Andrew J. T. George

The safety and side effects of monoclonal antibodies.

Monoclonal antibodies (mAbs) are now established as targeted therapies for malignancies, transplant rejection, autoimmune and infectious diseases, as well as a range of new indications. However, administration of mAbs carries the risk of immune reactions such as acute anaphylaxis, serum sickness and the generation of antibodies. In addition, there are numerous adverse effects of mAbs that are related to their specific targets, including infections and cancer, autoimmune disease, and organ-specific adverse events such as cardiotoxicity. In March 2006, a life-threatening cytokine release syndrome occurred during a first-in-human study with TGN1412 (a CD28-specific superagonist mAb), resulting in a range of recommendations to improve the safety of initial human clinical studies with mAbs. Here, we review some of the adverse effects encountered with mAb therapies, and discuss advances in preclinical testing and antibody technology aimed at minimizing the risk of these events.

Thymic involution with ageing: obsolescence or good housekeeping?

Abstract The thymus undergoes premature ageing in comparison with other organs of the immune system, with involution starting soon after birth and continuing throughout life. Does this reflect a failure of repair or is the process of adaptive value? Here, Andrew George and Mary Ritter apply a cost-benefit analysis, and conclude that the scaling down of this organ has been evolutionarily advantageous to our ancestors.

The WHO 2014 global tuberculosis report--further to go.

This article discusses how the 19th WHO global tuberculosis report 2014 provides an opportunity to think about the global tuberculosis strategy, and to assess just how much further effort is needed before global tuberculosis control can be achieved.

Inhibition of NF-κB and Oxidative Pathways in Human Dendritic Cells by Antioxidative Vitamins Generates Regulatory T Cells

Dendritic cells (DCs) are central to T cell immunity, and many strategies have been used to manipulate DCs to modify immune responses. We investigated the effects of antioxidants ascorbate (vitamin C) and α-tocopherol (vitamin E) on DC phenotype and function. Vitamins C and E are both antioxidants, and concurrent use results in a nonadditive activity. We have demonstrated that DC treated with these antioxidants are resistant to phenotypic and functional changes following stimulation with proinflammatory cytokines. Following treatment, the levels of intracellular oxygen radical species were reduced, and the protein kinase RNA-regulated, eukaryotic translation initiation factor 2α, NF-κB, protein kinase C, and p38 MAPK pathways could not be activated following inflammatory agent stimulation. We went on to show that allogeneic T cells (including CD4+CD45RO, CD4+CD45RA, and CD4+CD25− subsets) were anergized following exposure to vitamin-treated DCs, and secreted higher levels of Th2 cytokines and IL-10 than cells incubated with control DCs. These anergic T cells act as regulatory T cells in a contact-dependent manner that is not dependent on IL-4, IL-5, IL-10, IL-13, and TGF-β. These data indicate that vitamin C- and E-treated DC might be useful for the induction of tolerance to allo- or autoantigens.

Function of indoleamine 2,3‐dioxygenase in corneal allograft rejection and prolongation of allograft survival by over‐expression

Indoleamine 2,3‐dioxygenase (IDO) suppresses T cell responses by its action in catabolising tryptophan. It is important in maintenance of immune privilege in the placenta. We investigated the activity of IDO in the cornea, following corneal transplantation and the effect of IDO over‐expression in donor corneal endothelium on the survival of corneal allografts. IDO expression was analysed and functional activity was quantified in normal murine cornea and in corneas following transplantation as allografts. Low levels of IDO, at both mRNA and protein levels, was detected in the normal cornea, up‐regulated by IFN‐γ and TNF. Expression of IDO in cornea was significantly increased following corneal transplantation. However, inhibition of IDO activity in vivo had no effect on graft survival. Following IDO cDNA transfer, murine corneal endothelial cells expressed functional IDO, which was effective at inhibiting allogeneic T cell proliferation. Over‐expression of IDO in donor corneal allografts resulted in prolonged graft survival. While, on one hand, our data indicate that IDO may augment corneal immune privilege, up‐regulated IDO activity following cytokine stimulation may serve to inhibit inflammatory cellular responses. While increasing IDO mRNA expression was found in allogeneic corneas at rejection, over‐expression in donor cornea was found to significantly extend survival of allografts.

Activated polyamidoamine dendrimers, a non-viral vector for gene transfer to the corneal endothelium.

We investigated the efficiency of activated polyamidoamine dendrimers, a new class of nonviral vectors, to transfect rabbit and human corneas in ex vivo culture. In addition to assessing the expression of a marker gene we have demonstrated that this approach can be used to induce the production of TNF receptor fusion protein (TNFR-Ig), a protein with therapeutic potential. Whole thickness rabbit or human corneas were transfected ex vivo with complexes consisting of dendrimers and plasmids containing lacZ or TNFR-Ig genes. Following optimisation 6–10% of the corneal endothelial cells expressed the marker gene. Expression was restricted to the endothelium and was maximal after transfection with 18:1 (w/w) activated dendrimer:plasmid DNA ratio and culture for 3 days. The supernatant of corneas transfected with TNFR-Ig plasmid contained TNFR-Ig protein which was able to inhibit TNF-mediated cytotoxicity in a bioassay. We have therefore shown that activated dendrimers are an efficient nonviral vector capable of transducing corneal endothelial cells ex vivo. They may have applications in gene-based approaches aimed at prevention of corneal allograft rejection or in treatment of other disorders of corneal endothelium.

Cytokines, Chaos, and Complexity

Mathematical models will not replace laboratory experimentation, but they do have an important complementary role for understanding the complexities of the cytokine network and other biological systems. Such models cannot incorporate every component of the network, as the model itself would then be impossible to analyze. Rather, they should be considered as virtual laboratories in which numerical experiments can be performed that could not otherwise be undertaken. Such virtual experiments can deal with more parameters than in vitro or in vivo experimentation and can give insights not available through more conventional investigations. A dialogue between the two disciplines is required. The biologists should define the problem and provide quantitative information about the system from which a model can be constructed. Mathematical analysis of the model can then make predictions about the behavior of the biological system that can be tested in the laboratory. The more refined data obtained from these experiments can then be fed back into the model. By this iterative process, mathematics and biology can combine to give a deeper understanding of the cytokine network and other biological processes.∣∣To whom correspondence should be addressed (e-mail: rcallard@ich.ucl.ac.uk).

Adenovirus-mediated gene delivery to the corneal endothelium.

Genetic manipulation of donor cornea prior to transplantation has the potential to modulate the allogeneic response, as well as the endothelial cell function. This study examined the feasibility of gene transfer to corneal endothelial cells using replication-defective recombinant adenoviral vectors. Adult rabbits corneas were infected with recombinant adenovirus RAd35, containing the Escherichia coli beta-galactosidase (lacZ) gene. Localization of gene transfer was assessed by histochemical staining for beta-galactosidase and recombinant protein production was quantified by a soluble assay. In initial experiments, the efficiency of gene transfer and kinetics of expression were studied ex vivo, using organ culture of transfected corneas. Following coculture of whole corneal fragments with RAd35, high levels of gene expression were evident on days 107, diminishing after that time. Gene transfer was found to be almost entirely restricted to corneal endothelial cells, with scattered expression in epithelial cells. Following these ex vivo studies, genetically modified corneas were transplanted as orthotopic allografts in rabbits. Similar kinetics of gene expression were seen after transplantation as in the ex vivo experiment, with maximal levels of gene expression in endothelial cells on days 1-4 after grafting. Corneal function following transplantation was not affected by the gene transfer, with the corneas attaining clarity within 1 day of grafting, and thereafter showing the expected thinning on ultrasonic pachymetry. In the absence of any immunosuppression, no inflammation was evident in graft recipient eyes, with the exception of allograft rejection in 1 animal 23 days after grafting. In this study we show that gene transfer to nonreplicating corneal endothelial cells is feasible using recombinant adenovirus vectors, and so may have potential application in the setting of corneal transplantation.

Antibody targeted gene transfer to endothelium

One of the drawbacks of the currently available vectors for gene therapy is the lack of selectivity in gene delivery. We have therefore investigated a strategy to generate immunoliposomes to target non‐viral vectors to cell surface receptors on endothelium.

Corneal Transplantation: The Forgotten Graft

The most commonly performed transplant is that of the cornea, with 2292 corneal grafts performed in the UK in 2002–03, compared with 1775 renal transplants [ 1]. In the USA approximately 40 000 transplants are performed every year [ 2]. However this preponderance is not reflected in the amount of attention given to this transplanted tissue by the scientific community: for example up till now there have been no papers published in the American Journal of Transplantation that have cornea as a key or title word (as determined by a Medline search in December 2003). There are several reasons for this. The first is that corneal grafting is the province of ophthalmologists, who (with notable exceptions) are isolated from the transplant community. The second is that there is a widespread belief that, because of the existence of immune privilege, corneal grafts are not rejected and so there is no need for further research. As we will discuss later, this is incorrect. In this article we will seek to show that study of corneal transplantation is important in its own right, and also that it has lessons for those interested in other forms of allograft.