Use of monoclonal antibodies in human transplantation

Neo-vascularization-based therapeutic perspectives in advanced ovarian cancer

The process of angiogenesis is well described for its potential role in the development of normal ovaries, and physiological functions as well as in the initiation, progression, and metastasis of ovarian cancer (OC). In advanced stages of OC, cancer cells spread outside the ovary to the pelvic, abdomen, lung, or multiple secondary sites. This seriously limits the efficacy of therapeutic options contributing to fatal clinical outcomes. Notably, a variety of angiogenic effectors are produced by the tumor cells to initiate angiogenic processes leading to the development of new blood vessels, which provide essential resources for tumor survival, dissemination, and dormant micro-metastasis of tumor cells. Multiple proangiogenic effectors and their signaling axis have been discovered and functionally characterized for potential clinical utility in OC. In this review, we have provided the current updates on classical and emerging proangiogenic effectors, their signaling axis, and the immune microenvironment contributing to the pathogenesis of OC. Moreover, we have comprehensively reviewed and discussed the significance of the preclinical strategies, drug repurposing, and clinical trials targeting the angiogenic processes that hold promising perspectives for the better management of patients with OC.

Pneumocystis Pneumonia in Solid-Organ Transplant Recipients

Pneumocystis pneumonia (PCP) is well known and described in AIDS patients. Due to the increasing use of cytotoxic and immunosuppressive therapies, the incidence of this infection has dramatically increased in the last years in patients with other predisposing immunodeficiencies and remains an important cause of morbidity and mortality in solid-organ transplant (SOT) recipients. PCP in HIV-negative patients, such as SOT patients, harbors some specificity compared to AIDS patients, which could change the medical management of these patients. This article summarizes the current knowledge on the epidemiology, risk factors, clinical manifestations, diagnoses, prevention, and treatment of Pneumocystis pneumonia in solid-organ transplant recipients, with a particular focus on the changes caused by the use of post-transplantation prophylaxis.

Functional aspects of binding of monoclonal antibody DCN46 to DC-SIGN on dendritic cells

Dendritic cell (DC)-specific ICAM-3 grabbing nonintegrin (DC-SIGN) is a DC-specific antigen that plays an important role in the induction of primary immune responses as well as during HIV infection. In the present study, we analyzed the effect of binding of monoclonal antibody DCN46 to DC surface, expressed DC-SIGN on DC function. DC-SIGN antibody treated, immature DC were able to differentiate into mature DC and had the same capacity as untreated DC to induce primary and secondary immune responses. In combination with flow cytometric cell sorting, DC-SIGN antibody treatment of DC yielded highly pure and functional DC. Given the apparent lack of functional effect of monoclonal antibody DCN46 on DC, the latter antibody may prove useful for research on and clinical use of highly pure and functional DC.

Patterns of graft infiltration and cytokine gene expression during the first 10 days of kidney transplantation

Understanding of the events preceding acute cellular rejection of kidney transplants would be useful in the development of immunosuppressive strategies to prevent rejection. Information about these events in humans has been scarce, because of the lack of early, serial, biopsy samples. We took daily fine needle aspirates from kidney allografts for the first 10 days after transplant. Samples were analyzed by morphological cytology of graft-infiltrating cells, and reverse transcriptase-polymerase chain reaction for detection of interleukin (IL)-2, IL-4, IL-6, IL-10, and gamma-interferon gene expression. During the first 4 days, all of the grafts developed a low-grade monocyte-rich mononuclear cell infiltrate, accompanied by IL-10 gene expression. Thereafter, the infiltrates either remained stable or intensified. Of the 13 grafts with dense infiltrates, seven developed graft dysfunction. The remaining six did not, despite significant interstitial infiltrates. Both rejecting and nonrejecting dense infiltrates were associated with a biphasic pattern of IL-2 and gamma-interferon gene expression, preceding and accompanying lymphocytic graft infiltration. Grafts that did not develop dense infiltrates had no detectable IL-2 or gamma-interferon gene expression and did not suffer cellular rejection during the study period. The development of both rejecting and nonrejecting infiltrates was strongly associated with DR mismatches between donor and recipient. IL-2 and gamma-interferon gene expression are necessary, but not sufficient, for the development of acute cellular rejection in the first 10 days of kidney transplantation, and are more closely associated with the period leading up to rejection than with the period of graft dysfunction.

A randomized multicenter trial comparing leukocyte function-associated antigen-1 monoclonal antibody with rabbit antithymocyte globulin as induction treatment in first kidney transplantations

Adhesion molecules are involved in several steps in the immune response: leukocyte adhesion to the endothelium, transendothelial migration, cooperation between immunocompetent cells, and cytotoxicity. Leukocyte function-associated antigen-1 plays a central role among adhesion molecules. In a multicenter randomized open trial, we compared a monoclonal antibody directed against the alpha chain of LFA-1 (Oduli-momab; IMTIX/Pasteur Mérieux Sérums et Vaccins) with rabbit antithymocyte globulin (rATG; IMTIX/Pasteur Mérieux Sérums et Vaccins), as part of a quadruple sequential protocol in 101 patients receiving a first kidney transplant. Clinical tolerance of anti-LFA-1 mAb was better than that of rATG. Short-term rejection rates (< 15 days) were not significantly different (15% and 16% for anti-LFA-1 mAb and rATG, respectively). However, 11% of the anti-LFA-1 mAb patients experienced rejection during the first 10 days of the treatment course compared with none of the patients treated with rATG. The incidence and severity of acute rejection in the first 3 months was not significantly different between groups. Of the LFA-1 and rATG patients, 96% and 92% of the grafts, respectively, were functioning at 12 months. The incidence and severity of infection, whatever the origin, were comparable in both groups. In addition, it was observed that fewer patients required posttransplantation dialysis in the anti-LFA-1 mAb group (19%, vs. 35% for rATG), although the difference was not statistically significant. Altogether, the beneficial action of this monoclonal antibody on short-term renal function recovery makes it a useful tool in the management of renal patients undergoing kidney transplantation.

A new and simple method to study the role of soluble factors in antibody-mediated cell modulation

This paper describes an in vitro method to study how interactions between cell suspensions incubated in two culture compartments can occur by diffusion of small molecules through a dialysis membrane. This consists of in vitro cultures of a human PBMC suspension, divided into two parts separated by a dialysis membrane. In one of the cultures, a mitogenic monoclonal antibody (mAb) is added. The porosity of the membrane permits cytokines secreted by activated cells to pass while blocking the antibodies. As a model, PBMC from the same blood donor were divided into two parts and one portion was incubated with an anti-CD3 monoclonal antibody (OKT3 Ortho-Cilag), known to induce IL-2 secretion whereas the other was enclosed in a dialysis bag without antibody. After a 4 day incubation, the cells incubated outside the bag proliferate and secrete cytokines which pass through the membrane and induce cell proliferation inside the bag. This method could complement the currently used methods for the analysis of antibody-mediated cell activation.

Muromonab CD3: a reappraisal of its pharmacology and use as prophylaxis of solid organ transplant rejection

The murine monoclonal antibody muromonab CD3 (OKT3) is directed against the CD3 antigen on peripheral human T cells and effectively blocks all T cell function. Prophylaxis with muromonab CD3 (5mg intravenously once daily for 10 to 14 days) as induction therapy together with corticosteroids, azathioprine and delayed cyclosporin (sequential therapy) optimises early graft function by delaying the potentially nephrotoxic and hepatotoxic effects of cyclosporin until graft function is established. Although clinical data are limited (by inconsistencies in trial design and trial size), prophylactic muromonab CD3-based sequential therapy is significantly more effective than standard triple therapy in the prophylaxis of allograft rejection in renal and hepatic, but not cardiac, transplant recipients. Benefits are particularly notable in patients with delayed graft function. No significant between-treatment differences in patient survival have been observed. The overall efficacy of muromonab CD3- and polyclonal-based prophylactic regimens appears to be similar, although results vary between investigators and confirmation is needed. An anti-interleukin-2 monoclonal antibody-based prophylactic regimen improved graft and patient survival compared with muromonab CD3-based prophylaxis in hepatic transplant recipients. Antimuromonab CD3 antibodies may develop; however, muromonab CD3 may be successfully reused in patients with low titres. Preliminary pharmacoeconomic data suggest that mean drug costs are greater with quadruple immunosuppressive regimens containing muromonab CD3, antithymocyte globulin (ATG) or antilymphocyte globulin (ALG) than with triple therapy. Drug costs with prophylactic muromonab CD3-based regimens were similar or greater than those with polyclonal-based protocols. The first doses of muromonab CD3 are associated with the 'cytokine-release syndrome'. More severe first-dose events include aseptic meningitis, intragraft thromboses, seizures and potentially fatal pulmonary oedema. The incidence and/or severity of cytomegalovirus infection with prophylactic muromonab CD3 based immunosuppression is similar to or greater than that with triple therapy and ATG- or ALG-based regimens. However, the risk of infection and also the observed increase in lymphoproliferative disorders appears to be related to the degree of immunosuppression rather than to the drug itself Thus, sequential muromonab CD3-based therapy is more effective than standard triple therapy (in renal and hepatic transplant recipients) and appears to be similar to that of polyclonal-based regimens in the prophylaxis of transplant rejection. Although the routine use of prophylactic muromonab CD3 in low-risk patients with primary graft function does not appear to be justified, prophylactic muromonab CD3-based therapy has a role in patients at high risk of rejection.

Tumor necrosis factor-induced hepatic DNA fragmentation as an early marker of T cell-dependent liver injury in mice

BACKGROUND & AIMS

The injection of mice with anti-CD3 monoclonal antibody causes activation of T lymphocytes and leads to a lethal shock syndrome. The aim of this study was to investigate T cell-dependent, cytokine-mediated target cell death that leads to organ injury.

METHODS

Anti-CD3 monoclonal antibody or staphylococcal enterotoxin B was injected into mice sensitized by D-galactosamine. Liver injury was assessed biochemically and histologically, and circulating cytokines were determined.

RESULTS

Mice sensitized with D-galactosamine developed severe liver injury within 8 hours after injection of anti-CD3 monoclonal antibody or staphylococcal enterotoxin B. Apoptotic bodies and chromatin condensation were detectable 5 hours after anti-CD3 monoclonal antibody challenge. DNA fragmentation in the liver preceded the increase in plasma alanine aminotransferase activity. Anti-CD3 monoclonal antibody induced the release of tumor necrosis factor and other cytokines. Passive immunization against tumor necrosis factor or pretreatment with immunosuppressive drugs protected mice from liver injury. Liver injury associated with apoptotic cell death and DNA fragmentation was also noted in D-galactosamine-sensitized mice injected with staphylococcal enterotoxin B.

CONCLUSIONS

Tumor necrosis factor-induced hepatic apoptosis followed by necrosis may represent a general pathomechanism of T-cell shock models using D-galactosamine-sensitized mice.

Monoclonal antibodies--immunotherapy for the critically ill

Monoclonal antibodies (mAb) have revolutionised many areas of medicine, particularly research and diagnostics. Murine, human and humanized mAb have all been developed. The most important clinical applications to date have been in the fields of transplantation and oncology. Experimental and limited clinical trials suggest mAb are emerging as a new therapeutic strategy in the critically ill. Antibodies against a variety of bacteria or their products are potentially useful in gram-positive and gram-negative shock. Anti-cytokine and anti-neutrophil adhesion molecule mAb may be effective not only in septic shock but also in other conditions associated with acute inflammation and cytokine release, e.g., acid aspiration, ischaemia/reperfusion injury (myocardial infarction, haemorrhagic shock, aortic aneurysm repair). Antibodies inhibiting neutrophil adhesion may also be efficacious in asthma, pulmonary fibrosis, meningitis and cerebral malaria. The use of these and other mAb in intensive care is an exciting prospect and future clinical studies will determine the extent of their role in the management of the critically ill.

In vivo administration to rhesus monkeys of a CD4-specific monoclonal antibody capable of blocking AIDS virus replication

Monoclonal antibodies (mAbs) specific for CD4 are potent inhibitors of HIV replication in vitro. These agents may be useful prophylactically or in chronic HIV infection if they can be administered without inducing immunosuppression. In the present study, we explored the safety of a CD4-specific murine mAb in rhesus monkeys. The mAb 5A8, which binds to domain 2 of the CD4 molecule, inhibits AIDS virus replication noncompetitively at a postvirus binding step. This antibody, which had a similar affinity for rhesus monkey and human CD4 cells, efficiently inhibited in vitro replication of both HIV-1 and the simian immunodeficiency virus of macaques. A single 3-mg/kg injection of mAb 5A8 into normal rhesus monkeys coated all circulating and lymph node CD4 cells for 4-6 days. CD4 cells were not cleared from circulation nor was the CD4 molecule modulated from the lymphocyte surface. In fact, administration of mAb 5A8 resulted in an approximately one-to twofold increase in absolute number of circulating CD4 cells. Repeated administration in normal rhesus monkeys resulted in CD4 lymphocyte coating with mAbs for > 9 days without CD4 cell clearance or modulation. While coated with mAbs, PBLs of these monkeys retained normal in vitro proliferative responses to mitogens and these animals generated normal humoral responses in vivo to tetanus toxoid. Loss of cell coating with mAbs in normal monkeys corresponded to the appearance of anti-mouse immunoglobulin antibodies. Thus, administration of certain anti-CD4 mAbs capable of blocking HIV replication can achieve coating of the entire CD4 cell pool in rhesus monkeys without inducing significant cell loss or immunosuppression.

Future directions in transplantation

Transplantation has become an established treatment for many diseases where organ replacement is the best or perhaps the only option, but it has not reached its full potential. The use of fetal and infant donors raises ethical problems, as does the use of other species for xenografts. Legal problems include the drafting of appropriate legislation to maximise the donor pool. Economic limitations are imposed by the competition for funding with other areas of medicine. Transplantation of cells, tissues, and organs is rapidly being expanded. Exciting progress in experimental models of new methods of immunosuppression may lead to immunological tolerance of grafts so that chronic non-specific immunosuppression becomes a thing of the past. Xenografts will probably have to become a major source of organs as transplantation is extended to more patients and a broader range of diseases. Genetic engineering may alleviate the problem of supply in some instances; free cell transplants of genetically modified cells are being studied.