Validation of an ADCC assay using human primary natural killer cells to evaluate biotherapeutic products bearing an Fc region.

The development of biotherapeutics requires continuous improvement in analytical methodologies for the assessment of their quality attributes. A subset of biotherapeutics is designed to interact with specific antigens that are exposed on the membranes of target cells or circulating in a soluble form, and effector functions are achieved via recognition of their Fc region by effector cells that induce mechanisms such as antibody-dependent cell-mediated cytotoxicity (ADCC). Thus, ADCC induction is a critical quality attribute (CQA) that must be evaluated to ensure biotherapeutic efficacy. Induction of ADCC can be evaluated by employing effector cells from different sources, such as peripheral blood mononuclear cells (PBMC) and genetically modified cell lines (e.g., transfected NKs or Jurkat cells), and different approaches can be used for detection and results interpretation depending on the type of effector cells used. In this regard, validation of the assays is relevant to ensure the reliability of the results according to the intended purpose. Herein, we show the standardization and validation of ADCC assays to test the potency of three biotherapeutic proteins using primary NK cells obtained from fresh blood as effector cells and detecting cell death by flow cytometry. The advantage of using primary NKs instead of modified cells is that the response is closer to that occurring in vivo since cytotoxicity is evaluated in a direct manner. Our results indicate that in all cases, the assays exhibited a characteristic sigmoidal dose/response curve complying with accurate, precise and specific parameters. Thereby, the validated ADCC assay is an appropriate alternative to evaluate the biological activities of these type of biotherapeutics.

Low pH impairs complement-dependent cytotoxicity against IgG-coated target cells.

Local acidosis is a common feature of allergic, vascular, autoimmune, and cancer diseases. However, few studies have addressed the effect of extracellular pH on the immune response. Here, we analyzed whether low pH could modulate complement-dependent cytotoxicity (CDC) against IgG-coated cells. Using human serum as a complement source, we found that extracellular pH values of 5.5 and 6.0 strongly inhibit CDC against either B lymphoblast cell lines coated with the chimeric anti-CD20 mAb rituximab or PBMCs coated with the humanized anti-CD52 mAb alemtuzumab. Suppression of CDC by low pH was observed either in cells suspended in culture medium or in whole blood assays. Interestingly, not only CDC against IgG-coated cells, but also the activation of the complement system induced by the alternative and lectin pathways was prevented by low pH. Tumor-targeting mAbs represent one of the most successful tools for cancer therapy, however, the use of mAb monotherapy has only modest effects on solid tumors. Our present results suggest that severe acidosis, a hallmark of solid tumors, might impair complement-mediated tumor destruction directed by mAb.

A B-Cell Superantigen Induces the Apoptosis of Murine and Human Malignant B Cells.

B-cell superantigens (Sags) bind to conserved sites of the VH or VL regions of immunoglobulin molecules outside their complementarity-determining regions causing the apoptosis of normal cognate B cells. No attempts to investigate whether B-cell Sags are able to induce the apoptosis of cognate malignant B cells were reported. In the present study we show that protein L (PpL), secreted by Finegoldia magna, a B-cell Sag which interacts with κ+ bearing cells, induces the apoptosis of murine and human κ+ lymphoma B cells both in vitro and in vivo. Apoptosis was not altered by caspase-8 inhibitor. No alterations in the levels of Bid, Fas and Fas-L were found suggesting that PpL does not activate the extrinsic pathway of apoptosis. The involvement of the intrinsic pathway was clearly indicated by: i) alterations in mitochondrial membrane potential (ΔΨm) both in murine and human lymphoma cells exposed to PpL; ii) decreased levels of apoptosis in the presence of caspase-9 inhibitor; iii) significant increases of Bim and Bax protein levels and downregulation of Bcl-2; iv) the translocation from the cytoplasm to the mitochondria of Bax and Bim pro-apoptotic proteins and its inhibition by caspase-9 inhibitor but not by caspase-8 inhibitor and v) the translocation of Bcl-2 protein from the mitochondria to the cytosol and its inhibition by caspase-9 inhibitor but not by caspase-8 inhibitor. The possibility of a therapeutic use of Sags in lymphoma/leukemia B cell malignancies is discussed.

Relevancia biológica y clínica del inmunofenotipaje celular en la leucemia linfoide aguda del niño / Biological and clinical importance of the cellular immunophenotyping in acute lymphocytic leukemia in children

Se estudiaron las características biológicas y clínicas de 238 niños con leucemia linfoide aguda (LLA) en un período de 13 años. El inmunofenotipaje celular de muestras procedentes de la médula ósea se realizó mediante un ultramicrométodo inmunocitoquímico. Del total de LLA estudiadas 81,4 por ciento fueron de fenotipo B y 18,5 por ciento de fenotipo T. El 48,4 por ciento de los niños con LLA de fenotipo B se encontraron en edades comprendidas entre 2-5 años, mientras que el 65,9 por ciento con LLA-T presentaron 6 o más años de edad. No se encontraron diferencias estadísticamente significativas cuando se analizaron el sexo y el color de la piel en relación con el fenotipo celular leucémico. Al diagnóstico de la enfermedad, el 59,3 por ciento de los pacientes con LLA-B mostraron cifras de leucocitos en sangre periférica < 20 x 109/L y en el 61,4 por ciento con LLA-T cifras superiores a 50 x 109/L. Se observó una mayor incidencia de organomegalia, adenopatías mediastinales, manifestaciones hemorrágicas e infiltración inicial del sistema nervioso central en enfermos con LLA-T en relación con los de LLA-B, con diferencias altamente significativas. Estos resultados demuestran que el fenotipo leucémico en la LLA del niño pudiera considerarse como un factor pronóstico positivo o negativo de la enfermedad.

The biological and clinical characteristics of 238 children with acute lymphocytic leukemia (ALL) were studied for 13 years. The cellular immunophenotyping of samples from the bone marrow was performed by an immunocytochemical ultramicromethod. Of the total of studied ALL, 81.4 percent were phenotype B and 18.5 percent phenotype T. 48.4 percent of the children with B-ALL were 2-5 years old, whereas 65.9 percent with T-ALL were 6 or over. No statistically significant differences were found when sex and colour of the skin were analyzed in relation to the cellular leukemic phenotype. On diagnosing the disease, 59.3 percent of the patients with B-ALL showed figures of leukocytes in peripheral blood < 20x109/L, whereas in 61.4 percent with T-ALL, the figures were higher than 50x109/L. It was observed a greater incidence of organomegaly, mediastinal adenopathies, hemorrhagic manifestations and initial infiltration of the central nervous system in patients with T-ALL compared with those suffering B-ALL. The differences were highly significant. These results proved that the leukemic phenotype in ALL in children could be considered as a positive or negative prognostic factor of the disease.

[Development of slides for Epstein-Barr virus diagnosis by indirect immunofluorescence]. / Desarrollo de improntas para el diagnóstico del virus Epstein-Barr por inmunofluorescencia indirecta.

Epstein-Barr virus (EBV) is the main oncogenic lymphotropic agent of the Herpesviridae family and is globally distributed. EBV acute infection occurs in young adults producing infectious mononucleosis. Detection of anti-viral capside antigen (VCA) antibodies indicates previous or present EBV infection. Moreover, high titles of anti-VCA antibodies are observed in EBV-associated neoplasic disorders, such as lymphomas in AIDS patients. The objective of this study was the development and optimization of P3HR1 cell slides for the EBV serologic detection by indirect immunofluorescence (IIF) assay. P3HR1 exponential growth culture cells were stimulated with phorbol-12-mirystoil-13-acetate, collected at different time points and used for slide preparation. IIF assay was performed in each slide using an anti-EBV positive serum as primary antibody. An 11% increase in VCA expression was observed at 40 hours post-stimulation. Data was confirmed by Western blot and immunodetection. Intra- and inter-lot precisions of the developed slides were evaluated for IgG and IgM antibodies using EBV-positive sera and positive samples for other members of the Herpesviridae family. Neither false-positive or false negative results were obtained for EBV detection nor cross-reaction was observed with other members of the Herpesviridae family with the developed slides. In conclusion, the slides here presented can be a useful instrument for acute EBV infection diagnosis and for the serologic detection of IgG anti-VCA antibodies in EBV-associated neoplastic disorders.

Desarrollo de improntas para el diagnostico del virus epstein-barr por inmunofluorescencia indirecta / Development of slides for Epstein-Barr virus diagnosis by indirect immunofluorescence

El vírus de Epstein-Barr (VEB) es el principal agente oncogénico linfotrópico dentro de la família Herpesviridae y se encuentra mundialmente distribuído. La primoinfección se produce en adultos jovenes y se manifesta como mononucleosis infecciosa. La detección de anticuerpos anti-viral cápside antigen (VCA) indica infección previa o presente com VEB. Además, se observan títulos elevados de anticuerpos anti-VCA en las enfermidades neoplásicas asociadas al VEB como los linfomas, em indivíduois HIV-positivos. El objetivo de este estúdio fue el desarrollo y puesta a punto de improntas de células P3HR1 para la detección serológica del VEB por técnicas de inmunofluorescencia indirecta (IFI). Se estimularon cultivos de células P3HR1 en crecimiento exponencial com phorbol-12-mirystoil-13-acetato y se recolectaron alícuotas a distintos tiempos para realizar improntas. Se realizó uma IFI com cada impronta usando como anticuerpo primário um suero VEB-positivo. Se observo un aumento del 11% em la expresión del VCA a las 40 horas post-estimulación, deyendo al 3.5% a las 48 horas. Estos datos fueron corroborados por ensayo de Western blot com inmunodetección. La precisión intra- e inter-lote de las improntas fue evaluada para anticuerpos IgM e IgG, com sueros probados previamente por equipos para esta determinación disponibles en el mercado para el VEB y com sueros reactivos para otros miembros de la família Herpesviridae. No se obtuvieron resultados falsos-negativos ni falsos-positivos para el VEB ni se observo reactividad cruzada com otros herpesvirus. Las improntas desarrolladas constituyen un instrumento para el diagnóstico de la primoinfección del VEB y la detección serológica de anticuerpos IgG anti-VCA de neoplasias asociadas al VEB.

Desarrollo de improntas para el diagnostico del virus epstein-barr por inmunofluorescencia indirecta / Development of slides for Epstein-Barr virus diagnosis by indirect immunofluorescence

El vírus de Epstein-Barr (VEB) es el principal agente oncogénico linfotrópico dentro de la família Herpesviridae y se encuentra mundialmente distribuído. La primoinfección se produce en adultos jovenes y se manifesta como mononucleosis infecciosa. La detección de anticuerpos anti-viral cápside antigen (VCA) indica infección previa o presente com VEB. Además, se observan títulos elevados de anticuerpos anti-VCA en las enfermidades neoplásicas asociadas al VEB como los linfomas, em indivíduois HIV-positivos. El objetivo de este estúdio fue el desarrollo y puesta a punto de improntas de células P3HR1 para la detección serológica del VEB por técnicas de inmunofluorescencia indirecta (IFI). Se estimularon cultivos de células P3HR1 en crecimiento exponencial com phorbol-12-mirystoil-13-acetato y se recolectaron alícuotas a distintos tiempos para realizar improntas. Se realizó uma IFI com cada impronta usando como anticuerpo primário um suero VEB-positivo. Se observo un aumento del 11% em la expresión del VCA a las 40 horas post-estimulación, deyendo al 3.5% a las 48 horas. Estos datos fueron corroborados por ensayo de Western blot com inmunodetección. La precisión intra- e inter-lote de las improntas fue evaluada para anticuerpos IgM e IgG, com sueros probados previamente por equipos para esta determinación disponibles en el mercado para el VEB y com sueros reactivos para otros miembros de la família Herpesviridae. No se obtuvieron resultados falsos-negativos ni falsos-positivos para el VEB ni se observo reactividad cruzada com otros herpesvirus. Las improntas desarrolladas constituyen un instrumento para el diagnóstico de la primoinfección del VEB y la detección serológica de anticuerpos IgG anti-VCA de neoplasias asociadas al VEB. (AU)

Burkitt-like lymphoma in an infant: a case report.

Childhood non-Hodgkin's lymphomas, including Burkitt and Burkitt-like, are rarely diagnosed in infants. A case of B-cell lymphoma in a 13-month-old girl with extensive abdominal disease, ascites, pleural effusion, and tumor lysis syndrome is reported. Phenotypic analysis showed a germinal center B-cell phenotype, and a B-cell clonality was confirmed by polymerase chain reaction. There was no evidence of Epstein-Barr and HIV infection. The case herein reported emphasizes the need for considering the diagnosis of lymphoma even in very young children.

Prognostic significance of bi/oligoclonality in childhood acute lymphoblastic leukemia as determined by polymerase chain reaction.

CONTEXT: The CDR-3 region of heavy-chain immunoglobulin has been used as a clonal marker in the study of minimal residual disease in children with acute lymphoblastic leukemia. Southern blot and polymerase chain reaction studies have demonstrated the occurrence of bi/oligoclonality in a variable number of cases of B-lineage acute lymphoblastic leukemia, a fact that may strongly interfere with the detection of minimal residual disease. Oligoclonality has also been associated with a poorer prognosis and a higher chance of relapse. OBJECTIVES: To correlate bi/oligoclonality, detected by polymerase chain reaction in Brazilian children with B-lineage acute lymphoblastic leukemia with a chance of relapse, with immunophenotype, risk group, and disease-free survival. DESIGN: Prospective study of patients outcome. SETTING: Pediatric Oncology Unit of the University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo. PARTICIPANTS: 47 children with acute lymphoblastic leukemia DIAGNOSTIC TEST: Polymerase chain reaction using consensus primers for the CDR-3 region of heavy chain immunoglobulin (FR3A, LJH and VLJH) for the detection of clonality. RESULTS: Bi/oligoclonality was detected in 15 patients (31.9%). There was no significant difference between the groups with monoclonality and biclonality in terms of the occurrence of a relapse (28.1% versus 26.1%), presence of CALLA+ (81.2% versus 80%) or risk group (62.5% versus 60%). Disease-free survival was similar in both groups, with no significant difference (p: 0.7695). CONCLUSIONS: We conclude that bi/oligoclonality was not associated with the factors investigated in the present study and that its detection in 31.9% of the patients may be important for the study and monitoring of minimal residual disease.

[Immunophenotyping of acute lymphoblastic leukemia in Mexican children]. / Inmunofenotipo de la leucemia aguda linfoblástica en niños mexicanos.

PURPOSE: To analyse the immunophenotype of leukaemic cells in a group of children diagnosed of lymphoblastic leukaemia in order to assess the frequency of the different immunologic subtypes. PATIENTS AND METHODS: In the period comprised between APR 1987 and MAR 1995, 402 Mexican children were studied in a prospective way. Conventional immunological markers were used, either associated to or specific for B, T, myelo-monocytic or megakaryocytic-platelet cell populations. RESULTS: Five major immunologic subtypes were disclosed, showing a series of specific surface markers: null-ALL, 5%; early pre-B, 7.5%; common, 74.6%; B-cell, 3.5%, and T-cell, 9.4%. A net predominance of B-cell precursor CD10- ALL was found in children under one year of age, and of CD10+ B-cells beyond that age. Although there was only slight predominance of male sex, the prevalence of B and TALL in males was not confirmed. CONCLUSIONS: These results show that the incidence of the different immunologic subtypes of lymphoblastic leukaemias and their distribution according to age and sex are closely similar to those reported among Caucasians in other parts of the world.

Penetration of anti-DNA antibodies into immature live cells.

Several data suggest that immature lymphoid cells are more prone to penetration and therefore are affected more by antibodies than their mature counterparts. In this study, we examined the penetration of monoclonal anti-DNA antibodies in several models of immature cells. Results confirm that most anti-DNA antibodies penetrate larger proportions of immature cells than normal adult cells. It was also proven that anti-DNA antibodies induce larger fractions of immature cells to undergo apoptosis than mature cells; however, there is not a numerical association between penetration and apoptosis. Additionally, the penetration and induction of apoptosis of several anti-DNA monoclonal antibodies into U937 and NIH-3T3 cells followed a rather heterogeneous pattern. When mature and immature cells were stimulated polyclonally, it was shown that polyreactive antibodies might act as an accessory signal to induce apoptosis in immature cells. This process could contribute to the edition of the immune repertoire. We propose that naturally occurring polyreactive antinuclear antibodies, through penetration and deletion of self-reacting cells, could participate, either as a unique or secondary signal, in the mechanism of self tolerance. If these polyreactive antibodies undergo affinity maturation, it is possible they may develop into pathogenic antibodies.

Blood bank leukocyte infusions as remission induction therapy in a case of acute lymphoblastic leukemia.

A 15-year-old female with pre-pre B ALL in third relapse was treated with administration of eight blood bank leukocyte concentrates per day for 5 days. The total number of mononuclear cells per kilogram of weight was 4.89 x 10(8). On the fifth day of infusions the patient was in complete remission (CR), asymptomatic and with a normal CBC. No secondary effects were found. The patient remained in CR without treatment for 10 weeks before relapsing again. The possibility of reaching a short-lived, clinically relevant response, using blood bank leukocyte infusions, is a promising new approach for the treatment of leukemia.

VH gene rearrangement events can modify the immunoglobulin heavy chain during progression of B-lineage acute lymphoblastic leukemia.

The presence of multiple VHDJH joinings in upwards of 30% of acute lymphoblastic leukemias (ALL) suggests a relative instability of the rearranged immunoglobulin heavy chain (IgH) gene, but the mechanisms involved are not completely understood. An investigation of the structure of the VHDJH joinings using complementarity determining region (CDR)3 polymerase chain reaction (PCR) in 12 leukemias at both diagnosis and relapse indicates that this instability may increase as a function of time. In only one of seven cases in which relapse occurred within 3 years from diagnosis was a new VHDJH joining identified and this coexisted with the original diagnostic joining. Most strikingly, new VHDJH joinings were identified in four of five cases in which relapse occurred more than 5 years from diagnosis. In this latter population, the instability of the joinings was generated from VH----VH gene replacement events in two cases, since the new joinings retained the original DJH sequences and partial N region homology at the VHD junction, and probably in a third case from a VH gene rearrangement to a common DJH precursor. Furthermore, in five of 23 (21.7%) additional cases studied at diagnosis, subclones were identified that had similar modifications of the VH-N region. These data indicate that VH gene replacement events and VH gene rearrangements to a common DJH joining contribute to the instability of the VHDJH joining in ALL. This phenomenon should be taken into consideration in those methodologies that exploit IgH rearrangements for detection of minimal residual disease.

Burkitt's lymphoma in Cuba. I. Clinical and morphological features and EBV association.

The first 7 cases of histologically and cytochemically confirmed Burkitt's lymphoma have recently been studied in Cuba. Some of them presented with facial bone involvement and high anti-Epstein-Barr virus (EBV) antibody titers characteristic of endemic African cases. Others showed features of nonendemic cases. The distribution of patients in these two groups may be in relation to the behavior of the healthy Cuban population with respect to the EBV virus.