Haematopoietic Stem Cell Transplant for Norovirus-Induced Intestinal Failure in X-linked Agammaglobulinemia

Abnormal T Cells Function Associated With Intraspinal Cold Abscess Caused by Macrolide-resistant Mycoplasma pneumoniae in a Patient With X-linked Agammaglobulinemia

Intraspinal cold abscesses caused by macrolide-resistant Mycoplasma pneumoniae in patients with X-linked agammaglobulinemia have not yet been described to our knowledge. Here we describe a patient with X-linked agammaglobulinemia who developed an intraspinal cold abscess caused by macrolide-resistant M. pneumoniae . Genetic analysis revealed a hemizygous c.1566 + 1G > C (IVS15 + 1G > C) mutation in BTK gene. The patient showed relatively naive T cells and a significant proliferative defect.

Outcomes of X-Linked Agammaglobulinaemia Patients

BACKGROUND

X-linked agammaglobulinaemia (XLA), caused by mutations in BTK, is characterised by low or absent peripheral CD19 + B lymphocytes and agammaglobulinaemia. The mainstay of treatment consists of immunoglobulin replacement therapy (IgRT). As this cannot fully compensate for the immune defects in XLA, patients may therefore continue to be at risk of complications.

OBJECTIVES

To describe the clinical outcomes of XLA patients in the United Kingdom and Hong Kong and evaluate current treatment strategies.

METHODS

Patients with a definitive diagnosis of XLA were included in this cross-sectional and retrospective analysis of clinical health outcomes. Data pertaining to diagnosis, infection incidence, IgG trough levels and lung function were collected and analysed.

RESULTS

99 patients with a median age of 29.02 years (IQR 12.83-37.41) and a total follow up of 1922 patient years, were included this study. The median age at diagnosis was 3.30 years (IQR 1.04-8.38) which decreased over time (p = 0.004). 40% of the cohort had radiological evidence of bronchiectasis. Risk of bronchiectasis was not significantly associated with clinical infection incidence (p = 0.880) or IgG trough levels (p = 0.407). Two patients demonstrated novel complications, namely persistent norovirus infection, leading to haemopoietic stem cell transplantation (HSCT).

CONCLUSIONS

Despite modern therapy, most XLA patients continue to experience complications, most notably bronchiectasis, likely due to absence of IgA/M in current therapies, but lack of B lymphocytes may also lead to additional sequalae. These data strongly support the need for further research, particularly that of curative modalities including HSCT and gene therapy.

Protective role of antibodies in enteric virus infections: Lessons from primary and secondary immune deficiencies

Enteric viruses are the main cause of acute gastroenteritis worldwide with a significant morbidity and mortality, especially among children and aged adults. Some enteric viruses also cause disseminated infections and severe neurological manifestations such as poliomyelitis. Protective immunity against these viruses is not well understood in humans, with most knowledge coming from animal models, although the development of poliovirus and rotavirus vaccines has extended our knowledge. In a classical view, innate immunity involves the recognition of foreign DNA or RNA by pathogen recognition receptors leading to the production of interferons and other inflammatory cytokines. Antigen uptake and presentation to T cells and B cells then activate adaptive immunity and, in the case of the mucosal immunity, induce the secretion of dimeric IgA, the more potent immunoglobulins in viral neutralization. The study of Inborn errors of immunity (IEIs) offers a natural opportunity to study nonredundant immunity toward pathogens. In the case of enteric viruses, patients with a defective production of antibodies are at risk of developing neurological complications. Moreover, a recent description of patients with low or absent antibody production with protracted enteric viral infections associated with hepatitis reinforces the prominent role of B cells and immunoglobulins in the control of enteric virus.

Hematopoietic stem cell gene editing rescues B-cell development in X-linked agammaglobulinemia

BACKGROUND

X-linked agammaglobulinemia (XLA) is an inborn error of immunity that renders boys susceptible to life-threatening infections due to loss of mature B cells and circulating immunoglobulins. It is caused by defects in the gene encoding the Bruton tyrosine kinase (BTK) that mediates the maturation of B cells in the bone marrow and their activation in the periphery. This paper reports on a gene editing protocol to achieve "knock-in" of a therapeutic BTK cassette in hematopoietic stem and progenitor cells (HSPCs) as a treatment for XLA.

METHODS

To rescue BTK expression, this study employed a clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 9 system that creates a DNA double-strand break in an early exon of the BTK locus and an adeno-associated virus 6 virus that carries the donor template for homology-directed repair. The investigators evaluated the efficacy of the gene editing approach in HSPCs from patients with XLA that were cultured in vitro under B-cell differentiation conditions or that were transplanted in immunodeficient mice to study B-cell output in vivo.

RESULTS

A (feeder-free) B-cell differentiation protocol was successfully applied to blood-mobilized HSPCs to reproduce in vitro the defects in B-cell maturation observed in patients with XLA. Using this system, the investigators could show the rescue of B-cell maturation by gene editing. Transplantation of edited XLA HSPCs into immunodeficient mice led to restoration of the human B-cell lineage compartment in the bone marrow and immunoglobulin production in the periphery.

CONCLUSIONS

Gene editing efficiencies above 30% could be consistently achieved in human HSPCs. Given the potential selective advantage of corrected cells, as suggested by skewed X-linked inactivation in carrier females and by competitive repopulating experiments in mouse models, this work demonstrates the potential of this strategy as a future definitive therapy for XLA.

An International Survey of Allogeneic Hematopoietic Cell Transplantation for X-Linked Agammaglobulinemia

PURPOSE

X-linked agammaglobulinemia (XLA) is an inborn error of immunity caused by variants in Bruton's tyrosine kinase (BTK). XLA patients require lifelong immunoglobulin replacement therapy (IgRT). Only few XLA patients are indicated for allogeneic hematopoietic cell transplantation (HCT) because of severe complications. Accordingly, the published transplantation experience in XLA is minimal. We aimed to collect clinical data of XLA patients who received HCT in an international framework and to establish appropriate transplantation criteria and methods for XLA patients.

METHODS

XLA patients were recruited through a questionnaire and a literature review. The data are on patient characteristics and transplantation methods and outcomes.

RESULTS

In this study, twenty-two XLA patients who underwent HCT were recruited. The indication for HCT was recurrent or life-threatening infection in sixteen patients, malignancy in three, and other factors in three. A myeloablative conditioning, reduced toxicity myeloablative conditioning (RT-MAC), and reduced intensity conditioning (RIC) were selected in four, ten, and eight patients, respectively. Engraftment was achieved in 21 patients (95%). In all patients, 2-year overall survival (OS) and event-free survival (EFS) were 86% and 77%, respectively. In patients who received RT-MAC or RIC using treosulfan, busulfan, or melphalan, 2-year OS and EFS were 82% and 71%, respectively. Finally, twenty-one patients (95%) obtained complete or stable high-level mixed chimerism (50-95%), and the 1-year discontinuation rate of IgRT was 89%.

CONCLUSION

Based on the concept in which IgRT is the standard treatment for XLA, HCT may be an effective and safe alternative treatment option for XLA patients, and IgRT can be discontinued following transplantation. It is ideal to perform HCT in XLA patients for whom transplantation is indicated before they develop organ damage.

Clinical Aspects of B Cell Immunodeficiencies: The Past, the Present and the Future

B cells and antibodies are indispensable for host immunity. Our understanding of the mechanistic processes that underpin how B cells operate has left an indelible mark on the field of clinical pathology, and recently has also dramatically reshaped the therapeutic landscape of diseases that were once considered incurable. Evaluating patients with primary immunodeficiency diseases (PID)/inborn errors of immunity (IEI) that primarily affect B cells, offers us an opportunity to further our understanding of how B cells develop, mature, function and, in certain instances, cause further disease. In this review we provide a brief compendium of IEI that principally affect B cells at defined stages of their developmental pathway, and also attempt to offer some educated viewpoints on how the management of these disorders could evolve over the years.

COVID-19 and X-linked agammaglobulinemia (XLA) - insights from a monogenic antibody deficiency

PURPOSE OF REVIEW

The clinical outcomes from COVID-19 in monogenic causes of predominant antibody deficiency have pivotal implications for our understanding of the antiviral contribution of humoral immunity. This review summarizes the lessons learned from COVID-19 infection in X-linked agammaglobulinemia (XLA) due to genetic defects in Bruton's tyrosine kinase (BTK).

RECENT FINDINGS

Key molecular pathways underlying the development of severe COVID-19 are emerging, highlighting the possible contribution of BTK to hyperinflammation. SARS-CoV-2 specific T-cell responses and complement activation appear insufficient to achieve viral clearance in some B-cell deficient individuals. Whilst appearing efficacious in this group, use of convalescent plasma has been recently associated with the evolution of viral escape variants. Early data suggests individuals with XLA can mount a viral-specific T-cell vaccine response, however, the clinical significance of this is still emerging.

SUMMARY

In contrast to reports made early in the pandemic, we show XLA patients remain susceptible to severe disease. Persistent infection was common and is likely to carry a significant symptom burden and risk of novel variant evolution. COVID-19 infection in this vulnerable, antibody deficient group due to genetic, therapeutic or disease causes may require prompt and specific intervention for both patient and societal benefit.

Serological Humoral Immunity Following Natural Infection of Children with High Burden Gastrointestinal Viruses

Acute gastroenteritis (AGE) is a major cause of morbidity and mortality worldwide, resulting in an estimated 440,571 deaths of children under age 5 annually. Rotavirus, norovirus, and sapovirus are leading causes of childhood AGE. A successful rotavirus vaccine has reduced rotavirus hospitalizations by more than 50%. Using rotavirus as a guide, elucidating the determinants, breath, and duration of serological antibody immunity to AGE viruses, as well as host genetic factors that define susceptibility is essential for informing development of future vaccines and improving current vaccine candidates. Here, we summarize the current knowledge of disease burden and serological antibody immunity following natural infection to inform further vaccine development for these three high-burden viruses.