Stem cell transplantation in primary immunodeficiencies

Combined immunodeficiencies

OBJECTIVES

Inborn Errors of Immunity (IEI), also known as primary immunodeficiencies, correspond to a heterogeneous group of congenital diseases that primarily affect immune response components. The main clinical manifestations comprise increased susceptibility to infections, autoimmunity, inflammation, allergies and malignancies. The aim of this article is to review the literature on combined immunodeficiencies (CIDs) focusing on the diagnosis and treatment and the particularities of the clinical management of these patients.

SOURCE OF DATA

Critical integrative review, aimed to present articles related to primary immunodeficiencies combined with a searchin the PubMed and SciELO databases, with evaluation of publications from the last twenty years that were essential for the construction of knowledge on this group of diseases.

SUMMARY OF DATA

We highlight the main characteristics of CIDs, dividing them according to their pathophysiological mechanisms, such as defects in the development of T cells, TCR signaling, co-stimulatory pathways, cytokine signaling, adhesion, migration and organization of the cytoskeleton, apoptosis pathways, DNA replication and repair and metabolic pathways. In CIDs, clinical manifestations vary widely, from sinopulmonary bacterial infections and diarrhea to opportunistic infections, caused by mycobacteria and fungi. Neonatal screening makes it possible to suspect these diseases before clinical manifestations appear.

CONCLUSIONS

The CIDs or IEI constitute a complex group of genetic diseases with T-cell involvement. Neonatal screening for these diseases has improved the prognosis of these patients, especially in severe ones, known as SCIDs.

Diagnostic approach to primary immunodeficiency disorders

Primary immunodeficiency disorders (PIDs) are a heterogeneous group of inherited disorders that affect different components of the immune system. There are more than 150 different disorders which have been described till date. Despite major advances in the molecular characterization of PIDs over the last 20 years, many patients remain undiagnosed or are diagnosed too late with severe consequences. Recognizing different clinical manifestations of PID is the first most important step. It should be followed by use of appropriate diagnostic tools from a vast number of investigations available. This review will focus on important presenting features of PID and laboratory approach for diagnosis of suspected cases of PID.

Establishing diagnostic criteria for severe combined immunodeficiency disease (SCID), leaky SCID, and Omenn syndrome: the Primary Immune Deficiency Treatment Consortium experience

BACKGROUND

The approach to the diagnosis of severe combined immunodeficiency disease (SCID) and related disorders varies among institutions and countries.

OBJECTIVES

The Primary Immune Deficiency Treatment Consortium attempted to develop a uniform set of criteria for diagnosing SCID and related disorders and has evaluated the results as part of a retrospective study of SCID in North America.

METHODS

Clinical records from 2000 through 2009 at 27 centers in North America were collected on 332 children treated with hematopoietic stem cell transplantation (HCT), enzyme replacement therapy, or gene therapy for SCID and related disorders. Eligibility for inclusion in the study and classification into disease groups were established by using set criteria and applied by an expert review group.

RESULTS

Two hundred eighty-five (86%) of the patients were determined to be eligible, and 47 (14%) were not eligible. Of the 285 eligible patients, 84% were classified as having typical SCID; 13% were classified as having leaky SCID, Omenn syndrome, or reticular dysgenesis; and 3% had a history of enzyme replacement or gene therapy. Detection of a genotype predicting an SCID phenotype was accepted for eligibility. Reasons for noneligibility were failure to demonstrate either impaired lymphocyte proliferation or maternal T-cell engraftment. Overall (n = 332) rates of testing were as follows: proliferation to PHA, 77%; maternal engraftment, 35%; and genotype, 79% (mutation identified in 62%).

CONCLUSION

Lack of complete laboratory evaluation of patients before HCT presents a significant barrier to definitive diagnosis of SCID and related disorders and prevented inclusion of subjects in our observational HCT study. This lesson is critical for patient care, as well as the design of future prospective treatment studies for such children because a well-defined and consistent study population is important for precision in outcomes analysis.

Artemis splice defects cause atypical SCID and can be restored in vitro by an antisense oligonucleotide

Artemis deficiency is known to result in classical T-B- severe combined immunodeficiency (SCID) in case of Artemis null mutations, or Omenn's syndrome in case of hypomorphic mutations in the Artemis gene. We describe two unrelated patients with a relatively mild clinical T-B- SCID phenotype, caused by different homozygous Artemis splice-site mutations. The splice-site mutations concern either dysfunction of a 5' splice-site or an intronic point mutation creating a novel 3' splice-site, resulting in mutated Artemis protein with residual activity or low levels of wild type (WT) Artemis transcripts. During the first 10 years of life, the patients suffered from recurrent infections necessitating antibiotic prophylaxis and intravenous immunoglobulins. Both mutations resulted in increased ionizing radiation sensitivity and insufficient variable, diversity and joining (V(D)J) recombination, causing B-lymphopenia and exhaustion of the naive T-cell compartment. The patient with the novel 3' splice-site had progressive granulomatous skin lesions, which disappeared after stem cell transplantation (SCT). We showed that an alternative approach to SCT can, in principle, be used in this case; an antisense oligonucleotide (AON) covering the intronic mutation restored WT Artemis transcript levels and non-homologous end-joining pathway activity in the patient fibroblasts.

Children with frequent infections: a proposal for a stepwise assessment and investigation of the immune system

Although many children develop frequent infections, only a few have an underlying immune disorder. Children with dysfunction of the immune system develop frequent infections and/or recurrent, persistent, severe, and rare infections. The aim of this review is to provide to the clinician a valuable tool for recognizing any 'discords' of the 'immune-system symphonic orchestra'. By following a reverse route, it will be possible to brighten up the dark and winding road of immunodeficiencies and identify the exact point of immune dysfunction. This is fundamental and crucial to perceive etiologic management and subsequently achieve the best for these young patients and their families.

Chronic graft-versus-host disease (GVHD) in children

Five-year survival rates for childhood cancer now exceed 80% and with the significant progress made by the transplant community in developing less toxic conditioning regimens and in the treatment of posttransplant complications, allo-hematopoietic stem cell transplantation (HSCT) contributes significantly to that population of long-term survivors. In this context, the acute and long-term toxicities of chronic graft-versus-host disease (cGVHD) have an ever-increasing effect on organ function, quality of life, and survival; patients and families who initially felt great relief to be cured from the primary disease, now face the challenge of a chronic debilitating illness for which preventative and treatment strategies are suboptimal. Hence, the development of novel strategies that reduce and or control cGVHD, preserve graft-versus-tumor effects, facilitate engraftment and immune reconstitution, and enhance survival after allo-HSCT represents one of the most significant challenges facing physician-scientists and patients.

New approaches to treatment of primary immunodeficiencies: fixing mutations with chemicals

PURPOSE OF REVIEW

This review is to highlight the most current mutation-targeted therapeutic approaches and provide insights into new developments for treating primary immunodeficiencies.

RECENT FINDINGS

Significant progress in mutation-targeted treatment was achieved in the past year with the identification and characterization of a translational read-through compound, PTC124. PTC124 demonstrates a new class of nontoxic bioavailable small drugs. Antisense oligonucleotide-mediated techniques such as splicing redirection, exon skipping, and mismatch repair have been successfully used to correct splicing, frameshift, and missense mutations, respectively. Delivery of antisense oligonucleotides to mammalian cells, including primary leukocytes and neurons, saw great progress during the past year. Recent advances for other approaches to correct frameshift and missense mutations are also considered.

SUMMARY

Primary immunodeficiencies are monogenic disorders. The characterization and classification of disease-causing mutations facilitate the design and development of new mutation-targeted treatments. To date, using ataxia-telangiectasia (A-T) as a model primary immunodeficiency, the most promising advances have been with chemicals that read through various premature stop codons as well as with antisense oligonucleotides that mask aberrant splice sites. These principles can now be applied to other primary immunodeficiencies.

Primary immune deficiencies with aberrant IgE production

IgE antibodies play a central role in the pathogenesis of atopic diseases and in host immunity against parasitic infections. IgE has potent activities on mast cells and basophils. IgE class switching is a very tightly controlled process, and serum IgE levels are very low compared with other immunoglobulin isotypes. Transcription factors that activate or inhibit the IgE gene promoter, as well as T(H)1 and T(H)2 cytokines are important in the regulation of IgE levels. Hyper-IgE syndrome; Wiskott-Aldrich syndrome; immunodysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX); Omenn syndrome; and atypical complete DiGeorge syndrome are primary immune deficiencies that are associated with elevated serum IgE levels. Increased IgE levels in IPEX, Wiskott-Aldrich syndrome and Omenn syndrome are likely related to increased T(H)2 cytokine production caused by decreased a number or function of CD4(+)CD25(+)forkhead box protein P3(+) regulatory T cells. The link between signal transducer and activator of transcription 3 mutations and elevated serum IgE levels in hyper-IgE syndrome is unclear. Insight into IgE regulation provided by the study of primary immune deficiencies with elevated IgE has important implications for allergic diseases.

Clinical immunology review series: an approach to the patient with recurrent infections in childhood

Recurrent or persistent infection is the major manifestation of primary immunodeficiency, which also results in atypical infection with opportunistic organisms. Young children are also vulnerable to infection and recurrent infection is common. While most children with recurrent infection have a normal immunity, it is important to recognize the child with an underlying primary immunodeficiency and investigate and treat appropriately and yet not over investigate normal children. Prompt, accurate diagnosis directs the most appropriate treatment, and early and judicious use of prophylactic antibiotics and replacement immunoglobulin can prevent significant end organ damage and improve long-term outlook and quality of life. This paper describes important presenting features of primary immunodeficiency and indicates when further investigation is warranted.