Conjugation of new DNA vaccine with polyethylenimine induces cellular immune response and tumor regression in neuroblastoma mouse model

AIM

To estimate immunogenicity and antitumor effect of new DNA vaccine against neuroblastoma using tyrosine hydroxylase as an antigen and linear polyethylenimine (PEI) 20 kDa as a synthetic DNA carrier in syngeneic mouse tumor model.

MATERIALS AND METHODS

DNA vaccine was made by cloning the tyrosine hydroxylase minigene fused to the potato virus X coat protein gene into the expression vector. The A/J mice were vaccinated by three intramuscular injections. For immunogenicity study, immune response was estimated by target cells cytotoxicity assay, interferon-gamma production in enzyme-linked immunospot assay and antigen-specific antibodies in 14 days after the final vaccination. Antitumor effect was assessed by measurement of tumor volume and event-free survival rate in mice with engrafted NB41A3 murine neuroblastoma cells following three intramuscular injections of the vaccine: 7 days before, 5 and 10 days after tumor engraftment. The immune response was also assessed on the 30^th day after tumor engraftment.

RESULTS

The immunogenicity and antitumor effect of the vaccine in the form of aqueous solution of DNA and DNA-PEI conjugate were compared. Splenocytes cytotoxicity was the highest in the group of DNA-PEI vaccines (37.3 ± 6.9% lysis of target cells) compared with the unconjugated DNA vaccine (26.2 ± 4.0%) and placebo control (21.9 ± 3.7%). The production of interferon-gamma in the enzyme-linked immunospot assay was about ten times higher in the DNA-PEI group than in the other groups. The vaccine slowed or prevented the growth of the tumor. Mice vaccinated with the DNA-PEI vaccine had significantly better survival compared to control group (p < 0.0003).

CONCLUSIONS

DNA vaccine against tyrosine hydroxylase, administered as a DNA-PEI 20 kDa conjugate, slows down the growth of neuroblastoma cells engrafted to mice.

Multi-antigen DNA vaccine delivered by polyethylenimine and Salmonella enterica in neuroblastoma mouse model

Neuroblastoma is an example of a difficult-to-treat tumor with high incidence of relapse. DNA vaccination could be applied as a relapse prophylactic option for patients with high-risk neuroblastoma. Its efficacy depends directly on a target antigen of choice and a delivery method. Three neuroblastoma-associated antigens (tyrosine hydroxylase, Survivin, PHOX2B) and two delivery methods were investigated. Our data suggest that antigen PHOX2B is a more immunogenic target that induces cellular immune response and tumor regression more effectively than tyrosine hydroxylase and Survivin. Immunogenicity testing revealed that the delivery of DNA vaccine by Salmonella enterica was accompanied by a stronger immune response (cytotoxicity and IFNγ production) than that by DNA-polyethylenimine conjugate. Nevertheless, intramuscular immunization with PEI led to higher decrease of tumor volume compared to that after oral gavage with Salmonella vaccine.

Autocrine-based selection of ligands for personalized CAR-T therapy of lymphoma

We report the development of a novel platform to enhance the efficacy and safety of follicular lymphoma (FL) treatment. Since lymphoma is a clonal malignancy of a diversity system, every tumor has a different antibody on its cell surface. Combinatorial autocrine-based selection is used to rapidly identify specific ligands for these B cell receptors on the surface of FL tumor cells. The selected ligands are used in a chimeric antigen receptor T cell (CAR-T) format for redirection of human cytotoxic T lymphocytes. Essentially, the format is the inverse of the usual CAR-T protocol. Instead of being a guide molecule, the antibody itself is the target. Thus, these studies raise the possibility of personalized treatment of lymphomas using a private antibody binding ligand that can be obtained in a few weeks.

Phase I clinical trial of idiotypic DNA vaccine administered as a complex with polyethylenimine to patients with B-cell lymphoma

We report on the design of a phase I, non-randomized, open-label study of idiotypic DNA vaccination in patients with B-cell non-Hodgkin's lymphoma (ISRCTN31090206). The study uses DNA fusion gene vaccination encoding patient-specific single chain variable fragment, or idiotype, linked to an immunostimulatory sequence. Two types of immunostimulatory sequence are being explored: potato virus X coat protein and human chemokine MIP3α. Linear polyethylenimine with low molecular weight (8 kDa) is used as a synthetic vehicle for vaccine delivery. Humoral and T-cellular immune responses to vaccination will be measured by ELISA and ELISPOT, respectively. The primary study endpoints are safety, tolerability and immunogenicity of DNA-PEI vaccination.

Response monitoring in follicular lymphoma by synchronous evaluation of minimal residual disease and diffusion-weighted MRI

AIM

To demonstrate quantitative assessment of tumor response to treatment in patients with follicular lymphoma using parallel monitoring of minimal residual disease (MRD) and diffusion-weighted MRI (MRI-DWI) derived apparent diffusion coefficient (ADC).

MATERIALS AND METHODS

Two patients with follicular lymphoma were undergone synchronous evaluation of MRD and MRI-DWI at definite time points before, during and after chemotherapy. MRD level was calculated in diagnostic and follow up samples relative to the highest level of amplification of the target. Allele-specific primer for clonal IgH gene rearrangement was used as a target for real-time quantitative polymerase chain reaction (PCR). 1.5 Tesla scanner was used for MRI-DWI. The largest non necrotic lymph node was chosen for serial ADC measurement.

RESULTS

In first patient MRD reduced drastically in blood after chemotherapy but persisted at low level in bone marrow. Whole body MRI-DWI demonstrated regression of most of tumor lesions except one -marginally enlarged iliac lymph node and allowed to predict tumor progression in this particular anatomical site based on low ADC value after treatment. In the second patient all three methods (MRD, ADC and radiologic evaluation) gave concordant result of complete tumor response and patient remained in a clinical remission during follow-up time.

CONCLUSION

Quantitative PCR measurement may detect very low level of MRD in patients with follicular lymphoma which may have prognostic value. Combination of both PCR-based MRD and quantitative evaluation of MRI-DWI derived ADC provides safe added-value disease monitoring in lymphoma.

Cloning of variable fragments of tumor immunoglobulin, assembling and expressing of human SCFV protein in E. coli for anti-idiotype vaccination

AIM

Idiotype, the unique part of immunoglobulin molecule expressed on the surface of B-cells, represents a specific antigen for vaccination against lymphoma. We have developed a rapid method for immunoglobulin variable fragments cloning, assembling and expression of recombinant idiotype protein in Escherichia coli.

METHODS

PCR with specially designed panel of primers was used for direct amplification of variable regions of tumor immunoglobulin. Overlapping extension PCR, restriction and ligation was applied for assembling and cloning of vaccine construction. Idiotype protein was purified by metal-chelate chromatography.

RESULTS

Methods of idiotype cloning from lymphoma cells and production of recombinant protein were developed and optimized. Several samples of idiotypic proteins originating from B-cell lines and lymphoma patients were produced.

CONCLUSION

The proposed method of vaccine production is relatively cheap, not very laborious and requires as long as 6-7 week to perform. The expressed protein was soluble, did not accumulate in inclusion bodies and harvested at sufficient for vaccination quantity and concentration.

Prognostic value of MRD-dynamics in childhood acute lymphoblastic leukemia treated according to the MB-2002/2008 protocols

Detection of minimal residual disease (MRD) during the treatment of acute lymphoblastic leukemia (ALL) by RQ-PCR analysis of clonal Ig/TCR rearrangements is used for risk group stratification in European treatment protocols. In Belarus patients with childhood ALL are treated according to ALL-MB protocols, which do not use MRD-based risk stratification. To evaluate the prognostic significance of MRD for ALL-MB-2002/2008 protocols, MRD was quantified by RQ-PCR in 68 ALL patients at four time points: on day 15, on day 36, before and after maintenance therapy (MT). MRD positivity, as well as quantitative level of MRD were analyzed and compared between patients who stayed in remission and relapsed. Relapse-free survival revealed to be significantly associated with MRD levels at different time points. Unfavorable prognosis was shown for MRD≥10(-3) on day 36 (p<0.001), and any positive MRD before (p<0.001) and after (p=0.001) MT. Multivariate Cox regression analysis proved MRD as independent significant prognosis factor at day 36 (p=0.005) and before MT (p=0.001). We conclude, that MRD quantified by RQ-PCR in children with ALL treated with ALL-MB protocols is feasible and independently associated with outcome. MRD may be a suitable parameter for treatment stratification in MB protocols in future.

Relative expression of different Ikaros isoforms in childhood acute leukemia

Ikaros is a zinc-finger transcriptional factor playing an essential role in lymphoid lineage commitment and differentiation. Animal models and analysis of human Ikaros in leukemic cells demonstrate deregulation of Ikaros expression. Short isoforms with a truncated DNA-binding domain suppress functions of Ikaros in a dominant-negative manner. Previous studies demonstrated that human leukemias are heterogeneous for Ikaros expression. We estimate the relative level of Ikaros mRNA transcripts in 80 childhood ALL cases in comparison with AML and healthy donor groups. We detected eight major isoforms and several minor mutant isoforms in most patients with acute lymphoblastic and myeloid leukemia and in healthy donors, but the relative level of expression varied. The relatively high level of Ik4A isoform, rarely mentioned in previous reports, was detected in all analyzed groups. The ratio between functional and all isoforms was used to determine functional activity of Ikaros. The ratio was significantly less in AML (p=0.027) and BCR-ABL positive ALL (p=0.0028) than in healthy bone marrow. We found a negative association between the Ikaros ratio and myeloid coexpression in B-cell ALL, the most prominent was for CD15. The Ikaros ratio positively correlates with CD5 and negatively with CD7 expression in T-ALL. We suggest that an anti-proliferation and anti-activation effect of full-length Ikaros may be mediated through regulation of CD5 and CD7.

The incidence of T-cell receptor gene rearrangements in childhood B-lineage acute lymphoblastic leukemia is related to immunophenotype and fusion oncogene expression

Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangement is conventionally used for assessment of lymphoid malignant cells. TCR genes rearrangements were reported to occur at high frequency in B-lineage acute lymphoblastic leukemia (ALL). Therefore, we have analyzed 83 children with acute B-lineage ALL (67 de novo patients and 19 relapses) by PCR analysis for clonal IgH, incomplete TCRD (Vdelta2-Ddelta3 and Ddelta2-Ddelta3) and TCRG rearrangements. It was shown that clonal cross-lineage TCR rearrangements were associated with more immature immunophenotype (CD34+, CD117+, CyIgM-) of leukemic cells from patients' bone marrow (BM) samples as compared to cell samples without cross-lineage TCR rearrangements. That was equally detected both in de novo and relapsed cases of disease. Low frequency of clonal TCRG rearrangements was associated with expression of E2A/PBX chimeric oncogene. We suggest that TCRG and TCRD clonal rearrangements in leukemic B-cells are associated with early stages of their differentiation.

Rearrangements of IgH, TCRD and TCRG genes as clonality marker of childhood acute lymphoblastic leukemia

AIM

Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements are excellent patient-specific targets for clonality studies and monitoring of acute lymphoblastic leukemia (ALL). THE AIMS of the study were to select the optimum panel of primers, evaluate incidence of particular types of monoclonal and oligoclonal gene rearrangements and observe alteration of rearrangement profile between diagnosis of ALL and subsequent relapse(s).

METHODS

We used polymerase chain reaction (PCR) for amplification of junctional region of rearranged IgH, TCRD and TCRG genes in combination with heteroduplex analysis in polyacrylamide gel.

RESULTS

TCRD gene rearrangements were detected in 64%, TCRG - in 45%, and IgH - in 79% of B-precursor ALL patients. For patients with T-ALL, TCRD gene rearrangements were found in 47%, TCRG gene - in 66%, and IgH - in 19% of cases. Evaluation of biallelic and oligoclonal rearrangements was performed in the study. The highest incidence of oligoclonal rearrangements - 25% was shown for IgH gene in patients with B-precursor ALL. Seven pair cases of patients with de novo leukemia and relapses were analyzed and revealed subclonal deviation in rearrangements of IgH or TCR genes during disease evolution.

CONCLUSION

We propose a panel of 13 types of rearrangements (primer pairs) sufficient for tumor cell clonality detection in 96% of patients with ALL. Applications of PCR-based analysis of rearranged IgH, TCRD and TCRG genes for discrimination of mono- and oligoclonality and identification of the origin of relapse were demonstrated.

[Detection of rearranged immunoglobulin and T-cell receptor genes as a method for characterization of tumor cell clonality in acute lymphoblast leukemia in children]

Selection of primers for polymerase chain reaction (PCR) as used in detection of the reconstructed genes of immunoglobulins and T-cells receptor in tumor cells in children with acute lymphatic leukemia is described in the paper. PCR potentialities and limitations in characterizing the monoclonality observed in primary acute lymphatic leukemia are demonstrated. Cross linkages of the heavy chain of immunoglobulins and of T-cell receptor were found between T- and B-linear acute lymphatic leukemia forms, but not between acute lymphatic leukemia forms and myeloleukemia in children.