FDA-approved drug screening in patient-derived organoids demonstrates potential of drug repurposing for rare cystic fibrosis genotypes.

BACKGROUND: Preclinical cell-based assays that recapitulate human disease play an important role in drug repurposing. We previously developed a functional forskolin induced swelling (FIS) assay using patient-derived intestinal organoids (PDIOs), allowing functional characterization of CFTR, the gene mutated in people with cystic fibrosis (pwCF). CFTR function-increasing pharmacotherapies have revolutionized treatment for approximately 85% of people with CF who carry the most prevalent F508del-CFTR mutation, but a large unmet need remains to identify new treatments for all pwCF. METHODS: We used 76 PDIOs not homozygous for F508del-CFTR to test the efficacy of 1400 FDA-approved drugs on improving CFTR function, as measured in FIS assays. The most promising hits were verified in a secondary FIS screen. Based on the results of this secondary screen, we further investigated CFTR elevating function of PDE4 inhibitors and currently existing CFTR modulators. RESULTS: In the primary screen, 30 hits were characterized that elevated CFTR function. In the secondary validation screen, 19 hits were confirmed and categorized in three main drug families: CFTR modulators, PDE4 inhibitors and tyrosine kinase inhibitors. We show that PDE4 inhibitors are potent CFTR function inducers in PDIOs where residual CFTR function is either present, or created by additional compound exposure. Additionally, upon CFTR modulator treatment we show rescue of CF genotypes that are currently not eligible for this therapy. CONCLUSION: This study exemplifies the feasibility of high-throughput compound screening using PDIOs. We show the potential of repurposing drugs for pwCF carrying non-F508del genotypes that are currently not eligible for therapies. ONE-SENTENCE SUMMARY: We screened 1400 FDA-approved drugs in CF patient-derived intestinal organoids using the previously established functional FIS assay, and show the potential of repurposing PDE4 inhibitors and CFTR modulators for rare CF genotypes.

Tissue distribution and biochemical and functional properties of Tp55 (CD27), a novel T cell differentiation antigen.

Two monoclonal antibodies (CLB-CD 27/1 and CLB-CD 27/2) were raised against a novel determinant on human T lymphocytes. One of these antibodies, CLB-CD 27/1 (clone 9F4), was grouped by the Third International Workshop and Conference on Human Leucocyte Differentiation Antigens together with three other monoclonal antibodies (VIT 14, OKT 18A, and S152) in the new cluster CD27. In this paper we show that antibodies belonging to this cluster recognize an antigen present on a large subset of peripheral T lymphocytes and most medullary thymocytes. At least two different nonoverlapping epitopes were identified with directly labeled monoclonal antibodies. Immunoprecipitation studies indicate that the target antigen of CD27 antibodies is a polypeptide of 55 kDa, which appears in the form of a disulfide-linked homodimer on the T lymphocyte membrane (Tp55). Stimulation of T cells via the T3/T cell antigen-receptor complex, with either phytohemagglutinin or CD3 monoclonal antibodies, resulted in a fivefold increase in the membrane expression of Tp55, whereas activation by phorbol myristate acetate caused a marked down-regulation. Moreover, an additional molecule of 32 kDa was precipitated from the membrane of activated but not of resting T cells. Addition of CD27 antibodies to cultures stimulated with either phytohemagglutinin or CD3 monoclonal antibody led to enhanced proliferation, whereas no effect was observed in phorbol myristate acetate or interleukin 2-stimulated cultures. The possible role of the Tp55 antigen in T cell activation is discussed.

Anti-MHC immunity detected prior to intentional alloimmunization. IV. Natural monoclonal H-2-specific antibodies.

Naturally occurring H-2-specific antibodies can be detected rather frequently in sera of non-alloimmunized mice by sufficiently sensitive techniques (Cerny-Provaznik et al., 1985a; Cerny-Provaznik & Ivanyi, 1985). In this report, we summarize our experiences with the preparation of monoclonal anit-H-2 antibodies obtained from hybridization experiments from non-alloimmunized mice. From a total of 30 spleen cell hybridization experiments, we could isolate only four anti-H-2 monoclonal antibodies (mAB). Two of the mAB are described in this report. Monoclonal antibody By-2 is anti-Kf and mAB By-3 is anti-Db, Ds. We investigated which conditions favour the isolation of monoclonal H-2-specific antibodies from non-alloimmunized mice. The presence of naturally occurring serum antibodies, the age of the spleen donor mouse or non-specific B cell stimulation were not critical for the isolation of natural anti-H-2 mAB. We hypothesise that the 'natural' H-2-specific antibodies represent compartments of the B cell repertoire which were triggered by modified or aberrant self-MHC expression.

Colony-forming cells in chronic granulocytic leukemia--II. Analysis of membrane markers.

Membrane markers and functional properties in vitro of blast cells from the peripheral blood of 2 patients with chronic granulocytic leukemia were studied. Buffy-coat cells were enriched for colony-forming cells by density centrifugation (d less than or equal to 1.062 g cm-3). Upon culture, a large proportion of the (cryopreserved) low-density cells from both patients formed hemopoietic colonies that were heterogeneous with respect to size and cellular composition. Expression of membrane markers on the cells, which had the morphology of undifferentiated blasts, was studied using flow cytometry with a panel of monoclonal antibodies. A striking heterogeneity was observed in that variable numbers of cells were found to express myelomonocytic, megakaryocytic and erythroid membrane markers. Antigenic properties of colony-forming cells were studied by sorting of cells with a fluorescence activated cell sorter. Low numbers of cells (10, 4 and 1, respectively) were sorted directly into the wells of Terasaki microtest plates. With this system, it was shown that myeloid colony-forming cells from patient 1 were exclusively present in HLA-DR-positive cell fractions. Colony formation from the level of a single sorted cell was documented. Sorting of cells labeled with anti-blood-group-H antibody showed that small erythroid colony-forming cells from patient 2 were blood-group-H antigen-positive. These cells did not express HLA-DR. The other colony-forming cells from this patient and essentially all colony-forming cells from patient 1 were HLA-DR-positive and blood-group-H-negative. Although only 2 patients were tested, our studies clearly demonstrate that low-density cell fractions from the blood of patients with CGL provide distinct advantages for the study of membrane properties of hemopoietic cells and of hemopoietic differentiation in general.

Anti-MHC immunity detected prior to intentional alloimmunization. III. Natural autoreactive H-2-specific antibodies.

Cell fusion was performed between spleen cells from young BALB/cBy (H-2d) mice which have never been immunized and SP2/0 mouse plasmacytoma cells. A monoclonal H-2 specific cytotoxic IgM antibody was obtained (By-1) which detected a new public biregional H-2 specificity, H-2.m210. The mcAb By-1 reacted strongly with H-2Kd, Dd, and H-2s antigens, gave weak cross-reactions with H-2Kk, Dq, H-2r, and H-2v antigens and was negative with H-2b, H-2f, H-2p, and H-2Ld antigens. A polymorphic reaction pattern was also observed on a panel of lymphocytes from B10.W strains. The intriguing finding on this reaction pattern was the reactivity on H-2d cells, including the syngeneic BALB/cBy and truly autologous cells. As shown by capping and immunoprecipitation experiments on H-2d cells and by studies on H-2d-transfected mouse L cells, the target molecules for McAb By-1 were H-2Kd and H-2Dd molecules. The BALB/cBy mouse, from whose spleen cells the McAb By-1 was obtained, survived after the fusion experiment, and serum was examined for the presence of cytotoxic H-2-specific antibodies during the rest of its life. At the time of the fusion, no autoreactive serum antibodies were found, but about 4 months later, we found in the serum of this mouse autoreactive H-2-specific cytotoxic IgM antibodies. The serum antibodies followed the same reaction pattern as that of the McAb By-1. As far as we know, this is the first report of autoreactive H-2-specific antibodies in serum of a mouse which has never been immunized and of the first natural autoreactive H-2-specific monoclonal antibody.

Anti-major histocompatibility complex immunity detected prior to intentional alloimmunization. I. Naturally occurring H-2-specific antibodies in C57BL/KaLwRij (H-2b) mice.

Naturally occurring, H-2-specific, lymphocytotoxic antibodies were detected in 3-10% of young adult and in 10-40% of aged C57BL/KaLwRij (H-2b) mice. The antibodies were of the IgM class and occurred in low titers, but occasionally a high titer was found. The antibodies detected public lymphocyte-membrane antigens controlled by genes identical with, or closely linked to class-I H-2K and H-2D genes. Antibodies against 7 different allogeneic H-2 haplotypes were detected but sera of individual mice exerted different reaction patterns and some specificities occurred more frequently than others. Although the occurrence of the antibodies was age dependent, thymus involution, gammapathies, autoimmunity, the presence of other natural lymphocyte-specific antibodies, and polyclonal or nonspecific stimulation could not be related to the occurrence of natural H-2-specific antibodies. Several possible explanations of natural H-2-specific antibodies exist. We propose that determinants of complex altered self-MHC (MHC + X) antigen(s) triggered the production of H-2-restricted antibodies that recognize H-2-public determinants on normal allogeneic cells.

Anti-major histocompatibility complex immunity detected prior to intentional alloimmunization. II. Monoclonal H-2-specific antibodies obtained from an unimmunized C57BL/KaLwRij (H-2b) mouse.

A monoclonal 'natural' anti-H-2 IgM antibody produced by a hybridoma cell line OL-3.17 (H-2 m. 209) is described. The OL-3.17 monoclonal antibody was obtained by hybridization of spleen B cells from an unimmunized C57BL/Ka (H-2b) mouse in the serum of which simultaneously an IgM kappa paraprotein of high concentration and a natural H-2-specific antibody of high titer was detected. The monoclonal antibody OL-3.17 reacted strongly with H-2d and H-2s and weakly with H-2k,q,r lymphocytes, thereby detecting a hitherto unknown H-2 public determinant. The target molecules for OL-3.17 cocapped with class-I H-2 antigens, but immunoprecipitation of H-2 antigens was not achieved. This is the first monoclonal H-2-specific antibody obtained from a mouse without intentional immunization and, with high probability, was derived from a B-cell clone which produced natural H-2-specific antibodies detectable in the serum of the original mouse.

Density separation of spleen cells increases fusion frequency and yield of Ig-producing hybridomas.

The efficiency of hybridoma formation and growth after cell fusion can be much improved by fractionation of the mouse splenocytes. A simple procedure is described in which splenocytes with a specific gravity of more than 1.065 g/cm3 are selected by centrifugation on a Percoll gradient. The resulting cell suspension is largely depleted of macrophages and fibroblasts while the cell viability is improved. In fusion experiments performed with these cells, overgrowth of hybridomas by macrophages, fibroblasts and P-cells is avoided. The fusion efficiency and the frequency of immunoglobulin-secreting hybridomas is increased compared with fusions carried out with unfractionated spleen cells.

Allo-immune anti-Iak sera of individual mice detect HLA-DR-associated polymorphism on human B cells.

A murine allo-immune A.TH anti-A.TL (anti-Iak) serum pool and sera from individual immunized mice were tested on a large panel of human DR typed B cells, obtained from peripheral blood (PBL-B cells), and human lymphoid tumour cells. The anti-Iak serum pool appeared to be a useful reagent both in cytotoxicity and immunofluorescence for the examination of the presence of class-2 HLA molecules on tumour cells. Only one discrepancy was observed when the pool was tested in parallel with a xeno-anti-human B-cell serum on the cells of 56 lymphoid tumours. Nine sera from individual mice were tested on a panel of 93 PBL-B cells. Some of these sera reacted significantly more weakly with human B cells positive for the DR5 and/or DR7 antigens.

Naturally occurring cytotoxic human antibodies recognize H-2-controlled murine lymphocyte antigens.

Human sera contain cytotoxic naturally occurring (CyNa) antibodies which discriminate between lymph node cells from mice differing only at the H-2 complex. Sera from three healthy subjects (normal human sera, NH sera) and one serum from a patient with multiple sclerosis reacted with cells expressing Db, Kd, Kk, and Kp molecules, respectively. However, the following observations suggested that the binding specificity of these CyNa antibodies is to antigens that are distinct from the classical H-2 antigens: (i) the NH sera did not contain cytotoxic anti-HLA antibodies, (ii) redistribution (capping) of H-2 antigens did not induce resistance to lysis for CyNa antibodies, and (iii) individual variation was demonstrated in the expression of the murine lymphocyte antigens detected by the human CyNa antibodies. The reason for this variation appeared to be different for individual NH serum. A maternal effect influenced the expression of the murine lymphocyte antigen detected by one NH serum (anti-H-2b). The differences detected by another NH serum (anti-H-2p) appeared to be inherited, as shown by progeny testing. We hypothesize that the human CyNa antibodies may be directed against antigens controlled or modified by murine viruses (milk borne or endogenous), whose expression is under the influence of the H-2 complex, and that their production might have been stimulated by the products of human genes homologous to murine viruses.

Human Ia molecules carrying DC1 or BR4X7 determinants are not homologous to murine I-E molecules.

An anti-I-Ek alloantiserum was shown to react with purified human Ia preparation. All Ia preparations tested were actively bound irrespective of their HLA-DR phenotypes. However, from a quantitative point of view, DR7 molecules were significantly less reactive. No reaction was observed with isolated Ia subunits. Only molecules carrying DR determinants, but not those carrying either DC1 or BR4X7 determinants, were bound.

Constancy of cross-reactivity patterns in sera of individual mice during the anti-H-2 response.

H-2 alloimmunization evokes antibodies of differing cross-reactivity patterns among individual mice of one inbred strain. We investigated whether this is due to unknown variations at the time of bleeding or whether it remains constant for an individual mouse during long-term immunization. At various times during immunization, serum was collected from individual mice and it was tested on a panel of mouse and human lymphocytes. Sera from three donor-recipient combinations were examined. In some sera, a broadening of the cross-reactivity pattern occurred after prolonged immunization, but no major change in specificity was observed. We conclude that the differences in cross-reactivity pattern among sera from individual mice remain constant during the immunization period and do not reflect variations in the condition of the animals at the time of bleeding.

Unexpected lympho-cytotoxic reactions of anti-H-2 sera on normal lymph-node cells: are they due to altered H-2 structures or anti-viral antibodies?

When testing the serum of an individual anti-H-2 immunized mouse (B10 x A.SW)F1 anti-B10.M by the routine micro-lymphocytotoxicity test on lymph-node cells, unexpected antibodies were found. The most striking finding was that after absorption of anti-H-2.8 antibodies with B10.A(2R) (Kk) cells, antibodies remained which reacted with AKR, B10.AKM and B10.A V+ mice while B10.A V-, B10.BR and C3H mice were negative. While all these strains share the Kk allele, only the positively reacting strains express high titres of infectious RNA turnover viruses. Unexpected reactions were observed also with H-2d, H-2j and H-2r cells and absorption experiments indicated two or three antibody populations. These reactions could be interpreted by two different possibilities: (1) anti-H-2 antibodies react with virus-altered H-2 structures; and (2) anti-viral antibodies react with H-2 structures complexed with viruses. These possibilities should be taken into account when H-2 sera are tested on tumour or virus-infected cells.

Anti-H-2 antibodies induced by syngeneic immunization.

Abstract. Alloreactive cytotoxic antibodies were induced in BALB/c mice by syngeneic immunization with normal lymphoid cells. Sixteen out of 41 mice produced antibodies with distinct anti-H-2 specificity. Anti-Kk antibodies were present in all positive sera, but the individual sera produced different reactivity patterns when tested on a panel of H-2 haplotypes. Absorption and immunoprecipitation experiments confirmed the H-2 specificity of the syngeneic sera. We hypothesize that virus-modified H-2d structures have triggered alloreactive B-cell clones to produce anti-H-2 antibodies.