patients with initial CD4+ T cell count of &gt;400 cells/mm3 and a normal proportion of C1.7 Ag+CD8+ T cells revealed that these patients were clinically stable with minimal HIV-associated symptoms. In contrast, 10 of 12 patients with CD4+ T cell counts of &gt;400 cells/mm3 and an elevated proportion of C1.7 Ag+CD8+ T cells were symptomatic. ANOVA analysis of patients indicates that C1.7 Ag is a better predictor of disease progression than CD4 count. Overall, our findings indicate that C1.7 Ag is the first described marker for activated/memory CD8+ T cells and a useful parameter for evaluating the level of CD8+ T cell activation in vivo.

Human CD28−CD8+ T Cells Contain Greatly Expanded Functional Virus-Specific Memory CTL Clones

At birth, almost all human peripheral blood CD8+ T cells express the costimulatory molecule CD28. With increasing age, the proportion of CD8+ T cells that lack CD28 increases. Because the Ag specificity of CD28−CD8+ T cells has not previously been defined, we studied the contribution of CD28−CD8+ T cells to the memory CD8+ CTL response against two human persistent viruses, human CMV (HCMV) and HIV. From PBMC of healthy virus carriers we generated multiple independent CTL clones specific for defined viral peptides and sequenced their TCR β-chains. We designed clonotypic oligonucleotides complementary to each β-chain hypervariable sequence and quantified the size of individual immunodominant CTL clones in PBMC. Some individual CTL clones were very large, comprising up to 3.1% of all CD8+ T cells in PBMC, and were generally maintained at a stable level for months. Individual virus-specific CTL clones were consistently more abundant in purified CD28− cells than in the CD8+ population as a whole. Because CD28−CD8+ cells as a population have been reported to proliferate poorly in response to mitogen, we studied the function of these virus-specific CD28− CTL clones by quantifying the frequency of peptide-specific CTL precursors using limiting dilution analysis. CD28−CD8+ T cells contained high frequencies of functional memory CTL precursors specific for peptides of HCMV or HIV, generally higher than in the CD8+ T cell population as a whole. We conclude that in asymptomatic HCMV and HIV infection, human CD28−CD8+ T cells contain high frequencies of functional virus-specific memory CTL clones.

Expression of CD28 and CD38 by CD8+ T lymphocytes in HIV-1 infection correlates with markers of disease severity and changes towards normalization under treatment. The Swiss HIV Cohort Study

The relationship between blood CD8+ T lymphocyte subsets, as defined by CD28 and CD38 expression, and plasma viraemia and CD4+ T cells in HIV-1 infection was investigated. In a cross-sectional study of 46 patients with either no or stable anti-retroviral treatment, there was a strong negative correlation between the percentage of CD8+CD28- and the percentage of CD4+ T cells (r = -0.75, P < 0.0001), and a positive correlation between absolute numbers of CD8+CD28+ and CD4+ T cells (r = 0.56, P < 0.0001). In contrast, the expression of CD38 by CD8+ T lymphocytes correlated primarily with plasma viraemia (e.g. the percentage of CD38+ in CD8bright cells, r = 0.76, P < 0.0001). In the 6 months following triple therapy initiation in 32 subjects, there was a close correlation between changes (delta) in CD8+CD28+ or CD8+CD28- and in CD4+ T cells (e.g. delta % CD8+CD28+ versus delta % CD4+, r = 0.37, P = 0.0002; delta % CD8+CD28- versus delta % CD4+, r = -0.66, P < 0.0001). A marked decline of the number of CD8+ T cells expressing CD38 was also observed. These results suggest the existence of a T cell homeostasis mechanism operating in blood with CD4+ and CD8+CD28+ cells on the one hand, and with CD8+CD28- cells on the other. In addition, the percentage of CD38+ cells in CD8+ cells, generally considered an independent prognostic factor, could merely reflect plasma viral load.