Objectives: Sepsis, a life-threatening organ dysfunction caused by a dysregulated host response to infection, is a leading cause of death and disability among children worldwide. Identifying sepsis in pediatric patients is difficult and can lead to treatment delay. Our objective was to assess the host proteomic response to infection utilizing an aptamer-based multiplexed proteomics approach to identify novel serum protein changes that might help distinguish between pediatric sepsis and infection-negative systemic inflammation and hence can potentially improve sensitivity and specificity of the diagnosis of sepsis over current clinical criteria approaches. Design: Retrospective, observational cohort study. Setting: PICU and cardiac ICU, Seattle Children's Hospital, Seattle, WA. Patients: A cohort of 40 children with clinically overt sepsis and 30 children immediately postcardiopulmonary bypass surgery (infection-negative systemic inflammation control subjects) was recruited. Children with sepsis had a confirmed or suspected infection, two or more systemic inflammatory response syndrome criteria, and at least cardiovascular and/or pulmonary organ dysfunction. Interventions: None. Measurements and Main Results: Serum samples from 35 of the sepsis and 28 of the bypass surgery subjects were available for screening with an aptamer-based proteomic platform that measures 1,305 proteins to search for large-scale serum protein expression pattern changes in sepsis. A total of 111 proteins were significantly differentially expressed between the sepsis and control groups, using the linear models for microarray data (linear modeling) and Boruta (decision trees) R packages, with 55 being previously identified in sepsis patients. Weighted gene correlation network analysis helped identify 76 proteins that correlated highly with clinical sepsis traits, 27 of which had not been previously reported in sepsis. Conclusions: The serum protein changes identified with the aptamer-based multiplexed proteomics approach used in this study can be useful to distinguish between sepsis and noninfectious systemic inflammation.

An amendment to this paper has been published and can be accessed via the original article.

Anti-CD83 Ab capable of Ab-dependent cellular cytotoxicity can deplete activated CD83(+) human dendritic cells, thereby inhibiting CD4 T cell-mediated acute graft-versus-host disease. As CD83 is also expressed on the surface of activated B lymphocytes, we hypothesized that anti-CD83 would also inhibit B cell responses to stimulation. We found that anti-CD83 inhibited total IgM and IgG production in vitro by allostimulated human PBMC. Also, Ag-specific Ab responses to immunization of SCID mice xeno-grafted with human PBMC were inhibited by anti-CD83 treatment. This inhibition occurred without depletion of all human B cells because anti-CD83 lysed activated CD83(+) B cells by Ab-dependent cellular cytotoxicity and spared resting (CD83(-)) B cells. In cultured human PBMC, anti-CD83 inhibited tetanus toxoid-stimulated B cell proliferation and concomitant dendritic cell-mediated CD4 T cell proliferation and expression of IFN-gamma and IL-17A, with minimal losses of B cells (<20%). In contrast, the anti-CD20 mAb rituximab depleted >80% of B cells but had no effect on CD4 T cell proliferation and cytokine expression. By virtue of the ability of anti-CD83 to selectively deplete activated, but not resting, B cells and dendritic cells, with the latter reducing CD4 T cell responses, anti-CD83 may be clinically useful in autoimmunity and transplantation. Advantages might include inhibited expansion of autoantigen-or alloantigen-specific B cells and CD4 T cells, thus preventing further production of pathogenic Abs and inflammatory cytokines while preserving protective memory and regulatory cells.

Objectives: SeptiCyte Lab (Immunexpress, Seattle, WA), a molecular signature measuring the relative expression levels of four host messenger RNAs, was developed to discriminate critically ill adults with infection-positive versus infection-negative systemic inflammation. The objective was to assess the performance of Septicyte Lab in critically ill pediatric patients.Design: Prospective observational study.Setting: Pediatric and Cardiac ICUs, Seattle Children's Hospital, Seattle, WA.Patients: A cohort of 40 children with clinically overt severe sepsis syndrome and 30 children immediately postcardiopulmonary bypass surgery was recruited. The clinically overt severe sepsis syndrome children had confirmed or highly suspected infection (microbial culture orders, antimicrobial prescription), two or more systemic inflammatory response syndrome criteria (including temperature and leukocyte criteria), and at least cardiovascular +/- pulmonary organ dysfunction.Interventions: None (observational study only).Measurements and Main Results: Next-generation RNA sequencing was conducted on PAXgene blood RNA samples, successfully for 35 of 40 (87.5%) of the clinically overt severe sepsis syndrome patients and 29 of 30 (96.7%) of the postcardiopulmonary bypass patients. Forty patient samples (+/- 60% of cohort) were reanalyzed by reverse transcription-quantitative polymerase chain reaction, to check for concordance with next-generation sequencing results. Postcardiopulmonary bypass versus clinically overt severe sepsis syndrome descriptors included the following: age, 7.3 +/- 5.5 versus 9.0 +/- 6.6 years; gender, 41% versus 49% male; Pediatric Risk of Mortality, version III, 7.0 +/- 4.6 versus 8.7 +/- 6.4; Pediatric Logistic Organ Dysfunction, version II, 5.1 +/- 2.2 versus 4.8 +/- 2.8. SeptiCyte Lab strongly differentiated postcardiopulmonary bypass and clinically overt severe sepsis syndrome patients by receiver operating characteristic curve analysis, with an area-under-curve value of 0.99 (95% CI, 0.96-1.00). Equivalent performance was found using reverse transcription-quantitative polymerase chain reaction. There was no significant correlation between the score produced by the SeptiCyte Lab test and measures of illness severity, immune compromise, or microbial culture status.Conclusions: SeptiCyte Lab is able to discriminate clearly between clinically well-defined and homogeneous postcardiopulmonary bypass and clinically overt severe sepsis syndrome groups in children. A broader investigation among children with more heterogeneous inflammation-associated diagnoses and care settings is warranted.

The presence of activated CMRF-44+ (Lau, 2007, Transplantation, 83:839) and CCR5+ CD16+ (Shahin, 2013, Transplantation, 96:753) dendritic cells (DC) predicted for acute graft versus host disease (GVHD) after clinical allogeneic hematopoietic cell transplantation (alloHCT). We are developing anti-DC monoclonal antibodies (mAb) as novel immunosuppressive agents and have shown that polyclonal rabbit anti-human CD83 antibodies prevented GVHD in mouse and human preclinical alloHCT models. A second generation human mAb 3C12C has been evaluated as a novel therapeutic (Seldon et al, in prep) and its ability to deplete activated DC and preserve protective T cell responses was investigated. Control human IgG1 (trastazumab) and 3C12C mAb were tested in human peripheral blood mononuclear cell (PBMC) cultures and in allogeneic mixed lymphocyte cultures (alloMLC) for their ability to deplete DC. The antibody was tested in a human xenogeneic TBI and anti-NK conditioned SCID mouse model of GVHD. Survival, clinical scoring and histology were used to document the effect of 3C12C compared to the control mAb. Flow cytometry and immunohistology were used to investigate CD83 induction and the effect of 3C12C on human DC and T cell biology. 3C12C but not the control mAb reduced the number of CD83+ DC in PBMC cultures. The 3C12C mAb reduced T cell proliferation in the alloMLC but did not affect Cytomegalovirus specific CD8+ T cell numbers. Human cells were identified in the liver, lung, spleen and gut of the control mAb treated PBMC transplanted mice, which developed histological GVHD d+8-13. Human DC were activated by d+2 and expressed the CMRF-44 activation marker plus CD83, CD80 and CD86. Treatment with 3C12CmAb eliminated CD83+ CMRF44+ DC early post-transplant and reduced T cell activation in terms of CD25, CD69 and CD137 and cytokine expression but maintained Treg cells. A potential therapeutic human anti-CD83 mAb appears to induce significant immunosuppression, associated with the depletion of CMRF-44+ activated DC, whilst preserving T cell numbers.

Current immunosuppressive/anti-inflammatory agents target the responding effector arm of the immune response and their nonspecific action increases the risk of infection and malignancy. These effects impact on their use in allogeneic haematopoietic cell transplantation and other forms of transplantation. Interventions that target activated dendritic cells (DCs) have the potential to suppress the induction of undesired immune responses (for example, graft versus host disease (GVHD) or transplant rejection) and to leave protective T-cell immune responses intact (for example, cytomegalovirus (CMV) immunity). We developed a human IgG(1) monoclonal antibody (mAb), 3C12, specific for CD83, which is expressed on activated but not resting DC. The 3C12 mAb and an affinity improved version, 3C12C, depleted CD83(+) cells by CD16(+) NK cell-mediated antibody-dependent cellular cytotoxicity, and inhibited allogeneic T-cell proliferation in vitro. A single dose of 3C12C prevented human peripheral blood mononuclear cell-induced acute GVHD in SCID mouse recipients. The mAb 3C12C depleted CMRF-44(+)CD83(bright) activated DC but spared CD83(dim/-) DC in vivo. It reduced human T-cell activation in vivo and maintained the proportion of CD4(+) FoxP3(+) CD25(+) Treg cells and also viral-specific CD8(+) T cells. The anti-CD83 mAb, 3C12C, merits further evaluation as a new immunosuppressive agent in transplantation.

Introduction: CD83 is an important marker of activated dendritic cells (DC) but it is also expressed on other immune cells. Polyclonal anti-CD83 antibody depletes activated DC and prevents human peripheral blood mononuclear cell (PBMC) induced xenogeneic graft versus host disease (GVHD) in immunosuppressed SCID mice (J Exp Med 2009;206;387). We therefore generated a potential therapeutic human anti-CD83 mAb (3C12C), which had similar efficacy and T cell sparing effects in the same model (Leukemia 2015; in press). To investigate the specific immunosuppressive effect of 3C12C further, we undertook a comprehensive analysis of CD83 expression and its glycosylation pattern on various immune cell populations and tested the effect of 3C12C on T cell function using preclinical models, including a human CD83 (hCD83) knock in (KI) mouse. Methods: A panel of mouse and recombinant mAbs to hCD83 were used to analyse its expression by flow cytometry on resting and activated healthy donor PBMC. The expression of potential CD83 splice variants was examined by PCR. T cell expression was examined by flow cytometry and confocal microscopy after PHA, CD3/CD28 beads and allogeneic mixed leukocyte reaction (alloMLR) culture. Control human IgG1 (trastuzumab) and 3C12C mAbs were tested (0.125mg d-1) in a xenogeneic model of GVHD utilizing human PBMC transplanted into total body irradiation and anti-NK conditioned SCID mice. The genetically engineered hCD83 KI mouse was shown to be immune-competent and used to test the effect of 3C12C on LPS activated DC and T cells. Results: There were distinct CD83 splice variants (full length CD83, splicing variant CD83a, CD83b and CD83c) in different immune cells. CD83 glycosylation status also differed with high glycosylation required for surface expression on activated DC, whereas its expression on activated B cells and monocytes was resistant to de-glycosylation. Increases in CD83 expression on T cells occurred early with different kinetics, underlining the distinct signal pathway involved. The 3C12C mAb reduced T cell proliferation in the alloMLR but did not affect cytomegalovirus (CMV) or influenza (Flu) specific CD8+T cell numbers. Treatment with 3C12C prevented GVHD in human PBMC transplanted SCID mice, which otherwise developed histological GVHD between d8-13. Human DC were activated by d2 and expressed the CMRF-44 activation marker plus CD83, CD80 and CD86. Treatment with 3C12C mAb eliminated CD83+ CMRF44+ DC early post-transplant and reduced T cell activation. Further studies, established CMV and Flu specific T cells were retained and responded to antigen by IFNg production. Furthermore, Treg numbers were preserved. The 3C12C mAb depleted LPS activated DC in hCD83 KI mice in experiments performed prior to commencing transplant studies. Conclusion: These findings suggest that the potential therapeutic human anti-CD83 mAb induced significant immune suppression, by depletion of activated DC and consequential modulation of T cell activation. The reduction in allo/xeno activated T cells may result in part from a direct effect of anti-CD83 on early T cell responses. This apparently selective immunosuppressive effect preserves anti-viral T cell immunity and Treg pathways, suggesting that 3C12C merits further investigation as a novel agent for GVHD prophylaxis. Disclosures Hart:DendroCyte BioTech Pty Ltd: Equity Ownership. Clark:DendroCyte BioTech Pty Ltd: Equity Ownership.

Purpose of study: Having showed that polyclonal rabbit anti-CD83 antibodies, targeting activated dendritic cells (DC), induced T cell sparing immunosuppression in mouse and human preclinical models and that, activated CMRF-44+ DC and CCR5+ CD16+DC predicted for acute graft versus host disease (GVHD) after clinical allogeneic haematopoietic cell transplant, we developed a human anti-CD83 monoclonal antibody (mAb) as a novel therapeutic. Methods: A human scFv (3C12) specific for human CD83 was isolated from a phage library. Affinity maturation and engineering produced the fully recombinant human IgG1 mAb 3C12C. The 3C12C mAb was tested in a human xenogeneic SCID mouse model of GVHD and clinical scores, survival and histology used to document its effect compared to the control mAb (trastuzumab). Flow cytometry and immunohistology were used to document its effect on human DC and T cell biology. Results: The mAb 3C12C had greater affinity and in vitro antibody dependent cellular cytotoxicity against CD83 positive targets. It suppressed in vitro allo-immune responses. A dose of 0.125 mg administered 3 hr prior to transplanting TBI and anti-NK conditioned SCID mouse recipients with 50 x 106 human PBMC prevented acute GVHD and was as effective as purified polyclonal anti-human CD83 antibody. Reductions in activated human DC were documented but human T cell subsets were preserved with an altered (? regulatory) T cell derived cytokine profile. Conclusion: A potential therapeutic mAb targeting CD83 induced significant immunosuppression, whilst preserving T cell numbers. Ongoing studies will clarify how much of this effect relates to the predicted elimination of activated DC. The results to date have encouraged us to plan for a phase 1 study of 3C12C. DISCLOSURES:Coley, A.: Employee, Employed by CRC-BT, who has licensed 3C12.

Dispelling the linear view of intellectual property protection in biotechnology, intellectual property (IP) and patents are almost synonymous in the biotechnology industry. In this innovation-intensive industry, it is unsurprising that patents are the foremost means of protection, since they provide (at least) 20 years exclusivity. However, a recent seven-year international study challenged the preconception that patenting leads to heightened innovation (International Expert Group on Biotechnology 2008). The following analysis uses case studies to demonstrate that leading companies take a holistic approach to IP management.

Antibody-binding fragments (Fab) are generated from whole antibodies by treatment with papain and can be separated from the Fc component using Protein-A affinity chromatography. Commercial kits are available, which facilitate the production and purification of Fab fragments; however, the manufacturer fails to report that this method is inefficient for antibodies with V(H)3 domains as a result of the intrinsic variable region affinity for Protein-A. A commercially available, modified Protein-A resin (MabSelect SuRe) has been engineered for greater stability. Here, we report that an additional consequence of the modified resin is the ability to purify V(H)3 family Fab fragments, which cannot be separated effectively from other components of the papain digest by traditional Protein-A resin. This improvement of a commonly used procedure is of significance, as increasingly, therapeutic antibodies are being derived from human origin, where V(H)3 is the most abundantly used variable region family.

Recombinant monoclonal antibodies currently dominate the protein biologics marketplace. The path from target antigen discovery and screening, to a recombinant therapeutic antibody can be time-consuming and laborious. We describe a set of expression vectors, termed mAbXpress, that enable rapid and sequence-independent insertion of antibody variable regions into human constant region backbones. This method takes advantage of the In Fusion cloning system from Clontech, which allows ligation-free, high-efficiency insertion of the variable region cassette without the addition of extraneous amino acids. These modular vectors simplify the antibody reformatting process during the preliminary evaluation of therapeutic or diagnostic candidates. The resulting constructs can be used directly for transient or amplifiable, stable expression in mammalian cells. The effectiveness of this method was demonstrated by the creation of a functional, fully human anti-human CD83 monoclonal antibody.