Targeted next-generation sequencing for genetic diagnosis of 160 patients with primary immunodeficiency in south China

Inborn errors of immunity in mainland China: the past, present and future

Inborn errors of immunity (IEI), also known as primary immunodeficiency diseases, comprise a group of rare genetic disorders that affect the development or/and function of the immune system. These disorders predispose individuals to recurrent infections, autoimmunity, cancer and immune dysregulations. The field of IEI diagnosis and treatment in mainland China has made significant strides in recent years due to advances in genome sequencing, genetics, immunology and treatment strategies. However, the accessibility and affordability of diagnostic facilities and precision treatments remain variable among different regions. With the increasing government emphasis on rare disease prevention, diagnosis, and treatment, the field of IEI is expected to progress further in mainland China. Herein, we reviewed the development and current state of IEI in mainland China, highlighting the achievements made, as well as opportunities and challenges that lie ahead.

Genetic Testing in Egyptian Patients with Inborn Errors of Immunity: a Single-Center Experience

BACKGROUND

Inborn errors of immunity (IEI) are a group of heterogeneous disorders with geographic and ethnic diversities. Although IEI are common in Egypt, genetic diagnosis is limited due to financial restrictions. This study aims to characterize the genetic spectrum of IEI patients in Egypt and highlights the adaptation of the molecular diagnostic methods to a resource-limited setting.

METHODS

Genetic material from 504 patients was studied, and proper diagnosis was achieved in 282 patients from 246 families. Mutational analysis was done by Sanger sequencing, next-generation sequencing (NGS) targeting customized genes panels, and whole-exome sequencing (WES) according to the patients' phenotypes and availability of genetic testing.

RESULTS

A total of 194 variants involving 72 different genes were detected with RAG1/2 genes being the most encountered followed by DOCK8, CYBA, LRBA, NCF1, and JAK3. Autosomal recessive (AR) inheritance was detected in 233/282 patients (82.6%), X-linked (XL) recessive inheritance in 32/282 patients (11.3%), and autosomal dominant (AD) inheritance in 18/282 patients (6.4%), reflecting the impact of consanguineous marriages on the prevalence of different modes of inheritance and the distribution of the various IEI disorders.

CONCLUSION

The study showed that a combination of Sanger sequencing in selected patients associated with targeted NGS or WES in other patients is an effective diagnostic strategy for IEI diagnosis in countries with limited diagnostic resources. Molecular testing can be used to validate other nonexpensive laboratory techniques that help to reach definitive diagnosis and help in genetic counseling and taking proper therapeutic decisions including stem cell transplantation or gene therapy.

Global systematic review of primary immunodeficiency registries

INTRODUCTION

During the last 4 decades, registration of patients with primary immunodeficiencies (PID) has played an essential role in different aspects of these diseases worldwide including epidemiological indexes, policymaking, quality controls of care/life, facilitation of genetic studies and clinical trials as well as improving our understanding about the natural history of the disease and the immune system function. However, due to the limitation of sustainable resources supporting these registries, inconsistency in diagnostic criteria and lack of molecular diagnosis as well as difficulties in the documentation and designing any universal platform, the global perspective of these diseases remains unclear.

AREAS COVERED

Published and unpublished studies from January 1981 to June 2020 were systematically reviewed on PubMed, Web of Science and Scopus. Additionally, the reference list of all studies was hand-searched for additional studies. This effort identified a total of 104614 registered patients and suggests identification of at least 10590 additional PID patients, mainly from countries located in Asia and Africa. Molecular defects in genes known to cause PID were identified and reported in 13852 (13.2% of all registered) patients.

EXPERT OPINION

Although these data suggest some progress in the identification and documentation of PID patients worldwide, achieving the basic requirement for the global PID burden estimation and registration of undiagnosed patients will require more reinforcement of the progress, involving both improved diagnostic facilities and neonatal screening.

EuroFlow-Based Flowcytometric Diagnostic Screening and Classification of Primary Immunodeficiencies of the Lymphoid System

Guidelines for screening for primary immunodeficiencies (PID) are well-defined and several consensus diagnostic strategies have been proposed. These consensus proposals have only partially been implemented due to lack of standardization in laboratory procedures, particularly in flow cytometry. The main objectives of the EuroFlow Consortium were to innovate and thoroughly standardize the flowcytometric techniques and strategies for reliable and reproducible diagnosis and classification of PID of the lymphoid system. The proposed EuroFlow antibody panels comprise one orientation tube and seven classification tubes and corresponding databases of normal and PID samples. The 8-color 12-antibody PID Orientation tube (PIDOT) aims at identification and enumeration of the main lymphocyte and leukocyte subsets; this includes naïve pre-germinal center (GC) and antigen-experienced post-GC memory B-cells and plasmablasts. The seven additional 8(-12)-color tubes can be used according to the EuroFlow PID algorithm in parallel or subsequently to the PIDOT for more detailed analysis of B-cell and T-cell subsets to further classify PID of the lymphoid system. The Pre-GC, Post-GC, and immunoglobulin heavy chain (IgH)-isotype B-cell tubes aim at identification and enumeration of B-cell subsets for evaluation of B-cell maturation blocks and specific defects in IgH-subclass production. The severe combined immunodeficiency (SCID) tube and T-cell memory/effector subset tube aim at identification and enumeration of T-cell subsets for assessment of T-cell defects, such as SCID. In case of suspicion of antibody deficiency, PIDOT is preferably directly combined with the IgH isotype tube(s) and in case of SCID suspicion (e.g., in newborn screening programs) the PIDOT is preferably directly combined with the SCID T-cell tube. The proposed ≥8-color antibody panels and corresponding reference databases combined with the EuroFlow PID algorithm are designed to provide fast, sensitive and cost-effective flowcytometric diagnosis of PID of the lymphoid system, easily applicable in multicenter diagnostic settings world-wide.