Increasing FcγRIIa affinity of an FcγRIII-optimized anti-EGFR antibody restores neutrophil-mediated cytotoxicity

Antibody-dependent cell-mediated cytotoxicity (ADCC) has been suggested as an essential mechanism for the in vivo activity of cetuximab, an epidermal growth factor receptor (EGFR)-targeting therapeutic antibody. Thus, enhancing the affinity of human IgG1 antibodies to natural killer (NK) cell-expressed FcγRIIIa by glyco- or protein-engineering of their Fc portion has been demonstrated to improve NK cell-mediated ADCC and to represent a promising strategy to improve antibody therapy. However, human polymorphonuclear (PMN) effector cells express the highly homologous FcγRIIIb isoform, which is described to be ineffective in triggering ADCC. Here, non-fucosylated or protein-engineered anti-EGFR antibodies with optimized FcγRIIIa affinities demonstrated the expected benefit in NK cell-mediated ADCC, but did not mediate ADCC by PMN, which could be restored by FcγRIIIb blockade. Furthermore, eosinophils and PMN from paroxysmal nocturnal hemoglobinuria patients that expressed no or low levels of FcγRIIIb mediated effective ADCC with FcγRIII-optimized anti-EGFR antibody. Additional experiments with double FcγRIIa/FcγRIII-optimized constructs demonstrated enhanced PMN-mediated ADCC compared with single FcγRIII-optimized antibody. In conclusion, our data demonstrate that FcγRIIIb engagement impairs PMN-mediated ADCC activity of FcγRIII-optimized anti-EGFR antibodies, while further optimization of FcγRIIa binding significantly restores PMN recruitment.

[A rare case of successfully pregnancyand delivery in a woman with paroxysmal nocturnal hemoglobinuria]

We report a case of a pregnant woman with PNH. She was at 31 w.g. During the pregnancy our patient was hypertransfused and used anticoagulation treatment. The patient developed Preeclampsia, Intra-uterine growth retardation and Oligohydramnion. An induced vaginal delivery was done. A healthy child was delivered. There were no other postpartum complications. She was discharged from hospital in satisfactory condition.

The inherited bone marrow failure syndromes

Molecular pathogenesis may be elucidated for inherited bone marrow failure syndromes (IBMFS). The study and presentation of the details of their molecular biology and biochemistry is warranted for appropriate diagnosis and management of afflicted patients and to identify the physiology of the normal hematopoiesis and mechanisms of carcinogenesis. Several themes have emerged within each subsection of IBMFS, including the ribosomopathies, which include ribosome assembly and ribosomal RNA processing. The Fanconi anemia pathway has become interdigitated with the familial breast cancer syndromes. In this article, the diseases that account for most IBMFS diagnoses are analyzed.

Paroxysmal nocturnal hemoglobinuria and the age of therapeutic complement inhibition

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare disease of hematopoietic stem cells due to a mutation in the PIG-A gene leading to a deficiency of GPI-anchored proteins. Lack of two specific GPI-anchored proteins, CD55 and CD59, leads to uncontrolled complement activation that result in both intravascular and extravascular hemolysis. Free hemoglobin leads to nitric oxide depletion that mediates the pathophysiology of some of the common clinical signs of PNH. Clinical symptoms of PNH include evidence of hemolytic anemia, bone marrow failure, smooth muscle dystonias and thromboses. Treatment options for patients with PNH include bone marrow transplantation, a therapy associated with high morbidity and mortality, or treatment with the complement inhibitor eculizumab. Eculizumab is a first-in-class anti-complement drug that in PNH has been shown to block complement-mediated hemolysis, reduce transfusion dependency, reduce thromboembolic complications and improve the quality of life (QoL) of patients.

Improving cytopenia with splenic artery embolization in a patient with paroxysmal nocturnal hemoglobinuria on eculizumab

Paroxysmal nocturnal hemoglobinuria is a rare acquired stem cell disorder characterized by intravascular hemolysis, aplasia and an increased risk of thrombosis. We describe a patient under treatment with the anti-complement antibody eculizumab who developed pancytopenia, requiring blood transfusions, due to massive splenomegaly. The patient underwent two separate splenic embolizations, which reduced the size of the spleen and improved his blood count to the point that blood transfusions were no longer necessary. Splenic embolization was chosen over splenectomy due to the potential postoperative complications of splenectomy, especially that of thrombosis.

[Ex vivo expansion and clonal variation of CD34(+)CD59(+) cells from bone marrow in children with paroxysmal nocturnal hemoglobinuria]

OBJECTIVE

To investigate the isolation, purification and ex vivo expansion of CD34(+)CD59(+) cells from the bone marrow of children with paroxysmal nocturnal hemoglobinuria (PNH), to evaluate the capability of long-term hematopoietic reconstruction of the expanded CD34(+)CD59(+) cells, and to provide a laboratory basis for novel treatment of PNH.

METHODS

CD34(+)CD59(+) cells were isolated from the bone marrow mononuclear cells of children with PNH using immunomagnetic beads and flow cytometer in sequence. The isolated cells were subjected to ex vivo expansion in the presence of different combinations of hematopoietic growth factors for two weeks. The colony-forming cells and long-term culture-initiating cells (LTC-ICs) were cultured and counted.

RESULTS

The optimal combination of hematopoietic growth factors for ex vivo expansion was stem cell factor+interleukin (IL)-3+IL-6+FLT3 ligand+thrombopoietin+ery-thropoietin, and maximum expansion (30.4 ± 6.7 folds) was seen on day 7 of days 4 to 14 of ex vivo expansion. After ex vivo expansion, CD34(+)CD59(+) cells remained CD59-positive, retained strong capability of forming colony-forming units, and could still form LTC-ICs. There was no significant difference in capability of forming LTC-ICs between CD34(+)CD59(+) cells before and after expansion. The expansion capability of CD34(+)CD59(+) cells from children with PNH was significantly lower than that of CD34(+) cells from normal controls (P<0.01).

CONCLUSIONS

The CD34(+)CD59(+) cells from children with PNH can be expanded in vitro. Post-expansion CD34(+)CD59(+) cells retain capability of long-term hematopoietic reconstruction. CD34(+)CD59(+) cells showed no trend towards PNH clone during culture. Ex vivo expansion of CD34(+)CD59(+) cells from children with PNH might be practical in performing autologous transplantation clinically for these children.

[Modern condition and prospects of improvement of the specialized medical care for acute bone marrow syndrome of radiation etiology]

It is shown, that tactics of treatment of acute marrow failure of radiant etiology is based, first of all, on measures of supporting, replaceable and stimulating therapy. The modern means, used for prophylactic and treatment of infectious complications, are resulted. Opportunities and restrictions of transfusion of donor thrombocytes and granulocytes, erythrocytes and chilled plasma are described. Therapeutic efficiency of transplantation of a bone marrow, cells of embryonic liver and stem cells of peripheral or umbilical cord blood is analyzed. It is shown, that the greatest prospects in perfection of the specialized medical aid at acute radiation syndrome are connected to complex application of interleukin-1beta, interleukin-3, granulocyte or granulocyte/macrophage colony stimulated factor, thrombopoietin and others cytokines.

Clinical roundtable monograph: Paroxysmal nocturnal hemoglobinuria: a case-based discussion

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired disorder characterized by chronic intravascular hemolysis as the primary clinical manifestation and morbidities that include anemia, thrombosis, renal impairment, pulmonary hypertension, and bone marrow failure. The prevalence of the PNH clone (from <1-100% PNH granulocytes) is approximately 16 per million, and careful monitoring is required. The average age of onset of the clinical disease is the early 30s, although it can present at all ages. PNH is caused by the acquisition of a somatic mutation of the gene phosphatidylinositol glycan anchor (PIG-A) in a multipotent hematopoietic stem cell (HSC), with clonal expansion of the mutated HSC. The mutation causes a deficiency in the synthesis of glycosylphosphatidylinositol (GPI). In cells derived from normal HSCs, the complement regulatory proteins CD55 and CD59 are anchored to the hematopoietic cell membrane surface via GPI, protecting the cells from complement-mediated lysis. However, in patients with PNH, these 2 proteins, along with numerous other GPI-linked proteins, are absent from the cell surface of red cells, granulocytes, monocytes, and platelets, resulting in complement-mediated intravascular hemolysis and other complications. Lysis of red blood cells is the most obvious manifestation, but as other cell lineages are also affected, this complement-mediated attack contributes to additional complications, such as thrombosis. Eculizumab, a humanized monoclonal antibody against the C5 complement protein, is the only effective drug therapy for PNH patients. The antibody prevents cleavage of the C5 protein by C5 convertase, in turn preventing generation of C5b-9 and release of C5a, thereby protecting from hemolysis of cells lacking the CD59 surface protein and other complications associated with complement activation. Drs. Ilene C. Weitz, Anita Hill, and Jeff Szer discuss 3 recent cases of patients with PNH.

[Advancements in diagnosis and management of paroxysmal nocturnal hemoglobinuria - review]

Paroxysmal nocturnal hemoglobinuria (PNH) is a hemolytic disease of abnormally activated complement. FLAER diagnosis is a higher sensitive and specific method, which makes PNH patients to be early discovered and treated. Non-typical symptoms including thrombosis, pulmonary hypertension and chronic kidney disease in PNH have been caused increasing attention. Eculizumab monoclonal antibody has greatly improved the current treatment status of PNH. PNH can be cured thoroughly by allogeneic hematopoietic stem cell transplantation. In this article, the FLAER diagnosis, clinic symptoms and progress of treatment in patients with PNH are reviewed.