An IL-15 Dependent CD8 T Cell Response to Selected HIV Epitopes is Related to Viral Control in Early-Treated HIV-Infected Subjects

In some early-treated HIV+ patients, Structured Treatment Interruption (STI) is associated to spontaneous control of viral rebound. Thus, in this clinical setting, we analyzed the immunological parameters associated to viral control. Two groups of early treated patients who underwent STI were retrospectively defined, according to the ability to spontaneously control HIV replication (Controller and Non-controller). Plasma cytokine levels were analyzed by multiplex analysis. CD8 T cell differentiation was determined by polychromatic flow cytometry. Antigen-specific IFN-Γ production was analyzed by ELISpot and intracellular staining after stimulation with HIV-peptides. Long-term Elispot assays were performed in the presence or absence of IL-15. Plasma IL-15 was found decreased over a period of time in Non-Controller patients, whereas a restricted response to Gag (aa.167–202 and 265–279) and Nef (aa.86–100 and 111–138) immunodominant epitopes was more frequently observed in Controller patients. Interestingly, in two Non-Controller patients the CD8-mediated T cells response to immunodominant epitopes could be restored in vitro by IL-15, suggesting a major role of cytokine homeostasis on the generation of protective immunity. In early-treated HIV+ patients undergoing STI, HIV replication control was associated to CD8 T cell maturation and sustained IL-15 levels, leading to HIV-specific CD8 T cell responses against selected Gag and Nef epitopes.

Different Cytokine Production and Effector/Memory Dynamics of αβ+ or γδ+ T-Cell Subsets in the Peripheral Blood of Patients with Active Pulmonary Tuberculosis

Immunity to M.tuberculosis (MTB) infection consists of interactions between various T-cell subsets that control the infection and prevent further reactivation. We analysed the effector/memory T-cell dynamics and cytokines production in the peripheral blood of patients with pulmonary tuberculosis (TB). We observed that the frequency of CD4+ T-cell effectors was significantly increased during active TB, confirming a major role of this T-cell subset in TB immunity. Pre-terminally differentiated CD8+ T-lymphocytes were increased in the peripheral blood as well. In contrast, we observed a reduced number of effector mycobacteria-reactive γδ+ T-lymphocytes with a specific defects in reacting to mycobacterial nonpeptidic antigens, suggesting that this innate response is rapidly lost during TB infection. Nevertheless, the frequency of γδ+ T-cells effectors in TB patients was higher than the αβ+ T-cell response to peptide from MTB-ESAT-6 protein and quantitatively similar to PPD reactivity. Thus, αβ+and γδ+ T-cell differentiation and function are differently triggered by active TB infection.

Activation of interferon response genes and of plasmacytoid dendritic cells in HIV-1 positive subjects with GB virus C co-infection

GB virus C (GBV-C) coinfection has a protective role in Human Immunodeficiency Virus (HIV) infection, and increases the duration of suppression of HIV-1 viremia in patients under Highly Active Anti-Retroviral Therapy (HAART). Since innate antiviral response may be involved in the protection, we analyzed the possible role of GBV-C as activator of innate immunity. To this aim, we measured the extent of activation of the interferon (IFN) system and of circulating Dendritic Cells (DC) in vivo, and the ability of GBV-C to activate these functions in vitro. Activation of IFN system and of circulating DC was compared in GBV-positive and -negative HIV-1 co-infected patients with HAART-driven suppression of HIV-1 viremia. Endogenous levels of IFN-gamma and RNA-dependent protein kinase (PKR) mRNA were significantly higher in peripheral blood mononuclear cells (PBMC) from GBV-C-positive when compared to GBV-C-negative patients. IFN-gamma expression was correlated with all the Interferon response genes (IRGs) and with GBV-C viremia. The frequency of circulating plasmacytoid DC (pDC) expressing the CD80 activation marker was increased in GBV-C-positive patients, and was correlated with GBV-C viral load. In vitro experiments indicated that GBV-C is able to induce IFN-gamma expression in PBMC. In addition, in PBMC cultures GBV-C induced an increase of CD80 expression by pDC, that was reduced by antibody to IFN-gamma. Our data indicate that in HIV-positive patients GBV-C coinfection promotes the activation of IFN-gamma and downstream IRG expression, as well as with the activation/maturation of circulating pDC. GBV-C-driven IFN-gamma activation is, at least in part, responsible for the increased maturation of pDC. This crosstalk may suggest a role for GBV-C coinfection in boosting the innate antiviral response to HIV infection.

Sphingosine 1-Phosphate Interferes on the Differentiation of Human Monocytes into Competent Dendritic Cells

Sphingosine 1-phosphate (S1P) is a lipidic messenger known to exert several physiological functions within the cell. We tested here whether the stimulation of human monocytes with different doses of S1P might interfere with their differentiation into competent dendritic cells (DC). Monocytes cultured with granulocyte macrophage colony stimulating factor, interleukin-4 (IL-4) and S1P differentiated into a DC population lacking CD1a molecules on the surface and acquired some aspects of mature DC (mDC), though in the absence of maturation stimuli. When stimulated with lipopolisaccharide (LPS), CD1a(-) DC produce high amounts of tumour necrosis factor-alpha and IL-10, but not IL-12. Accordingly, these CD1a(-) DC were not capable of stimulating allogenic T lymphocytes so well as CD1a(+) DC generated from untreated monocytes and maturated with LPS. S1P monocyte-derived DC lost their polarizing capacity abrogating the production of gamma-interferon/IL-4 by co-cultured naïve CD4(+)CD45RA(+) T cells. Our findings suggest a mechanism through which S1P can favour the development of immune-related pathological states.

Influence of GBV-C infection on the endogenous activation of the IFN system in HIV-1 co-infected patients

BACKGROUND

GB virus C (GBV-C) co-infection is associated with a better prognosis in HIV-infected persons. Since interferon activation can be one of the possible mechanisms involved in GBV-C-driven protection against HIV, we compared the endogenous activation of the interferon system in PBMC from GBV-C-positive and -negative patients infected with HIV-1.

METHODS

The expression of interferon related genes was analyzed in 20 GBV-C positive and 20 GBV-C-negative HIV-infected patients, comparable in terms of CD4 cell counts and HIV viral loads. The levels of mRNA for interferon-related genes (2-5-OAS, MxA, interferon AR-1 and PKR) in PBMC were measured by real time RT-PCR, using B-actin as internal control.

RESULTS

The endogenous levels of all the Interferon-related genes in HIV/GBV-C co-infected patients were higher than in HIV mono-infected subjects. The difference was statistically significant for PKR mRNA. Direct positive correlation was found between PKR and all the other interferon-related genes, suggesting a coordinated activation of the interferon system.

CONCLUSIONS

Enhanced activation of the interferon system occurs in GBV-C-positive, as compared to GBV-C-negative patients harbouring HIV-1. These data may be relevant to understand the GBV-C-driven protection against HIV, suggesting that the endogenous activation of the interferon system can contribute to the control of HIV replication.

T cell selection and differentiation in AIDS disease: the model of HIV-discordant monozygotic twins

The model of monozygotic twins has been repeatedly studied to control the genetic and age-specific effects on HIV disease. Focusing on this natural model, the expression of CD27/CD45RA differentiation markers and the distribution of the Vbeta TCR repertoire was analyzed on CD4+ and CD8+ T cells. In our HIV-discordant monozygotic twins, a significant reduction of naive T cells and a parallel accumulation of effector/memory T cells was induced by HIV infection, as well as a skewing of T cell repertoire evidenced by VbetaTCR analysis. The block of HIV replication by highly active antiretroviral therapy (HAART) restored most of the T cell maturation and selection process, with some exception among CTL differentiation and repertoire. Altogether, the model of HIV-discordant monozygotic twins is a valuable tool showing that HAART is not able to completely restore the CTL profile.

T-Cell response profiling to biological threat agents including the SARS coronavirus

The emergence of pathogens such as SARS and the increased threat of bioterrorism has stimulated the development of novel diagnostic assays for differential diagnosis. Rather than focusing on the detection of an individual pathogen component, we have developed a T cell profiling system to monitor responses to the pathogens in an array format. Using a matrix of antigens specific for different pathogens, a specific T cell profile was generated for each individual by monitoring the intracellular production of interferon-gamma by flow cytometry. This assay allows for the testing of multiple proteins or peptides at a single time and provides a quantitative and phenotypic assessment of CD4(+) and CD8(+) responding cells. We present profiling examples for several positive individuals, including those vaccinated with the smallpox and anthrax vaccines. We also show antigen optimization for the SARS-hCoV, as studies revealed that these proteins contain peptides which cross-react with more common coronaviruses, a cause of the common cold. The T cell array is an early and sensitive multiplex measure of active infection, exposure to a pathogen, or effective, recent vaccination.

HLA-E up-regulation induced by HIV infection may directly contribute to CD94-mediated impairment of NK cells

Alterations in NK cell numbers and function have been repeatedly shown during HIV infection. In this study, NK cell number and MHC class I expression on CD4+ T cells were studied in HIV patients at different stages of disease progression. An increased expression of HLA-E was seen on CD4+ T cells. In parallel, a reduced number of CD94+ NK cells was observed in advanced disease stages. Moreover, a decline in CD94 expression on NK cells was observed at the HIV replication peak in patients undergoing antiretroviral treatment interruption, suggesting a role of viral replication on NK cells alterations. In vitro HIV infection induced a rapid down-regulation of HLA-A,B,C expression, paralleled by an increased expression of HLA-E surface molecules, the formal ligands of CD94 NK receptors. HIV-infected HLA-E expressing cells were able to inhibit NK cell cytotoxicity through HLA-E expression, since cytotoxicity was restored by antibody masking experiments. These data indicate that the CD94/HLA-E interaction may contribute to NK cell dysfunction in HIV infection, suggesting a role of HIV replication in this process.

CD1d expression by hepatocytes is a main restriction element for intrahepatic T-cell recognition

The liver has specific mechanisms to protect itself from infectious agents and to avoid autoimmunity, indicating an important role of the hepatic tissues in antigen presentation and tolerance induction. Since intrahepatic lymphocytes may contribute to the innate immunity and to the liver pathology, it is of interest to analyze the expression of antigen presenting molecules and of the related T cell recognition in liver, and how these change in relation to different diseases. We analyzed the expression of MHC class I, and of CD1-a, -b, -c, and -d proteins on liver tissues from patients with different hepatic diseases. Moreover, in the same patients we studied the intrahepatic and peripheral NKT cell recognition of alpha-galactosyl ceramide antigen in the context of CD1d. Unlike in other tissues, classical MHC class I molecules were poorly expressed in the hepatic compartment, suggesting that inflamed hepatocytes may trigger weak MHC-restricted T cell responses. Nevertheless, we observed a prevalent expression of HLA class I-like CD1d isoform on the hepatocyte surface, indicating that CD1d is the main restriction element in the liver. In patients with viral hepatitis, the intrahepatic CD1d expression parallels the recruitment of CD56+Valpha24Vbeta11+ NKT cells in the liver which recognize CD1d presenting glycolipids such as alpha-galactosyl ceramide, suggesting that the intrahepatic T cell immunity may focus on glycolipid antigens.

Innate T-cell immunity in HIV infection: the role of Vgamma9Vdelta2 T lymphocytes

There is growing interest in the use of innate immune reactions in the therapy and prophylaxis of various diseases. Natural T (NT) lymphocytes that recognize infected cells or microbial compounds without the classical genetic restriction by polymorphic MHC molecules are crucial components of innate immunity. NT cells bearing the Vgamma9Vdelta2 T-cell receptor (TCR) are broadly reactive against intracellular pathogens, can lyse human immunodeficiency virus (HIV) infected cells, and release cytokines capable of regulating HIV replication. The potent antiviral activities of Vgamma9Vdelta2 T cells may help to contain viral spread during acute HIV infection and/or to prevent the establishment of viral persistence. Substantial changes in the composition and function of circulating gammadelta T-cell pools occur in HIV-infected patients. These changes a) may contribute to the etiopathogenesis of opportunistic infections and neoplasms, and b) are partly reversed by highly active anti-retroviral therapy (HAART). In addition to direct antiviral activities, activated gammadelta T cells influence dendritic cell maturation and the adaptive alphabeta T-cell response. Vgamma9Vdelta2 T cells can be stimulated in vivo and in vitro by various nonpeptidic antigens (NpAgs) and recent animal experimental data suggest that activated Vgamma9Vdelta2 T cells may help to control SIV replication. Currently, NpAgs are being assessed as potential therapeutic agents in AIDS, tuberculosis and certain cancers susceptible to Vgamma9Vdelta2 T-cell effector mechanisms.

Innate T cell immunity to HIV-infection. Immunotherapy with phosphocarbohydrates, a novel strategy of immune intervention?

Natural T (NT) lymphocytes recognize infected cells or microbial compounds without the classical genetic restriction of polymorphic major histocompatibility complex (MHC) molecules. NT cells are mainly composed of alphabeta and gammadelta T lymphocytes that express natural killer (NK) receptors and recognize preferentially various nonpeptidic antigens. Similar to NK cells, NT lymphocytes can see and kill target cells deficient in the expression of one or more MHC class I molecules. NT cells expressing the alphabeta TCR can recognize lipid and lipoglycan antigens presented in the context of nonpolymorphic CD1 molecules, whereas phosphocarbohydrates and alkylamines induce constitutive response of Vgamma9Vdelta2 T cells. The stimulation of Vgamma9Vdelta2 T cells with phosphocarbohydrates induces the production of cytokines (IFNgamma and TNFalpha) and the release of chemokines with suppressive activity on HIV replication. In addition, stimulated Vgamma9Vdelta2 T cells exert a cytolytic activity against HIV-infected targets. In HIV-infected patients, a quantitative and qualitative alteration is observed early during the infection. Vgamma9Vdelta2 T cells are deleted and the remaining gammadelta cells are anergic. Th1 cytokines (IL-12 and IL-15) positively regulate cytokine production by Vgamma9Vdelta2 T cells but they are inefficient in restoring normal functions in patients' gammadelta T cells. Interestingly, partial restoration of the immune system under highly active antiretroviral therapies (HAART) is associated to the recovery of functional Vgamma9Vdelta2 T cells. A large panel of phosphocarbohydrates able to selectively stimulate Vgamma9Vdelta2 T cells is currently available, and preliminary experiments in monkeys suggest their in vivo efficacy in helping to control SIV replication. These observations prompt the question of new immune intervention involving molecules that stimulate NT cells.

Gammadelta T cell activation by chronic HIV infection may contribute to intrahepatic vdelta1 compartmentalization and hepatitis C virus disease progression independent of highly active antiretroviral therapy

HIV and hepatis C virus (HCV) coinfection is frequently associated with rapid progression of HCV-related disease, resulting in a higher risk of cirrhosis. Data suggest that natural T cells expressing the Vdelta1 T cell receptor rearrangement are recruited in the liver of chronically HCV-infected patients and are increased in the peripheral blood of HIV-infected persons. We studied gammadelta T cell distribution in the peripheral blood and liver of HCV-infected and HIV/HCV-coinfected patients in the presence and absence of antiretroviral therapy. We observed that Vdelta1+ T cells releasing helper T cell type 1 cytokines are compartmentalized not only in the liver of HCV+ patients, but also of HIV/HCV-coinfected persons. HIV/HCV patients showed an increased frequency of both peripheral and intrahepatic Vdelta1 natural T lymphocytes, resulting in a higher degree of hepatic inflammation when compared with patients with other liver diseases. Finally, highly active antiretroviral therapy (HAART) was unable to restore Vdelta1T cell circulation to normal levels in chronically HIV-infected persons. We conclude that gammadelta T lymphocytes released from tissue to the bloodstream circulation under the influence of chronic HIV infection may contribute to intrahepatic Vdelta1 compartmentalization and progression of liver disease, independently of HAART.

Antiviral activity and anergy of gammadeltaT lymphocytes in cord blood and immuno-compromised host

Gammadelta T lymphocytes recognize nonpeptidic microbial antigens without MHC restriction and display both lytic and proliferative responses to human immunodeficiency virus (HIV)-infected cells. This innate recognition involves both T Cell Receptor (TCR) and NK-receptor mediated signalling through non-peptidic metabolites and HLA class I down-regulation. We observed that HLA-masking and nonpeptidic phosphoantigens induce the expression of CD25 and CD69 activation markers on the surface of gammadelta T cells. Interestingly, CD94+ cell depletion by magnetic beads showed that the expression of this antigen is essential for Vdelta2 T cell activation by HLA-masking. Moreover, both phosphoantigen-stimulation and in vitro HIV infection resulted in marked Vgamma9Vdelta2 T cell expansion, whereas HLA-masking was unable to induce proliferative responses. Finally, we observed a relevant hyporesponsiveness to non-peptidic antigens in HIV-infected persons and in cord blood cells from healthy donors when compared to adult PBMC from uninfected donors. Altogether, the reduced ability to naturally recognize the infected cells may contribute to HIV-disease progression and may facilitate maternal transmission of HIV infections.

Natural T cell immunity to intracellular pathogens and nonpeptidic immunoregulatory drugs

Natural T (NT) lymphocytes recognize infected cells or microbial compounds without the classical genetic restriction of polymorphic major histocompatibility complex (MHC) molecules. This innate recognition pathway results in a broad and rapid antimicrobial response that may be critical for controlling the spread of intracellular pathogens, requiring the elimination of the infecting agent from both extracellular spaces and host cells. NT cells are mainly composed of alphabeta and gammadelta T lymphocytes that express natural killer (NK) receptors and recognize preferentially various nonpeptidic antigens. Similar to NK cells, NT lymphocytes can 'see' and kill target cells deficient in the expression of one or more MHC class I molecules. NT cells expressing the alphabeta TCR can recognize lipid and lipoglycan antigens presented in the context of nonpolymorphic CD1 molecules, whereas phosphocarbohydrates and akilamines induce constitutive responses in most Vgamma9Vdelta2 NT lymphocytes. The remaining fraction of gammadelta NT cells express the Vdelta1 chain associated with different Vgamma-chains and may directly recognize self-antigens such as MICA, MICB or CD1 molecules. It is possible that NT lymphocytes may play two opposite roles during intracellular infections. First, in the acute phase, they may be critical for the initiation of pathogen elimination. Second, in the chronic phase, NT cells may be dangerous, if their potential autoreactivity is not well controlled. It is conceivable that novel strategies of immune intervention against emerging and re-emerging intracellular pathogens, such as human immundeficiency virus (HIV), hepatitis-C virus (HCV) and Mycobacterium tuberculosis (MTB) may involve the control of NT cell activation/anergy by (nonpeptidic) immunoregulatory drugs.

Vdelta1 T lymphocytes expressing a Th1 phenotype are the major gammadelta T cell subset infiltrating the liver of HCV-infected persons

BACKGROUND

Hepatitis C infection induces an acute and chronic liver inflammation that may lead to cirrhosis, liver failure, or hepatocarcinoma. Since the role of alphabeta T lymphocytes in hepatitis C virus (HCV) immunopathology has been analyzed extensively, we investigated the distribution and functional activation of gammadelta T cell subsets in chronically HCV-infected patients.

MATERIALS AND METHODS

Blood samples and liver biopsies from 35 patients with compensated chronic HCV infection were compared in terms of T cell subset distribution, expression of activation markers, gammadelta T cell receptor (TCR) repertoire, and pattern of cytokine production. Moreover, we analyzed whether these immunological parameters were associated with other clinical observations (plasma viremia, ALT levels, Ishak index).

RESULTS

Differing from peripheral blood distribution, a specific compartmentalization of Vdelta1 T cells (p < 0.001) was observed in the liver of HCV patients. These cells represented a relevant fraction of intrahepatic T lymphocytes (1.8-8.7%) and expressed the memory/effector phenotype (CD62-L- CD45-RO+CD95+). This phenotype was consistent with selective homing upon antigen recognition. Mitogenic stimulation of Vdelta1 + T lymphocytes recruited in the liver revealed the T helper cell type 1 (Th1) pattern of cytokine secretion. Interestingly, the frequency of interferon-gamma (IFN-gamma)-producing Vdelta1 T cells was associated with an higher degree of liver necroinflammation, measured by the Ishak index. Finally, the T-cell repertoire analysis revealed the absence of Vgamma selection in the TCR repertoire of intrahepatic Vdelta1 T cells.

CONCLUSIONS

gammadelta T cell distribution in the peripheral blood differs from the Vdelta1 T cell subset because it is policlonally activated and recruited in the liver of chronic HCV-infected patients. During HCV-infection, this T cell subset may release Th1 cytokines and contribute to the necroinflammatory liver disease.

gammadelta T-cell anergy in human immunodeficiency virus-infected persons with opportunistic infections and recovery after highly active antiretroviral therapy

gammadelta T lymphocytes recognize non-peptidic microbial antigens without antigen processing and major histocompatibility complex (MHC) restriction, representing an early defence mechanism against invading pathogens. As a defective response to non-peptidic antigens was observed in human immunodeficiency virus-positive (HIV+) persons, the aims of this study were twofold: to analyse the incidence of gammadelta T-cell anergy in HIV+ positive patients with opportunistic infections/co-infections (HIV-OIC), and to investigate the role of highly active antiretroviral therapy (HAART) on gammadelta T-cell functions. Peripheral gammadelta T-cell distribution and in vitro reactivity to a non-peptidic mycobacterial antigen, isopentenyl pyrophosphate (IPP), were analysed. gammadelta T-cell subset distribution was altered more in HIV-OIC patients than in asymptomatic HIV+ subjects (HIV-ASY). Specifically, the Vdelta2/Vdelta1 ratio was inverted as a consequence of a decrease in Vdelta2 T-cell number. Moreover, IPP-stimulated Vdelta2 T cells from the HIV-OIC group displayed a major defect in interferon-gamma (IFN-gamma) production. Interestingly, HAART induced a sustained recovery of naive CD45RA+ and CD62L+ T cells and restored gammadelta T-cell function. Accordingly, in vitro CD45RA depletion resulted in gammadelta T-cell hyporesponsiveness. Altogether, the incidence of gammadelta T-cell anergy was increased in HIV-OIC patients and dependent on CD45RA helper function. Moreover, HAART was able to restore gammadelta T-cell reactivity, extending the immune recovery to non-peptide microbial antigens.

Decreased CD95 expression on naive T cells from HIV-infected persons undergoing highly active anti-retroviral therapy (HAART) and the influence of IL-2 low dose administration. Irhan Study Group

The functional recovery of the immune system in HIV-infected persons receiving HAART and the role of adjuvant immune therapy are still matters of intensive investigation. We analysed the effects of HAART combined with cytokines in 22 naive asymptomatic individuals, randomized to receive HAART (n = 6), HAART plus a low dose (1000 000 U/daily) of rIL-2 (n = 8), and HAART plus rIL-2 after previous administration of granulocyte colony-stimulating factor (n = 8). After 3 months of therapy, increased CD4+ T cell counts and diminished viral loads were observed in all patients, independently of cytokine addition. A decreased expression of CD95 (Apo 1/Fas) was evident in all groups when compared with values before therapy. The percentages of peripheral blood mononuclear cells (PBMC) expressing CD95 after therapy decreased by 15%, 22% and 18% in the three treatment groups, respectively (P < 0.05). Analysis of PBMC subsets demonstrated that CD95 expression was significantly reduced on CD45RA+CD62L+ naive T cells (25.3%, 22.4%, and 18.6%, respectively; P < 0.05) in each group, after therapy. Accordingly, all patients showed a reduced rate of in vitro spontaneous apoptosis (P < 0.05). Another effect induced by HAART was a significant increase in IL-2Ralpha expression on total PBMC (P < 0.05), independently of cytokine addition. Altogether, our results suggest that very low dose administration of rIL-2 (1000 000 U/daily) may be not enough to induce a significant improvement in the immune system as regards HAART alone. The employment of higher doses of recombinant cytokines and/or different administration protocols in clinical trials might however contribute to ameliorate the immune reconstitution in patients undergoing HAART.

Different expression of CD44, ICAM-1, and HSP60 on primary tumor and metastases of a human pancreatic carcinoma growing in scid mice

Surface adhesion molecules play an important, but still not completely clarified, role in tumor metastasization. In this research, FACS analysis was employed to analyze surface expression of CD44H, CD44v5, CD44v6, ICAM-1 and HSP60 in human pancreatic adenocarcinoma cells growing in vitro or collected ex vivo from primary tumors and lung metastases of tumor-engrafted SCID mice. It was found that, in metastatic cells, the standard form of CD44 (CD44H) is down,-regulated, while a large fraction of cells express on membrane the splice variants v5/v6 and, in addition, ICAM-1 and HSP60. It was also apparent that two cell populations are present in lung metastases: a CD44neg population, including cells expressing CD44v5/v6, ICAM-1 and HSP60 and a population of CD44pos, CD44v5/v6neg, ICAM-1neg and HSP60neg cells. These results demonstrate that, in pancreatic adenocarcinomas, metastasization is correlated with expression of the CD44 variants v5 and v6. Moreover, this is the first report demonstrating HSP60 surface expression on metastatic cells.

Hematopoietic reconstitution after lethal irradiation and bone marrow transplantation: effects of different hematopoietic cytokines on the recovery of thymus, spleen and blood cells

Lethally irradiated mice were grafted with syngeneic bone marrow cells or left ungrafted. Mice of each group were injected with different hematopoietic cytokines for 5 consecutive days starting immediately after irradiation or left uninjected. The recovery of lymphoid tissues induced by hematopoietic cytokines 7 days after irradiation and bone marrow cell transplantation was comparable to that observed at days 21-28 in irradiated, bone marrow-grafted, but cytokine-uninjected mice. IL-11 or IL-6, in combination with IL-3, was able to hasten thymus, spleen and blood cell numbers and functions. SCF also displayed a detectable effect when used with IL-3. Conversely, the IL-6 superagonist K-7/D-6 was able, when injected alone, to induce significant recovery of thymus, spleen and blood cells. Thus, K-7/D-6 appears to be a most efficient cytokine for fast reconstitution of lymphoid tissues after irradiation and bone marrow transplantation.

Phenotypic and functional properties of gamma delta T cells from patients with Guillain Barré syndrome

In this study we have examined the phenotypic and functional properties of circulating gamma delta T cells in patients with Guillain Barre syndrome (GBS), in normal healthy controls, and in patients with active multiple sclerosis (MS). Cells expressing the Vdelta2 T cell receptor showed elevated expression of the C-lectin receptor NKRP1A in both GBS and MS, suggestive of an activated state. However, in patients with GBS these cells failed to respond to pyrenil-pyrophosphate derivatives and Vdelta2 + T cell clones derived from these patients released lower levels of IFNgamma than Vdelta2 + clones derived from controls and MS patients. In contrast, in patients with GBS the Vdelta1 + subset was expanded, showed elevated expression of NKRPIA and Vdelta1 + clones derived from these patients secreted high levels of IL-4. Our findings of expanded NKRP-1A +, IL-4-producing Vdelta1 T cells in the GBS patients suggests the possibility that these cells are activated by the recognition of non-protein antigens in an MHC-unrestricted manner and contribute to the humoral response to glycolipids that is a hallmark of this disease.

Activation of C-C beta-chemokines in human peripheral blood gammadelta T cells by isopentenyl pyrophosphate and regulation by cytokines

Human gammadelta T lymphocytes respond to viral, bacterial, protozoal, and tumoral antigens, but their precise function remains unknown. In adults the major circulating gammadelta T-cell subset expresses the Vgamma9Vdelta2 T-cell receptor and responds to protease-resistant phosphorylated derivatives found in many pathogens. In this study we show that activation of Vdelta2(+) cells with the nonpeptidic antigen isopentenyl pyrophosphate (IPP) rapidly induces (within 4-12 hours) the C-C chemokines MIP-1alpha, MIP-1beta, and lymphotactin but not MCP-1. The most robust response was obtained for MIP-1beta. IPP induction of MIP-1alpha and MIP-1beta was not affected by costimulation with interleukin-4 (IL-4), IL-10, TGF-beta, or interferon-gamma (INF-gamma). However, IL-12 significantly enhanced IPP-induced expression and release of MIP-1alpha that was down-regulated by TGF-beta whereas the induction of MIP-1beta by IPP+IL-12 was refractory to cotreatment with TGFbeta indicating that these chemokines are differentially regulated by these cytokines. Vdelta2(+) T cells also expressed a wide range of C-C chemokine receptors including CCR1, CCR5, and CCR8, all of which were down-regulated following activation. We conclude that Vdelta2(+) cells can be rapidly induced by components of bacterial cell walls to express high levels of proinflammatory chemokines, supporting an important role for these cells in the early stages of the inflammatory responses to many common pathogens. (Blood. 2000, 95:39-47)

Phosphoantigen-reactive Vgamma9Vdelta2 T lymphocytes suppress in vitro human immunodeficiency virus type 1 replication by cell-released antiviral factors including CC chemokines

Vgamma9Vdelta2 T lymphocytes are broadly reactive against various intracellular pathogens and display both lytic and proliferative responses to human immunodeficiency virus (HIV)-infected cells. HIV infection of peripheral blood mononuclear cell cultures led to absolute increases in Vgamma9Vdelta2 T cells accompanied by decreased p24 levels. Strong gammadelta T cell activation with nonpeptidic mycobacterial phosphoantigens (TUBAg1 extract or synthetic isopentenyl pyrophosphate) resulted in potent inhibition of HIV replication through soluble released factors. Subsequent analyses showed that phosphoantigen-activated gammadelta T cells produced substantial amounts of beta-chemokines (macrophage inflammatory protein [MIP]-1alpha, MIP-1beta, and regulated-on-activation, normal T-cell-expressed and -secreted beta-chemokine [RANTES]), which represent the natural ligand for the CCR5 HIV coreceptor. Accordingly, anti-beta-chemokine antibodies neutralized the inhibition of monocytotropic HIV strains by gammadelta T cell-released factors. Moreover, a T-tropic HIV strain using the CXCR4 coreceptor for virus entry was potently inhibited. Together, these data reveal that phosphoantigen-activated gammadelta T cells are an important source of CC chemokines and may suppress HIV replication through cell-released antiviral factors.

In vivo gammadelta T cell priming to mycobacterial antigens by primary Mycobacterium tuberculosis infection and exposure to nonpeptidic ligands

BACKGROUND

The recognition of phosphorylated nonpeptidic microbial metabolites by Vgamma9Vdelta2 T cells does not appear to require the presence of MHC molecules or antigen processing, permitting rapid responses against microbial pathogens. These may constitute an important area of natural anti-infectious immunity. To provide evidence of their involvement in immune reactivities against mycobacteria, we measured the responsiveness of peripheral blood Vgamma9Vdelta2 T cells in children with primary Mycobacterium tuberculosis (MTB) infections.

MATERIALS AND METHODS

Peripheral blood mononuclear cells from 22 children with MTB infections and 16 positivity of tuberculin (PPD)-negative healthy children were exposed to nonpeptidic antigens in vitro and the reactivity of the Vgamma9Vdelta2 T cell subset with these antigens was determined using proliferation and cytokine assays. Also, responses of gammadelta T cells from rhesus monkeys stimulated with phosphoantigens in vivo were measured.

RESULTS

The Vgamma9Vdelta2 T cell responses were highly increased in infected children in comparison with age-matched controls. This augmented Vgamma9Vdelta2 T cell reactivity subsided after successful antibiotic chemotherapy, suggesting that persistent exposure to mycobacterial antigens is required for the maintenance of gammadelta T cell activation in vivo. The in vivo reactivity of Vgamma9Vdelta2 T cells to phosphoantigens was also analyzed in a rhesus monkey model system. Intravenous injections of phosphoantigens induced an activated state of simian Vgamma9Vdelta2 T cells which decreased after 2 months, i.e., with a time course similar to that seen in MTB-infected children.

CONCLUSIONS

The increased reactivity of Vgamma9Vdelta2 T cells to phosphoantigens appears to be dependent on constant antigenic exposure. Consequently, the assessment of Vgamma9Vdelta2 responses may be useful for monitoring the efficacy of antimycobacterial therapies.

Age-related propensity to peripheral expansion of Vgamma3+ gammadelta+ T lymphocytes after irradiation and bone marrow transplantation

The age-related decline in T cell functions is generally considered to be due to changes in the responding alphabeta T cell populations as a result of impairment of T cell differentiation in the thymus. T cells bearing the gammadelta TCR are normally a minor subset of circulating T cells, but often the major T cell type among lymphocytes in epithelial tissues. In this paper we show that gammadelta T cells are expanded in lymph nodes of irradiated mice after syngenic bone marrow transplantation. Interestingly, these gammadelta T cells express mainly the Vgamma3 TCR, which is characteristic of dendritic epithelial T cells that can develop in athymic nude mice and may recognize self antigens. Since the peripheral expansion of Vgamma3 T lymphocytes is closely related to bone marrow age, these observations indicate that the age-related propensity to extrathymic development of Vgamma3+ gammadelta+ T lymphocytes is mainly due to stem cell dysregulation in aging. This phenomenon may contribute to T cell impairment and to the increased natural cytotoxic activity of lymphoid cells in aged mice.

Possible protective and pathogenic roles of gamma delta T lymphocytes in HIV-infections (Review)

alpha beta and gamma delta T lymphocytes are largely responsible for the specificity of coordinated immune responses that are of crucial importance for protection from exogenous invaders and elimination of endogenous aberrations. One of the prominent distinguishing characteristics of primate gamma delta T lymphocytes is that most of their T cell receptors for antigen (gamma delta TCRs) are, unlike alpha beta TCRs, capable of recognizing nonpeptidic antigens in an MHC-unrestricted manner. Another interesting feature is that the gamma delta T cell subpopulation displays profound qualitative and quantitative changes in individuals with various infectious diseases. For example, the most frequent human peripheral blood gamma delta T cell subset expressing Vgamma9Vdelta2 TCRs is functionally disabled and numerically decreased in some HIV-infected persons. The nonresponsiveness of Vgamma9Vdelta2 T cells is accompanied by their decreased IFNç and TNFá production. The overall level of gamma T cell activation at different stages of HIV-infection may be clinically relevant. At an initial stage of HIV-infection, the extremely potent antiviral cytotoxic activities of Vgamma9Vdelta2 T cells may limit the viral spread. At later stages of disease, Vgamma9Vdelta2 T cell dysfunction may contribute to the loss of resistance to opportunistic pathogens (such as atypical mycobacteria) and neoplasms (e.g., lymphomas) frequently associated with HIV-infections. Also, it is possible that chronic stimulation of gamma delta T cells may result in immunopathology. In particular, the massive immunologic activation that appears to be the major contributing element of AIDS immunopathogenesis could be, at least in part, driven by gamma delta T cells overstimulated by repetitive exposures to HIV.

CD94/NKG2 inhibitory receptor complex modulates both anti-viral and anti-tumoral responses of polyclonal phosphoantigen-reactive V gamma 9V delta 2 T lymphocytes

Viral, bacterial, protozoal, and cancer-associated Ags elicit strong responses in human gammadelta T lymphocytes. The majority of these cells in the peripheral blood express the Vgamma9Vdelta2-encoded TCR and recognize nonpeptidic phosphoantigens without an apparent MHC restriction. We have shown that Vgamma9Vdelta2 T cells express the inhibitory CD94/NKG2 receptor for HLA class I molecules. The anti-CD94 mAb inhibits 1) the Vgamma9Vdelta2 T cell proliferation in response mycobacterial phosphoantigens and 2) the HIV-induced Vgamma9Vdelta2 T cell expansion. Vgamma9Vdelta2 T cells stimulated with nonpeptidic mycobacterial antigens produce IFN-gamma and TNF-alpha. Signaling through the CD94/NKG2 receptor interferes with the synthesis of these cytokines. The CD94/HLA class I interaction is also involved in the cytotoxic activity of Vgamma9Vdelta2 T cells. The Vgamma9Vdelta2 T cell regulation through the CD94 receptor may be important for the potentially dual function in innate immunity, i.e., 1) NK-like and 2) TCR ligand-induced cytolytic activities.

CD94/NKG2 inhibitory receptor complex modulates both anti-viral and anti-tumoral responses of polyclonal phosphoantigen-reactive V gamma 9V delta 2 T lymphocytes

Viral, bacterial, protozoal, and cancer-associated Ags elicit strong responses in human gammadelta T lymphocytes. The majority of these cells in the peripheral blood express the Vgamma9Vdelta2-encoded TCR and recognize nonpeptidic phosphoantigens without an apparent MHC restriction. We have shown that Vgamma9Vdelta2 T cells express the inhibitory CD94/NKG2 receptor for HLA class I molecules. The anti-CD94 mAb inhibits 1) the Vgamma9Vdelta2 T cell proliferation in response mycobacterial phosphoantigens and 2) the HIV-induced Vgamma9Vdelta2 T cell expansion. Vgamma9Vdelta2 T cells stimulated with nonpeptidic mycobacterial antigens produce IFN-gamma and TNF-alpha. Signaling through the CD94/NKG2 receptor interferes with the synthesis of these cytokines. The CD94/HLA class I interaction is also involved in the cytotoxic activity of Vgamma9Vdelta2 T cells. The Vgamma9Vdelta2 T cell regulation through the CD94 receptor may be important for the potentially dual function in innate immunity, i.e., 1) NK-like and 2) TCR ligand-induced cytolytic activities.

Phenotypic and cytokine analysis of human peripheral blood gamma delta T cells expressing NK cell receptors

The presence of NK receptors (NKR) on populations of T cells has been proposed to play a regulatory role in T cell function, fine tuning the response to Ag, and influencing the nature of the immune response through rapid secretion of large amounts of cytokines. In this study, we assessed the nature and distribution of NKR on human peripheral blood gamma delta T cells and established clones to study cytokine release. In circulating gamma delta T cells, approximately 80% expressed CD94, approximately 25% expressed NKR-P1A, and approximately 20% expressed p58, values substantially higher than those found on alpha beta T cells from the same donors. When cloned for specific NKR expression, most cells in culture were NKR-P1A+ whereas p58 expression was variable, suggesting that the NKR-P1A phenotype can be acquired in culture whereas expression of p58 is more stable. Some clones were triple positive for CD94, NKR-P1A, and p58. V delta 2+ cells generally expressed a wider range of NKR than V delta 1+ cells. Following activation through CD3, all gamma delta T cell clones released large amounts of IFN-gamma, commencing as early as 4 h postactivation. Some clones also released TNF-alpha and IL-4, but no correlation with specific NKR expression was noted. Activation through NKR-P1A induced moderate levels of IFN-gamma without inducing IL-4. The results suggest that activation of most gamma delta T cells is regulated by signaling events occurring via both the TCR and the NKR. They further show that peripheral blood gamma delta T cells may function as a source of the proinflammatory cytokines IFN-gamma and TNF-alpha.

Phenotypic and cytokine analysis of human peripheral blood gamma delta T cells expressing NK cell receptors

The presence of NK receptors (NKR) on populations of T cells has been proposed to play a regulatory role in T cell function, fine tuning the response to Ag, and influencing the nature of the immune response through rapid secretion of large amounts of cytokines. In this study, we assessed the nature and distribution of NKR on human peripheral blood gamma delta T cells and established clones to study cytokine release. In circulating gamma delta T cells, approximately 80% expressed CD94, approximately 25% expressed NKR-P1A, and approximately 20% expressed p58, values substantially higher than those found on alpha beta T cells from the same donors. When cloned for specific NKR expression, most cells in culture were NKR-P1A+ whereas p58 expression was variable, suggesting that the NKR-P1A phenotype can be acquired in culture whereas expression of p58 is more stable. Some clones were triple positive for CD94, NKR-P1A, and p58. V delta 2+ cells generally expressed a wider range of NKR than V delta 1+ cells. Following activation through CD3, all gamma delta T cell clones released large amounts of IFN-gamma, commencing as early as 4 h postactivation. Some clones also released TNF-alpha and IL-4, but no correlation with specific NKR expression was noted. Activation through NKR-P1A induced moderate levels of IFN-gamma without inducing IL-4. The results suggest that activation of most gamma delta T cells is regulated by signaling events occurring via both the TCR and the NKR. They further show that peripheral blood gamma delta T cells may function as a source of the proinflammatory cytokines IFN-gamma and TNF-alpha.

Expression of a Cu,Zn superoxide dismutase typical of familial amyotrophic lateral sclerosis induces mitochondrial alteration and increase of cytosolic Ca2+ concentration in transfected neuroblastoma SH-SY5Y cells

We have set up a model system for familial amyotrophic lateral sclerosis (FALS) by transfecting human neuroblastoma cell line SH-SY5Y with plasmids directing constitutive expression of either wild-type human Cu,Zn superoxide dismutase (Cu,ZnSOD) or a mutant of this enzyme (G93A) associated with FALS. We have tested mitochondrial function and determined cytosolic Ca2+ concentration in control cells (untransfected) and in cells expressing either wild-type Cu,ZnSOD or G93A. We report that G93A induces a significant loss of mitochondrial membrane potential, an increased sensitivity toward valinomycin and a parallel increase in cytosolic Ca2+ concentration. The above phenomena are not related to total Cu,ZnSOD content and activity in the cell.

Gammadelta T cell activation or anergy during infections: the role of nonpeptidic TCR ligands and HLA class I molecules

Vgamma9Vdelta2-encoded T cell receptors (TCR) expressed by most human peripheral blood gammadelta T cells mediate the recognition of nonpeptidic phosphoantigens from various pathogens without any known requirement for HLA molecules. Functionally mature Vgamma9Vdelta2 T cells display a potent natural killer (NK)-like cytotoxic activity, share with NK cells the expression of inhibitory receptors for HLA class I molecules, and release a plethora of cytokines, most notably interferon-gamma and tumor necrosis factor alpha. Hence, through local activation, the early recruitment and stimulation of Vgamma9Vdelta2 T cells may promote efficient anti-infectious immunity. However, a chronic overactivation of this T cell subset may result in immunopathology. The meeting held in St. Vincent, Val d'Aosta, Italy (symposium on gammadelta T cells in natural immunity to infections: a rationale for vaccine development organized by the World Foundation for AIDS Research and Prevention, the UNESCO, and the Italian National Research Council, December 2-4, 1996) focused on the importance of gammadelta T cell activation and anergy for the pathogenesis of tuberculosis, malaria, and HIV infections.

Induction of "tissue" transglutaminase in HIV pathogenesis: evidence for high rate of apoptosis of CD4+ T lymphocytes and accessory cells in lymphoid tissues

Peripheral blood mononuclear cells and lymphoid tissues from HIV-infected individuals display high levels of "tissue" transglutaminase (tTG) with respect to seronegative persons. In asymptomatic individuals, > 80% of the circulating CD4+ T cells synthesize tTG protein and the number of these cells matches the level of apoptosis detected in the peripheral blood mononuclear cells from the same patients. In HIV-infected lymph nodes tTG protein is localized in large number of cells (macrophages, follicular dendritic cells, and endothelial cells), showing distinctive morphological and biochemical features of apoptosis as well as in lymphocytes and syncytia. These findings demonstrate that during the course of HIV infection, high levels of apoptosis also occur in the accessory cells of lymphoid organs. The increased concentration of epsilon(gamma-glutamyl)lysine isodipeptide, the degradation product of tTG cross-linked proteins, observed in the blood of HIV-infected individuals demonstrates that the enzyme accumulated in the dying cells actively cross-links intracellular proteins. The enhanced levels of epsilon(gamma-glutamyl)lysine in the blood parallels the progression of HIV disease, suggesting that the isodipeptide determination might be a useful method to monitor the in vivo rate of apoptosis.

Peripheral V gamma 9/V delta 2 T cell deletion and anergy to nonpeptidic mycobacterial antigens in asymptomatic HIV-1-infected persons

Gamma delta T cells represent a minor population of human peripheral lymphocytes, the majority of them expressing the V delta 2/V gamma 9 TCR. Their accumulation in infectious disease lesions and their reactivity toward mycobacterial Ags suggest that V gamma 9/V delta 2 T cells play a role during infectious diseases. We have shown previously a significant expansion of the V delta 1 subset parallel to a dramatic decrease of the V delta 2 subset in PBMC from HIV-infected persons. To understand the mechanisms involved in the deletion of V delta 2 T cells, we analyzed their ability to respond in vitro to several V gamma 9/V delta 2 t cell-specific ligands. We observed that in 60% of asymptomatic HIV-infected persons, V delta 2 T cells exhibited a functional anergy to Daudi and to Mycobacterium tuberculosis stimulations. These observations were supported by the defective expansion of this subset to the recently described nonpeptidic phosphorylated Ag, TUBAg-1. Since V delta 2 responsiveness to mycobacterial Ags was shown to be normally dependent on IL-2 secretion by Th1-type CD4 T cells, the ability of IL-2 to restore V delta 2 T cells' responsiveness to TUBAg-1 was tested. V delta 2 T cell anergy persisted in spite of the presence of IL-2, and was frequently correlated with a defect in CD25 expression on stimulated V delta 2 T cells. Since V delta 2 anergy was associated with an in vivo depletion of this subset, we studied whether programmed cell death could be involved in this process, particularly because of their activated phenotype. Although peripheral V delta 2 T cells from some HIV-infected persons showed an increased susceptibility to spontaneous and activation-induced apoptosis, statistical comparison between HIV+ and HIV- donors indicated that there was no difference between both groups in the rate of V delta 2 apoptosis. Finally, V delta 2 complementarity-determining region 3 TCR analysis indicated that, in vivo, the remaining V delta 2 T cells were still polyclonal. All together these results suggest that the qualitative and quantitative alterations of the V delta 2 subset in the course of HIV infection are the consequence of a chronic antigenic stimulation, and raise the question of the contribution of a cellular ligand induced or modified by chronic HIV infection.

Peripheral V gamma 9/V delta 2 T cell deletion and anergy to nonpeptidic mycobacterial antigens in asymptomatic HIV-1-infected persons

Gamma delta T cells represent a minor population of human peripheral lymphocytes, the majority of them expressing the V delta 2/V gamma 9 TCR. Their accumulation in infectious disease lesions and their reactivity toward mycobacterial Ags suggest that V gamma 9/V delta 2 T cells play a role during infectious diseases. We have shown previously a significant expansion of the V delta 1 subset parallel to a dramatic decrease of the V delta 2 subset in PBMC from HIV-infected persons. To understand the mechanisms involved in the deletion of V delta 2 T cells, we analyzed their ability to respond in vitro to several V gamma 9/V delta 2 t cell-specific ligands. We observed that in 60% of asymptomatic HIV-infected persons, V delta 2 T cells exhibited a functional anergy to Daudi and to Mycobacterium tuberculosis stimulations. These observations were supported by the defective expansion of this subset to the recently described nonpeptidic phosphorylated Ag, TUBAg-1. Since V delta 2 responsiveness to mycobacterial Ags was shown to be normally dependent on IL-2 secretion by Th1-type CD4 T cells, the ability of IL-2 to restore V delta 2 T cells' responsiveness to TUBAg-1 was tested. V delta 2 T cell anergy persisted in spite of the presence of IL-2, and was frequently correlated with a defect in CD25 expression on stimulated V delta 2 T cells. Since V delta 2 anergy was associated with an in vivo depletion of this subset, we studied whether programmed cell death could be involved in this process, particularly because of their activated phenotype. Although peripheral V delta 2 T cells from some HIV-infected persons showed an increased susceptibility to spontaneous and activation-induced apoptosis, statistical comparison between HIV+ and HIV- donors indicated that there was no difference between both groups in the rate of V delta 2 apoptosis. Finally, V delta 2 complementarity-determining region 3 TCR analysis indicated that, in vivo, the remaining V delta 2 T cells were still polyclonal. All together these results suggest that the qualitative and quantitative alterations of the V delta 2 subset in the course of HIV infection are the consequence of a chronic antigenic stimulation, and raise the question of the contribution of a cellular ligand induced or modified by chronic HIV infection.

Heat-shock protein expression on the membrane of T cells undergoing apoptosis

Heat-shock proteins (hsp) represent a highly conserved family of proteins, normally localized in the cytoplasm and nucleus, whose expression is induced in situations involving cell stress. This paper reports the unusual translocation of hsp to the cell membrane of T cells undergoing apoptosis. We observed that glucocorticosteroid-induced thymocyte death is associated to the surface expression of hsp 60 and hsp 70 in a discrete fraction of apoptotic cells. hsp surface expression is closely related to a thymic subset of immature CD3low/- T cells. The expression of surface hsp 60 appears early after treatment with dexamethasone (3 hr) whereas the membrane expression of hsp 70 follows different kinetics and peaks later. Morphological analysis of the hsp+ apoptotic cells suggest that this subset represents late-stage apoptotic cells at their minimal volume before fragmentation into apoptotic bodies. Membrane expression of hsp is also associated with apoptosis in peripheral blood mononuclear cells from AIDS patients cultured in vitro. Altogether, we show that a discrete fraction of cells undergoing apoptosis expresses membrane hsp 60 and hsp 70, supporting the hypothesis that apoptosis causes a radical alteration in the expression of cell surface molecules. Surface hsp expressed during apoptosis may constitute a novel immune-context able to generate packages of self- and exogenous antigens, originating from degradation of altered cells.

In vitro and in vivo efficacy of heat shock protein specific immunotoxins on human tumor cells

The presence of heat shock proteins (HSPs) on the surface of tumor cells suggested the possibility of using stress proteins as immunological target for specific immunotoxins (ITs). Flow cytometry analysis showed that U937 cells constitutively express both 28 and 60 kDa HSP in vitro, while the HPC-4 cells only express surface HSPs when grown in vivo, i.e. explanted from SCID mice. Incubation of U937 cells with monoclonal antibodies against 28 or 60 kDa HSP, and then with an immunotoxin consisting of a goat anti-mouse antibody linked to the ribosome inactivating protein Saporin-6 specifically inhibits cell proliferation in vitro. Moreover, an anti-HSP60 immunotoxin prepared by direct linking of the specific monoclonal antibody (MoAb) ML30 to saporin was able to inhibit the proliferation of the U937 line in vitro, and tumor growth in SCID mice bearing the human pancreatic carcinoma line HPC-4 in vivo. Finally, low expression of HSPs on the membrane of peripheral blood mononuclear cells, and their resistance to the toxic effect exerted by anti-HSP immunotoxins, suggest further evaluation of the possible applications of anti-HSP immunotoxins for HSP+tumors.

CDR3-independent gamma delta V delta 1+ T cell expansion in the peripheral blood of HIV-infected persons

A majority of circulating gamma delta T cells in humans express the V delta 2 variable segment associated with the V gamma 9 segment. A minor subset uses the V delta 1 gene mainly paired with a V gamma-chain from group I. Although little is known about the function and the Ags recognized by V delta 1 T cells, their expansion has been described in several diseases. Significant alterations of gamma delta subset distribution have been observed in PBMC from HIV-infected persons. In addition to their significant increase, gamma delta T cells showed an alteration in their subset representation because most of them expressed the V delta 1 receptor and, concomitantly, the V delta 2+ subset was under-represented. To gain insight into the mechanisms involved in this selective expansion, we characterized the V delta 1-J delta 1 junctional diversity in PBMC from healthy donors and HIV-infected individuals at different stages of the disease. We confirmed that the V delta 1 repertoire is restricted in most of the healthy donors. In HIV-infected subjects, we found that the increase of V delta 1 T cells is independent to a particular V gamma-chain expression, and the characterization of the TCR-delta diversity demonstrated a similar restricted V delta 1-J delta 1 rearrangement pattern, not significantly different from the pattern of healthy donors. Moreover, no amino acid junctional motif could be identified either in control or in HIV-infected donors. This report demonstrates that the V delta 1 selective expansion in the course of HIV infection is not the consequence of the emergence of some specifically CDR3-dependent expanded V delta 1 T cell clones. Interestingly, this subset showed an increased ability to be expanded in vitro in the presence of IL-2 alone and, although they did not harbor ex-vivo the phenotype of fully activated cells, they did express the activation marker CD38, a marker for disease progression. Altogether this report indicates that, although the patients' V delta 1 T cells seem to be in a pre-activated state, their selective expansion in the course of HIV infection is not the consequence of a peripheral CDR3-dependent antigenic selection.

CDR3-independent gamma delta V delta 1+ T cell expansion in the peripheral blood of HIV-infected persons

A majority of circulating gamma delta T cells in humans express the V delta 2 variable segment associated with the V gamma 9 segment. A minor subset uses the V delta 1 gene mainly paired with a V gamma-chain from group I. Although little is known about the function and the Ags recognized by V delta 1 T cells, their expansion has been described in several diseases. Significant alterations of gamma delta subset distribution have been observed in PBMC from HIV-infected persons. In addition to their significant increase, gamma delta T cells showed an alteration in their subset representation because most of them expressed the V delta 1 receptor and, concomitantly, the V delta 2+ subset was under-represented. To gain insight into the mechanisms involved in this selective expansion, we characterized the V delta 1-J delta 1 junctional diversity in PBMC from healthy donors and HIV-infected individuals at different stages of the disease. We confirmed that the V delta 1 repertoire is restricted in most of the healthy donors. In HIV-infected subjects, we found that the increase of V delta 1 T cells is independent to a particular V gamma-chain expression, and the characterization of the TCR-delta diversity demonstrated a similar restricted V delta 1-J delta 1 rearrangement pattern, not significantly different from the pattern of healthy donors. Moreover, no amino acid junctional motif could be identified either in control or in HIV-infected donors. This report demonstrates that the V delta 1 selective expansion in the course of HIV infection is not the consequence of the emergence of some specifically CDR3-dependent expanded V delta 1 T cell clones. Interestingly, this subset showed an increased ability to be expanded in vitro in the presence of IL-2 alone and, although they did not harbor ex-vivo the phenotype of fully activated cells, they did express the activation marker CD38, a marker for disease progression. Altogether this report indicates that, although the patients' V delta 1 T cells seem to be in a pre-activated state, their selective expansion in the course of HIV infection is not the consequence of a peripheral CDR3-dependent antigenic selection.

CD4-8- T-cells increase in MRI/lpr mice treated with thymic factors

The in vivo effect of thymic factors on immature lymphocytes was analysed in MRL/lpr mice. This strain carries a genetic defect that causes during their life cycle a block of T-cell differentiation and abnormal proliferation of CD4-8- (double-negative, DN) T-lymphocytes. In vivo administration of four preparations of thymic factors, thymopentin (TP-1), thymopoietin (TP-5), thymolymphotropin (TLT), and thymomodulin (TMD) into young (2-month-old) MRL/lpr mice induced a significant increase of DN T-cells both in the thymus and in the peripheral lymph nodes, with a concomitant decrease of double-positive (DP) T-cells in the thymus and of single-positive (SP) T-cells in the lymph nodes. The level of DNA fragmentation measured as propidium iodide fluorescence was increased in the thymus population of young mice and in the lymph node population of old mice treated with TLT. SCID mice transplanted with lymph node cells from MRL/lpr donors (MRL-->SCID) developed graft versus host (GvH) reaction due to the activation of MRL CD8+ alloreactive T-cells. This model was used to analyse the effect of TMD/TLT in vivo on MRL cell proliferation and expansion; in fact, spleen cells from MRL-->SCID mice after treatment with TMD/TLT showed an increased cell proliferation, and an expansion of DN T-cells with a concomitant decrease of SP cells (both CD4+ and CD8+ cells). Decreased SP cell numbers in this context could explain why TMD/TLT treatment of SCID mice engrafted with MRL cells increased their survival compared to untreated MRL-->SCID mice.

Induction of graft versus host disease in SCID mice by MRL/lpr cell transfer

We have investigated the graft versus host (GvH) disease induced in immunodeficient SCID (H-2d) mice by intravenous (iv) or intraperitoneal (ip) transfer of either spleen or lymph node cells from autoimmune (MRL/lpr and MRL/++ mice, H-2k) and normal (CBA, H-2k) mice. Rapid and lethal GvH disease was observed when cells from MRL/lpr or MRL/++ were iv transferred into SCID mice, while spleen cells from nonautoimmune CBA donors were partially tolerized into SCID recipients and induced only lower levels of GvH reaction. No GvH reaction (complete tolerance) was observed when CBA lymph node cells were iv transferred into SCID recipients. In contrast, the ip injection of MRL/lpr or CBA spleen cells induces similar levels of GvH. The development of GvH disease in SCID recipients was due to the expansion of alloreactive CD8+ cells displaying significant cytotoxic activity against H-2d, but not against autologous targets. Also, a significant decrease of CD4/CD8 ratio was observed in the course of GvH caused by the iv transfer of cells from MRL/lpr mice. Altogether, these data support the hypothesis that lymphocytes from the MRL/lpr mice may escape tolerance in the GvH reaction.

Epitope specificity, antibody-dependent cellular cytotoxicity, and neutralizing activity of antibodies to human immunodeficiency virus type 1 in autoimmune MRL/lpr mice

The specificity and functional activity of antibodies to human immunodeficiency virus (HIV) in the sera of MRL/lpr mice were analyzed by peptide-ELISA, antibody-dependent cellular cytotoxicity, and virus neutralization. The specificity of the antibodies in the sera of autoimmune MRL/lpr mice was similar to that of HIV-infected persons; the mouse sera specifically recognized the V3 loop of gp120 and immunodominant regions of gp41 and p24. Moreover, such binding was inhibited both by human HIV-positive sera and by soluble peptides in competition experiments. MRL/lpr sera displayed anti-HIV antibody-dependent cellular cytotoxicity using human peripheral blood lymphocytes as effector cells and HIV-infected H9 cells. Furthermore, the fact that MRL/lpr sera neutralized in vitro infectious HIV (both strains IIIB and MN) suggests these antibodies recognize viral epitopes on the membrane of infected T cells.

Recognition and killing of tumour cells expressing heat shock protein 65 kD with immunotoxins containing saporin

The expression of heat shock proteins (HSP) of the 65 kD family (groEL) has been observed by flow cytometry using murine monoclonal antibody (MoAb) anti-HSP 65 kD (ML30) on the surface of B (Daudi) or T (H9) lymphoma cells, on a monocyte cell line (U937) and also on a primary culture of a human pancreatic carcinoma (HPC). Moreover, the MoAb ML30 was coupled to Saporin 6, a ribosome-inactivating protein recovered from the seeds of Saponaria officinalis, to kill HSP-expressing cells with a specific immunotoxin. An indirect method using first MoAb ML30 and then anti-mouse IgG1 immunotoxin was also performed. With this method a human serum positive for HSP65-antibodies was tested using anti-human IgG1 or IgM immunotoxins. All cell lines were inhibited when preincubated with the specific immunotoxin directed to HSP65 (ML30 SO6), although H9 cells were susceptible to immunotoxin only after thermal stress. Daudi and HPC cells were inhibited both after long-term culture and when freshly explanted from SCID mice. Proliferation of the U937 monocytic cell line, that constitutively expresses high levels of HSP65 on the surface (as determined by flow cytometry), was completely inhibited (100% inhibition) by the ML30 SO6. However, not all tumour cells constitutively express high levels of surface HSP65, as determined by cytometric analysis. For this reason it was not always possible to obtain complete inhibition of cellular proliferation.