Chitinase and Fizz family members are a generalized feature of nematode infection with selective upregulation of Ym1 and Fizz1 by antigen-presenting cells.
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Ym1 and Fizz1 are secreted proteins that have been identified in a variety of Th2-mediated inflammatory settings. We originally found Ym1 and Fizz1 as highly expressed macrophage genes in a Brugia malayi infection model. Here, we show that their expression is a generalized feature of nematode infection and that they are induced at the site of infection with both the tissue nematode Litomosoides sigmodontis and the gastrointestinal nematode Nippostrongylus brasiliensis. At the sites of infection with N. brasiliensis, we also observed induction of other chitinase and Fizz family members (ChaFFs): acidic mammalian chitinase (AMCase) and Fizz2. The high expression of both Ym1 and AMCase in the lungs of infected mice suggests that abundant chitinase production is an important feature of Th2 immune responses in the lung. In addition to expression of ChaFFs in the tissues, Ym1 and Fizz1 expression was observed in the lymph nodes. Expression both in vitro and in vivo was restricted to antigen-presenting cells, with the highest expression in B cells and macrophages. ChaFFs may therefore be important effector or wound-repair molecules at the site of nematode infection, with potential regulatory roles for Ym1 and Fizz1 in the draining lymph nodes. (+info)
Field validation of sensitivity and specificity of rapid test for detection of Brugia malayi infection.
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We conducted a field study of a rapid test (Brugia Rapid) for detection of Brugia malayi infection to validate its sensitivity and specificity under operational conditions. Seven districts in the state of Sarawak, Malaysia, which are endemic for brugian filariasis, were used to determine the test sensitivity. Determination of specificity was performed in another state in Malaysia (Bachok, Kelantan) which is non-endemic for filariasis but endemic for soil-transmitted helminths. In Sarawak both the rapid test and thick blood smear preparation were performed in the field. The rapid test was interpreted on site, whereas blood smears were taken to the district health centres for staining and microscopic examination. Sensitivity of Brugia Rapid dipstick as compared with microscopy of thick blood smears was 87% (20/23; 95% CI: 66.4-97.2) whereas the specificity was 100% (512/512). The lower sensitivity of the test in the field than in laboratory evaluations (> or =95%), was probably due to the small number of microfilaraemic individuals, in addition to difficulties in performing the test in remote villages by field personnel. The overall prevalence of brugian filariasis as determined by the dipstick is 9.4% (95% CI: 8.2-0.5) while that determined by microscopy is 0.90% (95% CI: 0.5-1.3) thus the dipstick detected about 10 times more cases than microscopy. Equal percentages of adults and children were found to be positive by the dipstick whereas microscopy showed that the number of infected children was seven times less than infected adults. The rapid dipstick test was useful as a diagnostic tool for mapping and certification phases of the lymphatic filariasis elimination programme in B. malayi-endemic areas. (+info)
Chemokine receptors of T cells and of B cells in lymphatic filarial infection: a role for CCR9 in pathogenesis.
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We examined the expression of chemokine receptors on the surfaces of T cells and B cells from 27 individuals either with lymphatic filarial disease (lymphedema), with the asymptomatic or subclinical form of filarial infection, or without filarial infection. Individuals with lymphedema exhibited increased percentages of CCR9-expressing T cells and CCR9-expressing B cells and decreased percentages of both CXCR1-and-CXCR3-expressing T cells and CXCR1-and-CXCR3-expressing B cells, compared with asymptomatic or uninfected individuals. A significant correlation was found between the grade of lymphedema and the percentage of CCR9-expressing T cells and CCR9-expressing B cells. The percentages of CCR9-expressing T cells and CCR9-expressing B cells from patients with lymphedema was significantly up-regulated in response to live, infective-stage larvae of Brugia malayi but not to microfilariae of this parasite. Finally, individuals with lymphedema had significantly higher concentrations of interleukin-8, macrophage inflammatory protein (MIP)-1alpha , MIP-1beta , monocyte chemotactic protein 1, thymus-and-activation-regulated chemokine, and interferon-inducible protein 10 in their serum than did uninfected individuals. These results suggest that chemokine receptors (particularly CCR9) are involved in the pathogenesis of lymphatic filarial disease and that trafficking of particular cellular subsets may influence clinical outcome. (+info)
The Wolbachia genome of Brugia malayi: endosymbiont evolution within a human pathogenic nematode.
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Complete genome DNA sequence and analysis is presented for Wolbachia, the obligate alpha-proteobacterial endosymbiont required for fertility and survival of the human filarial parasitic nematode Brugia malayi. Although, quantitatively, the genome is even more degraded than those of closely related Rickettsia species, Wolbachia has retained more intact metabolic pathways. The ability to provide riboflavin, flavin adenine dinucleotide, heme, and nucleotides is likely to be Wolbachia's principal contribution to the mutualistic relationship, whereas the host nematode likely supplies amino acids required for Wolbachia growth. Genome comparison of the Wolbachia endosymbiont of B. malayi (wBm) with the Wolbachia endosymbiont of Drosophila melanogaster (wMel) shows that they share similar metabolic trends, although their genomes show a high degree of genome shuffling. In contrast to wMel, wBm contains no prophage and has a reduced level of repeated DNA. Both Wolbachia have lost a considerable number of membrane biogenesis genes that apparently make them unable to synthesize lipid A, the usual component of proteobacterial membranes. However, differences in their peptidoglycan structures may reflect the mutualistic lifestyle of wBm in contrast to the parasitic lifestyle of wMel. The smaller genome size of wBm, relative to wMel, may reflect the loss of genes required for infecting host cells and avoiding host defense systems. Analysis of this first sequenced endosymbiont genome from a filarial nematode provides insight into endosymbiont evolution and additionally provides new potential targets for elimination of cutaneous and lymphatic human filarial disease. (+info)
Heterologous expression of the filarial nematode alt gene products reveals their potential to inhibit immune function.
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BACKGROUND: Parasites exploit sophisticated strategies to evade host immunity that require both adaptation of existing genes and evolution of new gene families. We have addressed this question by testing the immunological function of novel genes from helminth parasites, in which conventional transgenesis is not yet possible. We investigated two such novel genes from Brugia malayi termed abundant larval transcript (alt), expression of which reaches ~5% of total transcript at the time parasites enter the human host. RESULTS: To test the hypothesis that ALT proteins modulate host immunity, we adopted an alternative transfection strategy to express these products in the protozoan parasite Leishmania mexicana. We then followed the course of infection in vitro in macrophages and in vivo in mice. Expression of ALT proteins, but not a truncated mutant, conferred greater infectivity of macrophages in vitro, reaching 3-fold higher parasite densities. alt-transfected parasites also caused accelerated disease in vivo, and fewer mice were able to clear infection of organisms expressing ALT. alt-transfected parasites were more resistant to IFN-gamma-induced killing by macrophages. Expression profiling of macrophages infected with transgenic L. mexicana revealed consistently higher levels of GATA-3 and SOCS-1 transcripts, both associated with the Th2-type response observed in in vivo filarial infection. CONCLUSION: Leishmania transfection is a tractable and informative approach to determining immunological functions of single genes from heterologous organisms. In the case of the filarial ALT proteins, our data suggest that they may participate in the Th2 bias observed in the response to parasite infection by modulating cytokine-induced signalling within immune system cells. (+info)
Cloning and characterization of a novel immunogenic protein 3 (NIP3) from Brugia malayi by immuno screening of a phage-display cDNA expression library.
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Iterative screening of a phage display cDNA expression library of the third-stage larvae (L3) of Brugia malayi with sera from putatively immune individuals (endemic normal, EN) identified a novel clone with insert showing significant homology to Onchocerca volvulus novel immunogenic protein-3 (Ov-NIP3) gene and Caenorhabditis elegans NIP3-like protein and hence the gene was designated Brugia malayi NIP3-like protein (BmNIP3). EST database analysis showed that ESTs from several gastrointestinal nematodes such as Ancylostoma caninum, Teladorsagia circumcincta, Haemonchus contortus and Strongyloides stercoralis has BmNIP3 homologues, but the gene has not been described from these parasites. Sequence analyses showed that BmNIP3 has three potential mucin-type O-glycosylation sites and several serine/threonine phosphorylation sites. As expected, BmNIP3 protein isolated from the parasite was serine/threonine phosphorylated. Further analyses showed that BmNIP3 is differentially transcribed, with highest level of expression present in the larval (L3 and L4) stages. Mice immunized with rBmNIP3 developed strong antibody responses predominantly of the IgG1 and IgG2a subtype. A similar analyses of the sera samples from EN individuals showed that they also carry high levels of IgG1 and IgG2 antibodies against BmNIP3, whereas, chronically infected patients carry largely IgG3 antibodies and MF individuals carry high levels of IgG1 antibodies against BmNIP3. This study thus describes a novel protein from B. malayi that appears to be highly immunogenic in both humans and mice. (+info)
Diminished expression and function of TLR in lymphatic filariasis: a novel mechanism of immune dysregulation.
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Lymphatic filariasis is a disease characterized by immune dysregulation involving APC and T cell populations. To assess the contribution of TLR in mediating this dysregulation, we examined the expression of TLR1, TLR2, TLR4, and TLR9 on B cells and monocytes of filaria-infected and uninfected individuals. Baseline expression of TLR was significantly lower in B cells but not in monocytes of the filaria-infected group compared with the uninfected group. Upon stimulation with filarial Ag, a diminished up-regulation of TLR was observed in both B cells and monocytes of infected individuals. Finally, stimulation of B cells and monocytes with TLR ligands resulted in decreased B cell and monocyte activation/cytokine production, indicating a state of immune tolerance. This dysregulation is associated with diminished CD4(+) T cell production of IFN-gamma and IL-5. The diminished expression and function of TLR is thus a likely consequence of chronic Ag stimulation and could serve as a novel mechanism underlying the dysfunctional immune response in filariasis. (+info)
Wolbachia genomes: insights into an intracellular lifestyle.
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The genome sequence of the Wolbachia endosymbiont that infects the nematode Brugia malayi has recently been determined together with three partial Wolbachia genomes from different Drosophila species. These data along with the previously published Wolbachia genome from Drosophila melanogaster provide new insights into how this endosymbiont has managed to become so successful. (+info)