Prevention of lymph node metastases by adoptive transfer of CD4+ T lymphocytes admixed with irradiated tumor cells

CD4⁺8^– T lymphocytes with potent antitumor activity in vivo were obtained in peritoneal exudate cells by immunizing mice with irradiated MM48 tumor cells admixed with OK-432. These immune CD4⁺ T cells were used in adoptive immunotherapy for prevention of lymph node metastases after removal of the primary tumor. Complete cure of metastases was obtained by adoptive transfer of CD4⁺ T cells admixed with irradiated MM48 tumor cells, but not by CD4⁺ T cells alone. To analyze the curative effect of admixing tumor cells on the prevention of metastases, a model of 1-day tumor inoculated with macrophages was used. Administration of immune CD4⁺ T cells alone resulted in the regression of local tumor in more than half of the mice, although all of them eventually died of lymph node metastases. On the other hand, adoptive transfer of immune CD4⁺ T cells plus irradiated tumor cells resulted in the complete regression of local tumors in all the mice, which survived without any sign of metastasis. The curative effect of the immune CD4⁺ T cells obtained by admixing irradiated tumor cells was tumor-specific. Macrophages induced by OK-432 (tumoricidal), implanted together with tumor, assisted tumor regression more than did macrophages elicited by proteose peptone (nontumoricidal) in the same adoptive transfer system. Administration of recombinant interleukin-2 instead of stimulant tumor cells did not enhance, but rather eliminated the constitutive antitumor activity of CD4⁺ T cells. On the other hand, exogenous recombinant interleukin-1 was more effective in the enhancement of antitumor activity of the CD4⁺ T cells as compared with stimulant tumor cell administration. In this case, the activating states of macrophages at the implanted tumor site had no influence on the therapeutic efficacy. A possible role of macrophages for induction of tumor-specific cytotoxic T cells that were mediated by tumor-specific CD4⁺ T cells is discussed.     

IL-21 induces apoptosis of antigen-specific CD8+ T lymphocytes

IL-21, a member of the common gamma-chain family of cytokines, has pleiotropic effects on T, B, and NK cells. We found that IL-21 and the prototype common gamma-chain cytokine IL-2 can stimulate proliferation and cytokine secretion by Ag-specific rhesus monkey CD8+ T cells. However, unique among the members of this family of cytokines, we found that IL-21 drives these cells to apoptosis by down-regulation of Bcl-2. These findings suggest that IL-21 may play an important role in the contraction of CD8+ T cell responses.     

Cutting edge: Lipopolysaccharide induces IL-10-producing regulatory CD4+ T cells that suppress the CD8+ T cell response

TLR ligands are potent activators of dendritic cells and therefore function as adjuvants for the induction of immune responses. We analyzed the capacity of TLR ligands to enhance CD8+ T cell responses toward soluble protein Ag. Immunization with OVA together with LPS or poly(I:C) elicited weak CD8+ T cell responses in wild-type C57BL/6 mice. Surprisingly, these responses were greatly increased in mice lacking CD4+ T cells indicating the induction of regulatory CD4+ T cells. In vivo, neutralization of IL-10 completely restored CD8+ T cell responses in wild-type mice and OVA-specific IL-10 producing CD4+ T cells were detected after immunization with OVA plus LPS. Our study shows that TLR ligands not only activate the immune system but simultaneously induce Ag specific, IL-10-producing regulatory Tr1 cells that strongly suppress CD8+ T cell responses. In this way, excessive activation of the immune system may be prevented.     

foxp3转染的CD4~+ CD25~- T细胞治疗急性肺损伤的研究

目的通过基因转染技术将foxp3基因导入CD4+CD25-T淋巴细胞,生成CD4+CD25-Foxp3+T细胞,通过输入急性肺损伤小鼠模型体内,促进炎症消退,为体外定向操纵调节T细胞生成和细胞过继治疗急性肺损伤奠定基础。方法采用RT-PCR法从小鼠胸腺来源cDNA文库中扩增获得foxp3 cDNA,亚克隆至构建pIRES2-EGFP质粒中,构建并筛选出重组质粒pmFoxp3-IRES2-EGFP;采用免疫磁珠法分离CD4+CD25-T淋巴细胞,穿孔法转染Foxp3基因至CD4+CD25-T淋巴细胞,流式细胞仪检测CD4+和EGFP共表达的细胞比例;将foxp3基因转染的小鼠CD4+CD25-T细胞通过尾静脉输注急性小鼠体内,通过ELISA法检测小鼠肺泡灌洗液中TNF-α以及IL-1β细胞因子的表达,通过肺组织病理研究肺部炎症的消退状况。结果成功构建双基因共表达重组质粒pmFoxp3-IRES2-EGFP;免疫磁珠法较高纯度分离CD4+CD25+、CD4+CD25-T淋巴细胞,电穿孔法成功将重组质粒pmFoxp3-IRES2-EGFP转染致CD4+CD25-T细胞,CD4+和EGFP共表达的细胞比例为35.5%;过继Foxp3基因转染的小鼠CD4+CD25-T细胞以及Treg均能抑制急性肺损伤小鼠肺泡灌洗液中TNF-α以及IL-1β炎性细胞因子的表达,促进炎症的消退。结论转染Foxp3基因的CD4+CD25-细胞同Treg(CD4+CD25-)细胞一样可以通过细胞过继治疗急性肺损伤。     

Therapeutic effects of tumor-reactive type 1 and type 2 CD8+ T cell subpopulations in established pulmonary metastases.

Cytolytic CD8+ T cells fall into two subpopulations based on cytokine-secretion. Type 1 CD8+ cells (Tc1) characteristically secrete IFN-gamma, whereas type 2 CD8+ cells (Tc2) secrete IL-4 and IL-5. We assessed the relative therapeutic effects of adoptively transferred OVA-specific Tc1 and Tc2 CD8+ cells in mice bearing established OVA-transfected B16 melanoma lung metastases. Both Tc1 and Tc2 subpopulations mediated a reduction in lung tumor growth that subsequently prolonged survival times in mice with both early (day 7) and more advanced (day 14) levels of tumor development. CD8+ T cell populations recovered from spleens of tumor-bearing mice receiving Tc1 or Tc2 cells showed markedly enhanced tumor Ag-specific cytolytic and cytokine-releasing activities that correlated with delays in tumor cell growth and progression. Initially, both tumor-reactive Tc1 and Tc2 effector cells accumulated at the tumor site with nearly equal frequency. Tc1 cells persisted, whereas Tc2 cell numbers progressively diminished over time. Titration of Tc1 and Tc2 effector cells showed that protection was dose dependent with the former being 5-fold more effective. Tc2 cells achieved a comparable reduction in lung tumor cell growth at higher concentrations of cell transfer. Tc1 effectors from IFN-gamma-deficient mice were less therapeutically effective than wild-type mice, but there was no significant reduction in activity between corresponding Tc2 populations. We speculate that the effectiveness of Tc1 and Tc2 cells may depend on different mechanisms. These studies suggest a potential role for Tc1 and Tc2 CD8+ subpopulations in tumor regression and immunotherapy.     

T cell tumor cure by T cell receptor-mediated activation requires the development of CD8-dependent host immunity

The participation of the host in eliminating Ag-specific T hybridoma cells after their in vivo activation was studied. In our model system, treatment of the cytochrome c-specific T cell hybridoma 2B4.11 in vitro with Ag in the context of histocompatible APC results in cellular activation, as shown by IL-2 release and growth inhibition. In vivo treatment with Ag results in tumor cell elimination as a result both of a direct inhibitory effect of cytochrome c that is mediated through the 2B4.11 TCR and to the induction of host immunity. In vivo lymphocyte-depletion studies showed that CD8-bearing cells were critical to the successful elimination of tumor cells mediated by Ag, whereas depletion of CD4-bearing cells had only minor effects on the outcome. Cytotoxic cells from mice cured by Ag treatment lysed only 2B4.11 among a panel of related tumors, although in vivo cross-protection studies showed that 2B4.11-immune mice were also resistant to the growth of BW5147 and C10.9. Because spleen cells from 2B4.11 immune mice did not recognize 2B4.11 or other related tumors in proliferation assays, we concluded that a participant(s) with memory and specificity, not assayed in vitro, was also involved in the mediation of the immune effects observed. For therapies based on the use of less selective agents, i.e. mAb that share the activating properties of Ag but can react with T cell neoplasms of unknown specificity, it would appear that a relatively intact immune system is required for maximal success.     

CD4 T cell dependent tumor immunity stimulated by dendritic cell based vaccine

CD8 CTLs have been accountable for the major effector cells responsible for the rejection of tumor cells. And CD40 signaling and IL-12 have been shown to be the essential pathways involved in the activation process. Immunizing mice with dendritic cells transduced with an adenovirus expressing the human melanoma antigen gp100, an immunization strategy of xenoimmunization, stimulated potent tumor protection dependent on effective CD4 T cells in the absence of CD8 T cells. Further studies revealed that neither CD40 signaling nor IL-12 was indispensable for the activation of dendritic and CD4 T cells in this model. Stimulation of effective antitumor immunity targeting the self-antigen did not elicit autoimmunity. The implications of this study were discussed.     

CD8 T cells inhibit IgE via dendritic cell IL-12 induction that promotes Th1 T cell counter-regulation.

Th1 and Th2 cells are counterinhibitory; their balance determines allergic sensitization. We show here that CD8 T cell subsets break these rules as both T cytotoxic (Tc)1 and Tc2 cells promote Th1 over Th2 immunity. Using IL-12(-/-), IFN-gamma(-/-), and OVA(257-264)-specific Valpha2Vbeta5 TCR-transgenic mice, we have identified the key steps involved. OVA-specific IFN-gamma(-/-) CD8 T cells inhibited IgE responses equivalent to wild-type CD8 T cells (up to 98% suppression), indicating that CD8 T cell-derived IFN-gamma was not required. However, OVA-specific CD8 T cells could not inhibit IgE in IFN-gamma(-/-) recipients unless reconstituted with naive, wild-type CD4 T cells, suggesting that CD4 T cell-derived IFN-gamma did play a role. Transfer of either Tc1 or Tc2 Valpha2Vbeta5 TCR-transgenic CD8 T cells inhibited IgE and OVA-specific Th2 cells while promoting OVA-specific Th1 cell responses, suggesting a potential role for a type 1 inducing cytokine such as IL-12. CD8 T cells were shown to induce IL-12 in OVA(257-264)-pulsed dendritic cells (DC) in vitro. Furthermore, CD8 T cells were unable to inhibit IgE responses in IL-12(-/-) recipients without the addition of naive, wild-type DC, thus demonstrating a pivotal role for IL-12 in this mechanism. These data reveal a mechanism of IgE regulation in which CD8 T cells induce DC IL-12 by an IFN-gamma-independent process that subsequently induces Th1 and inhibits Th2 cells. Th1 cell IFN-gamma is the final step that inhibits B cell IgE class switching. This demonstrates a novel regulatory network through which CD8 T cells inhibit allergic sensitization.     

Persistence, immune specificity, and functional ability of murine mutant ras epitope-specific CD4(+) and CD8(+) T lymphocytes following in vivo adoptive transfer.

Adoptive T-cell transfer has been shown to be a potentially effective strategy for cellular immunotherapy in some murine models of disease. However, several issues remain unresolved regarding some of the basic features involved in effective adoptive transfer, such as the influence of specific peptide antigen (Ag) boost after T-cell transfer, the addition of IL-2 post-T-cell transfer, the trafficking of transferred T cells to lymphoid and nonlymphoid tissues, and the functional stability of recoverable CD4(+) and CD8(+) T cells. We investigated several of these parameters, particularly as they relate to the persistence and maintenance of effector functions of murine CD4(+) and/or CD8(+) T lymphocytes after adoptive cellular transfer into partially gamma-irradiated syngeneic hosts. Our laboratory previously identified murine (H-2(d)) immunogenic CD4(+) and CD8(+) T-cell peptide epitopes reflecting codon 12 ras mutations as tumor-specific Ag. Therefore, the model system chosen here employed epitope-specific MHC class II-restricted CD4(+) T cells and MHC class I-restricted CD8(+) T cells produced from previously immunized BALB/c mice. Between 2 and 7 days after T-cell transfer, recipient mice received various combinations of peptide boosts and/or IL-2 treatments. At different times after the T-cell transfer, spleen and lung tissues were analyzed phenotypically to monitor the persistence of the immune T cells and functionally (via proliferation or cytotoxicity assays) to assess the maintenance of peptide specificity. The results showed that immune donor T lymphocytes (uncultured immune T cells or cloned T cells) were recoverable from the spleens and lungs of recipient mice after transfer. The recovery of Ag-specific T-cell responses was greatest from recipient mice that received peptide boosts and IL-2 treatment. However, mice that received a peptide boost without IL-2 treatment responded nearly as well, which suggested that including a peptide boost after T-cell transfer was more obligatory than exogenous IL-2 treatment to sustain adoptively transferred T cells in vivo. Ag-specific T-cell responses were weak in mice that either received IL-2 alone or did not receive the cognate peptide boost after T-cell transfer. The T-cell clones were also monitored by flow cytometry or RT-PCR based on expression of the T-cell receptor Vbeta-chain, which was previously characterized. Ag-specific T cells were recovered from both spleens and lungs of recipient mice, demonstrating that the T-cell clones could localize to both lymphoid and nonlymphoid tissues. This study demonstrates that both uncultured and in vitro-cloned T lymphocytes can migrate to lymphoid tissues and nonlymphoid (e.g., lung) tissues in recipient hosts and that their functional activities can be maintained at these sites after transfer, if they are exposed to peptide Ag in vivo.     

Reinforcement of cancer immunotherapy by adoptive transfer of cblb-deficient CD8+ T cells combined with a DC vaccine

The success of cancer immunotherapy is limited by potent endogenous immune-evasion mechanisms, which are at least in part mediated by transforming growth factor-β (TGF-β). The E3 ubiquitin ligase Cbl-b is a key regulator of T cell activation and is established to regulate TGF-β sensitivity. cblb-deficient animals reject tumors via CD8(+) T cells, which make Cbl-b an ideal target for improvement of adoptive T-cell transfer (ATC) therapy. In this study, we show that cblb-deficient CD8(+) T cells are hyper-responsive to T-cell receptor (TCR)/CD28-stimulation and are in part protected against the negative cues induced by TGF-β in vitro. Notably, adoptive transfer of polyclonal, non-TCR transgenic cblb-deficient CD8(+) T cells is not sufficient to reject B16-ova or EG7 tumors in vivo. Thus, cblb-deficient ATC requires proper in vivo re-activation by a dendritic cell (DC) vaccine. In strict contrast to ATC monotherapy, this approach delayed tumor outgrowth and significantly increased survival rates, which is paralleled by increased CD8(+) T-cells infiltration to the tumor site and enrichment of ova-specific and interferon-γ (IFN-γ)-secreting CD8(+) T cell in the draining lymph node (LN). Moreover, CD8(+) T cells from cblb-deficient mice vaccinated with the DC vaccine show increased cytolytic activity in vivo. In summary, our data using cblb-deficient polyclonal, non-TCR-transgenic adoptively transferred CD8(+) T cells into immuno-competent non-lymphodepleted recipients suggest that targeting Cbl-b might serve as a novel 'adjuvant approach', suitable to augment the effectiveness of established anti-cancer immunotherapies.     

Induction of high level IL-2 production in CD4+8- T helper lymphocytes requires post-thymic development.

Triggering of the CD3:TCR complex by optimal concentrations of anti-CD3, anti-TCR beta-chain, and allogeneic stimulator cells induced dramatically higher levels (fivefold for anti-CD3, greater than 10-fold for anti-TCR beta-chain, 84-fold for alloantigen) of IL-2 production in spleen CD4+8- T cells than their thymic counterparts, despite comparable levels of CD3 and TCR beta-chain expression. The nature of the reduced IL-2 production was examined by analysis of anti-CD3-induced IL-2 production at the single cell level. The frequency of IL-2-producing cells in spleen CD4+8- T cells (40.0%) was approximately threefold that of thymus CD4+8- T cells (14.5%). Furthermore, the average IL-2 levels among positive IL-2 producers was also approximately threefold higher in spleen CD4+8- T cells than their thymic counterparts. Adoptive transfer of purified Thy-1.2+ CD4+8- T cells into Thy-1.1-congenic hosts provided a physiologic and histocompatible system that enabled identification of transferred donor (Thy-1.2+) among a sea of host (Thy-1.2-) CD4+ T cells, whose immune function with respect to IL-2 inducibility was examined after isolation by electronic cell sorting. Donor CD4+ T cells thus isolated from host spleen shortly (1 day) after i.v. transfer of thymus CD4+8- T cells were similar to freshly isolated thymus CD4+8- T cells in that they both produced little IL-2 in response to anti-CD3. However, by day 3 post-transfer, IL-2 production by donor CD4+8- T cells had more than doubled and by day 8, they produced IL-2 levels comparable to those of host spleen CD4+8- T cells. A similar acquisition of high level IL-2 inducibility in thymus CD4+8- T cells upon i.v. transfer into Thy-1.1-congenic hosts was also observed using allogeneic cells as the stimulus of IL-2 production. When thymus CD4+8- T cells were intra-thymically transferred into Thy-1.1-congenic hosts, those donor cells that emigrated to the periphery became high IL-2 producers in a time-dependent manner, whereas those that remained inside the thymus showed no signs of up-regulation in IL-2 inducibility. Intrathymic transfer of CD4-8- thymocytes revealed that the most recent thymic emigrant CD4+8- T cells contained few IL-2-producing cells and were not functionally mature with respect to high level IL-2 inducibility.     

Uncoupling of IL-2 signaling from cell cycle progression in naive CD4+ T cells by regulatory CD4+CD25+ T lymphocytes

Prior reports have shown that CD4(+)CD25(+) regulatory T cells suppress naive T cell responses by inhibiting IL-2 production. In this report, using an Ag-specific TCR transgenic system, we show that naive T cells stimulated with cognate Ag in the presence of preactivated CD4(+)CD25(+) T cells also become refractory to the mitogenic effects of IL-2. T cells stimulated in the presence of regulatory T cells up-regulated high affinity IL-2R, but failed to produce IL-2, express cyclins or c-Myc, or exit G(0)-G(1). Exogenous IL-2 failed to break the mitotic block, demonstrating that the IL-2 production failure was not wholly responsible for the proliferation defect. This IL-2 unresponsiveness did not require the continuous presence of CD4(+)CD25(+) regulatory T cells. The majority of responder T cells reisolated after coculture with regulatory cells failed to proliferate in response to IL-2, but were not anergic and proliferated in response to Ag. The mitotic block was also dissociated from the antiapoptotic effects of IL-2, because IL-2 still promoted the survival of T cells that had been cocultured with CD4(+)CD25(+) T cells. IL-2-induced STAT5 phosphorylation in the cocultured responder cells was intact, implying that the effects of the regulatory cells were downstream of receptor activation. Our results therefore show that T cell activation in the presence of CD4(+)CD25(+) regulatory T cells can induce an alternative stimulation program characterized by up-regulation of high affinity IL-2R, but a failure to produce IL-2, and uncoupling of the mitogenic and antiapoptotic effects of IL-2.     

Dendritic cells prime in vivo alloreactive CD4 T lymphocytes toward type 2 cytokine- and TGF-beta-producing cells in the absence of CD8 T cell activation

The mechanisms that influence the polarization of CD4 T cells specific for allogeneic MHC class II molecules in vivo are still poorly understood. We have examined the pathway of alloreactive CD4 T cell differentiation in a situation in which only CD4 T cells could be activated in vivo. In this report we show that priming of adult mice with allogeneic APC, in the absence of MHC class I-T cell interactions, induces a strong expansion of type 2 cytokine-producing allohelper T cells. These alloantigen-specific CD4 T cells directly recognize native allogeneic MHC class II molecules on APC and secrete, in addition to the prototypic Th2 cytokines IL-4, IL-5, and IL-10, large amounts of TGF-beta. The default Th2-phenotype acquisition is not genetically controlled and occurred both in BALB/c and C57BL/6 mice. CD8 T cells are the principal cell type that controls CD4 T cell differentiation in vivo. Furthermore, we demonstrate that strong Th2 priming can be induced not only with allogeneic splenocytes but also with a low number of bone marrow-derived dendritic cells. Finally, using a passive transfer system, we provide direct evidence that CD8 T cell expansion in situ promotes alloreactive Th1 cell development principally by preventing their default development to the Th2 pathway in a mechanism that is largely IFN-gamma independent. Therefore, this work demonstrates that type 2 cytokine production represents a dominant pathway of alloreactive CD4 T cell differentiation in adult mice, a phenomenon that was initially thought to occur only during the neonatal period.     

Immunization with a mimotope of GD2 ganglioside induces CD8+ T cells that recognize cell adhesion molecules on tumor cells

The GD2 ganglioside expressed on neuroectodermal tumor cells has been used as a target for passive and active immunotherapy in patients with malignant melanoma and neuroblastoma. We have reported that immunization of mice with a 47-LDA mimotope of GD2, isolated from a phage display peptide library with anti-GD2 mAb 14G2a, induces MHC class I-restricted CD8(+) T cell responses to syngeneic neuroblastoma tumor cells. The cytotoxic activity of the vaccine-induced CTLs was independent of GD2 expression, suggesting recognition of a novel tumor-associated Ag cross-reacting with 47-LDA. Glycan microarray and immunoblotting studies using 14G2a mAb demonstrated that this Ab is highly specific for the entire carbohydrate motif of GD2 but also cross-reacts with a 105 kDa glycoprotein expressed by GD2(+) and GD2(-) neuroblastoma and melanoma cells. Functional studies of tumor cells grown in three-dimensional collagen cultures with 14G2a mAb showed decreases in matrix metalloproteinase-2 activation, a process regulated by the 105 kDa-activated leukocyte cell adhesion molecule (ALCAM/CD166). A recombinant CD166 glycoprotein was shown to be recognized by 14G2a Ab and inhibition of CD166 expression by RNA interference ablated the cell sensitivity to lysis by 47-LDA-induced CD8(+) T cells in vitro and in vivo. The binding of 14G2a to CD166 was not disruptable by a variety of exo- and endo-glycosidases, implying recognition of a non-glycan epitope on CD166. These results suggest that the vaccine-induced CTLs recognize a 47-LDA cross-reactive epitope expressed by CD166, and reveal a novel mechanism of induction of potent tumor-specific cellular responses by mimotopes of tumor-associated carbohydrate Ags.     

Cutting edge: control of CD8+ T cell activation by CD4+CD25+ immunoregulatory cells

CD4(+)CD25(+) regulatory T cells inhibit organ-specific autoimmune diseases induced by CD4(+)CD25(-) T cells and are potent suppressors of CD4(+)CD25(-) T cell activation in vitro. We demonstrate that CD4(+)CD25(+) T cells also suppress both proliferation and IFN-gamma production by CD8(+) T cells induced either by polyclonal or Ag-specific stimuli. CD4(+)CD25(+) T cells inhibit the activation of CD8(+) responders by inhibiting both IL-2 production and up-regulation of IL-2Ralpha-chain (CD25) expression. Suppression is mediated via a T-T interaction as activated CD4(+)CD25(+) T cells suppress the responses of TCR-transgenic CD8(+) T cells stimulated with soluble peptide-MHC class I tetramers in the complete absence of APC. These results broaden the immunoregulatory role played by CD4(+)CD25(+) T cells in the prevention of autoimmune diseases, but also raise the possibility that they may hinder the induction of effector CD8(+) T cells to tumor or foreign Ags.     

OX40 ligation of CD4+ T cells enhances virus-specific CD8+ T cell memory responses independently of IL-2 and CD4+ T regulatory cell inhibition

We have previously shown that CD4(+) T cells are required to optimally expand viral-specific memory CD8(+) CTL responses using a human dendritic cell-T cell-based coculture system. OX40 (CD134), a 50-kDa transmembrane protein of the TNFR family, is expressed primarily on activated CD4(+) T cells. In murine models, the OX40/OX40L pathway has been shown to play a critical costimulatory role in dendritic cell/T cell interactions that may be important in promoting long-lived CD4(+) T cells, which subsequently can help CD8(+) T cell responses. The current study examined whether OX40 ligation on ex vivo CD4(+) T cells can enhance their ability to "help" virus-specific CTL responses in HIV-1-infected and -uninfected individuals. OX40 ligation of CD4(+) T cells by human OX40L-IgG1 enhanced the ex vivo expansion of HIV-1-specific and EBV-specific CTL from HIV-1-infected and -uninfected individuals, respectively. The mechanism whereby OX40 ligation enhanced help of CTL was independent of the induction of cytokines such as IL-2 or any inhibitory effect on CD4(+) T regulatory cells, but was associated with a direct effect on proliferation of CD4(+) T cells. Thus, OX40 ligation on CD4(+) T cells represents a potentially novel immunotherapeutic strategy that should be investigated to treat and prevent persistent virus infections, such as HIV-1 infection.     

A CD8+ T cell heptaepitope minigene vaccine induces protective immunity against Chlamydia pneumoniae

An intact T cell compartment and IFN-gamma signaling are required for protective immunity against Chlamydia. In the mouse model of Chlamydia pneumoniae (Cpn) infection, this immunity is critically dependent on CD8(+) T cells. Recently we reported that Cpn-infected mice generate an MHC class I-restricted CD8(+) Tc1 response against various Cpn Ags, and that CD8(+) CTL to multiple epitopes inhibit Cpn growth in vitro. Here, we engineered a DNA minigene encoding seven H-2(b)-restricted Cpn CTL epitopes, the universal pan-DR epitope Th epitope, and an endoplasmic reticulum-translocating signal sequence. Immunization of C57BL/6 mice with this construct primed IFN-gamma-producing CD8(+) CTL against all seven CTL epitopes. CD8(+) T cell lines generated to minigene-encoded CTL epitopes secreted IFN-gamma and TNF-alpha and exhibited CTL activity upon recognition of Cpn-infected macrophages. Following intranasal challenge with Cpn, a 3.6 log reduction in mean lung bacterial numbers compared with control animals was obtained. Using a 20-fold increase in the Cpn challenging dose, minigene-vaccinated mice had a 60-fold reduction in lung bacterial loads, compared with controls. Immunization and challenge studies with beta(2)-microglobulin(-/-) mice indicated that the reduction of lung Cpn burdens was mediated by the MHC class I-dependent CD8(+) T cells to minigene-included Cpn CTL epitopes, rather than by pan-DR epitope-specific CD4(+) T cells. This constitutes the first demonstration of significant protection achieved by immunization with a CD8(+) T cell epitope-based DNA construct in a bacterial system and provides the basis for the optimal design of multicomponent anti-Cpn vaccines for humans.     

Simultaneous production of IL-2, IL-4, and IFN-gamma by activated human CD4+ and CD8+ T cell clones

In the present study, we have investigated the ability of human T cells to secrete IL-2, IL-4, and IFN-gamma. IL-4 and IFN-gamma were quantified with enzymatic immunoassays and IL-2 with a biologic assay by using the murine IL-2-dependent cell line CTLL-2. PBL, stimulated with Con A or with a combination of the phorbol ester 13-O-tetradecanoylphorbol-12-acetate and the Ca2+ ionophore A23187 secreted IL-2, IL-4, and IFN-gamma. The kinetics of the secretion of the three lymphokines was investigated with two CD4+ clones; one (GEO-2) that produced IL-2, IL-4, and IFN-gamma and another (HY640), that produced only IL-2 and IFN-gamma. Significant IL-2, IL-4, and IFN-gamma production was observed after only 8 h of activation. Maximal levels of IL-2 and IL-4 were found 20 h after the onset of the stimulation which subsequently decreased. In contrast, IFN-gamma levels continued to increase in a period up to 40 h and then leveled off. In spite of these differences in secretion, the kinetics of accumulation of mRNA did not differ. The IL-2, IL-4, and IFN-gamma mRNA were detectable 2 h after stimulation and continued to accumulate for a period up to 20 h. In a series of 22 CD4+ clones, 21 were able to secrete all three lymphokines upon stimulation. Almost all CD8+ clones were able to produce IL-2 and IFN-gamma, but only six of the 23 CD8+ T cell clones secreted IL-4. In addition, five CD4+ (allo)antigen-specific T cell clones were tested for IL-2, IL-4, and IFN-gamma secretion upon specific stimulation. Two alloantigen-specific and two tetanus toxoid-specific T cell clones secreted IL-2, IL-4, and IFN-gamma simultaneously, whereas one alloantigen-specific T cell clone secreted IL-2 and IFN-gamma, but not IL-4. A supernatant of the CD4+ T cell clone GEO-2, that contained high levels of IFN-gamma and IL-4, was unable to induce the low affinity receptor for IgE, CD23, on a Burkitt lymphoma cell line. However, after separation of IL-4 from IFN-gamma by using HPLC, the IL-4-containing fraction-induced CD23, which could be blocked by the fraction that contained IFN-gamma and by a polyclonal rabbit anti-IL-4 antiserum. Finally, the partly purified IL-4, that was devoid of IL-2, promoted the growth of the clone GEO-2.     

IL-1 induces high affinity IL-2 receptor expression of CD4-8- thymocytes

We investigated the role of cytokines for the growth of CD4-8-thymocytes (double negative thymocytes) (DNT) in vitro and found that IL-1-induced IL-2-dependent proliferation of only the IL-2R-positive DNT subpopulation. The presence of IL-1 during the first 18 h of culture was sufficient for an optimal response and suggested that IL-1 induced DNT differentiation. We could indeed show by RNA dot blot analysis that IL-1 stimulated de novo expression of the p55 chain of the IL-2R thus initiating high affinity IL-2 binding and a proliferative response. Because macrophages and epithelial cells in the thymus produce IL-1 we propose that IL-1 is involved in early events during maturation of immature thymocytes.