Normal ICOS, ICOSL and AID Alleles in Danish Patients with Common Variable Immunodeficiency

Epidemiology and pathophysiology of malignancy in common variable immunodeficiency?

Common variable immunodeficiency (CVID) is a diagnostic category of primary immunodeficiency (PID) which may present with heterogeneous disorders including recurrent infections, autoimmunity, granulomatous diseases, lymphoid and other types of malignancies. Generally, the incidence of malignancy in CVID patients is around 1.5-20.7% and usually occurs during the 4th-6th decade of life. Non-Hodgkin lymphoma is the most frequent malignancy, followed by epithelial tumours of stomach, breast, bladder and cervix. The exact pathological mechanisms for cancer development in CVID are not fully determined; however, several mechanisms including impaired genetic stability, genetic predisposition, immune dysregulation, impaired clearance of oncogenic viruses and bacterial infections, and iatrogenic causes have been proposed to contribute to the high susceptibility of these patients to malignancies.

AICDA single nucleotide polymorphism in common variable immunodeficiency and selective IgA deficiency

BACKGROUND

Primary antibody deficiencies (PADs) are a heterogeneous group of disorders, characterised by increased susceptibility to recurrent bacterial infections. Common variable immunodeficiency (CVID) is the most important PAD from the clinical point of view and selective IgA deficiency (IgAD) is the most common PAD. However, the underlying gene defect in both is still unknown. As a recent study in Europe showed an association between a single nucleotide polymorphism (SNP) of AICDA gene with PADs, this study was performed to evaluate such an association in Iranian patients.

METHODS

Fifty-eight patients with PAD, including 39 CVID and 19 IgAD, as well as 34 healthy volunteers, were enrolled in this study. Genotyping was done in all groups for an intronic SNP in AICDA (rs2580874), using real-time PCR genotyping assay.

RESULTS

The less frequent genotype of AICDA in IgAD patients was AA, seen in 10.5% of the patients, which was much lower than the 30.8% in CVID patients and 38.2% in the controls. However, these differences were not significant. Indeed the GG genotype in the patients with PADs was seen in 20.7%, compared to 8.8% in the controls without any significant difference.

CONCLUSIONS

There was no significant association between the previously reported genetic variant of AICDA gene and the development of CVID or IgAD, but further multi-center studies are also needed.

Hyper-IgM, Neutropenia, Mild Infections and Low Response to Polyclonal Stimulation: Hyper-IgM Syndrome or Common Variable Immunodeficiency?

A young woman presenting respiratory infections, polyarthritis, severe neutropenia, and increased serum IgM was treated with Intravenous Immunoglobulin (IVIG) with good clinical and laboratory outcome followed by a loss of efficacy. The increased serum IgM associated to recurrent infections and autoimmune manifestations suggested the diagnosis of a hyper–IgM syndrome (HIGMs). The frequency of peripheral T cells, the expression of CD40 on the patients' B cells and CD40L on T cells and the Activation-Induced cytidine Deaminase (AID) and Uracyl-DNA glycosylase (UNG) at mRNA level was comparable to controls. In contrast, the frequency of B cells was one half of the healthy control and all cells showed an atypical phenotype. Although AID and UNG were normal, class-switch recombination was not very efficient because circulating switched memory were reduced and, once stimulated with CpG, generated less antibody-secreting cells than controls. An increase in serum B Lymphocytes stimulator (BLyS) was also found. The patient presented a peculiar clinical and immunological phenotype fitting for many aspects of both HIGM4 and Common Variable Immunodeficiency (CVID). These findings underline the need to better explore the complex link between these two diseases.

Altered spectrum of somatic hypermutation in common variable immunodeficiency disease characteristic of defective repair of mutations

Pathogenic common variable immunodeficiency diseases (CVID) are genetic, usually inherited diseases for which a limited number of genetic defects have been implicated. As CVID presents with a wide range of clinical characteristics, there are likely diverse and for the most part unidentified genetic causes. In some individuals, defects in somatic hypermutation (SHM) have been suggested as the underlying cause of CVID. To address the mechanisms of SHM defects in CVID, we conducted a comprehensive mutational analysis of immunoglobulin heavy chain sequences from CVID patients. We identified several remarkably specific alterations in the spectra of SHM in comparison to healthy individuals. We provide evidence that some CVID cases are associated with defective repair of AID-induced mutations by the DNA mismatch repair (MMR) machinery. Our findings together with reports of increased chromosomal radiosensitivity and associated lymphoproliferative disorders amongst CVID patients, suggest that altered DNA damage repair may be a cause of CVID.

No association between AICDA 7888 C/T polymorphism, Helicobacter pylori seropositivity, and the risk of atrophic gastritis and gastric cancer in Japanese

BACKGROUND

The aberrant expression of activation-induced cytidine deaminase (AICDA) was reportedly induced in gastric epithelial cells infected with cytotoxin-associated gene A (cagA)-positive Helicobacter pylori, resulting in the accumulation of alterations in the TP53 tumor suppressor gene in gastric cells. We investigated the association of the AICDA 7888 C/T polymorphism with H. pylori infection and the risk of gastric cancer and atrophic gastritis in Japanese subjects.

METHODS

The study subjects were 583 histologically diagnosed gastric cancer patients (cases) and 1637 age- and sex-frequency-matched control outpatients, who visited Aichi Cancer Center Hospital from the years 2001 to 2005. In the controls, serum anti-H. pylori IgG antibody and pepsinogens were measured to evaluate H. pylori infection and atrophic gastritis, respectively. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by a logistic model.

RESULTS

H. pylori seropositivity in the controls was not significantly associated with the AICDA 7888 C/T genotypes. Among the H. pylori seropositive control subjects, the age and sex-adjusted ORs of atrophic gastritis were not statistically significant: 0.84 (95% CI, 0.62-1.13) for C/T, 0.82 (95% CI, 0.56-1.21) for T/T, and 0.83 (95% CI, 0.63-1.11) for C/T+T/T, relative to the C/C genotype. The age- and sex-adjusted ORs of gastric cancer relative to atrophic gastritis were also not statistically significant, at 1.17 (95% CI 0.89-1.54), 1.21 (95% CI, 0.85-1.71), and 1.18 (95% CI, 0.91-1.53), respectively. The OR of gastric cancer cases compared with the whole cohort of control subjects was also not significant.

CONCLUSION

The hypothetical association of the AICDA 7888 C/T polymorphism with the risk of gastric cancer or gastric atrophy was not shown in this study.

The role of costimulation in antibody deficiencies: ICOS and common variable immunodeficiency

SUMMARY

The identification of mutations in the inducible costimulator (ICOS) gene in nine patients with common variable immunodeficiency (CVID) was a major breakthrough. CVID is a complex, highly heterogeneous primary immunodeficiency disease, and the discovery of these mutations revealed a molecular basis. ICOS belongs to the CD28 family of costimulatory molecules and is expressed exclusively on activated T cells. It has at least three critical functions: germinal center formation, isotype class switching, and the development of memory B cells. The discovery of human ICOS deficiency showed that a monogenic disorder could account for the full spectrum of manifestations seen in childhood and adulthood-onset CVID, including autoimmune, inflammatory, and malignant disease complications, as well as recurrent infections. Moreover, this discovery showed that a disorder which had previously been perceived as a B-cell disease might in fact have its genetic origin in human T cells. In this article, we review the role of ICOS in the mammalian immune system and human disease, as well as the discovery and characteristics of patients with ICOS deficiency. Finally, we also discuss how these 'human knockouts' have contributed to our understanding of ICOS functions and have suggested potential avenues for using therapeutic ICOS manipulation to treat other diseases.

Common variable immunodeficiency: etiological and treatment issues

One of the great advances in clinical medicine was the recognition of the pleomorphism of the immune response and the multiple afferent and efferent limbs of antigen processing and responsiveness. A significant contribution to this understanding was derived from studies of human immunodeficiency states, including both inherited and acquired syndromes. Amongst these syndromes, one of the most common, and least understood, is common variable immune deficiency (CVID). CVID is a syndrome that leads to a reduction in serum immunoglobulins and complications including recurrent infections. Management includes immunoglobulin replacement therapy; however, patients with CVID are at risk for complications of exogenous immunoglobulin administration as well as CVID-associated diseases such as autoimmune processes and malignancies. To assess the current state of knowledge in the field, we performed a literature review of a total of 753 publications covering the period of 1968 until 2008. From this list, 189 publications were selected for discussion. In this review, we demonstrate that while the molecular basis of CVID in many cases remains incompletely understood, significant strides have been made and it is now clear that there is involvement of several pathways of immune activation, with contributions from both T and B cells. Furthermore, despite the current gaps in our knowledge of the molecular pathogenesis of the syndrome, there have been dramatic advances in management that have led to improved survival and significantly reduced morbidity in affected patients.

Defective T-cell activation caused by impairment of the TNF receptor 2 costimulatory pathway in common variable immunodeficiency

BACKGROUND

Patients with common variable immunodeficiency have defective T-cell activation after stimulation via T-cell receptor (TCR)/CD28 or by recall antigens.

OBJECTIVE

In the current study, we investigated whether TNF-receptor 2 (RII) costimulation, which is important for sufficient TCR/CD28 stimulation, was significantly impaired in common variable immunodeficiency (CVID).

METHODS

We studied T-cell activation events such as CD69 induction, calcium flux through store operated calcium channels, protein kinase C-theta translocation, and costimulation via TNF-RII compared with costimulation via CD28.

RESULTS

By measuring TNF receptor-associated factor 1 expression, which is induced by TCR alone and can be upregulated by either CD28 or TNF-RII costimulation, we show that costimulation via CD28 is intact, whereas costimulation via TNF-RII in these patients is impaired. The ras-activation pathway as tested by CD69 induction, calcium flux through store operated calcium channels, and protein kinase C-theta translocation were comparable in CVID and control T cells.

CONCLUSION

Taken together, these data indicate that the primary TCR signal as well as the signal derived from CD28 are normal but that TNF-RII-supported TCR costimulation is defective, most likely leading to impairment of an important amplification loop, such as TNF-RII augmented nuclear factor-kappaB activation.

CLINICAL IMPLICATIONS

The finding of defective TNF-RII cosignaling in patients with CVID may help to define the activation pathway affected, thus potentially leading to a characterization of the molecular defect and molecular diagnosis in at least some of these patients.

Translational mini-review series on immunodeficiency: molecular defects in common variable immunodeficiency

Common variable immunodeficiency (CVID) is a primary immunodeficiency that typically affects adults and is characterized by abnormalities of quantative and qualitative humoral function that are heterogeneous in their immunological profile and clinical manifestations. The recent identification of four monogenic defects that result in the CVID phenotype also demonstrates that the genetic basis of CVID is highly variable. Mutations in the genes encoding the tumour necrosis factor (TNF) superfamily receptors transmembrane activator and calcium-modulating ligand interactor (TACI) and B cell activation factor of the TNF family receptor (BAFF-R), CD19 and the co-stimulatory molecule inducible co-stimulator molecule (ICOS) all lead to CVID and illustrate the complex interplay required to co-ordinate an effective humoral immune response. The molecular mechanisms leading to the immune defect are still not understood clearly and particularly in the case of TACI, where a number of heterozygous mutations have been found in affected individuals, the molecular pathogenesis of disease requires further elucidation. Together these defects account for perhaps 10-15% of all cases of CVID and it is highly likely that further genetic defects will be identified.

Grouping of patients with common variable immunodeficiency based on immunoglobulin biosynthesis: comparison with a classification system on CD4-naïve cells

The present study compared two different systems of classification of patients with common variable immunodeficiency (CVID); one based on in vitro immunoglobulin biosynthesis; and another on CD4-naïve cell counts. Peripheral blood mononuclear cells (PBMCs) were isolated from 35 patients with CVID and 20 healthy controls. They were stimulated for the secretion of IgM and IgG after stimulation with Staphylococcus aureus Cowan I (SAC) upon supplementation of interleukin-2 (IL-2) or with pokeweed mitogen. T cell subsets were estimated by flow cytometry. By the first system, patients were classified into group A (n=18) with secretion of neither IgG nor IgM; into group B (n=12) with detectable IgM but no IgG secretion; and into group C (n=5) with IgM and IgG secretion similar to controls. By the second system, patients were classified into group I (n=12) with less than 109 CD4-naïve cells/mul; into group II (n=12) with CD4-naïve cells within 109-225microl(-1); and into group III (n=11) with more than 225 CD4-naïve cells/mul. All groups I-III were defective for in vitro release of IgG and IgM. The likelihood ratio for splenomegaly in patients with <225 CD4-naïve cells/mul was 5.08 (p: 0.024). CD4-naïve cell counts of patients were positively correlated to serum levels of IgG and IgA of patients. The presented results revealed that the former system described adequately the function of B cells and the latter the clinical status of the patient. Our proposal is that both should be used for the characterization of patients with CVID.

Genetic defects in common variable immunodeficiency

Common variable immunodeficiency (CVID) is the most frequent clinically manifested primary immunodeficiency. According to clinical and laboratory findings, CVID is a heterogeneous group of diseases. Recently, the defects of molecules regulating activation and terminal differentiation of B lymphocytes have been described in some patients with CVID. In this study, we show the overview of deficiencies of inducible costimulator, transmembrane activator and calcium-modulator and cytophilin ligand interactor, CD19 molecules, their genetic basis, pathogenesis and clinical manifestations.

Common variable immunodeficiency: The power of co-stimulation

Common variable immunodeficiency (CVID) is the most frequent symptomatic primary immune deficiency in adults. CVID is characterized by the sequelae of an antibody deficiency syndrome: an impaired terminal B cell differentiation results in hypogammaglobulinemia and susceptibility to recurrent infections by encapsulated bacteria. The clinical course of CVID is complicated by a plethora of systemic immunopathology, including autoimmunity, lymphoproliferation, malignancy and sarcoid-like granulomas. Phenotypic and functional studies in CVID patients revealed multiple abnormalities within the innate and adaptive immune system. The recent description of monogenic defects in ICOS, TACI and CD19 focussed our interest to an impaired T cell-B cell collaboration within the germinal center and intrinsic B cell defects as possible explanations for the etiology of CVID.

Monogenetic defects in common variable immunodeficiency: what can we learn about terminal B cell differentiation?

PURPOSE OF REVIEW

In human primary immunodeficiencies, more than 100 different genetic defects have been described. For the most prevalent primary immunodeficiency requiring medical attention, however, termed common variable immunodeficiency, no genetic cause had been defined until recently. In this review we will summarize the current progress in the molecular genetics of common variable immunodeficiency and put them in context with other important developments in the field.

RECENT FINDINGS

In recent years the first three monogenetic defects in the inducible costimulator, transmembrane activator and CAML interactor (TACI), and CD19 were discovered in patients with common variable immunodeficiency revealing a multifaceted genetic background for this disease. As a concise phenotype cannot be assigned to each of these genetic defects, there is a need for further development of classification systems for common variable immunodeficiency and the search of epigenetic factors influencing the course of the disease. Subgroups of common variable immunodeficiency patients with low IgM memory B cells may suffer from an increased rate of infections. Human herpes virus type 8 infections were identified as a risk factor for the development of granulomatous disease complications.

SUMMARY

The pathogenesis of common variable immunodeficiency shows a convergence on impaired terminal B cell differentiation. Recently discovered genetic defects support this view. A combined effort of genetic analysis and standardized assessment of immunological and clinical phenotypes will be necessary to further unravel the conundrum of common variable immunodeficiency.

Hypogammaglobulinémies primitives découvertes à l’âge adulte

Hypogammaglobulinemia during adulthood can lead to recurrent infectious diseases, particularly pneumonia, otitis, and sinusitis, mainly due to Streptococcus pneumoniae and Haemophilus influenzae. Physicians must discriminate between primary and secondary hypogammaglobulinemia to provide appropriate treatment. Common variable immunodeficiency (CVID) is the most common cause of primary hypogammaglobulinemia diagnosed in adulthood. Clinical features include various combinations of infectious diseases, autoimmune diseases, lymphoproliferative disorders, and gastrointestinal diseases. Mutations in genes responsible for primary hypogammaglobulinemia in children are occasionally described in adults with CVID. ICOS and TACI deficiencies have recently been reported in a few CVID patients, although most cases have no proven genetic defects. The DefI cohort is recruiting adults with CVID throughout France. It will make it possible to describe the clinical, immunological, and genetic features of French patients with hypogammaglobulinemia and will help us to understand this immune deficiency better.

TACItly changing tunes: farewell to a yin and yang of BAFF receptor and TACI in humoral immunity?

PURPOSE OF REVIEW

The complex system of the tumour necrosis factor ligands BAFF and APRIL and their three receptors BCMA, TACI and BAFF receptor and its role in B-cell development and function is the objective of extensive research. Whereas the importance of BAFF/BAFF receptor interactions for B-cell survival could be clearly demonstrated, TACI is believed to counteract BAFF activity as a negative regulator in the murine model. The primarily immunodeficient phenotype of human TACI deficiency, however, claims a distinct function of this receptor in human peripheral B-cell development, class switch recombination and terminal differentiation.

RECENT FINDINGS

Common variable immunodeficiency comprises a heterogeneous group of antibody deficiency syndromes characterized by impaired terminal B-cell differentiation. By means of molecular genetics common variable immunodeficiency is still ill-defined, but the description of the deficiency of the inducible costimulator in a small subgroup of common variable immunodeficiency patients set the starting point for the molecular dissection of this disease entity. The recent discovery of genetic defects in the tumour necrosis factor receptor superfamily members TACI and BAFF receptor in patients with common variable immunodeficiency denotes further advances in this field.

SUMMARY

In this review we will discuss recent progress made in the understanding of the BAFF/APRIL-TACI/BCMA/BAFF receptor system in relation to the recent discovery that mutations in human TACI cause a primary humoral immunodeficiency. This suggests a refined role for TACI in human B-cell biology.