K562 cells express human major histocompatibility antigens

CAR-T cells and TRUCKs that recognize an EBNA-3C-derived epitope presented on HLA-B*35 control Epstein-Barr virus-associated lymphoproliferation

Background

Immunosuppressive therapy or T-cell depletion in transplant patients can cause uncontrolled growth of Epstein-Barr virus (EBV)-infected B cells resulting in post-transplant lymphoproliferative disease (PTLD). Current treatment options do not distinguish between healthy and malignant B cells and are thereby often limited by severe side effects in the already immunocompromised patients. To specifically target EBV-infected B cells, we developed a novel peptide-selective chimeric antigen receptor (CAR) based on the monoclonal antibody TÜ165 which recognizes an Epstein-Barr nuclear antigen (EBNA)−3C-derived peptide in HLA-B*35 context in a T-cell receptor (TCR)-like manner. In order to attract additional immune cells to proximity of PTLD cells, based on the TÜ165 CAR, we moreover generated T cells redirected for universal cytokine-mediated killing (TRUCKs), which induce interleukin (IL)-12 release on target contact.

Methods

TÜ165-based CAR-T cells (CAR-Ts) and TRUCKs with inducible IL-12 expression in an all-in-one construct were generated. Functionality of the engineered cells was assessed in co-cultures with EBNA-3C-peptide-loaded, HLA-B*35-expressing K562 cells and EBV-infected B cells as PTLD model. IL-12, secreted by TRUCKs on target contact, was further tested for its chemoattractive and activating potential towards monocytes and natural killer (NK) cells.

Results

After co-cultivation with EBV target cells, TÜ165 CAR-Ts and TRUCKs showed an increased activation marker expression (CD137, CD25) and release of proinflammatory cytokines (interferon-γ and tumor necrosis factor-α). Moreover, TÜ165 CAR-Ts and TRUCKs released apoptosis-inducing mediators (granzyme B and perforin) and were capable to specifically lyse EBV-positive target cells. Live cell imaging revealed a specific attraction of TÜ165 CAR-Ts around EBNA-3C-peptide-loaded target cells. Of note, TÜ165 TRUCKs with inducible IL-12 showed highly improved effector functions and additionally led to recruitment of monocyte and NK cell lines.

Conclusions

Our results demonstrate that TÜ165 CAR-Ts recognize EBV peptide/HLA complexes in a TCR-like manner and thereby allow for recognizing an intracellular EBV target. TÜ165 TRUCKs equipped with inducible IL-12 expression responded even more effectively and released IL-12 recruited additional immune cells which are generally missing in proximity of lymphoproliferation in immunocompromised PTLD patients. This suggests a new and promising strategy to specifically target EBV-infected cells while sparing and mobilizing healthy immune cells and thereby enable control of EBV-associated lymphoproliferation.

The beta2-microglobulin mRNA in human Daudi cells has a mutated initiation codon but is still inducible by interferon

The human Burkitt lymphoma cell line Daudi does not synthesize beta2-microglobulin (beta2m) and lacks the cell surface histocompatibility antigens. The cells, however, contain RNA hybridizing to a cloned human beta2m cDNA probe. cDNA from this Daudi beta2m RNA, was cloned and sequenced. By comparison with cDNA prepared from Ramos cells, which synthesized microglobulin, we determined the sequence of the 20 amino acid long leader peptide of pre-beta2m and show that in Daudi cells the initiator ATG has been mutated to ATC. Although Daudi beta2m RNA cannot be translated, interferon induces the beta2m RNA in Daudi cells as well as in normal human cells.

Interferon-gamma-induced expression of class I HLA antigens on K-562 cells grown in serum-free medium

Human interferon-gamma (IFN-gamma), encoded in Escherichia coli by recombinant human DNA, induces the expression of HLA antigens in the pluripotent hematopoietic stem cell line K-562 grown in serum-free growth medium. Expression was noted in 90% of the cells within 4 days and there was a high density of expression per cell, as determined by cytofluorography. Upon subculture, the cells rapidly lose their ability to express HLA, indicating that the continued presence of IFN-gamma is necessary for the expression. Reinduction of expression with IFN-gamma occurs in a high percentage of cells (up to 90%), which is comparable to the induction in freshly treated control cells.

Absence of HLA class I and class II antigens as well as beta 2-microglobulin from normal and pathological human spermatozoa

Human spermatozoa from 87 donors with normal or pathologic semen specimen were examined for the expression of HLA-class I and class II antigens as well as beta 2-microglobulin (beta 2m) using a panel of monoclonal antibodies in an indirect immunofluorescence test. The results make it very unlikely that HLA-class I and class II molecules as well as beta 2m are expressed on human sperm cells.

Diversity of cell surface hematopoietic antigens on K-562 sublines identified with monoclonal antibodies

The surface antigen profile of 8 sublines of K-562 cells, the original line, and the clone RA6 was determined with a panel of 12 monoclonal antibodies reactive with hematopoietic cell differentiation antigens. Cells from all sublines expressed the precursor hematopoietic antigen reactive with RFB-1, the T-cell antigen reactive with OKT17, the B cell/granulocyte antigen reactive with BA-1, the My-1 antigen, and glycophorin A which reacted with R10. A low percentage of cells in some of the sublines expressed platelet/monocyte glycoprotein I binding AN51, monocyte antigen binding 63D3, and an erythroblast/monocyte/platelet antigen binding 5F1. The use of a panel of K-562 sublines demonstrates that K-562 cells do share several "common" antigens but express a marked diversity and variability of other hematopoietic antigens.

Characterization of a monoclonal anti-Bw4 antibody (Tü109): evidence for similar epitopes on the Bw4 and Bw6 antigens

The production and serologic, as well as immunochemical properties of a cytotoxic murine IgG monoclonal antibody (Tü109) that precipitates HLA-class I molecules, are described. In the microcytotoxicity assay Tü109 supernatant was demonstrated on a panel of 424 HLA-ABC, -DR, -DQ, -MT typed normal Caucasian blood donors to define an epitope on HLA-B locus molecules in great association with the supertypic specificity Bw4. Reactivity of supernatant showed MHC linked inheritance of the Tü109 determinant and discriminated the HLA-Bw4/Bw6 associated HLA-B locus split antigens. Weak or lack of binding on lymphocytes from some HLA-Bw4 heterozygous individuals, particularly typing for HLA-Bw44, appeared to be due to qualitative and/or quantitative variations of HLA-B locus molecules on the cell surface. With Tü109 ascites fluid, however, extra-reactivity on all HLA-Bw6+ cells was demonstrated. Preferential binding of supernatant to HLA-Bw4, but reactivity of ascites fluid with HLA-Bw6+ molecules in addition, was furthermore confirmed by IEF analysis of antigens immunoprecipitated with Tü109 from cell lysates. Thus the antibody may help to analyze the evolutionary relationship of the diallelic specificities Bw4 and Bw6.

Expression of HLA-A and -B antigens on differentiating U-937 cells

Cells from the human immature monocytoid cell line U-937 were induced with 12-O-Tetradecanoyl-phorbol-13-acetate (TPA) to differentiate towards macrophage-like cells. The expression of HLA-antigens during differentiation was examined with a panel of monoclonal antibodies directed against monomorphic and polymorphic determinants. Class II antigens could be detected neither on uninduced nor on TPA-induced U-937 cells. While the expression of HLA-A3 did not change significantly during differentiation, the "supertypic" specificities HLA-Bw4 and Bw6 as well as the "private" specificity HLA-B18 could be detected only on a drastically decreased number of cells after 4 days of exposure to TPA. This may imply a selective loss of HLA-B molecules from the cell membrane and therefore a separate regulatory control of HLA-A and -B antigens.

Expression of myeloid-specific antigens on two human erythroleukaemia cell lines, HEL and K562

The cell-surface phenotype of the human erythroleukaemia cell line, HEL, was investigated using a panel of lineage-specific monoclonal antibodies by indirect immunofluorescence. Antigens specific for the erythroid, granulocytic and monocytic lineages were detected, but no lymphoid- or platelet-specific antigens were found. The data obtained for HEL were compared to findings for the K562 human erythroleukaemia cell line and considerable similarities were demonstrated between the phenotypes of the two. In particular it was noted that the majority of granulocyte/monocyte markers present on HEL were also present on K562. The occurrence on HEL of markers of several haemopoietic lineages would suggest an origin from the non-lymphopoietic multipotential stem-cell or CFU-GEMM.

Granulocyte specific cytotoxic antibodies in pregnancy and multitransfused sera

The myeloid cell line K562 was used to screen for specific antibodies in sera obtained from pregnant women and multitransfused patients. The alloantisera thus procured reacted with random granulocytes in a pattern suggestive of a polymorphic system. Some antibodies were found to react only in the cold. A simple reproducible method for the simultaneous separation of granulocytes and lymphocytes for microcytotoxicity is described.

HLA antigen expression at the single cell level on a K562 X B cell hybrid: an analysis with monoclonal antibodies using bacterial binding assays

The influence of different genetic environments on the expression of HLA complex-controlled antigens has been investigated using cell lines with various defects in the synthesis of these molecules and a somatic cell hybrid derived from them. A very sensitive bacterial binding assay allowing simultaneous evaluation of the morphology of a given cell and the quantity of a surface molecule has been developed for these studies. The fetal erythroid cell line K562, the Burkitt's lymphoma-derived cell line DAUDI, and their hybrid DUTKO1 have been employed. K562 and the hybrid, but not DAUDI, expressed HLA-A,B,C heavy chains as detected by the monoclonal antibody W6/32.HL, while two monoclonal antibodies (TU48 and 2BC4) against the supertypic specificities HLA-Bw4 and Bw6 showed no reactivity. The presence of human Ia-like antigens on the cell surfaces was investigated with a panel of eight monoclonal antibodies. K562 cells were completely unreactive, and DAUDI cells gave the expected positive reaction, but about 1% or less of the cells in the DUTKO1 population appeared to express these antigens as well. We discuss possible reasons for the failure to detect HLA-B antigens with monoclonal antibodies and the lack of complete "dominance" of the K562 genome in the hybrid cell line.

Interferon-dependent induction of mRNA for the major histocompatibility antigens in human fibroblasts and lymphoblastoid cells

In human cells treated with interferons, there is an increase in the amount of HLA-A,B,C and beta 2-microglobulin exposed on the cell surface. We have used a cloned HLA-A,B,C cDNA probe to demonstrate by molecular hybridization that this effect of interferon is preceded by a large increase in the amount of HLA mRNA in the cell. This effect was found in five different human cell lines, with purified leukocyte and fibroblast interferons. The increase in HLA mRNA is comparable in its kinetics and dose-response to the induction of (2'-5') oligo(A) synthetase mRNA by interferons. Therefore, interferons seem to activate at least two cellular genes which have different biochemical functions.