Immunotherapy with tumor cell lysate-pulsed CD8α+ dendritic cells modulates intra-tumor and spleen lymphocyte subpopulations

Using cellular adjuvants including dendritic cells (DCs) has provided a promising approach in immunotherapy of cancer. Our previous study showed that mice immunization with tumor cell lysate-pulsed DCs (TL-CD8α+DCs) could significantly suppress the tumor growth and increase mice survival. The aim of the present study was to investigate the impact of TL-CD8α+DC vaccine on intra-tumor and spleen lymphocyte subpopulations in tumor-bearing mice. ABalb/c mouse model of fibrosarcoma was used and changes in various lymphocyte subpopulations including CD4+, CD8+ and CD4+CD25+Foxp3+ T cells in mice immunized with TL-CD8α+ DCs were studied. The cytotoxic activity of the lymphocytes and tumor growth inhibitory rate were also measured. Immunotherapy with TL-CD8α+ DCs significantly enhanced both CD4+ and CD8+ lymphocytes, whereas decreased CD4+CD25+ Foxp3+ regulatory T cells as well as the tumor growth rate. There was also a decrease in the ratio of regulatory T cells to CD4+ and to CD8+ lymphocytes in both the tumor and spleen tissues as compared to that in the non-immunized control mice. Immunization with TL-CD8α+ DCs as well as CD8α+ DCs significantly increased the splenocytes cytotoxic activity by 45.1% and 18.2% of control, respectively. In conclusion, the current study indicated that TL-CD8α+ DCs can enhance tumor immunity against the fibrosarcoma by enhancing both the CD4+ and CD8+ lymphocytes and reducing regulatory T cells. This finding suggests the usefulness of TL-CD8α+DCs vaccine for cancer treatment.

Morphological and cytochemical characteristics of purified murine splenic dendritic cells

Dendritic cells function as the main cellular population responsible for professional antigen presentation and hence for induction of primary immune responses. Although they are present in virtually every tissue, nevertheless their number is usually so low that it makes their isolation for studies very difficult. In this study, we purified dendritic cells from mouse spleen by a three-step enrichment method and evaluated morphological and cytochemical characteristics of isolated cells. We showed that isolated dendritic cells from mouse spleen had all lobulated nuclei with multiple cytoplasmic projections and their morphological features changed after an overnight incubation. It was also shown that typical dendritic cells lacked both Myeloperoxidase (MPO) and Non Specific Esterase (NSE) activity. In conclusion, for reaching a reasonable purity in isolation of dendritic cells from lymphoid tissues, many enrichment steps should be taken, and for determining the purity of isolated cells, we recommend that a combination of morphological and cytochemical studies be used.

High expression of Fas ligand on cord blood dendritic cells: a possible immunoregulatory mechanism after cord blood transplantation

BACKGROUND

Allogeneic cord blood transplantation is associated with less severe graft-versus-host disease (GVHD). Dendritic cells (DCs), as the most potent antigen-presenting cells of the immune system, play a central role in the development of GVHD. Because apoptosis induction is one of the known mechanisms that DCs use to regulate T-cell responses, we studied the immunostimulatory and apoptosis induction capacities of cord blood dendritic cells (CBDCs) and peripheral blood dendritic cells (PBDCs) to evaluate the mechanisms underlying the lower incidence of GVHD after cord blood transplantation. Presence of apoptosis-related markers Fas, Fas ligand (FasL), and CD40 and costimulatory molecules, along with the proportion of myeloid and lymphoid DCs subsets, were also measured on CBDCs and PBDCs.

METHODS

Fresh CBDCs and PBDCs were isolated from cord and peripheral mononuclear cells as lineage-negative cells by using monoclonal antibodies against CD3, CD11b, CD14, CD16, CD19, CD56, CD34, and CD66b. DCs were cocultured with allogeneic T cells, and the effect of CBDCs and PBDCs on T-cell apoptosis and proliferation were determined through flow cytometric analysis and 3H-thymidine incorporation.

RESULTS

Our findings showed that CBDCs markedly augment apoptosis of CD3+ T-cells. FasL expression on CBDCs was significantly higher than on PBDCs. However, there was no difference between Fas expression on CBDCs and PBDCs. Moreover, CBDCs were poor stimulators of allogenic T cells in mixed leukocyte reaction compared with adult peripheral blood DCs. They also displayed decreased expression of HLA-DR and CD86 molecules. The ratio of lymphoid DCs (CD11c-, CD123+) to myeloid DCs (CD11c+, CD123-) was also significantly higher in CBDCs compared with PBDCs.

CONCLUSIONS

It seems that less severe GVHD after cord blood transplantation is due not only to a higher degree of immaturity of CBDCs, but also to delivery of apoptotic signals to the host T cells that recognize allo-MHC molecules on CBDCs in the early phase of immune response.

Antibody against recombinant heat labile enterotoxin B subunit (rLTB) could block LT binding to ganglioside M1 receptor

OBJECTIVES

Enterotoxigenic Escherichia coli (ETEC) is one of the most common agents of diarrhea among other bacterial agents. Designing and producing vaccine against these bacteria is one of the major purposes of World Health Organization (WHO). Due to presence of diverse clones of ETEC strains in the world, the use of global vaccines for ETEC infection is controversial. B subunit of heat labile toxin (LTB) was introduced as a vaccine candidate molecule by several investigators. The expression of LTB gene isolated from a local bacterial strain and investigation of its immunological property was the objective of this study.

MATERIALS AND METHODS

LTB gene was isolated from a local isolated ETEC, cloned and expressed using pET28a expression vector. For LTB gene expression, the three main expression parameters (IPTG concentration, time and temperature of induction) were investigated. The recombinant protein was purified (>95%) with Ni-NTA column using 6XHis-tag and used as an antigen in ELISA test.

RESULTS

The immunological analyses showed production of high titer of specific antibody in immunized mice. Anti LTB Antibody could bind to whole toxin and neutralize the toxin through inhibition of its binding to the Ganglioside M1 receptor.

CONCLUSION

The recombinant LTB protein is a highly immunogenic molecule. Considering the LTB role in ETEC pathogenesis, it can be taken into account as one of the most important components of vaccines against local ETEC.

Preparation, purification and virus inactivation of intravenous immunoglobulin from human plasma

IVIG can be prepared from fractionation of normal human plasma and it is used as a therapeutic drug for treatment of various diseases. IVIG has been for some time the high-growth product within the plasma derived products, at both a global and a national country level. Fractionation was performed according to Cohn method with some modifications. Fraction II was first produced and then it was used for purification and virus inactivation steps. Two methods of virus inactivation (pasteurization at 60 degrees C for 10 hours and solvent/detergent treatment with TnBP and Tween 80) were used and validated. A chromatography method (cation exchange chromatography on CM Sepharose FF) was also added to obtain high purity. The final product (in liquid and freeze dried formulation) meets European Pharmacopeias requirements. The amount of PKA and aggregates was beyond the acceptance limit. The intactness of the IVIG was also examined by circular dichroism (secondary and tertiary structure). It was stable after 6 months of storage. Since Iran market is completely dependant on importation of plasma derived products, it is important to develop such methods for production of IVIG to obtain regional demands.

The efficiency of CD40 down regulation by siRNA and antisense ODN: comparison of lipofectamine and FuGENE6

BACKGROUND

Dendritic cells (DCs) are ideal accessory cells in the field of gene therapy. Delivery of DNA and siRNA into mammalian cells is a useful technique in treating various diseases caused by single gene defects. Selective gene silencing by small interfering RNAs (siRNAs) and antisense oligodeoxynucleotides (ODN)s is an efficient method for the manipulation of cellular functions. An efficient, functional delivery system with no toxicity problems would be attractive.

OBJECTIVE

We compared two commercially available cationic lipids, Lipofectamine and FuGENE6, in the delivery of both siRNA and antisense ODNs into mice spleen-derived DCs.

METHODS

Cellular uptake was measured by the means of fluorescein-labelled non-silencing siRNA and antisense ODNs as a model system using flow cytometry. Cytotoxicity of the two delivery systems was compared with propidium iodide and annexin-V staining, and quantified with flow cytometry. The efficiency of our oligonucleotide delivery systems was compared by measuring CD40 expression by flow cytometry.

RESULTS

CD40 expression in DCs was 38%. After siRNA transfection by Lipofectamine, CD40 expression decreased to 13%, and after transfection by FuGENE6, it decreased to 18%. The difference was statistically significant. CD40 down regulation in DCs transfected with the two different antisense sequences by Lipofectamine was 21% and 23%, and down regulation after transfection by FuGENE6 was 19% and 18%, respectively. The differences were not statistically significant. The effects of siRNA and antisense ODNs were specific.

CONCLUSION

Lipofectamine was a more potent delivery system in siRNA effect, followed by FuGENE6. There was no significant difference between Lipofectamine and FuGENE6 as a delivery system of antisense ODNs.

The efficient generation of immunocompetent dendritic cells from leukemic blasts in acute myeloid leukemia: a local experience

Dendritic cells (DCs) are the most important antigen presenting cells with potentially useful applications in cancer immunotherapy. Leukemic cells of patients with acute myeloid leukemia (AML) could be differentiated to DC-like cells possessing the ability of stimulating anti-leukemic immune response. Despite obvious progress in DC-based immunotherapy, some discrepancies were reported in differentiation potential of AML blasts from all patients toward DC like cells. The present study, as a local experience, was set up to generate DCs from AML blasts of various subtypes. Leukemic Blasts from 16 Iranian AML patients were differentiated into functional DCs by culturing in the presence of rhGM-CSF, rhIL-4 and TNF-alpha for 8 days. The morphology, expression of key surface molecules and allostimulatory activity of resultant DCs were compared with primary blasts and cultured but cytokine untreated control groups. The pattern of angiotensin-converting enzyme (ACE) expression was used to approve the leukemic origin of generated DCs. Neo-expression or upregulation of DC-associated markers were occurred during culturing period in cytokine treated cells compared with primary blasts and cultured but cytokine untreated control groups: CD1a (63.22% vs. 3.22% and 11.79%), CD83 (41.27% vs. 0.11% and 0.70%), CD40 (15.17% vs. 0.00% and 0.04%), CD80 (49.96 vs. 0.02% and 0.32%), CD86 (56.49% vs. 0.50% and 5.71%) and HLA-DR (52.52% vs. 14.32% and 2.49%) respectively. The potency of generated DCs to induce allogeneic T cell proliferation increased significantly compared to pre and post culture control groups (27,533.4 +/- 2,548.3, 8,820.4 +/- 1,639.4 and 3,200.35 +/- 976 respectively). The expression pattern of ACE in AML-DCs, blast cells and DCs derived from normal monocytes (7.93%, 1.28% and 74.97% respectively) confirmed the leukemic origin of DCs. Our data confirmed the generation of sufficient AML-derived cells with the properties of DCs in all cases. This potency of AML blasts, offers a useful route for active immunotherapy of AML patients.

Inactivation of virus in intravenous immunoglobulin G using solvent/detergent treatment and pasteurization

The safety of plasma derived medicinal products, such as immunoglobulin, depends on viral inactivation steps that are incorporated into the production process. Several attempts have been made to validate the effectiveness of these inactivation methods against a range of physio-chemically diverse viruses. Treatment with solvent/detergent (S/D) and pasteurization (P) has been continuously used in our IgG production and these methods were analysed in this study as models of viral inactivation. Bovine Viral Diarrhoea Virus (BVDV), Herpes Simplex Virus (HSV) and Vesicular Stomatitis Virus (VSV) were employed as models of HCV, HBV and HIV respectively. Polio and Reo viruses also were used as stable viruses to chemical substances. The infectivity of a range of viruses before and after treatment with two methods of viral inactivation was measured by end point titration and their effectiveness expressed as Logarithmic Reduction Factors (LRF). Solvent/detergent treatment reduced the amount of enveloped viruses by 5-6 logs. The reduction factor was between 5-6 logs for all viruses used in the pasteurization process. A final log reduction factor was obtained as the sum of the two individual methods. Both inactivation methods have advantages and disadvantages with respect to their ability to inactivate viruses. Thus,combination of two robust virus inactivation steps, solvent/detergent and pasteurization, increases the safety margin of immunoglobulin preparations.

Preparation of antibody against horseradish peroxidase using hybridoma technology

BACKGROUND

Monoclonal antibody against horseradish peroxidase (HRP) has many applications which peroxidase anti-peroxidase. Peroxidase-antiperoxidase (PAP) complex formation is its most known and important usage. This complex is used in many immunohistochemical and immunocytochemical staining techniques.

OBJECTIVE

The aim of this study was the preparation of anti-HRP monoclonal antibody through hybridoma technology.

METHODS

The BALB/c mice were immunized by repeated injections of HRP. After the confirmation of their immunization by ELISA test, the spleen lymphocytes and SP2/0 myeloma cells were hybridized using PEG as fusing agent. The hybridoma cells were then selected by culturing in HAT medium. Identification and selection of anti-HRP producing clones were done by ELISA test on culture supernatants of the obtained clones. To acquire the monoclones, limiting dilution was performed twice and the effect of finally obtained antibodies on enzyme activity was investigated by a specific ELISA test. In vivo tumor induction method was used for production of concentrated antibody. At last class and subclass of the obtained antibodies were determined by Isostrip Kit.

RESULTS

After seven rounds of cell fusions, 224 clones were obtained, from which, six ones were anti-HRP producers. Two clones (P1F11 and P2F6) with higher antibody secretion were selected and subcloned. Both derived hybridoma monoclones (P1F11D2 and P2F6F3) were producing antibodies from IgG1 subclass with kappa (Kappa) light chains which didn't affect the enzyme activity. The electrophoresis of ascetic fluid of tumor induced mice showed an obvious band in gamma (gamma) position.

CONCLUSION

The obtained monoclonal antibodies are from IgG class and don't affect the enzyme activity, therefore it seems that they are suitable for PAP complex production.

APAAP complex: production and usage in immunocytochemical and immunohistochemical staining

BACKGROUND

The affinity of antibody to antigen, in addition to providing the possibility of measuring the antigen in tissue extracts through methods such as RIA (Radioimmunoassay) and EIA (Enzymimmunoassay) and possibility of isolating and analyzing dispersed cell colonies using flowcytometry, makes it possible to determine the site of antigen in tissues (Immunohistochemistry) or in cells (Immunocytochemistry).

OBJECTIVE

Production of APAAP complexes and comparing them with similar foreign products to determine the site of antigen in tissues or in cells.

METHODS

Secreted antibodies of the two hybridomas (A(1)G(9)G(3) and A(1)G(8)F(7) produced in our laboratory) were concentrated, purified and characterized. Then the monoclonal antibodies were mixed with alkaline phosphatase enzyme (ALP) to use in immunocytochemistry (ICC) and immunohistochemistry (IHC) staining.

RESULTS

Both of the cell colonies had the potentiality of producing anti- alkaline phosphatase monoclonal antibody with high affinity. The complex from mAb and enzyme - for the third phase of APAAP technique - was very effective and its sensitivity was comparable to that of the similar foreign kit.

CONCLUSION

Considering the high affinity of the mAb of the two hybridomas and the stability of the complex resulted from mixing mAb and the enzyme ALP for a long time, it is possible to use the obtained APAAP complex in the immunocyto (or histo) chemistry - as the third phase.

Production of monoclonal antibody against alkaline phosphatase

BACKGROUND

Monoclonal antibody against alkaline phosphatase (Alp) has many applications which Alp-anti Alp complex (APAAP) formation is one of the most important ones. This complex is applicable in many immunohistochemical and immunocytochemical techniques such as diagnosis of various kinds of leukemias, lymphomas, skin diseases, kidney dysfunctions, etc.

OBJECTIVE

Production of anti-Alp monoclonal antibody for utilization in APAAP complex.

METHODS

After several arranged injections of Alp to Balb/c mice and determining the specific antibody titer by ELISA test, the spleen lymphocytes of immunized mice and Sp2/0 myeloma cells were fused using polyethylene glycol as fusing agent and hybridoma cells were cultured in HAT medium. Identification and selection of anti-Alp producing clones were done by performing ELISA test on supernatants of all resulting clones. Limiting dilution method was used to attain monoclones and the effect of obtained antibodies on enzyme activity was investigated by a specific ELISA test. For production of concentrated Ab, the hybridoma cells were injected to peritoneal cavity of mice and the produced ascetic fluids were collected. Finally class and subclass of the obtained antibodies were determined by Isostrip kit.

RESULTS

After six rounds of fusion, 104 Hybridoma clones were obtained and two Anti-Alp producing clones (A_1G_8 and A_1G_9) were selected and subcloned. Both antibodies were IgG_1 with kappa (kappa) light chains. These antibodies did not affect the enzyme activity and the electrophoresis of ascetic fluids showed an obvious band in gamma (gamma) position.

CONCLUSION

Because these antibodies are from IgG class and don't affect the enzyme activity, it seems that they are suitable for APAAP complex formation.

Role of rotaviruses in children with acute diarrhea in Tehran, Iran

BACKGROUND

Rotavirus illness is associated with significant cause of morbidity and is a common cause of hospitalization worldwide.

OBJECTIVE

This study was performed to assess the role of rotaviruses in children presenting with acute diarrhea in two main Children's Medical Centers and one general hospital in Tehran.

STUDY DESIGN

Stool specimens from 704 children less than 5 years of age suffering from diarrhea were tested for the presence of rotaviruses by a monoclonal antibody-based enzyme immunoassay. A total of 176 fecal specimens collected from healthy children in similar age group were studied as controls.

RESULTS

Rotavirus antigen was detected in 15.3% of patients. Infants between 6 and 12 months of age were most frequently affected. Rotavirus infection was significantly less frequent in breast-fed than among bottle-fed babies. Watery diarrhea was present in 68.5% of children. Detection rate was highest in the spring and lowest in summer. Rotavirus can be regarded as a major etiologic agent of acute diarrhea in infants and children up to 5-years-old in Iran, immunization at birth may protect the children before their first symptomatic infection.

HLA antigens in Iranian patients with B-cell chronic lymphocytic leukemia

The frequency of HLA class-I and class-II antigens was investigated in 32 Iranian patients with B-cell chronic lymphocytic leukemia (B-CLL), using the microlymphocytotoxicity method. A significant increase in the HLA-B13 (P<0.01) and DR53 (P < 0.05) and a significant negative association with the A11 (P < 0.05), B35 (P < 0. 05), Cw3 (P < 0.05), and DR1 (P < 0.02) antigens were observed in these patients, compared to the control normal population. These results suggest involvement of some HLA antigens in the multifactorial process of predisposition to B-CLL.