Detailed studies on expression and function of CD19 surface determinant by using B43 monoclonal antibody and the clinical potential of anti- CD19 immunotoxins

Abstract

Extensive immunologic surface marker analyses and binding competition assays demonstrated that B43 monoclonal antibody (MoAb) is a new member of the CD19 cluster that recognizes the same surface epitope as several other anti-CD19 MoAbs. We used B43 MoAb to test for CD19 expression on neoplastic cells from 340 leukemia and 151 malignant lymphoma patients and on nonneoplastic cells in normal lymphohematopoietic and nonlymphohematopoietic tissues. Our study more than doubles the total number of cases with classified hematologic malignancies that have been examined for CD19 antigen expression. The data presented confirm that CD19 is the most reliable B lineage surface marker and support our view that this B lineage-restricted surface determinant may be an important functional receptor. Our findings provide unique and direct evidence that (a) CD19 is expressed on leukemic B lineage lymphoid progenitor cells freshly obtained from B lineage acute lymphoblastic leukemia patients but not on normal myeloid, erythroid, megakaryocytic, or multilineage bone marrow progenitor cells; (b) ligation of CD19 with B43 MoAb induces sustained increases in [Ca2+]i when crosslinked and inhibits high-molecular weight B cell growth factor (HMW-BCGF)-induced proliferation of activated B cells without affecting their low- molecular weight B cell growth factor (LMW-BCGF) response; therefore CD19 may be a unique signal receptor; (c) HMW-BCGF and LMW-BCGF augment expression of CD19, which suggests that CD19 and BCGF receptors may be under coordinate regulatory control; (d) approximately two million B43 MoAb molecules per cell can be bound to target B lineage lymphoma cells with a Ka of 1.9 x 10(8)/mol/L; (e) CD19 can undergo B43 MoAb-induced internalization; and (f) the opportunity is thus provided for using anti-CD19 MoAb to deliver toxins to B lineage neoplastic cells for more effective treatment of high-risk leukemia/lymphoma patients.

Loss of CD19 expression in B‐cell neoplasms

“…The first of these, CD19, is present in both normal and malignant B cells and has long been considered to be the most reliable surface marker of this lineage over a wide range of maturational stages. [1][2][3][4] In normal lymphoid tissue CD19 is observed in germinal centres (on both B cells and follicular dendritic cells), in mantle zone cells and in scattered cells in the interfollicular areas, 3,5 with an overall immunoreactivity pattern similar to that of CD20 and CD22. However, in contrast to CD20, CD19 is also expressed in pre-B cells.…”

“…However, in contrast to CD20, CD19 is also expressed in pre-B cells. 3 CD19 has also been detected by flow cytometry in plasma cells isolated from human tissues. 6 Previous studies of CD19 in B-cell neoplasia have been limited to flow cytometric analysis of living cells 2,7-10 and its expression in B-cell neoplasia in routine tissue biopsy specimens has not been previously investigated.…”

Clinical Pharmacokinetics of the CD19 Receptor‐Directed Tyrosine Kinase Inhibitor B43‐Genistein in Patients with B‐Lineage Lymphoid Malignancies

“…Eligibility requirements included (1) active disease with . 25% blasts (M3) in the bone marrow (for ALL patients only); (2) no active central nervous system (CNS) leukemia); (3) Eastern Cooperative Oncology Group performance status of 2 or better; (4) a life expectancy of > 2 months; (5) adequate renal function (serum creatinine < 1.5 x normal and creatinine clearance or GFR . 70 ml/min/1.73 m2); (6) adequate liver function (serum bilirubin < 1.5 x normal); (7) adequate cardiac function (shortening fraction of > 27% measured by 2-D echocardiography or an ejection fraction .…”

At the Bench: Chimeric antigen receptor (CAR) T cell therapy for the treatment of B cell malignancies

“…CD19 as a TAA CD19 is a 95 kDa transmembrane glycoprotein that is found on most cells of the B lineage, excluding terminally differentiated plasma cells. CD19 is not present on pluripotent hematopoietic stem cells [26] and is expressed on most B cell-derived leukemias and lymphomas [27]. Given the restrictive expression pattern of this antigen, CD19-positive malignancies became an early target for antibody-mediated immunotherapy [28] and subsequently, CAR-mediated targeting.…”

“…The anti-CD19 CAR In 2003, we described the use of CD19-targeted CAR T cells in the treatment of human B cell malignancy xenografts [29]. The CAR construct used a human CD19-specific scFv derived from the SJ25C1 hybridoma [27,30], fused in line with the hinge and transmembrane domain of human CD8-a and the cytoplasmic domain of the CD3z: the construct was termed 19z1. As assessed by chromium release assay, primary human T cells retrovirally transduced with this 19z1 were able kill, in an antigen-specific manner, CD19 + human Burkitt lymphoma (Raji and Daudi) and BALL (Sup-B15 and NALM-6) cell lines.…”