Enhanced NK Cell Activity Research Articles

Nutritional Deficit And Volume Overload In Renal Transplant Patients.

The antitumour activity of the dendritic cell (DC)-based cellular vaccines is greatly reduced in hostile tumour microenvironment. Therefore, there are many attempts to eliminate or neutralize both suppressor cells and cytokines. The aim of the investigation was to verify if temporary elimination of IL-10 just before injection of bone marrow-derived DCs (BMDCs) enhance the antitumour activity of applied vaccines and help to overcome the immunosuppressive tumour barrier.Mice bearing colon carcinoma MC38 were given single dose of cyclophosphamide (CY) followed by alternate injections of anti-IL-10 antibodies and BMDC-based vaccines consisted of BMDCs stimulated with MC38 tumour antigen (BMDC/TAg) or the combination of BMDC/TAg with BMDCs transduced with IL-12 genes (BMDC/IL-12).The high tumour growth inhibition was observed in mice treated with CY + anti-IL-10 + BMDC/TAg as well as CY ± anti-IL-10 + BMDC/TAg + BMDC/IL-12. However, the mechanisms of action of particular treatment schemes were diversified. Generally, it was observed that application of anti-IL-10 Abs reduced suppressor activity of myeloid-derived suppressor cells (MDSCs). However, anti-IL-10 Abs in combination with diversely composed BMDC-based vaccines induced different components of an antitumour response. The high cytotoxic activity of spleen-derived NK cells and increased influx of these cells into tumours of mice treated with CY + anti-IL-10 + BMDC/TAg indicate that mice from the group developed strong NK-dependent response. Whereas, application of anti-IL-10 Abs just before injection of BMDC/TAg + BMDC/IL-12 did not enhanced NK cell activity. Furthermore, it significantly impaired effectiveness of therapy composed of CY + BMDC/TAg + BMDC/IL-12 vaccine in induction of Th1 type immune response.Taken together, our results indicate that temporary elimination of IL-10 is an important and effective way to decrease the immune suppression associated with MDSCs activity and represents a useful strategy for successful enhancement of the antitumour activity of BMDC/TAg-based vaccines.

Kidney Donors' Demographics And Motivation For Donation (a Tertiary Care Experience)

The antitumour activity of the dendritic cell (DC)-based cellular vaccines is greatly reduced in hostile tumour microenvironment. Therefore, there are many attempts to eliminate or neutralize both suppressor cells and cytokines. The aim of the investigation was to verify if temporary elimination of IL-10 just before injection of bone marrow-derived DCs (BMDCs) enhance the antitumour activity of applied vaccines and help to overcome the immunosuppressive tumour barrier.Mice bearing colon carcinoma MC38 were given single dose of cyclophosphamide (CY) followed by alternate injections of anti-IL-10 antibodies and BMDC-based vaccines consisted of BMDCs stimulated with MC38 tumour antigen (BMDC/TAg) or the combination of BMDC/TAg with BMDCs transduced with IL-12 genes (BMDC/IL-12).The high tumour growth inhibition was observed in mice treated with CY + anti-IL-10 + BMDC/TAg as well as CY ± anti-IL-10 + BMDC/TAg + BMDC/IL-12. However, the mechanisms of action of particular treatment schemes were diversified. Generally, it was observed that application of anti-IL-10 Abs reduced suppressor activity of myeloid-derived suppressor cells (MDSCs). However, anti-IL-10 Abs in combination with diversely composed BMDC-based vaccines induced different components of an antitumour response. The high cytotoxic activity of spleen-derived NK cells and increased influx of these cells into tumours of mice treated with CY + anti-IL-10 + BMDC/TAg indicate that mice from the group developed strong NK-dependent response. Whereas, application of anti-IL-10 Abs just before injection of BMDC/TAg + BMDC/IL-12 did not enhanced NK cell activity. Furthermore, it significantly impaired effectiveness of therapy composed of CY + BMDC/TAg + BMDC/IL-12 vaccine in induction of Th1 type immune response.Taken together, our results indicate that temporary elimination of IL-10 is an important and effective way to decrease the immune suppression associated with MDSCs activity and represents a useful strategy for successful enhancement of the antitumour activity of BMDC/TAg-based vaccines.

Vaccine with herbal adjuvant—A better cocktail to combat the infection

Cross-talk between microbe and the host makes important contribution to the subsequent course of infection. Edward Jenner and Louis Pasteur—Fathers of vaccinology have wisely thought of combating an infectious bug with the same bug in a non-infectious form. Then on, vaccines have taken a great toll as a prophylactic agent to improve the quality of human life. Vaccines are successful in controlling a substantial portion of the morbidity and mortality in the developing world. Though vaccines against few diseases like small pox, polio and cholera are highly successful, the stories of failed vaccines are far more. An ideal vaccine candidate should be able to elicit the correct response, either Th1 or Th2 to combat the infection along with a strong immune memory. Use of adjuvant in the vaccine preparation is a long standing practice. Despite major advances in our understanding of vaccine adjuvants, both old and new vaccines seem likely to depend on aluminium salts. However, these adjuvants can lead to serious adverse effects [1]. Herbal immuno-modulators are paving its way as a safe alternative [2-7]. These herbal modulators can be administered along with the vaccine to elicit a faster and stronger immune response. Various herbal preparations have been shown to exert strong immuno-modulatory properties like increase in the cytokine expression [6], enhanced activation of CD4 and CD8 T cells [4-6], enhanced NK cell activity [4], etc. The failure of various vaccines can be attributed to its inability to trigger a robust immune response necessary for protection due to subsequent exposure to an infectious agent. Use of herbal immuno-modulators perhaps might be helpful in overcoming the initial lag. For, e.g., Angelica sinensus polysaccharide (ASP) increased the production of IL-2 and IFNγ, while that of IL-4 was decreased [6]. Hence, in bacterial and viral infections, which need IFNγ for its clearance, can use ASP as an adjuvant along with the vaccine. Similarly, infections which need IL-4 for its clearance should be combined with herbal modulators favoring Th2 responses, like ginseng [3]. Herbs are usually considered to be safe. However, there is no database available which can summarize the immunological profile of the various herbs or polyherbs preparation. Hence, a note of caution is a must before choosing herbal immuno-modulators as an adjuvant.

Anti-Cancer Effects of Xanthones from Pericarps of Mangosteen

Mangosteen, Garcinia mangostana Linn, is a tree found in South East Asia, and its pericarps have been used as traditional medicine. Phytochemical studies have shown that they contain a variety of secondary metabolites, such as oxygenated and prenylated xanthones. Recent studies revealed that these xanthones exhibited a variety of biological activities containing anti-inflammatory, anti-bacterial, and anti-cancer effects. We previously investigated the anti-proliferative effects of four prenylated xanthones from the pericarps; alpha-mangostin, beta-mangostin, gamma-mangostin, and methoxy-beta-mangostin in various human cancer cells. These xanthones are different in the number of hydroxyl and methoxy groups. Except for methoxy-beta-mangostin, the other three xanthones strongly inhibited cell growth at low concentrations from 5 to 20 microM in human colon cancer DLD-1 cells. Our recent study focused on the mechanism of alpha-mangostin-induced growth inhibition in DLD-1 cells. It was shown that the anti-proliferative effects of the xanthones were associated with cell-cycle arrest by affecting the expression of cyclins, cdc2, and p27; G1 arrest by alpha-mangostin and beta-Mangostin, and S arrest by gamma-mangostin. alpha-Mangostin found to induce apoptosis through the activation of intrinsic pathway following the down-regulation of signaling cascades involving MAP kinases and the serine/threonine kinase Akt. Synergistic effects by the combined treatment of alpha-mangostin and anti-cancer drug 5-FU was to be noted. alpha-Mangostin was found to have a cancer preventive effect in rat carcinogenesis bioassay and the extract from pericarps, which contains mainly alpha-mangostin and gamma-mangostin, exhibited an enhancement of NK cell activity in a mouse model. These findings could provide a relevant basis for the development of xanthones as an agent for cancer prevention and the combination therapy with anti-cancer drugs.

High Numbers of NK Cell Clones Can Be Generated by Limiting Dilution in SCGM Medium Supplemented with IL-2, IL-15 and Anti-NKp46 Antibody 9E2.

NK cell clones obtained by limiting dilution have frequently been used for functional studies and as an analytical tool e.g. for assessment of alloreactivity in the context of haploidentical stem cell transplantation [Velardi et al., Blood 2007]. NK cell clones can be used in co-culture experiments with allogeneic target cells to determine the number of alloreactive clones and therefore to quantify NK cell alloreactivity. This method provides additional quantitative data, while PCR based methods for HLA and KIR typing only provide qualitative results of potential alloreactivity. Generation of NK cell clones usually is difficult and cloning efficiency is low (< 5% [Yssel et al., J. Immunol. Methods 1984]). Protocols have been developed to increase cloning efficiency [Wang et al., J. Immunol. Methods 2005] We evaluated whether cloning efficiency can be further increased by optimization of cell processing prior to culture and/or of medium components. Published reference methods use media supplemented with Interleukin-2 (IL-2). These conditions also stimulate proliferation of T cells, which usually overgrow NK cells in culture. Thus depletion of T cells prior to incubation with IL-2 may facilitate identifation of proliferating NK cells. T cells can be actively depleted upon CD3 magnetic labelling, by use of an NK cell isolation kit or passively by CD56 enrichment. CD 56 enrichment efficiently depletes CD3+CD56- T cells and residual CD3+CD56+ NKT cells do not expand under the chosen culture conditions. IL-15 is capable of preventing NK cell apoptosis at low concentrations [Caligiuri et al., J. Clin. Invest. 1997; Carson et al., J Clin Invest. 1997; Puzanov et al., J Immunol. 1996)] and plays a role in proliferation and survival of NK cells. Cross linking of NKp46 leads to NK cell activation [Long et al., Blood 2005]. As simultaneous engagement of two independent activating NK cell receptors (IL-2/IL-15 receptors and NKp46) may enhance NK cell activation and proliferation, we evaluated different combinations of IL-2, IL-15 and the anti-NKp46 antibody 9E2. Optimal results were obtained when CD56 selected cells were used (compared to CD3 depletion, NK cell enrichment, KIR2D selection). Supplementation of SCGM medium (Cell Genix) with IL-2 (500u/mL), IL-15 (10ng/mL) and anti NKp46 antibody (2μg/mL, CD335, clone 9E2) increased the number of NK cell clones by a factor of 2.3–2.5 (n=3) compared to medium and IL-2 alone. 37 NK cell clones with yields of > 2E6 cells per clone have been generated using this optimised method and will now be used for Killer Immunoglobulin-like receptor mRNA analyses and antibody based KIR phenotyping (CD158a/h, CD158b, CD158e, CD158i, anti KIR2D). KIR analysed NK cell clones may be used to generate novel highly specific anti KIR antibodies for flowcytometric, quantitative KIR phenotyping. Such a panel can be helpful for optimization of donor selection for allogeneic stem cell transplantation.

Expression of the p60 Autolysin Enhances NK Cell Activation and Is Required forListeria monocytogenesExpansion in IFN-γ-Responsive Mice

Both peptidoglycan and muropeptides potently modulate inflammatory and innate immune responses. The secreted Listeria monocytogenes p60 autolysin digests peptidoglycan and promotes bacterial infection in vivo. Here, we report that p60 contributes to bacterial subversion of NK cell activation and innate IFN-gamma production. L. monocytogenes deficient for p60 (Deltap60) competed well for expansion in mice doubly deficient for IFNAR1 and IFN-gammaR1 or singly deficient for IFN-gammaR1, but not in wild-type, IFNAR1(-/-), or TLR2(-/-) mice. The restored competitiveness of p60-deficient bacteria suggested a specific role for p60 in bacterial subversion of IFN-gamma-mediated immune responses, since in vivo expansion of three other mutant L. monocytogenes strains (DeltaActA, DeltaNamA, and DeltaPlcB) was not complemented in IFN-gammaR1(-/-) mice. Bacterial expression of p60 was not required to induce socs1, socs3, and il10 expression in infected mouse bone marrow macrophages but did correlate with enhanced production of IL-6, IL-12p70, and most strikingly IFN-gamma. The primary source of p60-dependent innate IFN-gamma was NK cells, whereas bacterial p60 expression did not significantly alter innate IFN-gamma production by T cells. The mechanism for p60-dependent NK cell stimulation was also indirect, given that treatment with purified p60 protein failed to directly activate NK cells for IFN-gamma production. These data suggest that p60 may act on infected cells to indirectly enhance NK cell activation and increase innate IFN-gamma production, which presumably promotes early bacterial expansion through its immunoregulatory effects on bystander cells. Thus, the simultaneous induction of IFN-gamma production and factors that inhibit IFN-gamma signaling may be a common strategy for misdirection of early antibacterial immunity.

Interleukin-21 (IL-21): Tolerability and anti-tumor activity following two 5-day cycles in patients with stage IV melanoma (MM) or renal cell carcinoma (RCC)

2505 Background: IL-21 enhances NK cell activity and the proliferation and activation of CD8+ T cells. A Phase 1 outpatient dose-escalation trial of IL-21 in patients with MM or RCC established a maximum tolerated dose and demonstrated biologic effects as measured by increased soluble CD25 levels and decreased lymphocyte counts. Partial responses (PR) were observed in 2 patients with RCC (J Immunother. 2005; 28:641–642). Methods: IL-21 was administered by intravenous push at 30 μg/kg/day for two 5-day cycles separated by a 9- or 16-day rest to a total of 34 patients (18 MM and 16 RCC) to further characterize safety and evaluate preliminary signs of anti-tumor activity. Results: All patients received 2 cycles of treatment with the exception of one patient who discontinued secondary to pleural effusion. Common drug-related Grade 1–2 adverse events (AEs) included pyrexia (n=27), fatigue (n=25), chills (n=18), headache (n=18), and rash (n=16). Related Grade 3 AEs included pleural effusion, abdominal pain, hypophosphatemia, and thrombocytopenia (n=1 each). Laboratory abnormalities commonly observed were decreased lymphocytes (n=31), platelets (n=31), albumin (n=29), and hemoglobin (n=27); increased triglycerides (n=27) and ALT (n=26). Except for lymphopenia (an expected pharmacodynamic response), most toxicities were Grade 1–2. AEs and laboratory abnormalities were generally transient. Final study results, including response data, will be presented. To date, of 28 patients evaluable for response (i.e., those who received at least 8 of 10 doses and have had a final evaluation), one PR has been confirmed in a patient with MM and 18 patients have stable disease two months following initiation of therapy. Conclusions: Two 5-day outpatient cycles of IL-21 at 30 μg/kg/day have been reasonably well tolerated and have demonstrated preliminary evidence of anti-tumor activity in patients with advanced MM or RCC. [Table: see text]

Interleukin-21 Enhances NK Cell Activation in Response to Antibody-Coated Targets

NK cells express an activating FcR (FcgammaRIIIa) that mediates Ab-dependent cellular cytotoxicity and the production of immune modulatory cytokines in response to Ab-coated targets. IL-21 has antitumor activity in murine models that depends in part on its ability to promote NK cell cytotoxicity and IFN-gamma secretion. We hypothesized that the NK cell response to FcR stimulation would be enhanced by the administration of IL-21. Human NK cells cultured with IL-21 and immobilized IgG or human breast cancer cells coated with a therapeutic mAb (trastuzumab) secreted large amounts of IFN-gamma. Increased secretion of TNF-alpha and the chemokines IL-8, MIP-1alpha, and RANTES was also observed under these conditions. NK cell IFN-gamma production was dependent on distinct signals mediated by the IL-21R and the FcR and was abrogated in STAT1-deficient NK cells. Supernatants derived from NK cells that had been stimulated with IL-21 and mAb-coated breast cancer cells were able to drive the migration of naive and activated T cells in an in vitro chemotaxis assay. IL-21 also enhanced NK cell lytic activity against Ab-coated tumor cells. Coadministration of IL-21 and Ab-coated tumor cells to immunocompetent mice led to synergistic production of IFN-gamma by NK cells. Furthermore, the administration of IL-21 augmented the effects of an anti-HER2/neu mAb in a murine tumor model, an effect that required IFN-gamma. These findings demonstrate that IL-21 significantly enhances the NK cell response to Ab-coated targets and suggest that IL-21 would be an effective adjuvant to administer in combination with therapeutic mAbs.

A DNA-based cancer vaccine enhances lymphocyte cross talk by engaging the NKG2D receptor

AbstractThe NKG2D receptor is a stimulatory receptor expressed on NK cells and activated CD8 T cells. We previously demonstrated that engaging the NKG2D receptor markedly improved the efficacy of a survivin-based DNA vaccine. The combination vaccine, encoding both the NKG2D ligand H60 and survivin, activates innate and adaptive antitumor immunity and results in better protection against tumors of different origin and NKG2D expression levels. Here we demonstrate that the enhanced vaccine efficacy is in part attributable to increased cross talk between lymphocytes. Depletion of CD8 T cells during priming reduces the vaccine-induced activation of dendritic cells (DCs) and NK cell activity. Depletion of NK cells during priming leads to reduced DC activation and CTL activity. However, depletion of CD4 T cells results in the activation of DCs, NK cells, and CD8 T cells and enhances NK cell activity. The pH60/Survivin vaccine also increases DCs and NK cells but decreases CD4 T cell homing to Peyer patches, presumably as a result of changes in the homing receptor profile. Thus, by preferentially activating and attracting positive regulators and reducing negative regulators in Peyer patches, this dual-function DNA vaccine induces a microenvironment more suitable for NK cell activation and T cell priming.

Cytoskeleton rearrangement induced by tetraspanin engagement modulates the activation of T and NK cells

The hepatitis C virus (HCV) binds to human cells through the interaction of its envelope glycoprotein E2 with the tetraspanin CD81. We have previously reported that engagement of CD81 has opposite effects on T and NK cell function, as it enhances T cell receptor-mediated T cell activation and inhibits CD16- or IL-12-mediated NK cell activation. We further investigated this dichotomy and found that another tetraspanin, CD82, induces the same opposing effects on human primary T and NK cells. Activation by other unrelated stimuli such as NKG2D- and beta-1 integrin is also reduced by CD81 ligation on NK cells. CD81 engagement by monoclonal antibody or HCV-E2 enhances zeta and Erk phosphorylation in T cells and reduces them in NK cells, reflecting the opposite functional outcomes. CD81 engagement induces dramatic morphological changes and local F-actin accumulation in both NK and T cells, indicating rearrangement of the actin cytoskeleton. Pharmacological inhibition of actin polymerization reduces T cell activation, whereas it greatly enhances NK cell activation. Importantly, treatment with actin blockers abolishes the inhibitory effect of CD81 ligation on NK cells. We propose that tetraspanin engagement leads to comparable cytoskeleton reorganization in T and NK cells, which in turn results in opposite functional outcomes.

Cholinergic and serotonergic activities are required in triggering conditioned NK cell response

The purpose of the study was to examine the importance of the cholinergic system in triggering the conditioned NK cell response. The fact that serotonergic system can modulate cholinergic functions suggested that it might be involved in conditioned NK cell response. To evaluate the potential pathways, cholinergic and serotonergic antagonists were applied centrally at either the conditioned association or recall stage, to interfere with the conditioned NK cell response. The results showed that both the cholinergic and serotonergic systems were necessary for eliciting the conditioned enhancement of NK cell activity. Involvements of the two systems were found to be critical for establishing the conditioned association and recall of the conditioned response. The blocks are believed to be receptor mediated. The receptors identified to be involved in the regulation of the conditioned NK cell response were: M 1, M 2 and M 3 muscarinic; nicotinic; 5 HT 1 and 5 HT 2 receptors.

IRAK and TAK1 are required for IL-18-mediated signaling.

Interleukin-18 (IL-18), a pleiotropic cytokine produced by activated macrophages, plays significant roles in the immune response, inducing the secretion of IFN-gamma, TNF-alpha and IL-2, enhancing NK cell activity and potentiating the differentiation of Th1 cells. The intercellular signal transduction pathways through which IL-18 functions have not been thoroughly defined. We have generated a mutant cell line, I1A, that lacks the IRAK protein. In this line which has low or no expression of the other known IRAK family members, we find that the IL-1 receptor-associated kinase (IRAK) is essential for the activation of NFkappaB and JNK in response to IL-18. Furthermore, the death domain, but not the kinase activity of IRAK, is necessary for NFkappaB activation in response to IL-18. Interestingly, the N-proximal undetermined region of IRAK is necessary for NFkappaB activation, but not for JNK activation in response to IL-18, indicating IRAK may be a branchpoint in IL-18 signaling. In addition to IRAK, we implicate two other components in IL-18 signaling, TAK1 (TGF-beta-activated kinase 1) and its activator and substrate TAB1. A dominant negative mutant of TAK1 inhibits the IL-18-mediated NFkappaB activation, while IL-18 stimulation leads to the phosphorylation of TAB1. Finally, analysis of IL-18 signaling in IL-1-unresponsive mutant cell lines suggests that the IL-1- and IL-18-mediated pathways are similar, but may not be identical.

Immunomodulation of early engrafted natural killer cells with interleukin-2 and interferon-alpha in autologous stem cell transplantation.

High relapse rates during the first year after autologous stem cell transplantation (ASCT) for multiple myeloma or non-Hodgkin lymphoma are due to the failure of high-dose chemotherapy to eradicate minimal residual disease. Post-ASCT immunorecovery studies have shown that quantities of natural killer (NK) cells return to normal within 1 month post-ASCT in contrast to the recovery of T and B cell populations (up to 1 year). Preclinical studies have demonstrated that NK cells have potent antitumor activity. IL-2 and IFN-alpha enhance NK-cell activity. We investigated the efficacy of IL-2 and IFN-alpha to up-regulate NK-cell cytotoxicity at 14 days post ASCT. Twenty patients undergoing ASCT had PBMCs collected pretransplantation and at 14 days post transplantation. PBMCs (effector cells) from each blood sample were incubated in vitro with IFN-alpha and IL-2 at 10000 IU/ml. NK cell activity was determined by sodium chromate (51)Cr release assay for lysis of K562 target cells. IL-2 and IFN-alpha each increased lysis of K562 cells compared with placebo (effector-to-target ratio, 50:1, P < 0.001). Increased NK cell activity occurred in samples from all patients. IL-2 and IFN-alpha up-regulated NK cell activity at 14 days post ASCT. They may be useful as immunomodulators as early as 14 days post ASCT to eradicate or control minimal residual disease.

Gamma-globulin inhibits tumor spread in mice.

Intravenous (i.v.) Ig is the human serum Ig fraction that is mainly composed of IgG prepared from plasma pools of over 15,000 healthy blood donors and is suitable for i.v. use. High-dose i.v. Ig is currently used to treat patients with diverse autoimmune conditions. Autoimmunity and malignancy co-exist frequently, and share etiological and pathological mechanisms. Since the two diseases are similarly treated, we studied the efficacy of i.v. Ig as a treatment for malignant conditions. The administration of i.v. Ig to mice inoculated i.v. with melanoma or sarcoma cells induced a statistically significant inhibition of metastatic lung foci and prolongation of survival time. Similar results were seen with SCID mice inoculated with SK-28 human melanoma cells. In a different model, melanoma was induced in the foot pad, followed by leg amputation, after the development of the tumor lesion. A lower number of melanoma recurrences and prolongation of survival time were demonstrated in the i.v. Ig-treated groups. In vitro studies revealed that i.v. Ig was found to stimulate the production of IL-12, an anti-tumor and anti-angiogenic cytokine. Moreover, it enhanced NK cell activity, thus explaining its beneficial effect in SCID mice (which lack B and T but possess NK cells). The results indicate that i.v. Ig acts as an anti-tumor agent. Since it has only minor side effects and is used extensively for other clinical conditions, i.v. Ig may be considered as a potential therapy for the prevention of tumor spread in humans.

Early gene expression of NK cell-activating chemokines in mice resistant to Leishmania major.

Susceptibility of mice to Leishmania major is associated with an insufficient NK cell-mediated innate immune response. We analyzed the expression of NK cell-activating chemokines in vivo during the first days of infection in resistant and susceptible mice. The mRNA expression of gamma interferon-inducible protein 10 (IP-10), monocyte chemoattractant protein 1 (MCP-1), and lymphotactin was upregulated 1 day after infection in the draining lymph nodes of resistant C57BL/6 mice but not in those of susceptible BALB/c mice. In vivo local treatment of BALB/c mice with recombinant IP-10 shortly after infection resulted in an enhanced NK cell activity in the draining lymph node. The data suggest that although the recruitment of NK cells is normal in susceptible mice, the lack of NK cell-activating chemokines is a factor resulting in a suboptimal NK cell-mediated defense.

A Single Intramuscular Injection with an Adenovirus- Expressing IL-12 Protects BALB/c Mice AgainstLeishmania majorInfection, While Treatment with an IL-4-Expressing Vector Increases Disease Susceptibility in B10.D2 Mice

AbstractExperimental infection of the susceptible BALB/c (H-2d) mouse with the intracellular parasite Leishmania major induces a predominant Th2-type T cell response that eventually leads to death. In contrast, the resistant B10.D2 (H-2d) strain develops Th1 cells that control parasite replication and disease. In this study, we tested the ability of a recombinant adenovirus vector-expressing IL-12 to skew the immune response in a Th1 direction and prevent leishmaniasis in susceptible mice. We report that BALB/c mice treated with the Ad5IL-12 vector on the same day as parasitic challenge are significantly protected against leishmaniasis and acquired long-lasting immunity, because upon rechallenge with L. major parasites they were resistant to disease. The vector-derived IL-12 expression was transient and highly localized to the tissue after i.m. injection; it caused an increase in the number of Ag-specific IFN-γ-secreting lymphocytes and enhanced NK cell activity in the draining popliteal node. In contrast, resistant B10.D2 mice given i.m. injections with a recombinant adenovirus-expressing IL-4 displayed greater susceptibility to disease, and severe lesions were produced in some of the infected animals. These results suggest the potential use of recombinant adenoviruses expressing cytokines as potent immunomodulatory agents for the generation of protective immune responses against intracellular pathogens.

Prophylactic effect of Korean mistletoe (Viscum album coloratum) extract on tumor metastasis is mediated by enhancement of NK cell activity

We here demonstrated the prophylactic effect of an extract (KM-110) from Viscum album coloratum, a Korean mistletoe, on tumor metastasis produced by highly metastatic tumor cells, colon 26-M3.1 carcinoma, B16-BL6 melanoma and L5178Y-ML25 lymphoma cells, using experimental models in mice. Intravenous (i.v.) adminstration of KM-110 (100 μg/mouse) 2 days before tumor inoculation significantly inhibited lung metastasis of B16-BL6 and colon 26-M3.1 cells, and liver and spleen metastasis of L5178Y-ML25 cells. The prophylactic effect of KM-110 on tumor metastasis was evident with various administration routes, i.e. subcutaneous, oral, intranasal as well as i.v., and was dependent upon the dose of KM-110 administered. Furthermore, mice given KM-110 (100 μg) 2 days before tumor inoculation showed significantly prolonged survival rates compared with the untreated mice. In a time course analysis of NK activity, i.v. administration of KM-110 (100 μg) significantly augmented NK cytotoxicity to Yac-a tumor cells from 1 to 3 days after KM-110 treatment. Furthermore, depletion NK cells by injection of rabbit anti-asialo GM1 serum completely abolished the inhibitory effect of KM-110 on lung metastasis of colon 26-M3.1 cells. These results suggest that KM-110 possesses immunopotentiating activity which enhances the host defense system against tumors, and that its prophylactic effect on tumor metastasis is mediated by NK cell activation.

Enhancement of natural killer cell cytotoxicity by the human herpesvirus-7 via IL-15 induction.

NK cells, a key component of the innate immune system, are known to play an important role against viral infections. Previously, we reported that the human herpesvirus-6 (HHV-6) induces IL-15 in human PBMC and increases their NK activity. We describe in this work that another human herpesvirus, HHV-7, which shares genomic homology with HHV-6, also causes up-regulation of NK cell cytotoxicity via IL-15 induction. The NK cell activity of the PBMC from different donors displayed a variable range of enhancement after treatment with HHV-7. This enhancement occurred within a few hours of exposure to the virus and was blocked by Abs to IL-15, but not to other cytotoxicity-enhancing cytokines (i.e., to IFN-gamma, IL-2, TNF-alpha, or IL-12). Our results also show that this HHV-7-induced IL-15-mediated activation of NK cells occurs via IL-2R, since HHV-7-enhanced NK cytotoxic activity could be blocked completely by anti-IL-2R beta-chain mAb (anti-CD122). The up-regulation of NK cell cytotoxicity did not require infectious virus, as the use of UV-irradiated HHV-7 produced similar results. This effect was virus specific because it was abrogated by neutralizing the virus with human sera containing Abs to HHV-7. We also found increased amount of IL-15 transcripts in HHV-7-treated PBMC as compared with the untreated PBMC. Taken together, these results would suggest that host responds to HHV-7 infection by up-regulating IL-15 production, which then results in an enhancement of NK cell activity; this, in turn, may play a major role in the control of the viral infection.

IL-15 Mediates Anti-tumor Effects after Cyclophosphamide Injection of Tumor-Bearing Mice and Enhances Adoptive Immunotherapy: The Potential Role of NK Cell Subpopulations

The daily administration of IL-15 to cyclophosphamide (CY)-injected mice bearing the 76-9 rhabdomyosarcoma was shown to prolong the period of remission induced by CY. In addition, IL-15 was shown to enhance the efficacy of adoptive immunotherapy. Cytotoxicity assays using spleens from normal and tumor-bearing mice indicated that IL-15 enhanced NK cell activity but there was no evidence for class I-restricted cytolytic T cell activity. To determine whether IL-15 was likely to induce different cytotoxic effectors at the tumor site compared with the spleen, tumors were removed after CY injection and cell suspensions were incubated with IL-15 in parallel with isolated spleen cells. Both populations were seen to expand to yield predominantly cells coexpressing NK1.1 and B220 antigens. However, tumor-associated NK cells were shown to differ from expanded spleen NK cells in terms of the proportions of LGL-1+cells and cells expressing early and late NK cell differentiation antigens. Both expanded populations expressed high NK cell cytotoxic activity but only the spleen cells expressed lymphocyte-activated killer cell activity. It was apparent that the expanded tumor-associated NK cells expressed low-level class I-restricted lytic activity. The potential of activated NK cells in the circulation to exert anti-tumor effects was shown by the adoptive transfer of expanded NK cells to tumor-bearing mice after CY injection when significant prolongation of life was seen in all cases. The data indicate that IL-15 may serve as a useful anti-cancer adjuvant by activating initially the NK cell arm of the immune network.

Effect of immunosuppressive treatment on Eperythrozoon suis infection and porcine peripheral-blood natural-killer-(NK) cell activity.

The effects of immunosuppressive treatment on natural-killer-cell activity and the manifestation of eperythrozoonosis in swine were investigated. After infection with Eperythrozoon suis (E. suis), German Landrace piglets received daily intravenous (i.v.) applications of cyclophosphamide (CY, Endoxan) on 6 consecutive days. A combined immunosuppressive treatment using azathioprine (Imurek), a single application of dexamethasone (Devan), and two injections of anti-asialo GM1 serum (1:50) was performed with a piglet over a period of 9 days. Leucocyte counts, differential blood-cell count, and microhaematocrit and rectal temperature were controlled. Direct microscopic observation of E. suis organisms was performed in Giemsastained blood smears. Immunosuppressive treatment resulted in relative lymphocytosis and transient agranulocytosis. CY and azathioprine therapy caused a temporary increase of E. suis organisms in red blood cells. Natural-killer-(NK) cell activity mediated by nylon-wool non-adherent peripheral-blood mononuclear leucocytes (NAD-PBML) was recorded during and after immunosuppressive treatment of pigs infected with E. suis. Cytotoxic activity of NK cells was consistently reduced after two CY injections and further decreased to 70-100% of the initial NK-mediated tumor cell lysis. NAD-PBML of two E. suis infected animals were monitored for cytotoxicity during CY immunosuppressive treatment and were compared to Percoll density separated NK effector cells derived from the same blood sample. Enhancement of NK-cell activity by density separation of NAD-PBML was not longer possible on days 3 and 4 during CY treatment, indicating a decrease of NK cells in peripheral blood. In vitro, only a high dose of CY (4 microgram/ml) suppressed cytolytic activity of NAD-PBML. Short-term treatment with immunosuppressive agents did not replace splenectomy in inducing clinically apparent eperythrozoonosis.