HLAII peptide presentation of infliximab increases when complexed with TNF.

CD4+ T-cell activation through recognition of Human Leukocyte Antigen II (HLAII)-presented peptides is a key step in the development of unwanted immune response against biotherapeutics, such as the generation of anti-drug antibodies (ADA). Therefore, the identification of HLAII-presented peptides derived from biotherapeutics is a crucial part of immunogenicity risk assessment and mitigation strategies during drug development. To date, numerous CD4+ T-cell epitopes have been identified by HLAII immunopeptidomics in antibody-based biotherapeutics using either their native or aggregated form. Antibody-target immune complexes have been detected in patients with ADA and are thought to play a role in ADA development by enhancing the presentation of CD4+ T-cell epitopes at the surface of antigen presenting cells (APCs). The aim of this study was to investigate the effect of biotherapeutic antibody-target immune complexes on the HLAII peptide presentation of biotherapeutics in human primary monocyte-derived dendritic cells (DCs). The trimeric tumor necrosis factor (TNF) and its biotherapeutic antagonists infliximab (INFL), adalimumab (ADAL), and a single armed Fab' were used as a model system. The HLAII immunopeptidome of DCs loaded with antagonists or their immune complexes with TNF was analyzed by trapped ion mobility time-of-flight mass spectrometry (timsTOF MS) leading to the identification of ~ 12,000 unique HLAII-associated peptides per preparation. Anti-TNF sequences were detected at a median of 0.3% of the total immunopeptidome, against a majority background of peptides from endogenous and media-derived proteins. TNF antagonist presentation spanned the variable and constant regions in a widespread manner in both light and heavy chains, consistent with previously discovered HLAII peptides. This investigation extends the collection of observed HLAII peptides from anti-TNF biotherapeutics to include sequences that at least partially span the complementary determining regions (CDRs), such as the LCDR1 for both INFL and ADAL. Although antagonist presentation varied significantly across donors, peptides from both bivalent antagonists INFL and ADAL were more highly presented relative to the Fab'. While TNF immune complexes did not alter overall HLAII presentation, a moderate increase in presentation of a subset of peptide clusters was observed in the case of INFL-TNF, which included HCDR2, HCDR3 and LCDR2 sequences.

Evidence for intermolecular domain exchange in the Fab domains of dimer and oligomers of an IgG1 monoclonal antibody.

Recombinant protein therapeutics have become increasingly useful in combating human diseases, such as cancer and those of genetic origin. One quality concern for protein therapeutics is the content and the structure of the aggregated proteins in the product, due to the potential immunogenicity of these aggregates. Collective efforts have led to a better understanding of some types of protein aggregates, and have revealed the diversity in the structure and cause of protein aggregation. In this work we used a broad range of analytical techniques to characterize the quinary structure (complexes in which each composing unit maintains native quaternary structure) of the stable non-covalent dimer and oligomers of a monoclonal IgG1λ antibody. The results supported a mechanism of intermolecular domain exchange involving the Fab domains of 2 or more IgG molecules. This mechanism can account for the native-like higher order (secondary, tertiary and disulfide bonding) structure, the stability of the non-covalent multimers, and the previously observed partial loss of the antigen-binding sites without changing the antigen-binding affinity and kinetics of the remaining sites (Luo et al., 2009, mAbs 1:491). Furthermore, the previously observed increase in the apparent affinity to various Fcγ receptors (ibid), which may potentially promote immunogenicity, was also explained by the quinary structure proposed here. Several lines of evidence indicated that the formation of multimers by the mechanism of intermolecular domain exchange took place mostly during expression, not in the purified materials. The findings in this work will advance our knowledge of the mechanisms for aggregation in therapeutic monoclonal antibodies.

Dimers and multimers of monoclonal IgG1 exhibit higher in vitro binding affinities to Fcgamma receptors.

The in vitro binding of monomeric, dimeric and multimeric forms of monoclonal IgG1 molecules, designated mAb1 and mAb2, to the extracellular domains of Fcgamma receptors RI, RIIA and RIIIB were investigated using a surface plasmon resonance (SPR) based biosensor technique. Stable noncovalent and covalent dimers of mAb1 and mAb2, respectively, were isolated from CHO cell expressed materials. The dissociation constants of monomeric mAb1 and mAb2 were determined to be 1 nM for the FcgammaRI-binding and 6-12 microM for the FcgammaRIIA- and FcgammaRIIIB-binding. Dimeric mAb1 and mAb2 exhibited increased affinities, by 2-3 fold for FcgammaRI and 200-800 fold for FcgammaRIIA and FcgammaRIIIB. Further increases in binding were observed when the antibodies formed large immune complexes with multivalent antigens, but not in a linear relation with size. The binding properties of monomeric mAb2 were identical with and without a bound monovalent antigen, indicating that antigen-binding alone does not induce measurable change in binding of antibodies to Fcgamma receptors. Dimerization is sufficient to show enhancement in the receptor binding. Given the wide distribution of the low-affinity Fcgamma receptors on immune effector cells, the increased affinities to aggregated IgG may lead to some biological consequences, depending on the subsequent signal transduction events. The SPR-based in vitro binding assay is useful in evaluating Fcgamma receptor binding of various species in antibody-based biotherapeutics.

Characterization and function of MYPT2, a target subunit of myosin phosphatase in heart.

Characterization of cardiac MYPT2 (an isoform of the smooth muscle phosphatase [MP] target subunit, MYPT1) is described. Several features of MYPT2 and MYPT1 were similar, including: a specific interaction with the catalytic subunit of type 1 phosphatase, delta isoform (PP1cdelta); interaction of MYPT2 with the small heart-specific MP subunit; interaction of the C-terminal region of MYPT2 with the active form of RhoA; phosphorylation by Rho-kinase at an inhibitory site, Thr646 and thiophosphorylation at Thr646 inhibited activity of the MYPT2-PP1cdelta complex. MYPT2 activated PP1cdelta activity, using light chains from smooth and cardiac muscle, by reducing K(m) and increasing k(cat). The extent of activation (k(cat)) was greater than for MYPT1 and could reflect distinct N-terminal sequences in the two MYPT isoforms. Adenovirus-mediated gene transfer of MYPT2 and PP1cdelta reduced the phosphorylation level of cardiac light chains following stimulation with A23187. Overexpression of MYPT2 and PP1cdelta blocked the angiotensin II-induced sarcomere organization in cultured cardiomyocytes. Electron microscopy indicated locations of MYPTs, at, or close to, the Z-line, the A band and mitochondria. Similarity of the two MYPT isoforms suggests common enzymatic mechanisms and regulation. Cardiac myosin is a substrate for the MYPT2 holoenzyme, but the Z-line location raises the possibility of other substrates.

[Study of biological characteristics of the CD(34)(+) CD(59)(+) and CD(34)(+) CD(59)(-) cells from PNH patients' bone marrow].

OBJECTIVE: To explore the characteristics of CD(34)(+) CD(59)(+) cells from paroxysmal nocturnal hemoglobinuria(PNH) patients' bone marrow and the possible reasons of hematopoietic clonal dominance of PNH clones. METHODS: CD(34)(+) CD(59)(+) and CD(34)(+) CD(59)(-) cells from PNH patients and CD(34)(+) cells from normal control were selected from the bone marrow mononuclear cells by means of immunomagnetic microbead-flow cytometry two step sorting method undergone ex vivo expansion in liquid culture for two weeks and performed semisolid cultures before and after expansion. RESULTS: (1) Cultivation for seven days was the optimum for ex vivo expansion of PNH CD(34)(+) CD(59)(+) cells and normal CD(34)(+) cells, both cell populations remained CD(59) positive after expansion. (2) Normal CD(34)(+) cells had higher capacities of proliferation and expansion, and stronger potential to survival than that of both PNH CD(34)(+) CD(59)(+) and PHN CD(34)(+) CD(59)(-) cells. (3) In terms of semisolid culture, there was no significant difference in the yields of CFU formation between CD(34)(+) CD(59)(+) and CD(34)(+) CD(59)(-) cells. (4) In liquid culture with combinations of hematopoietic factors SCF + IL-3 + IL-6 + FL + Tpo or SCF + IL-3 + IL-6 + FL + Tpo + Epo, there was no significant difference in the capabilities of survival, proliferation and expansion between CD(34)(+) CD(59)(+) and CD(34)(+) CD(59)(-) cells; but with combination of SCF + IL-3 + IL-6 + FL + Tpo + Epo + GM-CSF, CD(34)(+) CD(59)(-) cells had better proliferation and expansion capacities and stronger potential to survival than that of CD(34)(+) CD(59)(+) cells. CONCLUSIONS: (1) Normal CD(34)(+) cells had better proliferation, expansion capacities and stronger potential to survival than that of PNH CD(34)(+) CD(59)(+)cells. (2) In semisolid and liquid culture with hematopoietic factor combinations, there was no significant difference in the capabilities of survival, proliferation and expansion between CD(34)(+) CD(59)(+) and CD(34)(+) CD(59)(-) cells. It was suggested that CD(34)(+) CD(59)(-) cells had no clonal hemotopoiesis dominance. GM-CSF might be one of the reasons for PHN clones to possess clonal hematopoiesis dominance.

[Application of double immunomagnetic positive sorting to ex vivo expansion of marrow CD34(+)CD59(+) cells from patients with paroxysmal nocturnal hemoglobinuria].

Since flow cytometry was not feasible for sorting a huge amount of cells for clinical use, the method of double immunomagnetic positive sorting was used for selection of CD34(+)CD59(+) cells from bone marrow mononuclear cells in patients with paroxysmal nocturnal hemoglobinuria (PNH), which laid the groundwork for clinical ABMT/APBSCT of patients with PNH. Immunomagnetic positive selection was used for two times, the microbeads were removed from the CD34(+) cells selected firstly by means of overnight culture, then the sufficient CD34(+)CD59(+) cells were used for ex vivo expansion. The results showed that the survival, proliferation and colony-forming units of the selected CD34(+)CD59(+) cells by double immunomagnetic positive sorting had no significant difference as compared with that of CD34(+)CD59(+) cells selected by flow cytometry technique. It is suggested that the double immunomagnetic positive sorting promotes the use for separation and purification hematopoietic stem/progenitor cells and other cells with double or multiple markers cells for autologous hematopoietic stem cell transplantation in PNH patients.

[Ex vivo expansion of CD34(+) CD59(+) cells from bone marrow of paroxysmal nocturnal hemoglobinuria patients].

OBJECTIVE: To study the separation, purification and ex vivo expansion of CD(34)(+) CD(59)(+) cells from patients with paroxysmal nocturnal hemoglobinuria (PNH), and explore the new treatment for the PNH patients. METHODS: CD(34)(+) CD(59)(+) cells were selected from the bone marrow mononuclear cells of PNH patients by means of immunomagnetic microbead-flow cytometry two step sorting method, followed by ex vivo expansion of the cells with combination of hematopoietic factors for two weeks. RESULTS: The best combination for the ex vivo expansion was SCF + IL-3 + IL-6 + FL + Tpo + Epo, and the seventh day was the most suitable time for the best harvest when the CD(34)(+) CD(59)(+) cells were 22.42 +/- 3.73 fold expanded. After ex vivo expansion, the cells remained CD(59) positive and potent capacity of colony formation, but their potentialities to multilineage differentiation were decreased. CONCLUSION: The present study shows that ex vivo expansion of CD(34)(+) CD(59)(+) cells from PNH patients might promise the possibility of performing ABMT or APBSCT clinincally for the patients.

[Proliferative capacity of the isolated single CD(34)(+) glycosylphosphatidylinesitol-anchored (GPI) protein negative and positive hematopoietic cells in paroxysmal nocturnal hemoglobinuria].

OBJECTIVES: To investigate the stroma-independent growth ability, multilineage differentiation and expansion of the single hematopoietic stem/progenitor cell from patients with paroxysmal nocturnal hematoglobinuria (PNH). METHOD: The CD(34)(+) CD(59)(+) and CD(34)(+) CD(59)(-) cells from PNH patients and CD(34)(+) CD(59)(+) cells from normal volunteers were sorted as each single cell into a well of 96 well culture plates containing culture medium supplemented with SCF, IL-3, Epo, GM-CSF, G-CSF, IL-6, Tpo and Flt-3 ligand. RESULTS: (1) Single PNH CD(34)(+) CD(59)(-) cell had a higher capacities for plating efficiency, colony (>/= 50 cells) formation and cell expansion than that of the PNH CD(34)(+) CD(59)(+) cells (P < 0.05); (2) Both the single CD(34)(+) CD(59)(-) cells from PNH patients and the single CD(34)(+) CD(59)(+) cells from normal controls had similar capacities for cell plating efficiency and colony and large colony formation. The PNH CD(34)(+) CD(59)(-) cells had a lower average cell production and cell expansion capacity. (3) The single CD(34)(+) CD(59)(+) cells from both PNH patients and normal controls showed the same capacities for cell plating efficiency and colony formation. The PNH CD(34)(+) CD(59)(+) cells exhibited much lower capacity for large colony formation, average cell production and total cell expansion. (4) A diminished secondary colony formation ability was also observed in the PNH CD(34)(+) CD(59)(+) and CD(34)(-) CD(59)(-) clones. CONCLUSION: The single PNH CD(34)(+) CD(59)(-) cells had growth advantage over the single PNH CD(34)(+) CD(59)(+) cells to some extent, but they both had impaired growth abilities as compared with CD(34)(+) cells from normal volunteers.

[Comparison of capabilities of survival, proliferation and expansion between CD34+CD59+ cells from patients with PNH and CD34+ cells from normal control].

OBJECTIVE: To explore in vitro expansion of CD34+CD59+ cells from patients with PNH, and compare the capabilities of survival, proliferation and expansion between CD34+CD59+ cells from patients with PNH and CD34+ cells from normal control. METHODS: CD34+CD59+ cells from patients with PNH and CD34+ cells from normal control were selected from the bone marrow mononuclear cells by means of two-step sorting method with immunomagnetic microbead-flow cytometry, then underwent in vitro expansion for two weeks and semi-solid culture in vitro before and after expansion. RESULTS: (1) CD34+CD59+ cells from patients with PNH can be expanded effectively in vitro, and the biggest expansion of CD34+CD59+ cells was about 23.49 fold on the 7th day. (2) There were some similar characteristics between CD34+CD59+ cells from patients with PNH and CD34+ cells from normal control, such as: the best combination of hematopoietic factors for in vitro expansion was SCF+ IL-3 + IL-6 + FL + Tpo + Epo, and the seventh day was the most suitable in course of 4-14 days for in vitro expansion, and after in vitro expansion, the cells remained CD59 positive and strong capability of performing colony-forming. (3) CD34+ cells from normal control had better proliferation, expansion and stronger potential to survive than CD34+CD59+ cells from patients with PNH. CONCLUSIONS: (1) In vitro expansion of CD34+CD59+ cells from patients with PNH can be performed. The present study showed the possibility of performing ABMT or APBSCT clinically for patients with PNH. (2) There were some similar characteristics between CD34+CD59+ cells from patients with PNH and CD34+ cells from normal control, but the latter had better proliferation, expansion and stronger potential to survive than the former. CD34+CD59+ cells from patients with PNH were not completely normal cells.

[GPI-Pr Deficiency and Apoptosis of PNH Granulocytes]

To study the relationship of Glycosyl phosphatidylinositol anchored proteins (GIP-Pr) and apoptosis of paroxysmal nocturnal hemoglobinuria (PNH) cells, we isolated peripheral granulocytes from 10 patients with PNH and 10 normal controls and measured apoptosis induced by serum starvation. The FCM analysis of phosphotidylserine (ps) externalization in granulocytes was determined using Annexin-V-FLUOS labeling. After the cells were induced for apoptosis in serum-free medium for 20 hours, the percentage of externalization was 78.6% in normal control cells but 39.5% in PNH cells. The results of FCM analysis of PI stained granulocytes showed that the PI positive rate was 51.5% in control cells and 30.2% in PNH cells. The gel electrophoresis analysis of DNA fragmentation all indicate that PNH granulocytes were relatively resistant to apoptosis as compared with normal controls. This resistance to apoptosis might not be related to the percentage of CD59 deficient granulocytes.