Comparison of elapegademase and pegademase in ADA-deficient patients and mice.

The absence of adenosine deaminase (ADA) causes severe combined immune deficiency (SCID), which has been treated with PEGylated bovine-extracted ADA (ADAGEN). ADAGEN was recently replaced by a PEGylated recombinant bovine ADA, expressed in Escherichia coli (elapegademase, ELA-ADA). Limited information on ELA-ADA is available.  ADA enzymatic activity of ELA-ADA and ADAGEN was assessed in vitro at diverse dilutions. ADA activity and immune reconstitution in an ADA-SCID patient treated with ELA-ADA were compared with age-matched patients previously treated with ADAGEN. ADA activity and thymus reconstitution were evaluated in ADA-deficient mice following ELA-ADA or ADAGEN administered from 7 days postpartum. In vitro, ADA activity of ELA-ADA and ADAGEN were similar at all dilutions. In an ADA-SCID patient, ELA-ADA treatment led to a marked increase in trough plasma ADA activity, which was 20% higher than in a patient previously treated with ADAGEN. A marked increase in T cell numbers and generation of naive T cells was evident following 3 months of ELA-ADA treatment, while T cell numbers increased following 4 months in 3 patients previously treated with ADAGEN. T cell proliferations stimulation normalized and thymus shadow became evident following ELA-ADA treatment. ADA activity was significantly increased in the blood of ADA-deficient mice following ELA-ADA compared to ADAGEN, while both treatments improved the mice weights, the weight, number of cells in their thymus and thymocyte subpopulations. ELA-ADA has similar in- vitro and possibly better in-vivo activity than ADAGEN. Future studies will determine whether ELA-ADA results in improved long-term immune reconstitution.

Matched unrelated bone marrow transplant for T+ combined immunodeficiency.

Little information is currently available on the outcome and the long-term restoration of immune function in infants with combined immunodeficiency and residual T cells (T+ CID) treated by BMT. We prospectively followed patients with T+ CID who received matched unrelated donor BMT at our center. Engraftment, immune reconstitution and transplant-related complications were recorded. Humoral and cellular immunity were evaluated. Ten patients with combined immune deficiency who had more than 1,000 circulating T cells/mul were designated as having T+ CID. They were diagnosed at a mean age of 9.7 months and received a matched unrelated donor BMT at the mean age of 17.4 months. All 10 patients are alive and well at a mean of 110 months after transplant. All patients have evidence of full hemopoietic engraftment and robust immune function. We have shown here that matched unrelated donor BMT is highly effective in curing patients with T+ CID. This mode of treatment should be preferred for patients with T+ CID when a related identical donor is not available.

Bone marrow transplantation for cartilage-hair-hypoplasia.

The association of cartilage hair hypoplasia (CHH) with severe combined immunodeficiency (SCID) has been known for more than three decades. Bone marrow transplantation (BMT) remains the only effective treatment that might cure SCID. Surprisingly little has been reported on the experience with BMT in CHH. We report here survival and long-term reconstitution of immunity after BMT in three patients with CHH. Regardless of whether a related human leukocyte antigen-matched or unrelated matched donors were used as the source of BMT, all patients are alive and well 5-20 years after BMT. Engraftment appears robust with most cells of donors origin. Repeated evaluation of the immune system showed normal cellular and humoral immunity. Our results should encourage the use of BMT in patients with CHH who have profound immunodeficiency.

Rituximab for congenital haemophiliacs with inhibitors: a Canadian experience.

When a high titre inhibitor develops in a patient with haemophilia, attempts are made to eradicate it through immune tolerance induction therapy (ITI) involving the frequent and regular administration of factor, usually for months to years. ITI is successful in only two thirds of patients prompting investigators to explore alternate regimens to use in haemophiliacs failing conventional ITI. Rituximab is an anti-CD20 monoclonal antibody, which has shown promise in the treatment of B-cell-mediated disorders. We developed a protocol for the use of rituximab in haemophilia A (HA) patients failing conventional ITI or in those haemophiliacs where the likelihood of success of conventional ITI is poor. Patients receive 375 mg m(-2) of intravenous rituximab weekly for 4 weeks followed by monthly (up to 5 months) until inhibitor disappearance and establishment of normal FVIII pharmacokinetics (recovery and half-life). Patients are concurrently placed on recombinant FVIII (100 U kg(-1) day(-1)). We have placed five haemophiliacs (four children with severe HA, and one adult with mild HA) on this protocol. In three patients (two with severe HA and one with mild HA) inhibitors disappeared although in neither severe haemophiliac did FVIII pharmacokinetics completely normalize. The fourth patient had a significant drop in inhibitor titres although not a complete disappearance of the inhibitor. All four of these patients ceased bleeding following rituximab. The fifth patient had no response to rituximab. This non-responding patient was not placed on concurrent FVIII. Our five cases suggest that rituximab may hold promise in the eradication of inhibitors. Prospective randomized studies are required to determine the value of this agent in inhibitor management.

The role of anti-endothelial cell antibodies in Kawasaki disease - in vitro and in vivo studies.

Kawasaki disease (KD) is a systemic vasculitis with cardiac and noncardiac complications. Anti--endothelial cell antibodies (AECA) are found among many patients with KD. The aim of this study was to investigate the pathogenic role of AECA in KD using in vitro and in vivo experimental models. F(ab)2 fragments of IgG-AECA and IgM-AECA were affinity purified from a patient with active KD. Their endothelial binding and ability to induce a pro-adhesive and a pro-inflammatory phenotype were evaluated in vitro. Twenty Balb/C mice were immunized with KD-AECA or with control Ig (N-Ig) to induce AECA in a murine model by the idiotypic manipulation method. Both KD-AECA isotypes bind significantly to human umbilical vein endothelial cell (HUVEC) compared to N-Ig. The in vitro activity was demonstrated by the antibodies ability to activate endothelial cells resulting in increased IL-6 secretion, adhesion molecule expression and monocytic cell line (U937) adherence to HUVEC. Five of the mice that received KD-AECA developed murine AECA after 3 months. None of the mice that received N-Ig produced AECA. The murine AECA increased monocyte adhesion to EC in vitro, similarly to the AECA used for immunization. Furthermore, all the mice that developed AECA had proteinuria and IgG deposition in the renal mesangium. No histological or immunofluorescence evidence of cardiac vasculitis could be detected. AECA might play a role in the emergence of some of KD manifestations.

Anti-endothelial cell antibodies (AECA) in systemic sclerosis--increased sensitivity using different endothelial cell substrates and association with other autoantibodies.

OBJECTIVE: One of the main features of systemic sclerosis (SSc) is vascular damage, the mechanism of which is not understood. In the present study we examined whether screening of SSc patients for different anti-endothelial cells antibodies (AECA) of various origins increase the sensitivity of AECA detection in SSc patients. Secondary aim was an attempt to correlate AECA with other common autoantibodies. MATERIALS & METHODS: 478 SSc patients were studied for the presence AECA, anti-cardiolipin (aCL), anti-dsDNA, anti-heparin (AHA), anti-pyruvate dehydrogenase (PDH) and anti-PDC-E2 autoantibodies. AECA levels were detemined using human umbilical vein EC (HUVEC), bone marrow EC (BMEC), EC hybridoma (EA.hy 926) and Kaposi sarcoma EC (KS). RESULTS: Positive AECA were found in 49.5% of SSc patients (27.1% HUVEC; 34.3% BMEC; 26.3% EaHy 926 and 22.7% KS). The highest percent reactivity of AECA was obtained using microvascular BMEC. When combining BMEC and either other cell lines the reactivity ranged from 41.4% to 46%. A significant association between AECA on the one hand and AHA (p<0.001)) and anti-PDH (p<0.05) on the other was secn. Cross-reactivity with anti-PDC-E2 was excluded by inhibition tests, but AHA and anti-PDH may be part of the spectrum of AECA. CONCLUSIONS: Since false-negative AECA may result from lack of expression of various antigens on a specific EC, analysis of AECA in SSc patients requires using several EC types, including microvascular EC.

Two novel mutations in a purine nucleoside phosphorylase (PNP)-deficient patient.

Purine nucleoside phosphorylase (PNP) deficiency is a rare autosomal recessive disease, which presents clinically as severe combined immunodeficiency (SCID). We report here two novel mutations in the PNP gene that result in SCID phenotype, in a single patient. The maternal-derived allele carries a C to T transition in exon 2 resulting in a premature stop codon at amino acid 57. The paternal-derived mutation is a G to A transition at position +1 in intron 3, causing a complete skipping of exon 3 and a reading frameshift at the exon 2-exon 4 junction. The predicted polypeptide encoded by the aberrantly spliced mRNA terminates prematurely after only 89 amino acids. Both mutations predict severely truncated proteins resulting in a complete deficiency of PNP enzymatic activity, yet the development of profound immunodeficiency in this patient is greatly delayed.

Noncompaction of the myocardium associated with Roifman syndrome.

Noncompaction of the ventricular myocardium, sometimes referred to as "spongy myocardium", appears as excessive and prominent trabeculations and deep intratrabecular recesses within the ventricular wall, usually involving the left ventricle, although the right ventricle and interventricular septum can also be affected. It may occur with or without additional heart malformations. Roifman syndrome is a constellation of antibody deficiency, spondyloepiphyseal dysplasia, facial dysmorphism, growth retardation, and retinal dystrophy. We report a patient with Roifman syndrome who presented with noncompaction of the left ventricular myocardium. Our findings expand the spectrum of diseases associated with noncompaction. The recognition of noncompaction among patients with Roifman syndrome is important, as the immune deficiencies may be subtle and undiagnosed until adulthood. Thus, some patients may first present with cardiac failure.

Signal-transduction defects in T cells.

In conclusion, multiple receptors and signal transduction cascades influence T-cell function and fate. During the past few years many of these important aspects of T-cell biology were identified. The complexity of the various signaling pathways has made appreciation of their clinical significance difficult. One way of studying the function of these molecules is to create mice deficient of these components. However, frequently the murine phenotype is far from reflecting the homologous human deficiency. It is therefore beneficial to define the human immunodeficiencies in order to understand the role of a certain signaling molecule in humans. Further, mutations that result in partial deficiencies may result in a different phenotype from null mutations. This information may aid in improving structure/function analysis of these signaling components.

Haemophagocytic lymphohistiocytosis in X-linked severe combined immunodeficiency.

Haemophagocytic lymphohistiocytosis (HLH) is characterized by destruction of haematopoietic elements, and is associated with a variety of manifestations including immune abnormalities. We describe an infant with HLH who had no evidence of infection or malignancy. He had markedly reduced natural killer (NK) and T-cell numbers and mitogen responses, consistent with severe combined immune deficiency. Western blot and flow cytometry analyses revealed an absence of interleukin (IL)-2 receptor gamma (gamma common) chain expression and a transition (C --> T) at nucleotide 684 in the gamma common gene. This novel case highlights the need for a thorough evaluation of immunological phenotype and genotype in patients with HLH.

Anti-topoisomerase-I and clinical findings in systemic sclerosis (scleroderma).

The relationship between anti-topoisomerase-I antibodies and clinical findings was studied in 191 patients with definite systemic sclerosis. This was done by performing ELISA to detect antibodies to recombinant topoisomerase-I. Antibodies to topoisomerase-I were found in 72 patients (37%) with systemic sclerosis, which is a higher percentage than reported in most previous reports on a large unselected population. In 43 patients the presence of antibodies to recombinant topoisomerase-I was confirmed using both the immunodiffusion method and ELISA, with similar results. When classified into diffuse versus limited disease, a significant difference in antibody prevalence was demonstrated (P < 0.005), thus indicating that anti-topoisomerase-I antibody detection with ELISA may assist in early identification of systemic sclerosis subtypes.

Breast mild jaundice: natural history, familial incidence and late neurodevelopmental outcome of the infant.

Jaundice associated with breast feeding is a frequent problem facing the paediatrician. Despite numerous reports on this subject, the natural history, familial occurrence and late neurodevelopment of children with breast milk jaundice remain unclear. The follow up of 60 infants with breast milk jaundice showed that there are two bilirubin peaks, on the 4th and 5th day and on the 14th-15th day of life. In the infants with uninterrupted breast feeding, the hyperbilirubinaemia disappeared slowly and could still be detected 12 weeks after birth. The familial incidence of 13.9%, indicating that in some cases a unique genetic factor is expressed. Late neurodevelopment or hearing defects were not observed, thus enabling the paediatrician to encourage continuation of breast feeding in most cases of healthy infants with breast milk jaundice.

Natural killer cells and autoimmunity.

In various autoimmune diseases it appears that NK activity is impaired, and that this phenomenon is significant in disease development. Impairment of NK activity may be the result of two different mechanisms. In systemic autoimmune diseases, in which various target organs are involved (nonorgan-specific), the peripheral blood NK level is generally lower than normal. This most likely allows the expression of autoimmune phenomena such as B cell hyperactivity and polyclonal antibody production, as is seen in SLE, due to a defect in the termination of the immune response. In autoimmune diseases with more localized, organ-specific lesions one can detect increased NK activity at the target organ itself. In these instances, the cytotoxic characteristic of the NK cell is more prominent. This theory explains why both increased and decreased NK activity may be observed in autoimmune diseases. In some disorders in which decreased NK activity was suspected of being crucial, immunomodulators, known to increase NK activity, were administered. Yet it is still difficult to separate the NK activity from the effect of the remaining immune system.