Molecular defects in T- and B-cell primary immunodeficiency diseases

More than 120 inherited primary immunodeficiency diseases have been discovered in the past five decades, and the precise genetic defect in many of these diseases has now been identified. Increasing understanding of these molecular defects has considerably influenced both basic and translational research, and this has extended to many branches of medicine. Recent advances in both diagnosis and therapeutic modalities have allowed these defects to be identified earlier and to be more precisely defined, and they have also resulted in more promising long-term outcomes. The prospect of gene therapy continues to be included in the armamentarium of treatment considerations, because these conditions could be among the first to benefit from gene-therapy trials in humans.     

Mechanisms of virus-induced immune suppression

The recent demonstration that the acquired immune deficiency syndrome (AIDS) is caused by a retrovirus that affects humans has given rise to widespread concern about the immunosuppressive properties of viruses in general. A wide variety of viruses have been shown to be able to compromise immune function. Sometimes immunosuppression results from the pathologic processes that viruses are able to induce. In other instances virus-induced immune derangements may themselves be responsible for the onset of pathologic change. In some cases a single infectious viral agent may be able to modulate several immunologic mechanisms simultaneously. This review discusses some of the various complex mechanisms through which viral infections can alter the function of the immune system.     

Mucosal modulation of immune responses to heat shock proteins in autoimmune arthritis

Induction of oral tolerance to antigens that are targets of self-reactive immune responses is an attractive approach to antigen-specific immune therapy of autoimmune diseases. Oral tolerization has indeed proven to be safe and effective in amelioration of autoimmune diseases in animal models. In humans, results have been somewhat controversial. The emphasis given to clinical outcome rather than to immunomodulation, and the difficulty in identifying appropriate candidate antigens contribute to the controversy. Heat shock proteins are promising targets for immune intervention. Immune reactivity to heat shock proteins has indeed been correlated with autoimmune arthritis in animal models, and abnormal immune responses to heat shock proteins have been described in human arthritis as well. Despite significant recent progress, little is known at a molecular level regarding the mechanisms which are responsible for a switch from autoimmunity to tolerance in humans. This is particularly true with respect to sequential analysis of several molecular and immunologic markers during both the course and treatment of disease. Novel approaches are currently under way to fill the gaps. We will briefly detail here the experience gained to date, and identify some of the avenues which future research will explore.     

Increased immune gene expression and immune cell infiltration in high-grade astrocytoma distinguish long-term from short-term survivors

Survival in the majority of high-grade astrocytoma (HGA) patients is very poor, with only a rare population of long-term survivors. A better understanding of the biological factors associated with long-term survival in HGA would aid development of more effective therapy and survival prediction. Factors associated with long-term survival have not been extensively studied using unbiased genome-wide expression analyses. In the current study, gene expression microarray profiles of HGA from long-term survivors were interrogated for discovery of survival-associated biological factors. Ontology analyses revealed that increased expression of immune function-related genes was the predominant biological factor that positively correlated with longer survival. A notable T cell signature was present within this prognostic immune gene set. Using immune cell-specific gene classifiers, both T cell-associated and myeloid linage-associated genes were shown to be enriched in HGA from long-term versus short-term survivors. Association of immune function and cell-specific genes with survival was confirmed independently in a larger publicly available glioblastoma gene expression microarray data set. Histology was used to validate the results of microarray analyses in a larger cohort of long-term survivors of HGA. Multivariate analyses demonstrated that increased immune cell infiltration was a significant independent variable contributing to longer survival, as was Karnofsky/Lansky performance score. These data provide evidence of a prognostic anti-tumor adaptive immune response and rationale for future development of immunotherapy in HGA.     

T-cell glucocorticoid receptor is required to suppress COX-2-mediated lethal immune activation

Glucocorticoids, acting through the glucocorticoid receptor, potently modulate immune function and are a mainstay of therapy for treatment of inflammatory conditions, autoimmune diseases, leukemias and lymphomas. Moreover, removal of systemic glucocorticoids, by adrenalectomy in animal models or adrenal insufficiency in humans, has shown that endogenous glucocorticoid production is required for regulation of physiologic immune responses. These effects have been attributed to suppression of cytokines, although the crucial cellular and molecular targets remain unknown. In addition, considerable controversy remains as to whether glucocorticoids are required for thymocyte development. To assess the role of the glucocorticoid receptor in immune system development and function, we generated T-cell-specific glucocorticoid receptor knockout mice. Here we show that the T-cell is a critical cellular target of glucocorticoid receptor signaling, as immune activation in these mice resulted in significant mortality. This lethal activation is rescued by cyclooxygenase-2 (COX-2) inhibition but not steroid administration or cytokine neutralization. These studies indicate that glucocorticoid receptor suppression of COX-2 is crucial for curtailing lethal immune activation, and suggest new therapeutic approaches for regulation of T-cell-mediated inflammatory diseases.     

Humoral immune responses to AAV gene therapy in the ocular compartment

Viral vectors can be utilised to deliver therapeutic genes to diseased cells. Adeno-associated virus (AAV) is a commonly used viral vector that is favoured for its ability to infect a wide range of tissues whilst displaying limited toxicity and immunogenicity. Most humans harbour anti-AAV neutralising antibodies (NAbs) due to subclinical infections by wild-type virus during infancy and these pre-existing NAbs can limit the efficiency of gene transfer depending on the target cell type, route of administration and choice of serotype. Vector administration can also result in de novo NAb synthesis that could limit the opportunity for repeated gene transfer to diseased sites. A number of strategies have been described in preclinical models that could circumvent NAb responses in humans, however, the successful translation of these innovations into the clinical arena has been limited. Here, we provide a comprehensive review of the humoral immune response to AAV gene therapy in the ocular compartment. We cover basic AAV biology and clinical application, the role of pre-existing and induced NAbs, and possible approaches to overcoming antibody responses. We conclude with a framework for a comprehensive strategy for circumventing humoral immune responses to AAV in the future.     

Molecular evolution of the vertebrate immune system

Adaptive immunity is unique to the vertebrates, and the molecules involved (including immunoglobulins, T cell receptors and the major histocompatibility complex molecules) seem to have diversified very rapidly early in vertebrate history. Reconstruction of gene phylogenies has yielded insights into the evolutionary origin of a number of molecular systems, including the complement system and the major histocompatibility complex (MHC). These analyses have indicated that the C5 component of complement arose by gene duplication prior to the divergence of C3 and C4, which suggests that the alternative complement pathway was the first to evolve. In the case of the MHC, phylogenetic analysis supports the hypothesis that MHC class II molecules evolved before class I molecules. The fact that the MHC-linked proteasome components that specifically produce peptides for presentation by class I MHC appear to have originated before the separation of jawed and jawless vertebrates suggests that the MHC itself may have been present at this time. Immmune system gene families have evolved by gene duplication, interlocus recombination and (in some cases) positive Darwinian selection favoring diversity at the amino acid level.     

What disorders of cortical development tell us about the cortex: one plus one does not always make two

The unique size and complexity of the human cerebral cortex are achieved via a long and precisely regulated developmental process controlling neurogenesis, neuronal migration and differentiation. Traditionally, disorders of cortical development have been classified on the basis of the most obvious defects in one of these developmental steps. However, the more we learn about the cellular biological roles of genes that are essential for cortical development, the more we realize that these functions map onto molecular processes, but not so cleanly onto anatomical processes. Essential genes might be involved in both proliferation and migration as well as differentiation, reflecting roles for underlying molecular mechanisms in different phases of development and causing a stunning variety of cortical defects.     

Reconstructing an ancestral mammalian immune supercomplex from a marsupial major histocompatibility complex

The first sequenced marsupial genome promises to reveal unparalleled insights into mammalian evolution. We have used theMonodelphis domestica (gray short-tailed opossum) sequence to construct the first map of a marsupial major histocompatibility complex (MHC). The MHC is the most gene-dense region of the mammalian genome and is critical to immunity and reproductive success. The marsupial MHC bridges the phylogenetic gap between the complex MHC of eutherian mammals and the minimal essential MHC of birds. Here we show that the opossum MHC is gene dense and complex, as in humans, but shares more organizational features with non-mammals. The Class I genes have amplified within the Class II region, resulting in a unique Class I/II region. We present a model of the organization of the MHC in ancestral mammals and its elaboration during mammalian evolution. The opossum genome, together with other extant genomes, reveals the existence of an ancestral “immune supercomplex” that contained genes of both types of natural killer receptors together with antigen processing genes and MHC genes.     

Genetic, cellular and immune approaches to disease therapy: past and future

Advances in immunology and molecular genetics have accelerated our understanding of the genetic and cellular basis of many diseases. At the same time, remarkable progress in recombinant DNA technology has enabled the development of molecular and cellular treatments for infectious diseases, inherited disorders and cancer. This Perspective is intended to give a sample of the progress over the past ten years in cellular, genetic and immune therapy of disease. During this time, monoclonal antibody technology and cellular transplantation have begun to come of age in biomedicine. Innovations in gene delivery have not only catalyzed the nascent field of human gene therapy, but may also ultimately impact human health by advancing recombinant vaccine technology.     

Signal transduction in cells of the immune system in microgravity

Life on Earth developed in the presence and under the constant influence of gravity. Gravity has been present during the entire evolution, from the first organic molecule to mammals and humans. Modern research revealed clearly that gravity is important, probably indispensable for the function of living systems, from unicellular organisms to men. Thus, gravity research is no more or less a fundamental question about the conditions of life on Earth. Since the first space missions and supported thereafter by a multitude of space and ground-based experiments, it is well known that immune cell function is severely suppressed in microgravity, which renders the cells of the immune system an ideal model organism to investigate the influence of gravity on the cellular and molecular level. Here we review the current knowledge about the question, if and how cellular signal transduction depends on the existence of gravity, with special focus on cells of the immune system. Since immune cell function is fundamental to keep the organism under imnological surveillance during the defence against pathogens, to investigate the effects and possible molecular mechanisms of altered gravity is indispensable for long-term space flights to Earth Moon or Mars. Thus, understanding the impact of gravity on cellular functions on Earth will provide not only important informations about the development of life on Earth, but also for therapeutic and preventive strategies to cope successfully with medical problems during space exploration.     

Innate immune response to adenoviral vectors is mediated by both Toll-like receptor-dependent and -independent pathways

Recombinant adenoviral vectors have been widely used for gene therapy applications and as vaccine vehicles for treating infectious diseases such as human immunodeficiency virus disease. The innate immune response to adenoviruses represents the most significant hurdle in clinical application of adenoviral vectors for gene therapy, but it is an attractive feature for vaccine development. How adenovirus activates innate immunity remains largely unknown. Here we showed that adenovirus elicited innate immune response through the induction of high levels of type I interferons (IFNs) by both plasmacytoid dendritic cells (pDCs) and non-pDCs such as conventional DCs and macrophages. The innate immune recognition of adenovirus by pDCs was mediated by Toll-like receptor 9 (TLR9) and was dependent on MyD88, whereas that by non-pDCs was TLR independent through cytosolic sensing of adenoviral DNA. Furthermore, type I IFNs were pivotal in innate and adaptive immune responses to adenovirus in vivo, and type I IFN blockade diminished immune responses, resulting in more stable transgene expression and reduction of inflammation. These findings indicate that adenovirus activates innate immunity by its DNA through TLR-dependent and -independent pathways in a cell type-specific fashion, and they highlight a critical role for type I IFNs in innate and adaptive immune responses to adenoviral vectors. Our results that suggest strategies to interfere with type I IFN pathway may improve the outcome of adenovirus-mediated gene therapy, whereas approaches to activate the type I IFN pathway may enhance vaccine potency.     

Species comparison of anatomical and functional immune system development

The components of the immune system have not been traditionally emphasized as potential target organs in standard developmental and reproductive toxicity (DART) protocols. A number of workshops have been organized in recent years to examine scientific questions that underlie developmental immunotoxicity tests, and the interpretation of results as they relate to human risk assessment. A key question that must be addressed is to determine the most appropriate species and strains to model the developing human immune system. The objective of this review is to compare the anatomical and functional development of the immune system in several species important to either preclinical studies for drug development or safety assessments for chemicals, with what is known in humans. The development of the immune system in humans will be compared to what is known in mice, rats, dogs and nonhuman primates.     

Design principles of adaptive immune systems

Both jawless vertebrates, such as lampreys and hagfish, and jawed vertebrates (encompassing species as diverse as sharks and humans) have an adaptive immune system that is based on somatically diversified and clonally expressed antigen receptors. Although the molecular nature of the antigen receptors and the mechanisms of their assembly are different, recent findings suggest that the general design principles underlying the two adaptive immune systems are surprisingly similar. The identification of such commonalities promises to further our understanding of the mammalian immune system and to inspire the development of new strategies for medical interventions targeting the consequences of faulty immune functions.     

Gene therapy and retinitis pigmentosa: advances and future challenges.

It may be possible, one day, to use gene therapy to treat diseases whose genetic defects have been discerned. Because many genes responsible for inherited eye disorders within the retina have been identified, diseases of the eye are prime candidates for this form of therapy. The eye also has the advantage of being highly accessible with altered immunological properties, important considerations for easy delivery of virus and avoidance of systemic immune responses. Currently, adenovirus, adeno-associated virus and lentivirus have been used to successfully transfer genetic material to retinal pigment epithelium and photoreceptor cells. By harnessing therapeutic genes to these viruses, researchers have been able to demonstrate rescue in rodent models of retinitis pigmentosa, providing evidence that this form of therapy can be effective in delaying photoreceptor cell death. Future challenges include confirming therapeutic effects in animal models with eyes more anatomically similar to those of humans and demonstrating long-term rescue with minimal toxicity.     

Two cases of digital defects in Macaca mulatta infants and a survey of the literature

Although congenital digital defects, particularly polydactyly, have been reported frequently in humans, their occurrence in rhesus macaques is relatively rare. We observed two cases of spontaneous digital defects in male rhesus monkey infants recently born at the California Regional Primate Research Center. One infant exhibited bilateral postaxial polydactyly and the other infant had bilateral oligodactyly with unilateral phalangeal duplication. In this report, we present the clinical/pathological details of these cases as well as discuss the embryology of normal and abnormal limb development. We will also summarize a variety of spontaneous and experimentally induced digital defects that have been reported in several nonhuman primate species.     

Targeting unique tumor antigens and modulating the cytokine environment may improve immunotherapy for tumors with immune escape mechanisms

Cytotoxic T-cell responses to shared tumor antigens have been characterized for several tumor types, and the MHC-associated peptides that comprise these antigens have been defined at a molecular level. These provide new tools to determine whether immune responses can be generated with these tumor antigens, and there are data to suggest that such immune responses can be generated. However, it is also clear that tumor cells can evade immune responses directed against some shared antigens, by downregulating expression of MHC or of the antigenic protein(s), as well as by more active methods such as secretion of immunosuppressive cytokines. Awareness of these mechanisms of immune escape will help to direct development of the next generation of tumor vaccines. Targeting unique antigens and modulating the cytokine environment likely will be critical to comprehensive vaccine systems in the future. Received: 20 March 1999 / Accepted: 3 May 1999     

Early OspA immune complex formation in animal models of Lyme disease

Infection with Borrelia burgdorferi, the cause of Lyme disease, has been accompanied by a puzzling delayed antibody (Ab) response to B. burgdorferi antigens (Ags) including the abundant organism-specific outer surface proteins, such as the 31-kD OspA. In humans the response to nonspecific B. burgdorferi Ags has required 3-6 weeks. The response to OspA has rarely been detected by conventional methodology until months after infection, despite demonstrable T cell reactivity. Tick inoculation and low-dose intradermal inoculation animal models have been characterized by a comparable response to OspA. Using more sensitive biotin-avidin immunoblots and immune complex (IC) dissociation techniques, we demonstrated in humans that Ab to OspA is formed early but may remain at low levels or bound in IC. To see if this was a universal biologic response, animal models were analyzed by these methods. The results with mice, monkeys and rabbits show that IC Ab to OspA may be detected at the onset of infection. The data suggest that these animal models may be used to understand the immune response to B. burgdorferi and the pathogenesis of Lyme disease. With attention to unique B. burgdorferi Ags, these results are likely to have both clinical and diagnostic importance.