Canine IgE monoclonal antibody specific for a filarial antigen: production by a canine x murine heterohybridoma using B cells from a clinically affected lymph node.
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Canine popliteal lymph node cells taken at the onset of clinical disease from a rear limb infected with the filarial nematode Brugia pahangi were fused with mouse myeloma cell line P3X63.Ag8.653 cells. Of the several canine immunoglobulin-producing clones from this fusion, one was found to produce canine IgE specific for a filarial nematode antigen. The cell line has undergone limiting dilution cloning six times over the past 3 years and continues to produce monoclonal antibody of the IgE subclass at a rate of greater than 3 mg/l. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of the cell culture supernatant protein that bound to protein A beads, showed bands at molecular weights (MW) of approximately 75,000 and 25,000 that were characteristic of epsilon and kappa or lambda chains, respectively. A mouse monoclonal antibody specific for canine IgE bound the 75,000 MW band, as demonstrated by Western blot. Western blots of aqueous extracts of adult filarial nematodes demonstrated binding of the canine IgE monoclonal antibody to a single 35,000 MW peptide from B. pahangi but not Dirofilaria immitis; immunochemistry using frozen sections of adult worms, microfilariae and fourth stage larvae revealed focal binding of the monoclonal IgE to worm tissue adjacent to dorsal and ventral cords of only Brugia adults. (+info)
Heterologous expression and enzymatic properties of a selenium-independent glutathione peroxidase from the parasitic nematode Brugia pahangi.
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A full-length cDNA from the parasitic nematode Brugia pahangi encoding a secreted homolog of glutathione peroxidase in which the codon for the active site selenocysteine is substituted naturally by a cysteine codon has been expressed in Spodoptera frugiperda (insect) cells via Autographa californica nuclear polyhedrosis virus (baculovirus). The recombinant protein was glycosylated and secreted from the cells in tetrameric form. The purified protein showed glutathione peroxidase activity with a range of organic hydroperoxides, including L-alpha-phosphatidylcholine hydroperoxide, but no significant activity against hydrogen peroxide. Glutathione was the only thiol tested that served as a substrate for the enzyme, which showed no activity with the thioredoxin system (thioredoxin, thioredoxin reductase, and NADPH). No glutathione-conjugating activity was detected against a range of electrophilic compounds that are common substrates for glutathione S-transferases. The apparent (pseudo)m for glutathione was determined as 4.9 mM at a fixed concentration of linolenic acid hydroperoxide (3 microM). The enzyme showed low affinity for hydroperoxide substrates (apparent Km for linolenic acid hydroperoxide and L-alpha-phosphatidylcholine hydroperoxide of 3.8 and 9.7 mM, respectively at a fixed glutathione concentration of 3 mM). (+info)
Impact of microfilaremia on maintenance of a hyporesponsive cellular immune response in Brugia-infected gerbils (Meriones unguiculatus).
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The purpose of these experiments was to define the significance of the microfilarial stage to the hyporesponsive condition seen in lymphatic filariasis. Two types of experiments were conducted with Brugia pahangi-infected gerbils. In one, in vitro lymphocyte blastogenesis and in vivo granuloma formation in response to parasite antigen were correlated to microfilaremia in chronically infected individuals. In a second set of experiments, the level of in vivo granuloma formation was assessed following chemotherapeutic removal of microfilariae with ivermectin. The results indicated that the microfilarial stage alone is not responsible for the maintenance of the low cellular responses seen during chronic infections in this model. Furthermore, the data suggest that the degree of downregulation of these responses may be related to parasite burden. (+info)
Extracellular and cytoplasmic CuZn superoxide dismutases from Brugia lymphatic filarial nematode parasites.
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We have isolated full-length cDNAs encoding two distinct types of CuZn superoxide dismutases (SODs) from the filarial nematode parasite Brugia pahangi. The derived amino acid sequences suggested that one class of cDNAs represented a cytoplasmic form of SOD and the second class represented an extracellular (EC) variant. The predicted proteins were highly homologous to each other, but the sequence of the latter contained an additional 43 residues at the N terminus, the first 16 of which were markedly hydrophobic, and four potential sites for N-linked glycosylation. Western blotting (immunoblotting) with an antiserum to a partial SOD expressed in Escherichia coli revealed two proteins with estimated molecular masses of 19 and 29 kDa. Digestion with N-glycanase indicated that the latter protein corresponded to the EC form, as it possessed N-linked oligosaccharide chains at three sites, leaving a peptide backbone with an estimated molecular mass of 22 kDa, which was consistent with the additional 27 amino acids predicted from the cDNA sequence. Gel filtration indicated that both enzymes were dimeric in their native forms, in contrast to the human EC-SOD, which is tetrameric. Comparison of the primary structure of the parasite EC-SOD with that of the human EC enzyme revealed two major differences: the N-terminal extension of the parasite enzyme was shorter by 25 residues, and it also lacked the C-terminal charged extension which mediates binding to cell surface sulfated proteoglycans. Lavage of Mongolian jirds infected intraperitoneally with Brugia malayi resulted in the recovery of filarial CuZn SODs, principally the EC form, indicating that this form of SOD is secreted in vivo. This EC enzyme may contribute to parasite persistence by neutralizing superoxide generated by activated leukocytes, thus acting as both an antioxidant and an anti-inflammatory factor. (+info)
Modulation of cellular and humoral immunity, and disease manifestation during onset of patency in Brugia pahangi-infected dogs.
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Recently, it has become possible to obtain as predicted disease manifestation in selectively bred dogs infected with the naturally occurring lymphatic nematode, Brugia pahangi. In this study, an attempt was made to correlate limb oedema with dynamic changes in immune cell responses occurring in the lymph node at the site of infection during onset of patency. Three litters of dogs were selectively bred; one for the expression of clinical disease, one for the lack of expression of clinical disease and one was of non-specific phenotype. Lymph node cells from 10 of 11 dogs showed a parasite-specific proliferative response at 4-6 weeks post-infection (p.i.), before the onset of patency. In six of 11 dogs, a loss of proliferative response to BpA in the infected node cells was detected around the time of onset of patency. In contrast, there was no reduction in the proliferative response to the mitogen phytohaemagglutinin (PHA). The proliferative response to BpA by unresponsive node cells could be restored by addition of substimulatory amounts of murine or human recombinant interleukin-2 (IL-2) to the culture medium. However, there was no correlation between the proliferative response of lymph node cells from infected limbs and the expression of clinical disease. Similarly, when in vitro parasite-specific antibody production by infected lymph node cells was examined, antibody production manifested by all dogs at 5 weeks p.i. was markedly changed at 8 weeks p.i., but these changes did not correlate with clinical disease. This lack of correlation indicates that the immune response to lymphatic filarial infection, as measured in this study, does not necessarily result directly in disease manifestation, and that other genetically determined factors may influence both the parasite-specific immune response and the clinical outcome of infection. (+info)
Anti-interleukin-4 modulation of the Th2 polarized response to the parasitic nematode Brugia pahangi.
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Lymphatic filariasis is a chronic disease characterized by a pronounced Th2 bias in the immune response and impaired antigen (Ag)-specific Th1 responses. We have used a mouse model of filariasis to investigate the role of the infective form (the third-stage larvae [L3]) in modulating the immune response. Subcutaneous infection of BALB/c mice with L3 of Brugia pahangi has a profound effect on Th cell function. By day 12 post-infection, spleen cells from these mice exhibited a dramatic reduction in concanavalin A-driven proliferation and interleukin-2 (IL-2) and gamma interferon (IFN-gamma) secretion in comparison with uninfected controls. However, exposure to L3 did not render the mice completely unresponsive; these animals mounted a strong Th2 response to the parasite, characterized by elevated levels of IL-4, IL-5, and IL-10 and parasite-specific serum immunoglobulin G (IgG), IgG1, and IgE. Treatment of spleen cells from L3-infected mice with neutralizing anti-IL-4 or recombinant IL-2 resulted in a dramatic increase in concanavalin A-induced proliferation and IL-2 and IFN-gamma production. Despite their defective polyclonal Th1 response, cells from L3 infected mice proliferated when stimulated with Ag, and this response was blocked by anti-IL-4. However, anti-IL-4 treatment failed to induce Ag-specific IL-2 or IFN-gamma production, indicating that B.pahangi-primed Th1 cells do not appear to be present or are still unable to respond even in the absence of IL-4. (+info)
Plasma levels of diethylcarbamazine and their effects on implanted microfilariae of Brugia pahangi in rats.
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Plasma level of diethylcarbamazine (DEC) was measured by using gas chromatography and was compared to the changes of microfilaremia after an intraperitoneal injection with 200 mg/kg of DEC in rats. The microfilaremia was induced artificially by an intravenous implantation with 2 x 10(5) Brugia pahangi microfilariae (mf) 1 day before DEC treatment. The rats treated with DEC showed a rapid and significant decrease in mf number in the circulation within 30 min, continued for 4 hr, and then increased rapidly. DEC seemed to cause transient but significant suppression of microfilaremia of B. pahangi in rats directly. (+info)