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J Immunol,
2003]
Although the early human immune response to the infective-stage larvae (L3) of Brugia malayi has not been well-characterized in vivo (because of the inability to determine the precise time of infection), the consensus has been that it must involve a predominant Th2 environment. We have set up an in vitro system to study this early immune response by culturing PBMC from unexposed individuals with live L3 of B. malayi. After 24 h of culture, T cell responses were examined by flow cytometry and by quantitative real-time RT-PCR for multiple cytokines. T cells were activated early following exposure to L3 as indicated by up-regulation of surface markers CD69 and CD71. The frequency of T cells expressing proinflammatory Th1 cytokines (IFN-gamma, TNF-alpha, GM-CSF, IL-1alpha, and IL-8) but not Th2 cytokines (IL-4, IL-5, IL-6, IL-10, and IL-13) was significantly increased in response to L3. This T cell response occurred in both the CD4 and CD8 T cell compartment and was restricted to the effector/memory pool (CD45RO(+)). This T cell response was not due to LPS activity from the parasite or from its endosymbiont, Wolbachia; moreover, it required the presence of APC as well as direct contact with live L3. Real-time RT-PCR analysis of multiple cytokines in the T cells confirmed the increased expression of proinflammatory Th1 cytokines. Up-regulation of these cytokines suggests that the primary immune response to the live infective stage of the parasite is not predominantly Th2 in nature but rather dominated by a proinflammatory response.
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[
Curr Opin Infect Dis,
2018]
PURPOSE OF REVIEW: With increasing international travel and mass global population migration, clinicians in nonendemic countries must be familiar with imported neglected tropical diseases including onchocerciasis, which is commonly known as 'river blindness'. RECENT FINDINGS: Imported onchocerciasis manifests differently in travelers compared with migrants from endemic areas and is likely underdiagnosed in both groups. Recent clinical studies confirm that eosinophilia is not a sensitive marker for Onchocerca volvulus, with one-third of patients having a normal eosinophil count. Novel diagnostics measuring antibodies to multiple recombinant O. volvulus antigens maintain a high sensitivity while improving specificity compared with conventional pan-filarial serologic testing. A 6-week course of doxycycline has macrofilaricidal activity through Wolbachia depletion and may be useful in nonendemic areas in addition to standard serial ivermectin. SUMMARY: Recent studies characterizing distinct clinical presentations in travelers and migrants may enable clinicians to better recognize imported onchocerciasis. Although novel diagnostics have improved specificity, most remain restricted to tropical disease reference laboratories and to date there is no marker of cure. Prolonged doxycycline treatment may reduce the need for serial ivermectin, though more potent short-course macrofilaricidal drugs are being developed.
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G3 (Bethesda),
2014]
In wild-type Caenorhabditis elegans, the synapse from motor neuron M4 to pharyngeal terminal bulb (TB) muscles is silent, and the muscles are instead excited by gap junction connections from adjacent muscles. An
eat-5 innexin mutant lacking this electrical connection has few TB contractions and is unable to grow well on certain foods. We showed previously that this defect can be overcome by activation of the M4 TB synapse. To identify genes that negatively regulate synaptic transmission, we isolated new suppressors of
eat-5. To our surprise, these suppressors included null mutations in NPQR-type calcium channel subunit genes
unc-2 and
unc-36. Our results are consistent with the hypothesis that Ca(2+) entry through the NPQR-type channel inhibits synaptic transmission by activating the calcium-activated K(+) channel SLO-1, thus antagonizing the EGL-19 L-type calcium channel.
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J Clin Tuberc Other Mycobact Dis,
2016]
A simple, affordable diagnostic test for pulmonary tuberculosis (TB) is urgently needed to improve detection of active <i>Mycobacterium tuberculosis.</i> Recently, it has been suggested that animal behavior can be used as a biosensor to signal the presence of human disease. For example, the giant African pouched rats can detect tuberculosis by sniffing sputum specimens while trained honeybees respond to three of the volatile organic compounds (VOCs) detected in the breath of TB positive patients by proboscis extension. However, both rats and honeybees require animal housing facilities and professional trainers, which are outside the scope of most disease testing facilities. Here, we report that the innate olfactory behavioral response of the roundworm nematode <i>Caenorhabditis elegans</i> can be used to detect the TB-specific VOCs methyl <i>p</i>-anisate, methyl nicotinate, methyl phenylacetate and <i>o</i>-phenylanisole, in chemotaxis assays. Dauer larvae, a long-lived stress resistant alternative development state of <i>C. elegans</i> in which the animals can survive for extended periods of time in dry conditions with no food, were also demonstrated to detect the VOCs. We propose that exposing naive dauer larvae to TB-related VOCs and recording their response in this behavioral assay could lead to the development of a new method for TB diagnostics using breath as the sample type.
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[
J Infect Dis,
2009]
BACKGROUND: Monocytes/macrophages from filaria-infected animals exhibit an alternatively activated phenotype; however, very little is known about the alternative activation phenotype of monocytes in human filarial infection. METHODS: To elucidate the activation and cytokine profile of monocytes in human filarial infection, we examined the expression patterns of genes encoding arginase, nitric oxide synthase 2, alternative activation markers, and cytokines in monocytes from individuals with asymptomatic filarial infection and individuals without filarial infection, ex vivo and in response to filarial antigen (Brugia malayi antigen [BmA]). RESULTS: Monocytes from patients with asymptomatic filarial infection exhibited significantly diminished expression of NOS2 and significantly enhanced expression of ARG1. These changes were associated with significantly increased expression of the genes encoding resistin, mannose receptor C type 1 (MRC1), macrophage galactose type C lectin (MGL), and chemokine ligand 18 (CCL18). In response to BmA, purified monocytes from infected individuals also expressed significantly lower levels of interleukin (IL)-12 and IL-18 but, in contrast, expressed significantly higher levels of transforming growth factor beta, IL-10, and suppressor of cytokine signaling 1 mRNA. Inhibition of arginase-1 resulted in significantly diminished expression of the genes encoding resistin, MRC1, MGL, and CCL18, as well as significantly enhanced expression of NOS2 and the genes encoding IL-12 and IL-18. CONCLUSION: Patent human filarial infection is associated with the presence of monocytes characterized by an alternatively activated immunoregulatory phenotype.
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[
Exp Parasitol,
1988]
To determine an optimal method for extracting immunoreactive proteins from filarial parasites, we have subjected Brugia malayi adult worms to a variety of solubilization regimens and compared the results. The parasites were extracted in one of seven detergents (including anionic, cationic, nonionic, and zwitterionic compounds) under varying conditions of pH, detergent concentrations, and incubation time. The individual antigen preparations were then compared both by one-dimensional SDS-PAGE and by immunoblotting analysis using a serum pool from individuals resident in an area endemic for lymphatic filariasis. The cationic detergent cetyltrimethylammonium bromide (CTAB) at 1.0% concentration, pH 7.2, consistently solubilized more proteins immunoreactive with the sera tested. Additionally, CTAB never failed to solubilize immunoreactive proteins solubilized by those other detergents or combinations of detergents studied.
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J Immunol,
2006]
Patent lymphatic filariasis is characterized by a profound down-regulation of immune responses with both parasite Ag-specific tolerance and bystander suppression. Although this down-regulation is confined to the Th1 arm of the immune system in response to parasite Ag, we hypothesized a more generalized suppression in response to live parasites. Indeed, when we examined the cytokine profile of a cohort of filaria-infected (n = 10) and uninfected (n = 10) individuals in response to live infective-stage larvae or microfilariae of Brugia malayi, we found significant impairment of both Th1 and Th2 cytokines characterized by diminished production of IFN-gamma, TNF-alpha, IL-4, IL-5, and IL-10 in infected patients. The molecular basis of this impaired Th1/Th2 response was examined, and we identified three major networks of immunoregulation and tolerance. First, impaired induction of T-bet and GATA-3 mRNA underlies the Th1/Th2 deficiency in infected individuals. Second, regulatory networks, as evidenced by significantly increased expression of Foxp3 (natural regulatory T cell marker) and regulatory effectors such as TGF-beta, CTLA-4, PD-1, ICOS, and indoleamine 2,3-dioxygenase play an important role in immunosuppression. Third, the compromise of effector T cell function is mediated by the enhanced induction of anergy-inducing factors cbl-b, c-cbl (cbl is abbreviation for Casitas B lymphoma), Itch, and Nedd4. Indeed, blocking CTLA-4 or neutralizing TGF-beta restored the ability to mount Th1/Th2 responses to live parasites and reversed the induction of anergy-inducing factors. Hence, we conclude that a profound impairment of live parasite-specific Th1 and Th2 immune responses occurs in lymphatic filariasis that is governed at the transcriptional level by a complex interplay of inhibitory mediators.
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[
Mol Med,
1996]
BACKGROUND: Bm2325, a major IgE-inducing antigen of the filarial parasite Brugia malayi has been implicated in the pathology of tropical pulmonary eosinophilia (TPE), a pulmonary syndrome thought to result from hypersensitivity to microfilariae. MATERIALS AND METHODS: Affinity-purified IgE to Bm2325 from patients with TPE was used to identify a complementary DNA (cDNA) from a B. malayi expression library. Sequence analysis of the cDNA revealed a hitherto unknown parasite protein. Immunoblotting of the recombinant filarial protein using sera of patients with TPE determined its IgE-binding capacity. Reactivity to human lung epithelial cell proteins was analyzed using murine anti-Bm2325 antibodies and serum from patients with TPE. RESULTS: The predicted protein is a homolog of the entire precursor of the gamma-glutamyl transpeptidase (gamma-GT), a key enzyme in the synthesis and degradation of glutathione. The filarial precursor encodes both the heavy (H) and the light (L) chain subunits and shares structural similarities with the mammalian enzymes. The Bm2325 allergen was identified as the homolog of the enzyme light chain subunit. Murine antibodies against the recombinant parasite gamma-GT cross-reacted with the human enzyme present in human airway epithelial cells, and human gamma-GT is a target of antibodies present in the serum of patients with TPE. CONCLUSION: Molecular mimicry between the parasite gamma-GT homolog and the host membrane-bound gamma-GT present in lung epithelial cells likely contributes to the pathogenesis observed in tropical pulmonary eosinophilia.
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Infect Immun,
2003]
A major allergen of the lymphatic filarial nematode Brugia malayi, a homologue of gamma-glutamyl transpeptidase (gamma-GT), is involved in the pathology of tropical pulmonary eosinophilia (TPE) through its potent allergenicity and the induction of antibodies against the host pulmonary epithelium. To investigate the immunoglobulin G (IgG) subclass and IgE responses to recombinant B. malayi gamma-GT, we analyzed the results obtained from 51 patients with differing clinical manifestations of bancroftian filariasis. gamma-GT-specific IgG1, rather than IgG4, was the predominant IgG subclass, particularly in patients with TPE (geomean, 6,321 ng/ml; range, 78 to 354,867 ng/ml) and was 75 times higher than in patients with elephantiasis (CP) (P < 0.003) and 185 times higher than in endemic normal individuals (ENL) (P < 0.010). IgG2 responses were low and IgG3 was almost absent, with no significant differences among the groups. gamma-GT-specific IgG4 responses were significantly elevated in those with subclinical microfilaremia (MF) compared to the CP and ENL groups and correlated with the presence of circulating filarial antigen (CAg). More significantly, gamma-GT-specific IgE antibody levels were strikingly elevated in patients with TPE (geomean, 681 ng/ml; range, 61 to 23,841 ng/ml) and in the ENL group (geomean, 106 ng/ml; range, 13 to 1,405 ng/ml) whereas the gamma-GT-specific IgE level was 44 and 61 times lower in those with MF and CP, respectively (P < 0.001). Elevated gamma-GT-specific IgE/IgG4 ratios were demonstrated in patients with TPE (ratio, 45) and ENL (ratio, 107). Because expression of gamma-GT in Brugia infective third-stage larvae (L3) was demonstrated by immunoblot analysis, the elevated gamma-GT-specific IgE antibodies appear to be associated not only with pulmonary pathology but also with possible resistance to infection in lymphatic filariasis.
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J Immunol,
2004]
Basophil contribution to the IL-4 pool in filarial infections was assessed using PBMC from 20 patients with active filarial infections and from 9 uninfected subjects. Patient basophils released histamine in response to Brugia malayi Ag (BmAg). They also released IL-4 within 2 h after exposure to BmAg, as assessed by intracellular cytokine flow cytometry. This IL-4 induction was Ag specific, as IL-4 was not detected in BmAg-exposed basophils obtained from uninfected subjects. Although there were, on average, 64 times more CD4(+) T cells than basophils in the peripheral circulation of filaria-infected patients, the absolute numbers of basophils and CD4(+) T cells producing IL-4 per 100000 PBMC were equivalent (geometric mean: 16 IL-4-producing basophils/100000 PBMC vs 22 IL-4-producing CD4(+) T cells/100000 PBMC). Basophils also released IL-4 in response to both low and high concentrations of BmAg, whereas CD4(+) T cells released IL-4 only after incubation with a high concentration of BmAg, raising the possibility that basophils, due to their lower threshold for activation, may actually release IL-4 more frequently than CD4(+) T cells in vivo. Furthermore, IL-4 production in vitro by Ag-stimulated purified basophils or CD4(+) T cells provided evidence that basophils release greater quantities of IL-4 per cell than CD4(+) T cells in response to BmAg. These results suggest that, when Ag-specific IgE is present in a filaria-infected individual, basophils function to amplify the ongoing Th2 response by releasing IL-4 in greater amounts and possibly more frequently than CD4(+) T cells in response to filarial Ag.