Enteroviral meningoencephalitis as a complication of X-linked hyper IgM syndrome

Of Mycelium and Men: Inherent Human Susceptibility to Fungal Diseases

In medical mycology, the main context of disease is iatrogenic-based disease. However, historically, and occasionally, even today, fungal diseases affect humans with no obvious risk factors, sometimes in a spectacular fashion. The field of “inborn errors of immunity” (IEI) has deduced at least some of these previously enigmatic cases; accordingly, the discovery of single-gene disorders with penetrant clinical effects and their immunologic dissection have provided a framework with which to understand some of the key pathways mediating human susceptibility to mycoses. By extension, they have also enabled the identification of naturally occurring auto-antibodies to cytokines that phenocopy such susceptibility. This review provides a comprehensive update of IEI and autoantibodies that inherently predispose humans to various fungal diseases.

Characteristics and therapy of enteroviral encephalitis: case report and systematic literature review

OBJECTIVES

Enterovirus (EV) is a frequent cause of encephalitis. The optimal therapeutic approach remains a matter of debate. We present the case of an immunosuppressed patient with EV encephalitis treated successfully with intravenous immunoglobulin (IVIG) and report the results of a systematic review on the characteristics of EV encephalitis, as well as the safety and efficacy of IVIG therapy.

METHODS

A systematic review was conducted using the PubMed, Cochrane Database, BIOSIS Previews, and ClinicalTrials.gov databases to identify all reports on patients with EV encephalitis as of December 31, 2020. The main outcomes assessed were the efficacy and safety of the respective therapeutic approach.

RESULTS

A total of 73 articles were included: one prospective trial, one retrospective and prospective case series, one purely retrospective case series, and 70 case reports. The case reports included a total of 101 patients. Immunosuppressed patients were at higher risk of contracting EV encephalitis and experiencing a fatal course. Hypogammaglobulinaemia particularly predisposes to EV disease, even with a moderate reduction in serum IgG levels. IVIG therapy in the immunosuppressed may confer a survival advantage.

CONCLUSIONS

IVIG therapy is rarely associated with severe adverse events and may be considered in immunosuppressed patients with EV encephalitis. Future trials should investigate the optimal IVIG dosing and route of application, the benefit of antibody-enriched IVIG preparations, and the serum immunoglobulin level that should trigger prophylactic replacement.

Human inborn errors of immunity caused by defects of receptor and proteins of cellular membrane

Inborn errors of immunity are diseases of the immune system resulting from mutations that alter the expression of encoded proteins or molecules. Total updated number of these disorders is currently 406, with 430 different identified gene defects involved. Studies of the underlying mechanisms have contributed in better understanding the pathophysiology of the diseases, but also the complexity of the biology of innate and adaptive immune system and its interaction with microbes. In this review we present and briefly discuss Inborn Errors of Immunity caused by defects in genes encoding for receptors and protein of cellular membrane, including cytokine receptors, T cell antigen receptor (TCR) complex, cellular surface receptors or receptors signaling causing predominantly antibody deficiencies, co-stimulatory receptors and others. These alterations impact many biological processes of immune-system cells, including development, proliferation, activation and down-regulation of the immunological response, and result in a variety of diseases that present with distinct clinical features or with overlapping signs and symptoms.

Hematopoietic stem cell transplantation for CD40 ligand deficiency: Results from an EBMT/ESID-IEWP-SCETIDE-PIDTC study

BACKGROUND

CD40 ligand (CD40L) deficiency, an X-linked primary immunodeficiency, causes recurrent sinopulmonary, Pneumocystis and Cryptosporidium species infections. Long-term survival with supportive therapy is poor. Currently, the only curative treatment is hematopoietic stem cell transplantation (HSCT).

OBJECTIVE

We performed an international collaborative study to improve patients' management, aiming to individualize risk factors and determine optimal HSCT characteristics.

METHODS

We retrospectively collected data on 130 patients who underwent HSCT for CD40L deficiency between 1993-2015. We analyzed outcome and variables' relevance with respect to survival and cure.

RESULTS

Overall survival (OS), event-free survival (EFS), and disease-free survival (DFS) were 78.2%, 58.1%, and 72.3% 5 years after HSCT. Results were better in transplantations performed in 2000 or later and in children less than 10 years old at the time of HSCT. Pre-existing organ damage negatively influenced outcome. Sclerosing cholangitis was the most important risk factor. After 2000, superior OS was achieved with matched donors. Use of myeloablative regimens and HSCT at 2 years or less from diagnosis associated with higher OS and DFS. EFS was best with matched sibling donors, myeloablative conditioning (MAC), and bone marrow-derived stem cells. Most rejections occurred after reduced-intensity or nonmyeloablative conditioning, which associated with poor donor cell engraftment. Mortality occurred mainly early after HSCT, predominantly from infections. Among survivors who ceased immunoglobulin replacement, T-lymphocyte chimerism was 50% or greater donor in 85.2%.

CONCLUSION

HSCT is curative in patients with CD40L deficiency, with improved outcome if performed before organ damage development. MAC is associated with better OS, EFS, and DFS. Prospective studies are required to compare the risks of HSCT with those of lifelong supportive therapy.

Chronic meningoencephalitis caused by Echo virus 6 in a patient with common variable immunodeficiency : Successful treatment with pleconaril

Chronic enteroviral meningoencephalitis, most commonly caused by echoviruses, can particularly be seen in agammaglobulinemic patients. In spite of the fact that no specific treatment for enteroviral infections exists, pleconaril is an antiviral drug reported to be efficient against enteroviral infections in infants and adults. We present a case of a 42-year-old male, previously diagnosed with common variable immunodeficiency, who presented with severe chronic meningoencephalitis caused by Echo virus 6 and was successfully treated with pleconaril. Enteroviruses usually cause mild symptoms, but some strains can cause life-threatening conditions especially in immunocompromised patients. Although pleconaril production is unprofitable due to the rarity of severe disease, our effective treatment should encourage further availability of pleconaril.

Enteroviruses and Parechoviruses

Infections with enteroviruses and human parechoviruses are highly prevalent, particularly in neonates, where they may cause substantial morbidity and mortality. Individuals with B-cell-related immunodeficiencies are at risk for severe enteroviral infections, usually a chronic and fatal meningoencephalitis. In transplant recipients and patients with malignancy, enterovirus infections typically involve the respiratory tract, but cases of severe, disseminated infection have been described. The mainstay of diagnosis for enterovirus and human parechovirus infections involves the use of molecular diagnostic techniques. However, routine nucleic acid-detection methods for enteroviruses will not detect human parechoviruses. Laboratory diagnosis of these viral infections is important in determining a patient's prognosis and guiding clinical management.

X-linked Hyper IgM Syndrome Presenting as Pulmonary Alveolar Proteinosis

PURPOSE

X-linked hyper IgM syndrome (XHIGM) is a combined immunodeficiency caused by mutations in the CD40 ligand (CD40L) gene that typically results in decreased or absent CD40L expression on activated T cells, leading to defective class switching and somatic hypermutation. We describe an infant who presented with respiratory failure due to pulmonary alveolar proteinosis (PAP) with a novel damaging missense mutation in the CD40L gene.

METHODS

Whole exome sequencing (WES) was used to identify a mutation in the CD40L gene. CD40L expression and function were determined by flow cytometry.

RESULTS

A 5-month-old previously-healthy male presented with respiratory failure and diffuse pulmonary ground glass opacities on CT scan of the chest. Laboratory evaluation revealed an undetectable IgG, normal IgA, and elevated IgM. A bronchoalveolar lavage demonstrated pulmonary alveolar proteinosis. WES demonstrated a c.608G > C mutation in the CD40L gene resulting in p.R203T. Flow cytometry demonstrated normal CD40L expression on activated T cells but absent binding of CD40-Ig to CD40L on activated patient T cells.

CONCLUSIONS

The clinical manifestations of XHIGM in our patient had several unique features, including the presentation with PAP, normal serum IgA, and expression of non-functional CD40L on activated T cells. To our knowledge, this is the first published case of PAP in a patient with XHIGM.

Nervous System Complications of Systemic Viral Infections

Invasion of the central nervous system (CNS) by viral agents typically produces a meningoencephalitis in which either meningitis or encephalitis may predominate. Viruses may also infect cranial or spinal blood vessels to produce ischemic injury. Viral and other infections may also elicit a host immune response which is cross-reactive with components of the neural tissue, resulting in encephalomyelitis, transverse myelitis, injury to peripheral nerves, or optic neuritis. This chapter discusses the pathogenesis of CNS viral infections and reviews clinical features of these disorders, major agents responsible in immunocompromised and immunocompetent individuals, and treatment. Prion diseases and postinfectious viral CNS syndromes including postinfectious encephalomyelitis, acute hemorrhagic leukoencephalitis, cerebellar ataxia, and transverse myelitis are also discussed.

Immunoglobulin class switch recombination deficiency type 1 or CD40 ligand deficiency: from bedside to bench and back again

The immunoglobulin class switch recombination deficiency or hyper-IgM syndrome is characterized by normal or elevated serum IgM and low serum levels of other immunoglobulins. Since the first reported patient with hyper-IgM, more than 200 patients with this phenotype resulted from CD40 ligand deficiency have been reported. However, in addition to this common finding, they presented with different manifestations like opportunistic infections, autoimmunity and malignancies each of them are worth a detailed look. In this review, we will focus on different underlying mechanisms of these presentations to review what we have learned from our patients. In the end, we will discuss different treatment options available for these patients using this knowledge.

CD40 ligand deficiency: neurologic sequelae with radiographic correlation

Patients with CD40 ligand deficiency are susceptible to central nervous system infections, but to date the neurologic progression or long-term outcome of central nervous system complications have not been reported in detail. Characterizing the central nervous system complications of immune deficiencies can lead to the identification of new pathogens. For this study, clinical data were reviewed on patients with both CD40 ligand deficiency and neurodegeneration, identified from a larger cohort of 31 patients. Five patients had progressive neurologic and cognitive decline in the absence of clinical signs of acute fulminant encephalitis, with anatomic brain abnormalities and high mortality (60%). Despite multiple evaluations, no pathogens were identified in four patients, all of whom were on standard intravenous immunoglobulin therapy at illness presentation. This clinical phenotype of progressive decline without acute fulminant encephalitis is similar to chronic enteroviral encephalitis in X-linked agammaglobulinemia, another condition with severe humoral immune defects. Whether infection secondary to subtherapeutic levels of central nervous system immunoglobulin G (IgG), inadequately protective levels of serum IgG, or impaired CD40 ligand-dependent IgG-independent antiviral responses contributed remains undetermined. Emerging gene-chip techniques applied in patients with primary immune deficiencies may identify heretofore unknown viruses. Prospective neurocognitive and evaluation of patients with CD40 ligand deficiency may identify affected patients before overt clinical signs appear.

Hyper-IgM syndrome in a boy with recurrent pneumonia and hepatosplenomegaly

Introduction. We present a boy diagnosed at age 14 years with hyper-immunoglobulin (Ig) M syndrome, a congenital immunodeficiency characterized by reduced plasma concentrations of IgA, IgE and IgG, with normal or elevated concentrations of IgM. This syndrome is caused by a defect of CD40 ligand (CD40L) on T-helper lymphocytes, impeding the 'second signal' during activation of B lymphocytes and interactions of T cells with dendritic cells and macrophages, resulting in the absence of secondary immune response (class switching, affinity maturation, immune memory), as well as responses to T-dependent antigens, with an impairment of cellular immunity. Case Outline. The history of the presented patient was dominated by frequent lower respiratory infections and failure to thrive. Physical examination demonstrated severe hepatosplenomegaly. The suspicion of hyper-IgM syndrome was raised by low plasma IgA (0.36 g/l) with high plasma IgM (35.5 g/l), while the concentration of IgG was within the normal range (12.1 g/l). The diagnosis was confirmed by flow cytometry, which demonstrated the absence of expression of CD40L on lymphocytes following stimulation by phorbolmyristylacetate and calcium ionophore. Since the time of diagnosis, intravenous immunoglobulin therapy has led to catch-up growth, recession of hepatosplenomegaly and reduction in the frequency of respiratory infections. Conclusion. Our report emphasizes the importance for the primary healthcare paediatrician to be well informed about the clinical presentation and pathogenesis of hyper-IgM syndrome, in order to provide early detection and increase the likelihood of success in treating this rare immunodeficiency. To the best of our knowledge, this is the first case of hyper-IgM syndrome reported in the Republic of Serbia.

X-linked hyper-IgM syndrome associated with poorly differentiated neuroendocrine tumor presenting as obstructive jaundice secondary to extensive adenopathy

X-Linked Hyper IgM Syndrome (XHIGM) is a rare B-cell immunodeficiency disease. Patients with XHIGM are unable to switch immunoglobulin production from IgM to IgG, IgA, and IgE. Patients with XHIGM require periodic intravenous immune globulin to help prevent infections, and are also at risk for a variety of neoplasms. We describe a young man with XHIGM who presented with obstructive jaundice from malignant adenopathy from widespread, poorly differentiated neuroendocrine tumor. This has not previously been reported and represents a new association with XHIGM.

X-Linked Hyper-Immunoglobulin M Syndrome: Molecular Genetic Study and Long-Time Follow-Up of Three Generations of a Chinese Family

BACKGROUND

X-linked hyper-immunoglobulin M (IgM) syndrome (XHIGM) is a rare immunodeficiency disease caused by mutations of the CD40 ligand gene. Patients are subject to recurrent infections and have normal or elevated levels of IgM but markedly decreased serum IgG.

OBJECTIVE

We describe molecular genetic studies and clinical manifestations in three generations of one family, as well as results of long-term treatment of 2 young men with the disorder.

METHODS

Of 37 living family members, mutational analysis of the CD40 ligand gene was performed in 36 members. Laboratory data for patients and carriers were reviewed.

RESULTS

Four male family members had died of unexplained causes. The 3 patients with XHIGM syndrome and the 5 carriers all had a novel mutation located at Tyr 169 Asn (T526A) in exon 5, the tumor necrosis factor domain of the CD40 ligand gene. In the 3 patients, CD40 ligand expression in activated CD4+ T cells was below 1%. In the carriers, about half of activated CD4+ cells expressed CD40 ligand. One carrier had malignant lymphoma. Long-term (>20 years) intravenous immunoglobulin therapy in 2 patients improved IgG levels but did not fully suppress the high levels of IgM, nor did it prevent late complications (bronchiectasis and sclerosing cholangitis).

CONCLUSIONS

Diagnosis of a genetic immunodeficiency, especially an X-linked disease such as XHIGM syndrome, should prompt a survey of the entire family.

Cryptococcal meningitis in a patient with X-linked hyper-IgM1 syndrome

A case is reported of cryptococcal meningitis in a 27-y-old male suffering from X-linked hyper-IgM1 syndrome. This congenital disorder is characterized by multiple infections of the respiratory and gastrointestinal tracts, but also opportunistic infections commonly seen in patients with cell-mediated immunity. His clinical recovery was good but the need for life-long secondary chemoprophylaxis to prevent relapses is unknown.

Hyper-IgM1 syndrome with interstitial pneumonia and diarrhea caused by coxsackievirus B4 in a 3-month-old infant

BACKGROUND

Hyper-IgM1 syndrome is a rare genetic primary immunodeficiency disease caused by mutations of the CD40 ligand gene. It is characterized by normal or elevated levels of IgM and markedly decreased serum IgG, IgA, and IgE levels. Patients with this syndrome often easily develop infections. During the past decade, it has become clear that enteroviral infections may also occur as a manifestation of hyper-IgM1 syndrome.

OBJECTIVE

To report a case of hyper-IgM1 syndrome in a 3-month-old boy who had interstitial pneumonia and intractable diarrhea.

METHODS

Chest radiography, bronchoscopy, immune studies, and open lung biopsy were performed.

RESULTS

Chest radiography revealed diffuse bilateral infiltrates. Immune studies revealed the following proportions of lymphocyte markers: CD3, 5,976/microL; CD4, 5,015/microL; CD8, 866/microL; CD19, 1,325/microL; CD16 + 56, 935/microL; and active T cells, 225/microL. The IgG level was 190 mg/dL; IgA, 2 mg/dL; IgM, 34 mg/dL; IgE, 1 IU/dL; and CH50, 23.8/mL. CD40L expression was less than 1%, and a Tyr 169 Asn (t526a) mutation in the exon 5 tumor necrosis factor domain of the CD40L gene was found. The patient was treated with intravenous immunoglobulin and had a dramatic improvement in symptoms. Open lung biopsy failed to demonstrate pneumocystis, and there was no evidence of cryptosporidium in the stool. However, coxsackievirus B4 was isolated by viral throat culture.

CONCLUSION

Interstitial pneumonia and diarrhea caused by coxsackievirus B4 may be a complication of hyper-IgM1 syndrome.

Molecular analysis of a large cohort of patients with the hyper immunoglobulin M (IgM) syndrome

The hyper immunoglobulin M (IgM) syndrome (HIGM), characterized by recurrent infections, low serum IgG and IgA, normal or elevated IgM, and defective class switch recombination and somatic hypermutation, is a heterogenous disorder with at least 5 distinct molecular defects, including mutations of the genes coding for the CD40 ligand (CD40L) and IKK-gamma (NEMO) genes, both X-linked; and mutations of CD40, activation-induced cytidine deaminase (AICDA), and uracil-DNA glycosylase (UNG), associated with autosomal recessive HIGM syndromes. To investigate the molecular basis of HIGM, we determined the prevalence of mutations affecting these 5 genes in a cohort of 140 patients (130 males and 10 females). Those patients without a molecular diagnosis were subsequently evaluated for mutations of the following genes: inducible CO-stimulator molecule (ICOS), ICOS ligand (ICOSL), and if male, Bruton tyrosine kinase (Btk) and SLAM-associated protein (SAP/SH2D1A). We found mutations of CD40L in 98 males; AICDA in 4 patients (3 males, 1 female); UNG in one adult male; and Btk in 3 boys. Of the remaining 25 males, one infant with hypohidrotic ectodermal dysplasia had a mutation of NEMO. None of the remaining 33 patients (24 males/9 females) had mutations affecting CD40, ICOS, ICOSL, or SH2D1, and are best classified as common variable immune deficiency (CVID), although other genes, including some not yet identified, may be responsible.

Flow cytometric diagnosis of X-linked hyper-IgM syndrome: application of an accurate and convenient procedure

Hyper-IgM (HIM) syndrome encompasses a family of congenital immunodeficiency states characterized by frequent infections and markedly low serum levels of IgG, IgA, and IgE but normal or elevated levels of IgM. Many patients have neutropenia. The major defect shared by all forms of HIM syndrome is a failure of immunoglobulin isotype-switching. Recently, a flow cytometric assay was described in the immunology literature for diagnosis of patients with inherited X-linked (X-HIM) syndrome. Using this assay, activated CD4 peripheral blood T lymphocytes from two patients suspected of having HIM syndrome, and from their mothers, were subjected to immunofluorescent flow cytometric analysis for the expression of CD40 ligand (CD154 antigen). Test results established the diagnosis of X-HIM syndrome that was inherited in one patient and spontaneous in the other. The authors' experience illustrates that the flow cytometric assay used and described in detail here can facilitate an accurate and timely diagnosis of X-HIM syndrome. Because the assay can be carried out in most clinical flow cytometry facilities, it lends itself to use by pediatric hematologists in the standard evaluation of patients whose differential diagnosis includes that disorder. The authors hope this report will raise awareness of the value of this procedure.

An imbalance of naive and memory/effector subsets and altered expression of CD38 on T lymphocytes in two girls with hyper-IgM syndrome

In this report we evaluated CD4(+) T, CD8(+) T and natural killer (NK) cell counts, the levels of naive/memory subsets within the CD4(+) T lymphocyte population, expression of CD38 on T lymphocytes, and CD4(+) and CD8(+) T cell cytokine production in two girls with hyper-IgM (HIM) syndrome. Both girls developed recurrent infections early in infancy, presenting a wide spectrum of clinical manifestations, with a strikingly different disease severity between them. CD4(+) T cell counts were low in both children (patient 1: 214 cells/mm(3) and patient 2: 392 cells/mm(3)), and the CD4/CD8 T cell ratio was 0.4 for patient 1, the patient with the more severe disease, and 1.4 for patient 2. NK cell numbers were low in patient 1 (60 cells/mm(3)) and borderline (286 cells/mm(3)) with regard to normal levels in patient 2. An imbalance of naive and memory/effector cell subsets was found in both girls, with the percentage of CD45RA(+) 27(+) (naive) CD4(+) T lymphocytes being 5.8 and 12.4 for patients 1 and 2, respectively. Expression of CD38 on the surface of T lymphocytes was low in patient 1. Detection of intracellular interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha in CD4(+) and CD8(+) T lymphocytes upon PMA-Io stimulus was preserved in both children. In conclusion, we found low numbers of CD4(+) T lymphocytes and a dramatic redistribution of naive and memory/effector CD4(+) T lymphocytes in two girls with non-X-linked HIM syndrome. Furthermore, we found low expression of CD38 on T lymphocytes and low numbers of NK cells in the patient with the more severe disease, indicating a possible role for these cells in the pathogenesis of this immunodeficiency.

Clinical, immunologic and genetic analysis of 29 patients with autosomal recessive hyper-IgM syndrome due to Activation-Induced Cytidine Deaminase deficiency

Mutations of the Activation-Induced Cytidine Deaminase (AID) gene have been found in patients with autosomal recessive hyper-IgM (HIGM) syndrome type 2. We retrospectively analyzed clinical, immunologic and genetic characteristics of 29 patients from 22 families with AID deficiency. Patients' median age at diagnosis and at last evaluation was 4.9 years (range: 0 to 53) and 14.2 years (range: 2.7 to 63), respectively. Most patients had suffered from recurrent and severe infections, however, intravenous immunoglobulin (IVIG) replacement therapy resulted in a dramatic decrease in the number of infections. Lymphoid hyperplasia developed in 22 patients and persisted in 7 at last follow-up. It is striking to note that six patients developed autoimmune or inflammatory disorders including diabetes mellitus, polyarthritis, autoimmune hepatitis, hemolytic anemia, immune thrombocytopenia, Crohn's disease and chronic uveitis. Fifteen distinct AID mutations were found but there was no significant genotype-phenotype correlation. In conclusion, AID-deficient patients are prone to infections and lymphoid hyperplasia, which may be prevented by early-onset IVIG replacement, but also to autoimmune and inflammatory disorders.

The X-linked hyper-IgM syndrome: clinical and immunologic features of 79 patients

The X-linked hyper-IgM (XHIGM) syndrome is an uncommon primary immunodeficiency disease caused by mutations in the gene for CD40 ligand and characterized by normal or elevated serum IgM, reduced levels of IgG and IgA, and defective T-cell function. Because of its rarity, it has been difficult for any single investigator or institution to develop a comprehensive clinical picture of this disorder. Accordingly, a national registry was developed in the United States to provide demographic, genetic, immunologic, and clinical information on a relatively large number of patients with the XHIGM syndrome.A total of 79 patients from 60 unrelated families were registered between January 1997 and July 2002. The estimated minimal incidence was approximately 1/1,030,000 live births. All of the patients had significant IgG deficiency and most had IgA deficiency, but only one-half had elevated IgM levels. Most patients presented initially with a history of an increased susceptibility to infection including Pneumocystis carinii pneumonia. The average age of diagnosis was significantly earlier in patients born into a family with a previously affected individual. However, only one-third of the patients born into a family with a previously affected individual were diagnosed exclusively because of the presence of the positive family history before any clinical symptoms developed. Over half the patients developed symptoms of immunodeficiency and were diagnosed by 1 year of age, and over 90% by 4 years of age. The most prominent clinical infections were pneumonia (81% of patients), upper respiratory infections (49%) including sinusitis (43%) and recurrent otitis (43%), recurrent/protracted diarrhea (34%), central nervous system infections (14%), sepsis (13%), cellulitis (13%), hepatitis (9%), and osteomyelitis (1%). In addition to infections caused by encapsulated bacteria, opportunistic infections were relatively common and were caused by P. carinii, members of the herpes virus family (including cytomegalovirus), Cryptosporidium, Cryptococcus, Candida, Histoplasma, and Bartonella. Sclerosing cholangitis occurred in 5 patients and in 4 of these was associated with Cryptosporidium infection. Eight patients had died at the time of their entry into the Registry; 2 of pneumonia (1 P. carinii and 1 cytomegalovirus), 2 of encephalitis (1 ECHO virus and 1 cytomegalovirus), 2 of malignancy (both hepatocellular carcinoma), 1 of sclerosing cholangitis caused by Cryptosporidium, and 1 of hemolytic uremic syndrome.

Clearance of Pneumocystis carinii in mice is dependent on B cells but not on P carinii-specific antibody

Both CD4(+) T cells and B cells are critical for defense against Pneumocystis carinii infection; however, the mechanism by which B cells mediate protection is unknown. We show that P. carinii-specific IgM is not sufficient to mediate clearance of P. carinii from the lungs since CD40-deficient mice produced normal levels of specific IgM, but were unable to clear the organisms. Using chimeric mice in which the B cells were deficient in CD40 (CD40KO chimeras) we found that clearance of P. carinii infection is delayed compared with wild-type controls. These CD40KO chimeric mice produced normal levels of P. carinii-specific IgM, but did not produce class-switched IgG or IgA. Similarly, clearance of P. carinii was delayed in mice deficient in FcgammaRI and III (FcgammaRKO), indicating that P. carinii-specific IgG partially mediates opsonization and clearance of P. carinii. Opsonization of organisms by complement did not compensate for the lack of specific IgG or FcgammaR, since C3-deficient and C3-depleted FcgammaRKO mice were still able to clear P. carinii. Finally, micro MT and CD40KO chimeric mice had reduced numbers of activated CD4(+) T cells in the lungs and lymph nodes compared with wild-type mice, suggesting that B cells are important for activation of T cells in response to P. carinii. Together these data indicate that P. carinii-specific IgG plays an important, but not critical, role in defense against P. carinii. Moreover, these data suggest that B cells also mediate host defense against P. carinii by facilitating CD4(+) T cell activation or expansion.

Viral meningitis and encephalitis: traditional and emerging viral agents

In the United States, the annual number of central nervous system (CNS) infections that occur as a result of viral agents far exceeds that of infections caused by bacteria, yeast, molds, and protozoa combined. The recent incursion of West Nile virus (WNV) into North America has led to a dramatic change in the incidence and epidemiology of summer-associated viral CNS disease. As a result of increased testing for WNV, lesser known viral causes of CNS infection have been identified. Even the epidemiology of such traditional viral neuropathogens as rabies has changed in recent years. This review provides an overview of viruses traditionally associated with meningitis and encephalitis (enteroviruses, La Crosse virus, St. Louis encephalitis virus, eastern and western equine viruses, varicella-zoster virus), as well as several of the less common (Powassan virus, lymphocytic choriomeningitis virus, Colorado tick fever virus, rabies virus, influenza viruses, etc.) and emerging (West Nile virus) viral pathogens.

Immunodeficiency and genetic conditions that cause arthritis in childhood

Many conditions can cause or be associated with arthritis in childhood. The authors of this paper will review the situations in which underlying immunodeficiency or defective regulation of lymphocyte homeostasis must be suspected, and discuss, for some of these diseases, the genetic bases and pathogenesis. In the second part of this article, the authors will focus on other diseases that can cause arthritis in childhood, often with other symptoms, and for which evidence of an association with genetic abnormalities has been recently discovered. Finally, the authors will discuss the implications of recent findings regarding the role of some genes as causing or modulating factors in juvenile idiopathic arthritis and related disorders, as well as observations made in adults and in animal models of inflammation and autoimmunity.

Diagnosis and Management of Enteroviral Infections of the Central Nervous System

Even with the approaching worldwide eradication of the polioviruses, the nonpolio enteroviruses remain major pathogens of the central nervous system. Our understanding of this important group of viral pathogens has increased dramatically in the past decade. The advent of molecular virology has yielded information that has been vital to the development of molecular diagnostic techniques for the detection of the enteroviruses and for the design of novel antienteroviral drugs. Advances in molecular diagnostics have allowed for a better definition of the diseases they cause and have impacted on patient care. This review discusses recent developments in the diagnosis and treatment of enterovirus infections of the central nervous system, including an overview of the molecular virology of the enteroviruses as it pertains to taxonomy, diagnosis, and treatment.

Bone marrow transplantation for CD40 ligand deficiency: a single centre experience

BACKGROUND

CD40 ligand (CD40L) deficiency is a rare X linked immunodeficiency disorder leading to recurrent bacterial infection, with cryptosporidial enteritis and subsequent hepatic cirrhosis. Bone marrow transplantation offers the only cure.

OBJECTIVE

To analyse retrospectively the outcome of bone marrow transplantation for this condition in one centre.

DESIGN

A retrospective case note analysis was performed, identifying all patients with CD40L deficiency who had undergone bone marrow transplantation between May 1988 and December 2000. Details of pre-existing infection, pretransplantation immunological and infective data, transplant procedure (particularly donor type and HLA match), conditioning regimen, and marrow manipulation were analysed. Post-transplantation data including infective episodes, engraftment details, immune function, complications, and outcome were recorded.

RESULTS

Eight boys (age 1-14 years, median 5.75) had transplants. Six received T cell depleted unrelated donor marrow. Four survive and have normal immune function. Six had previous Pneumocystis carinii pneumonia and three had histological liver damage. Survival was associated with younger age at transplantation and normal liver histology.

CONCLUSIONS

Bone marrow transplantation can be curative in CD40L deficiency. Better outcome is associated with younger age at transplantation and normal liver histology.

Infection in patients with primary immunodeficiency disorders

Recent advances in the understanding of the molecular basis of primary immunodeficiency disorders are reviewed, with particular emphasis on how these provide insights to the normal host's handling of particular microbes. Also reviewed are a number of reports on series of patients with these disorders, documenting the incidence and nature of the infective complications that occur and the effectiveness of treatment strategies.