Moin U. Vera

Scattering optics of foam

The multiple scattering of light by aqueous foams is systematically studied as a function of wavelength, bubble size, and liquid fraction. Results are analyzed in terms of the transport mean free path of the photons and an extrapolation length ratio for the diffuse photon concentration field. The wavelength dependence is minimal and may be attributed entirely to the wavelength dependence of the refractive index of water rather than thin-film interference effects. The transport mean free path is found to be proportional to the bubble diameter and the reciprocal of the square root of liquid fraction. The extrapolation length ratio varies almost linearly with liquid fraction between the values for water-glass-air and air-glass-air interfaces.

Specific antibody titer alters the effectiveness of intrathecal enzyme replacement therapy in canine mucopolysaccharidosis I.

Intrathecal enzyme replacement therapy is an experimental option to treat central nervous system disease due to lysosomal storage. Previous work shows that MPS I dogs receiving enzyme replacement with recombinant human alpha-l-iduronidase into the cisterna magna showed normal brain glycosaminoglycan (GAG) storage after three or four doses. We analyzed MPS I dogs that received intrathecal enzyme in a previous study using an assay that detects only pathologic GAG (pGAG). To quantify pGAG in MPS I, the assay measures only those GAG which display terminal iduronic acid residues on their non-reducing ends. Mean cortical brain pGAG in six untreated MPS I dogs was 60.9±5.93 pmol/mg wet weight, and was 3.83±2.64 in eight normal or unaffected carrier animals (p<0.001). Intrathecal enzyme replacement significantly reduced pGAG storage in all treated animals. Dogs with low anti-iduronidase antibody titers showed normalization or near-normalization of pGAG in the brain (mean 8.17±6.17, n=7), while in dogs with higher titers, pGAG was reduced but not normal (mean 21.9±6.02, n=4). Intrathecal enzyme therapy also led to a mean 69% reduction in cerebrospinal fluid pGAG (from 83.8±26.3 to 27.2±12.3 pmol/ml CSF). The effect was measurable one month after each dose and did not differ with antibody titer. Prevention of the immune response to enzyme may improve the efficacy of intrathecal enzyme replacement therapy for brain disease due to MPS I.

Immune response to intrathecal enzyme replacement therapy in mucopolysaccharidosis I patients

Background:Intrathecal (IT) enzyme replacement therapy with recombinant human α-L-iduronidase (rhIDU) has been studied to treat glycosaminoglycan storage in the central nervous system of mucopolysaccharidosis (MPS) I dogs and is currently being studied in MPS I patients.Methods:We studied the immune response to IT rhIDU in MPS I subjects with spinal cord compression who had been previously treated with intravenous rhIDU. We measured the concentrations of specific antibodies and cytokines in serum and cerebrospinal fluid (CSF) collected before monthly IT rhIDU infusions and compared the serologic findings with clinical adverse event (AE) reports to establish temporal correlations with clinical symptoms.Results:Five MPS I subjects participating in IT rhIDU trials were studied. One subject with symptomatic spinal cord compression had evidence of an inflammatory response with CSF leukocytosis, elevated interleukin-5, and elevated immunoglobulin G. This subject also complained of lower back pain and buttock paresthesias temporally correlated with serologic abnormalities. Clinical symptoms were managed with oral medication, and serologic abnormalities were resolved, although this subject withdrew from the trial to have spinal decompressive surgery.Conclusion:IT rhIDU was generally well tolerated in the subjects studied, although one subject had moderate to severe clinical symptoms and serologic abnormalities consistent with an immune response.

Angular distribution of diffusely backscattered light

We demonstrate that the angular distribution of light diffusely backscattered from an opaque slab depends not only on sample boundary reflectivity but also, in contrast to previous results for diffusely transmitted light, on the anisotropy of the scattering events. This influence of scattering anisotropy is modeled within diffusion theory by a discontinuity in the photon concentration at the source point that is proportional to the average cosine of the scattering angle. The resulting predictions are compared with random walk simulations and with measurements of transmitted and backscattered intensity versus angle for glass frits and aqueous suspensions of polystyrene spheres held in air or immersed in a water bath. Predicted distributions capture the features of experimental and simulation data to within 1% for the best case of high reflectivity and weak anisotropy and to within 10% for the worst case of low reflectivity and strong anisotropy.

Immune-Mediated Inflammation May Contribute to the Pathogenesis of Cardiovascular Disease in Mucopolysaccharidosis Type I

Background Cardiovascular disease, a progressive manifestation of α-L-iduronidase deficiency or mucopolysaccharidosis type I, continues in patients both untreated and treated with hematopoietic stem cell transplantation or intravenous enzyme replacement. Few studies have examined the effects of α-L-iduronidase deficiency and subsequent glycosaminoglycan storage upon arterial gene expression to understand the pathogenesis of cardiovascular disease. Methods Gene expression in carotid artery, ascending, and descending aortas from four non-tolerized, non-enzyme treated 19 month-old mucopolysaccharidosis type I dogs was compared with expression in corresponding vascular segments from three normal, age-matched dogs. Data were analyzed using R and whole genome network correlation analysis, a bias-free method of categorizing expression level and significance into discrete modules. Genes were further categorized based on module-trait relationships. Expression of clusterin, a protein implicated in other etiologies of cardiovascular disease, was assessed in canine and murine mucopolysaccharidosis type I aortas via Western blot and in situ immunohistochemistry. Results Gene families with more than two-fold, significant increased expression involved lysosomal function, proteasome function, and immune regulation. Significantly downregulated genes were related to cellular adhesion, cytoskeletal elements, and calcium regulation. Clusterin gene overexpression (9-fold) and protein overexpression (1.3 to 1.62-fold) was confirmed and located specifically in arterial plaques of mucopolysaccharidosis-affected dogs and mice. Conclusions Overexpression of lysosomal and proteasomal-related genes are expected responses to cellular stress induced by lysosomal storage in mucopolysaccharidosis type I. Upregulation of immunity-related genes implicates the potential involvement of glycosaminoglycan-induced inflammation in the pathogenesis of mucopolysaccharidosis-related arterial disease, for which clusterin represents a potential biomarker.

Loss-of-function in IRF2BPL is associated with neurological phenotypes

The Interferon Regulatory Factor 2 Binding Protein Like (IRF2BPL) gene encodes a member of the IRF2BP family of transcriptional regulators. Currently the biological function of this gene is obscure, and the gene has not been associated with a Mendelian disease. Here we describe seven individuals affected with neurological symptoms who carry damaging heterozygous variants in IRF2BPL. Five cases carrying nonsense variants in IRF2BPL resulting in a premature stop codon display severe neurodevelopmental regression, hypotonia, progressive ataxia, seizures, and a lack of coordination. Two additional individuals, both with missense variants, display global developmental delay and seizures and a relatively milder phenotype than those with nonsense alleles. The bioinformatics signature for IRF2BPL based on population genomics is consistent with a gene that is intolerant to variation. We show that the IRF2BPL ortholog in the fruit fly, called pits (protein interacting with Ttk69 and Sin3A), is broadly expressed including the nervous system. Complete loss of pits is lethal early in development, whereas partial knock-down with RNA interference in neurons leads to neurodegeneration, revealing requirement for this gene in proper neuronal function and maintenance. The nonsense variants in IRF2BPL identified in patients behave as severe loss-of-function alleles in this model organism, while ectopic expression of the missense variants leads to a range of phenotypes. Taken together, IRF2BPL and pits are required in the nervous system in humans and flies, and their loss leads to a range of neurological phenotypes in both species.

A Humoral Immune Response Alters the Distribution of Enzyme Replacement Therapy in Murine Mucopolysaccharidosis Type I

Antibodies against recombinant proteins can significantly reduce their effectiveness in unanticipated ways. We evaluated the humoral response of mice with the lysosomal storage disease mucopolysaccharidosis type I treated with weekly intravenous recombinant human alpha-l-iduronidase (rhIDU). Unlike patients, the majority of whom develop antibodies to recombinant human alpha-l-iduronidase, only approximately half of the treated mice developed antibodies against recombinant human alpha-l-iduronidase and levels were low. Serum from antibody-positive mice inhibited uptake of recombinant human alpha-l-iduronidase into human fibroblasts by partial inhibition compared to control serum. Tissue and cellular distributions of rhIDU were altered in antibody-positive mice compared to either antibody-negative or naive mice, with significantly less recombinant human alpha-l-iduronidase activity in the heart and kidney in antibody-positive mice. In the liver, recombinant human alpha-l-iduronidase was preferentially found in sinusoidal cells rather than in hepatocytes in antibody-positive mice. Antibodies against recombinant human alpha-l-iduronidase enhanced uptake of recombinant human alpha-l-iduronidase into macrophages obtained from MPS I mice. Collectively, these results imply that a humoral immune response against a therapeutic protein can shift its distribution preferentially into macrophage-lineage cells, causing decreased availability of the protein to the cells that are its therapeutic targets.

Mannose 6-phosphate conjugation is not sufficient to allow induction of immune tolerance to phenylalanine ammonia-lyase in dogs.

The immune response to exogenous protein has been shown to reduce therapeutic efficacy in animal models of enzyme replacement therapy. A previously published study demonstrated an immunosuppressive regimen which successfully induced immune tolerance to α-L-iduronidase in canines with mucopolysaccharidosis I. The two key requirements for success were high-affinity receptor-mediated enzyme uptake, conferred by mannose 6-phosphate conjugation, and immunosuppression with low-dose antigen exposure. In this study, we attempted to induce immune tolerance to phenylalanine ammonia-lyase by producing a recombinant mannose 6-phosphate conjugated form and administering it to normal dogs according to the previously published tolerance induction regimen. We found that the recombinant conjugated enzyme was stable, could bind to the mannose 6-phosphate receptor with high affinity, and its uptake into fibroblast cells was mediated by this receptor. However, at the end of a tolerance induction period, all dogs demonstrated an antigen-specific immune response when challenged with increasing doses of unconjugated phenylalanine ammonia-lyase. The average time to seroconvert was not significantly different among three separate groups of test animals (n = 3 per group) and was not significantly different from one group of control animals (n = 3). None of the nine test group animals developed immune tolerance to the enzyme using this method. This suggests that high-affinity cellular uptake mediated by the mannose 6-phosphate receptor combined with a previously studied tolerizing regimen is not sufficient to induce immune tolerance to an exogenous protein and that other factors affecting antigen distribution, uptake, and presentation are likely to be important.