Rachel Eren

Monoclonal antibody HCV-AbXTL68 in patients undergoing liver transplantation for HCV: results of a phase 2 randomized study.

A randomized, double‐blind, dose‐escalation study evaluated the safety and efficacy of hepatitis C virus (HCV)‐AbXTL68, a neutralizing, high‐affinity, fully human, anti‐E2 monoclonal antibody, in 24 HCV‐positive patients undergoing liver transplantation. HCV‐AbXTL68 or placebo was administered at doses from 20‐240 mg as 2‐4 infusions during the first 24 hours after transplantation, followed by daily infusions for 6 days, weekly infusions for 3 weeks, and either 2 or 4 weekly infusions for 8 weeks. Serum concentrations of total anti‐E2 obtained during daily infusions of 120‐240 mg HCV‐AbXTL68 were 50‐200 μg/mL above concentrations in the placebo group. Median serum concentration of HCV RNA dropped below baseline in all groups immediately after transplantation. On day 2, median change from baseline in HCV RNA was −1.8 and −2.4 log in the 120‐mg and 240‐mg groups, respectively, compared with −1.5 log with placebo. The difference was lost after day 7 when the dosing frequency was reduced. The coincidence of increases in anti‐E2 with decreases in HCV RNA concentration indicate that the dose‐related changes in HCV RNA concentration were a result of HCV‐AbXTL68 administration in the 120‐ and 240‐mg groups. The overall incidence of nonfatal serious adverse events was higher with placebo (60%) vs. all active treatments combined (42%). In conclusion, HCV‐AbXTL68 may decrease serum concentrations of HCV RNA in patients after liver transplantation. Studies evaluating more frequent daily dosing at doses >120 mg are necessary to investigate sustained viral suppression in this population. Liver Transpl 12:1381–1389. 2006.

Human monoclonal antibodies specific to hepatitis B virus generated in a human/mouse radiation chimera: the Trimera system.

An approach to develop fully human monoclonal antibodies in a human/mouse radiation chimera, the Trimera system, is described. In this system, functional human lymphocytes are engrafted in normal strains of mice which are rendered immuno‐incompetent by lethal total body irradiation followed by radioprotection with severe combined immunodeficient (SCID) mouse bone marrow. Following transplantation, human lymphocytes colonize murine lymphatic organs and secrete human immunoglobulins. We have established this system as a tool to develop fully human monoclonal antibodies, and applied it for the generation of monoclonal antibodies specific for hepatitis B virus surface antigen. A strong memory response to hepatitis B surface antigen was elicited in Trimera engrafted with lymphocytes from human donors positive for antibodies to hepatitis B surface antigen. The human specific antibody fraction in the Trimera was 102–103‐fold higher as compared with that found in the donors. Spleens were harvested from Trimera mice showing high specific‐antibody titres and cells were fused to a human–mouse heteromyeloma fusion partner. Several stable hybridoma clones were isolated and characterized. These hybridomas produce high‐affinity, IgG, anti‐hepatitis B surface antigen antibodies demonstrating the potential of the Trimera system for generating fully human monoclonal antibodies. The biological function and the neutralizing activity of these antibodies are currently being tested.

Age-related changes in the capacity of bone marrow cells to differentiate in thymic organ cultures

The capacity of the bone marrow to give rise to T cells in advanced age was studied in vitro by reconstituting fetal thymic lobes from 14-day C57BL/Ka (Thy-1.1) mice with bone marrow cells from old (24-month) or young (3-month) C57BL/6 (Thy-1.2) mice. The use of these congenic strains enabled distinguishing between donor and host contribution to the developing T cells. We found that bone marrow cells from aged mice maintained their capacity to reconstitute fetal thymic explants and to differentiate into various T-cell subsets as assessed by distinct T-cell-specific surface markers (Thy-1, Lyt-1, Lyt-2, and L3T4) and functions (concanavalin A-induced proliferative and cytotoxic responses). However, when mixtures of old and young bone marrow cells reconstituted fetal thymic explants, the cells of old mice were less efficient than those of young in their capacity to give rise to T cells. These results indicate that bone marrow cells from aged mice can reconstitute the thymus and differentiate into T cells; however, their reconstituting capacity is inferior to that of bone marrow cells from young mice.

Ontogeny of T cells: development of pre-T cells from fetal liver and yolk sac in the thymus microenvironment

The patterns of development of T cells from the very early stem cells that settle in the embryonic thymus have been studied. For this purpose, mouse embryonic thymuses (14 days) depleted of thymocytes were reconstituted with hemopoietic stem cells from fetal liver (FL) and yolk sac (YS) and T-cell development was followed in vitro in organ culture. It was found that cells derived from FL and YS of 10- to 14-day-old embryos were capable of reconstituting depleted thymic explants and exhibiting membrane markers in a pattern similar to that of thymocytes developing in intact thymic explants. Furthermore, these cells responded to concanavalin A in proliferative and cytotoxic assays as measured by limiting-dilution analysis. Thus, lymphohemopoietic stem cells emerging in the embryo prior to thymus lymphoid development are capable of differentiation in the thymus microenvironment into T cells, identified by phenotypic markers and functions that are characteristic of cells developing in the intact embryonic thymus.

Quantitative analysis of bone marrow thymic progenitors in young and aged mice

Our studies on the capacity of bone marrow (BM) to generate T lymphocytes in aging have revealed that under the competitive conditions of thymic reconstitution, cells of aged mice are significantly inferior to those of the young. The present study was designed to further investigate the basis of this age-related change. Two mechanisms were considered: (a) The potential of BM-derived T cell precursors from aged mice to proliferate and differentiate in the thymic microenvironment is impaired. (b) The frequency of T cell precursors is reduced in BM of aged mice, thus affecting their ability to compete efficiently in reconstituting the thymus. These possibilities were studied in vitro by colonizing thymocyte-depleted fetal thymic lobes with BM cells from aged (24-month) and young (3-month) C57BL/6 mice. By determining the cell cycle duration of BM-derived cells which have seeded the thymic lobes, we found that cells originating from aged mice proliferate in the thymus at the same rate as those from young mice. Reconstitution with limiting numbers of BM cells indicated that the frequency of thymic progenitors in the BM is significantly reduced in aged as compared to young mice. We thus conclude that aging is associated with a quantitative reduction in the frequency of thymic progenitors in the BM.

Novel mechanism of antibodies to hepatitis B virus in blocking viral particle release from cells

Antibodies are thought to exert antiviral activities by blocking viral entry into cells and/or accelerating viral clearance from circulation. In particular, antibodies to hepatitis B virus (HBV) surface antigen (HBsAg) confer protection, by binding circulating virus. Here, we used mathematical modeling to gain information about viral dynamics during and after single or multiple infusions of a combination of two human monoclonal anti‐HBs (HepeX‐B) antibodies in patients with chronic hepatitis B. The antibody HBV‐17 recognizes a conformational epitope, whereas antibody HBV‐19 recognizes a linear epitope on the HBsAg. The kinetic profiles of the decline of serum HBV DNA and HBsAg revealed partial blocking of virion release from infected cells as a new antiviral mechanism, in addition to acceleration of HBV clearance from the circulation. We then replicated this approach in vitro, using cells secreting HBsAg, and compared the prediction of the mathematical modeling obtained from the in vivo kinetics. In vitro, HepeX‐B treatment of HBsAg‐producing cells showed cellular uptake of antibodies, resulting in intracellular accumulation of viral particles. Blocking of HBsAg secretion also continued after HepeX‐B was removed from the cell culture supernatants. Conclusion: These results identify a novel antiviral mechanism of antibodies to HBsAg (anti‐HBs) involving prolonged blocking of the HBV and HBsAg subviral particles release from infected cells. This may have implications in designing new therapies for patients with chronic HBV infection and may also be relevant in other viral infections. (HEPATOLOGY 2010;)

Treatment of Recent-Onset Type 1 Diabetic Patients With DiaPep277: Results of a Double-Blind, Placebo-Controlled, Randomized Phase 3 Trial

OBJECTIVE To evaluate safety and efficacy of DiaPep277 in preserving β-cell function in type 1 diabetic patients. RESEARCH DESIGN AND METHODS DIA-AID 1 is a multinational, phase 3, balanced-randomized, double-blind, placebo-controlled, parallel-group clinical study. Newly diagnosed patients (N = 457, aged 16–45 years) were randomized to subcutaneous injections of DiaPep277 or placebo quarterly for 2 years. The primary efficacy end point was the change from baseline in the area under the glucagon-stimulated C-peptide curve. Secondary end points were the change from baseline in mixed-meal stimulated C-peptide secretion and in fasting C-peptide and achieving target HbA1c ≤7% (≤53 mmol/mol). Partial remission (target HbA1c on insulin ≤0.5 units/kg/day) and hypoglycemic event rate were exploratory end points. RESULTS DiaPep277 was safe and well tolerated. Significant preservation of C-peptide secretion was observed in the DiaPep277-treated group compared with the placebo (relative treatment effects of 23.4%, P = 0.037, and 29.2%, P = 0.011, in the modified intent-to-treat [mITT] and per-protocol [PP] populations, respectively). The mixed-meal stimulation failed to distinguish between the groups. There was a trend toward efficacy in fasting C-peptide levels, though not statistically significant. Significantly more DiaPep277-treated than placebo-treated patients maintained target HbA1c (mITT 56% versus 44%, P = 0.03; PP 60% versus 45%, P = 0.0082) and entered partial remission (mITT 38% versus 29%, P = 0.08; PP 42% versus 30%, P = 0.035). DiaPep277 treatment reduced the relative hypoglycemic event risk (mITT by 20%; PP by 28%). CONCLUSIONS DiaPep277 safely contributes to preservation of β-cell function and to improved glycemic control in patients with type 1 diabetes.

Therapy with anti-flagellin A monoclonal antibody limits Pseudomonas aeruginosa invasiveness in a mouse burn wound sepsis model

BACKGROUND The aim of this study was to evaluate the effect of an anti-flagellin sub-type monoclonal antibody (anti-fla-a) on Pseudomonas aeruginosa infection in a mouse burn model and to assay bacterial dissemination and invasiveness. METHODS After immediate post-burn infection with P. aeruginosa, mortality and morbidity (daily weight changes) were monitored in mice treated with anti-fla-a as compared to untreated mice. Bacterial dissemination and invasiveness were monitored by bacterial counts at the burn site and spleen. Three different timing regimens for anti-fla-a treatment were studied: (a) prophylaxis (pre-infection), (b) therapeutic (post-infection), and (c) combined mode. RESULTS Combined regimen of anti-fla-a markedly improved survival of mice infected with P. aeruginosa from 6% to 96% (p<0.0001), similar to treatment with Imipenem. Furthermore, a significant improvement in survival was obtained when anti-fla-a was given prior to (75% survival) or post-infection (50% survival). It reduced bacterial load in the spleen (p=0.01), preventing bacterial sepsis. CONCLUSION Anti-fla-a is effective in reducing mortality and morbidity in murine P. aeruginosa-infected burn model.

Oligonucleotide-assisted cleavage and ligation: a novel directional DNA cloning technology to capture cDNAs. Application in the construction of a human immune antibody phage-display library

The use of oligonucleotide-assisted cleavage and ligation (ONCL), a novel approach to the capture of gene repertoires, in the construction of a phage-display immune antibody library is described. ONCL begins with rapid amplification of cDNA ends to amplify all members equally. A single, specific cut near 5′ and/or 3′ end of each gene fragment (in single stranded form) is facilitated by hybridization with an appropriate oligonucleotide adapter. Directional cloning of targeted DNA is accomplished by ligation of a partially duplex DNA molecule (containing suitable restriction sites) and amplification with primers in constant regions. To demonstrate utility and reliability of ONCL, a human antibody repertoire was cloned from IgG mRNA extracted from human B-lymphocytes engrafted in Trimera mice. These mice were transplanted with peripheral blood lymphocytes from Candida albicans infected individuals and subsequently immunized with C.albicans glyceraldehyde-3-phosphate dehydrogenase (GAPDH). DNA sequencing showed that ONCL resulted in efficient capture of gene repertoires. Indeed, full representation of all VH families/segments was observed showing that ONCL did not introduce cloning biases for or against any VH family. We validated the efficiency of ONCL by creating a functional Fab phage-display library with a size of 3.3 × 1010 and by selecting five unique Fabs against GAPDH antigen.

Aging in the T Lymphocyte Compartment

A decline in the capacity of bone marrow cells to differentiate to T lymphocytes was found when cells from young and old donors were seeded onto an alymphoid fetal thymus. A step-by-step analysis of cell-cell interactions of the lymphohemopoietic cells and the thymic stroma indicated an effect of age on a variety of cell differentiation parameters. These included a decrease in the affinity of bone marrow cells to the stroma, and in their capacity to compete with the thymic lymphoid resident cells on colonization of the thymus. There was a significant decrease in the ability of cells of old donors to replicate sequentially within the thymic microenvironment. There was a reduced capacity of bone marrow cells from aging mice to express a developmental preference after seeding onto a syngeneic fetal thymus in a mixture with cells from allogeneic donors. We addressed the question whether the aging thymus contains increased levels of immature cells that fail to differentiate in the involuted thymic microenvironment by seeding thymocytes from young and old donors onto the fetal thymic stroma. The values of T cells that developed from the old donor inoculum were lower under these conditions. Our studies suggest that at least some of the manifestations of aging in the T cell compartment are related to developmentally programmed events in the lymphohemopoietic cell compartment.