Defining the mild variant of leukocyte adhesion deficiency type II (SLC35C1-congenital disorder of glycosylation) and response to l-fucose therapy: Insights from two new families and review of the literature.

Leukocyte adhesion deficiency type II (LAD II, also known as SLC35C1-congenital disorder of glycosylation) is an autosomal recessive disorder characterized by growth and cognitive impairment, peripheral neutrophilia, recurrent infections, and the Bombay blood phenotype. A subset of patients with a milder presentation has been described with short stature and developmental delay but minimal immune and hematologic features. Some patients with LAD II benefit from oral fucose therapy, though this has not been previously studied in patients with milder disease. In this study, we describe two new patients from separate families with the milder variant of LAD II and review the published literature on this rare disorder. We demonstrate improvement in speech and cognition, CD15 expression, and core fucosylation of serum glycoproteins after 27 months of oral fucose supplementation in one patient. These patients further support the stratification of this disorder into distinct subtypes, a classical severe and an attenuated variant, and provide preliminary evidence of benefit of fucose therapy in the latter group.

Incidental diagnosis of leukocyte adhesion deficiency type II following ABO typing.

Individuals with the Bombay phenotype (Oh) in the ABO blood group system do not express the H, A, and B antigens but have no clinical symptoms. Bombay phenotype with clinical symptoms has been described in leukocyte adhesion deficiency type II (LAD II), a fucosylation disorder caused by mutations in SLC35C1. Only few LAD II patients have been described so far. Here we describe an additional patient, a 22-year old male, born to unrelated parents, presenting with inflammatory skin disease, periodontitis, growth, and mental retardation, admitted to the department of dentistry for treatment under general anesthesia. Pre-operative routine investigations revealed the presence of the Bombay phenotype (Oh). Genomic sequencing identified two novel triplet deletions of the SLC35C1 gene. Functional investigations confirmed the diagnosis of LAD II. Therapy with oral fucose led to the disappearance of the chronic skin infections and improvements in behavior and attention span.

Type I leucocyte adhesion deficiency in Yemenian family managed with appropriate treatment: A case series.

Primary immunodeficiencies are rare, inherited diseases, characterized by altered function or absence of immune cells. Among them is leukocyte adhesion deficiency Type I (LAD-I), an autosomal recessive disorder characterized by primary immunodeficiency, caused by mutations in the ITGB2 gene which produces inability of leucocytes to migrate toward the area of inflammation and is associated with recurrent life-threatening bacterial and fungal infections. Pyoderma gangrenosum (PG) is an uncommon noninfectious neutrophilic dermatosis, characterized by recurrent, necrotic ulcers. It is a diagnosis of exclusion and can be challenging and its management is empirical, with local (topical tacrolimus or intralesional triamcinolone) or systemic immunosuppressive therapy (oral or intravenous glucocorticoids, sulfasalazine, especially in cases associated with Crohn's disease, cyclosporine and, recently, anti-tumor necrosis factor drugs such as Infliximab, Etanercept, and Adalimumab). Though skin ulcerations are common, predominant clinical presentation as PG can often mimic other diseases. It is unusual in children even more in LAD-I. Here, we present a Yemenian family with LAD-I from consanguineous relatives. All patients had history of chronic recurrent skin ulcerations without any bleeding tendency, associated with persistent neutrophilia and requiring steroids and antibiotics. There was no history of delayed cord separation and the condition was initially diagnosed as epidermolysis bullosa, but successively as PG. LAD-I should be kept in mind while evaluating patients with PG especially in children with persistent neutrophilia in the absence of other rheumatological disorders. Its diagnosis is extremely important from the management perspective, as treating these patients without adequate antibiotic cover may be fatal, as happened to one of our patient, and these patients often require hematopoietic stem cell transplantation for permanent cure. Therefore, genetic counseling especially in population with high consanguinity is mandatory.

Interleukin-12 and Interleukin-23 Blockade in Leukocyte Adhesion Deficiency Type 1.

A patient with leukocyte adhesion deficiency type 1 (LAD1) had severe periodontitis and an intractable, deep, nonhealing sacral wound. We had previously found a dominant interleukin-23-interleukin-17 signature at inflamed sites in humans with LAD1 and in mouse models of the disorder. Blockade of this pathway in mouse models has resulted in resolution of the immunopathologic condition. We treated our patient with ustekinumab, an antibody that binds the p40 subunit of interleukin-23 and interleukin-12 and thereby blocks the activity of these cytokines, inhibiting interleukin-23-dependent production of interleukin-17. After 1 year of therapy, our patient had resolution of his inflammatory lesions without serious infections or adverse reactions. Inhibition of interleukin-23 and interleukin-17 may have a role in the management of LAD1. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

The effect of gentamicin-induced readthrough on a novel premature termination codon of CD18 leukocyte adhesion deficiency patients.

BACKGROUND: Leukocyte adhesion deficiency 1 (LAD1) is an inherited disorder of neutrophil function. Nonsense mutations in the affected CD18 (ITB2) gene have rarely been described. In other genes containing such mutations, treatments with aminoglycoside types of antibiotics (e.g., gentamicin) were reported to partially correct the premature protein termination, by induction of readthrough mechanism. METHODOLOGY/PRINCIPAL FINDINGS: Genetic analysis was performed on 2 LAD1 patients. Expression, functional and immunofluorescence assays of CD18 in the patients were used to determine the in-vivo and in-vitro effects of gentamicin-induced readthrough. A theoretical modeling of the corrected CD18 protein was developed to predict the protein function. RESULTS: We found a novel premature termination codon, C562T (R188X), in exon 6 of the CD18 gene that caused a severe LAD1 phenotype in two unrelated Palestinian children. In-vivo studies on these patients' cells after gentamicin treatment showed abnormal adhesion and chemotactic functions, while in-vitro studies showed mislocalization of the corrected protein to the cytoplasm and not to the cell surface. A theoretical modeling of the corrected CD18 protein suggested that the replacement of the wild type arginine by gentamicin induced tryptophan at the position of the nonsense mutation, although enabled the expression of the entire CD18 protein, this was not sufficient to stabilize the CD18/11 heterodimer at the cell surface. CONCLUSION: A novel nonsense mutation in the CD18 gene causing a complete absence of CD18 protein and severe LAD1 clinical phenotype is reported. Both in vivo and in vitro treatments with gentamicin resulted in the expression of a corrected full-length dysfunctional or mislocalized CD18 protein. However, while the use of gentamicin increased the expression of CD18, it did not improve leukocyte adhesion and chemotaxis. Moreover, the integrity of the CD18/CD11 complex at the cell surface was impaired, due to abnormal CD18 protein and possibly lack of CD11a expression.

Insights into leukocyte adhesion deficiency type 2 from a novel mutation in the GDP-fucose transporter gene.

Leukocyte adhesion deficiency type 2 (LADII) is characterized by defective selectin ligand formation, recurrent infection, and mental retardation. This rare syndrome has only been described in 2 kindreds of Middle Eastern descent who have differentially responded to exogenous fucose treatment. The molecular defect was recently ascribed to single and distinct missense mutations in a putative Golgi guanosine diphosphate (GDP)-fucose transporter. Here, we describe a patient of Brazilian origin with features of LADII. Sequencing of the GDP-fucose transporter revealed a novel single nucleotide deletion producing a shift in the open-reading frame and severe truncation of the polypeptide. Overexpression of the mutant protein in the patient's fibroblasts did not rescue fucosylation, suggesting that the deletion ablated the activity of the transporter. Administration of oral L-fucose to the patient produced molecular and clinical responses, as measured by the appearance of selectin ligands, normalization of neutrophil counts, and prevention of infectious recurrence. The lower neutrophil counts paralleled improved neutrophil interactions with activated endothelium in cremasteric venules of nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. However, fucose supplementation induced autoimmune neutropenia and the appearance of H antigen on erythrocytes, albeit without evidence of intravascular hemolysis. The robust response to fucose despite a severely truncated transporter suggests alternative means to transport GDP-fucose into the Golgi complex.

Sweet solution: sugars to the rescue.

Sugar pills are usually placebos, but Smith et al. (2002, this issue) use one to rescue designer mice unable to make GDP-Fucose. Dietary fucose enters a salvage pathway and spares the mice. Sound simple? Not so. Unknown genetic factors determine life or death.

Impairment of the Golgi GDP-L-fucose transport and unresponsiveness to fucose replacement therapy in LAD II patients.

Leukocyte adhesion deficiency type II is an autosomal recessive syndrome characterized by generalized reduction of L-fucose in glycoconjugates; the specific molecular defect is still undefined. The most important clinical symptoms include severe growth and mental retardation and severe immunodeficiency. Patients from two ethnic groups have been reported, i.e. Arab and Turkish. We have observed that GDP-L-fucose transport into Golgi vesicles was specifically impaired in an Arab patient, with a significant reduction of the V:(max) but no significant differences in the K:(m) from control and parents. GDP-L-fucose transport showed simple saturation kinetics in all samples. Transport of UDP-galactose, UDP-N:-acetylglucosamine, and CMP-sialic acid was comparable into vesicles from the Arab patient, parents, and control. These kinetic parameters probably account for the failure to obtain any clinical and biochemical response to fucose therapy in Arab patients. This contrasts both with the distinctive kinetic properties of GDP-L-fucose transport and with the success of fucose therapy, which have been recently reported in one patient of Turkish origin. Accordingly, the biochemical properties of GDP-L-fucose transport into the Golgi are consistent with different variants of leukocyte adhesion deficiency type II that are probably the result of different molecular defects.

Discontinuation of fucose therapy in LADII causes rapid loss of selectin ligands and rise of leukocyte counts.

Leukocyte adhesion deficiency type II (LADII) is a rare inherited disorder of fucose metabolism. Patients with LADII lack fucosylated glycoconjugates, including the carbohydrate ligands of the selectins, leading to an immunodeficiency caused by the lack of selectin-mediated leukocyte-endothelial interactions. A simple and effective therapy has recently been described for LADII, based on the administration of oral fucose. Parallel to this treatment the lack of E- and P-selectin ligands on neutrophils was corrected, and high peripheral neutrophil counts were reduced to normal levels. This study reports that discontinuation of this therapy leads to the complete loss of E-selectin ligands within 3 days and of P-selectin ligands within 7 days. Peripheral neutrophil counts increased parallel to the decrease of selectin ligands. Selectin ligands reappeared promptly after resumption of the fucose therapy, demonstrating a causal relationship between fucose treatment and selectin ligand expression and peripheral neutrophil counts.

Analysis of the functional characteristics of L-selectin and its expression on normal and CD18-deficient bovine neutrophils.

In vivo responsiveness to epinephrine, expression of L-selectin on neutrophils, changes in intracellular calcium ([Ca2+]i), sulfatide-induced superoxide production and tyrosine phosphorylation in neutrophils were evaluated to elucidate the role of L-selectin-associated functions of normal and CD18-deficient bovine neutrophils. The number of neutrophils in peripheral blood was significantly increased (P < 0.05) in four normal calves at 5-20 min after in vivo administration of epinephrine; however, no significant increase of neutrophils was found in three calves with bovine leucocyte adhesion deficiency (BLAD). Expression of L-selectin on neutrophils from three calves with BLAD was 61-77% of that of normal calves. Pretreatment of neutrophils with phorbol myristate acetate caused a marked decrease in the expression of L-selectin on neutrophils from both normal and BLAD calves. The sulfatide-induced sustained phase of [Ca2+]i concentration in neutrophils from calves with BLAD was significantly (P < 0.05) decreased. Following stimulation with aggregated IgG, the transient phase of [Ca2+]i in neutrophils from normal and BLAD calves was increased; however, the sustained phase of [Ca2+]i in BLAD neutrophils was significantly lower (P < 0.05) than that of controls. Sulfatide-induced O2- production and chemiluminescent response in neutrophils from calves with BLAD were 48-51% of those of normal calves and were inhibited by genistein and wortmannin, respectively, in a dose-dependent manner. The amount of tyrosine phosphorylated 100 kDa protein in neutrophils from BLAD calves stimulated with sulfatides was 57% of that of controls. The degree of L-selectin expression on neutrophils was correlated with the intracellular signalling events and the related superoxide production.

Correction of leukocyte adhesion deficiency type II with oral fucose.

We describe a simple, noninvasive, and effective therapy for leukocyte adhesion deficiency type II (LAD II), a rare inherited disorder of fucose metabolism. This disorder leads to an immunodeficiency caused by the absence of carbohydrate-based selectin ligands on the surface of neutrophils as well as to severe psychomotor and mental retardation. The fucosylation defect in LAD II fibroblasts can be corrected by addition of L-fucose to the culture medium. This prompted us to initiate dietary fucose therapy on a patient with LAD II. Oral supplementation of fucose in this patient induced the expression of fucosylated selectin ligands on neutrophils and core fucosylation of serum glycoproteins. During 9 months of treatment, infections and fever disappeared, elevated neutrophil counts returned to normal, and psychomotor capabilities improved.