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ABSTRACT: The blood feeding behavior of disease-transmitting arthropods creates a unique intersection between vertebrate and invertebrate physiology. Here, we review host blood-derived factors that persist through blood digestion to affect the lifespan, reproduction, and immune responses of some of the most common arthropod vectors of human disease.
Microbes and Infection 01/2013; · 3.10 Impact Factor
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ABSTRACT: We showed previously that ingested human insulin activates the insulin/IGF-1 signaling pathway in Anopheles stephensi and increases the susceptibility of these mosquitoes to Plasmodium falciparum. In other organisms, insulin can alter immune responsiveness through regulation of NF-κB transcription factors, critical elements for innate immunity that are also central to mosquito immunity. We show here that insulin signaling decreased expression of NF-κB-regulated immune genes in mosquito cells stimulated with either bacterial or malarial soluble products. Further, human insulin suppressed mosquito immunity through sustained phosphatidylinositol 3-kinase activation, since inhibition of this pathway led to decreased parasite development in the mosquito. Together, these data demonstrate that activation of the insulin/IGF-1 signaling pathway by ingested human insulin can alter NF-κB-dependent immunity, and ultimately the susceptibility, of mosquitoes to P. falciparum.
Infection and immunity 04/2012; 80(6):2141-9. · 4.21 Impact Factor
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ABSTRACT: Reactive oxygen species (ROS) have been implicated in direct killing of pathogens, increased tissue damage, and regulation of immune signaling pathways in mammalian cells. Available research suggests that analogous phenomena affect the establishment of Plasmodium infection in Anopheles mosquitoes. We have previously shown that provision of human insulin in a blood meal leads to increased ROS levels in Anopheles stephensi. Here, we demonstrate that provision of human insulin significantly increased parasite development in the same mosquito host in a manner that was not consistent with ROS-induced parasite killing or parasite escape through damaged tissue. Rather, our studies demonstrate that ROS are important mediators of both the mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt signaling branches of the mosquito insulin signaling cascade. Further, ROS alone can directly activate these signaling pathways and this activation is growth factor specific. Our data, therefore, highlight a novel role for ROS as signaling mediators in the mosquito innate immune response to Plasmodium parasites.
Antioxidants & Redox Signaling 03/2011; 14(6):943-55. · 8.20 Impact Factor
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Vanessa Corby-Harris,
Anna Drexler,
Laurel Watkins de Jong,
Yevgeniya Antonova, Nazzy Pakpour,
Rolf Ziegler,
Frank Ramberg,
Edwin E Lewis,
Jessica M Brown,
Shirley Luckhart,
Michael A Riehle
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ABSTRACT: Malaria (Plasmodium spp.) kills nearly one million people annually and this number will likely increase as drug and insecticide resistance reduces the effectiveness of current control strategies. The most important human malaria parasite, Plasmodium falciparum, undergoes a complex developmental cycle in the mosquito that takes approximately two weeks and begins with the invasion of the mosquito midgut. Here, we demonstrate that increased Akt signaling in the mosquito midgut disrupts parasite development and concurrently reduces the duration that mosquitoes are infective to humans. Specifically, we found that increased Akt signaling in the midgut of heterozygous Anopheles stephensi reduced the number of infected mosquitoes by 60-99%. Of those mosquitoes that were infected, we observed a 75-99% reduction in parasite load. In homozygous mosquitoes with increased Akt signaling parasite infection was completely blocked. The increase in midgut-specific Akt signaling also led to an 18-20% reduction in the average mosquito lifespan. Thus, activation of Akt signaling reduced the number of infected mosquitoes, the number of malaria parasites per infected mosquito, and the duration of mosquito infectivity.
PLoS Pathogens 01/2010; 6(7):e1001003. · 9.13 Impact Factor
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ABSTRACT: Plasmodium parasites, the causative agent of malaria, are transmitted through the bites of infected Anopheles mosquitoes resulting in over 250 million new infections each year. Despite decades of research, there is still no vaccine against malaria, highlighting the need for novel control strategies. One innovative approach is the use of genetically modified mosquitoes to effectively control malaria parasite transmission. Deliberate alterations of cell signaling pathways in the mosquito, via targeted mutagenesis, have been found to regulate parasite development (1). From these studies, we can begin to identify potential gene targets for transformation. Targeted mutagenesis has traditionally relied upon the homologous recombination between a target gene and a large DNA molecule. However, the construction and use of such complex DNA molecules for generation of stably transformed cell lines is costly, time consuming and often inefficient. Therefore, a strategy using locked nucleic acid-modified oligonucleotides (LNA-ONs) provides a useful alternative for introducing artificial single nucleotide substitutions into episomal and chromosomal DNA gene targets (reviewed in (2)). LNA-ON-mediated targeted mutagenesis has been used to introduce point mutations into genes of interest in cultured cells of both yeast and mice (3,4). We show here that LNA-ONs can be used to introduce a single nucleotide change in a transfected episomal target that results in a switch from blue fluorescent protein (BFP) expression to green fluorescent protein (GFP) expression in both Anopheles gambiae and Anopheles stephensi cells. This conversion demonstrates for the first time that effective mutagenesis of target genes in mosquito cells can be mediated by LNA-ONs and suggests that this technique may be applicable to mutagenesis of chromosomal targets in vitro and in vivo.
Journal of Visualized Experiments 01/2010;
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ABSTRACT: The precise role of Leishmania glycoconjugate molecules including phosphoglycans (PGs) and lipophosphoglycan (LPG) on host cellular responses is still poorly defined. Here, we investigated the interaction of Leishmania major LPG2 null mutant (lpg2(-)), which lacks both PGs and LPG, with dendritic cells (DCs) and the subsequent early immune response in infected mice. Surprisingly, the absence of phosphoglycans did not influence expression pattern of major histocompatibility complex class II (MHC II), CD40, CD80, and CD86 on DCs in vitro and in vivo. However, lpg2(-) L. major induced significantly higher production of interleukin-12p40 (IL-12p40) by infected bone marrow-derived DCs (BMDCs) than wild-type (WT) parasites in vitro. Furthermore, the production of IL-12p40 by draining lymph node cells from lpg2(-) mutant-infected mice was higher than those from WT L. major-infected mice. In model antigen presentation experiments, DCs from lpg2(-) mutant-infected mice induced more gamma interferon (IFN-gamma) and IL-2 production by Leishmania-specific T cells than those from WT-infected mice. Lymphocytes isolated from mice infected for 3 days with lpg2(-) parasites produce similar levels of IFN-gamma, but significantly less IL-4 and IL-10 than WT controls. Decreased IL-4 production was also seen in another general PG-deficient mutant lacking the Golgi UDP-galactose transporters (lpg5A(-) lpg5B(-)), but not with the lpg1(-) mutant lacking only LPG, thereby implicating PGs generally in the reduction of IL-4 production. Thus, Leishmania PGs influence host early immune response by modulating DC functions in a way that inhibits antigen presentation and promotes early IL-4 response, and their absence may impact the balance between Th1 and Th2 responses.
Infection and immunity 07/2009; 77(8):3272-83. · 4.21 Impact Factor
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ABSTRACT: Central memory CD4(+) T cells provide a pool of lymph node-homing, Ag-experienced cells that are capable of responding rapidly after a secondary infection. We have previously described a population of central memory CD4(+) T cells in Leishmania major-infected mice that were capable of mediating immunity to a secondary infection. In this study, we show that the Leishmania-specific central memory CD4(+) T cells require IL-12 to produce IFN-gamma, demonstrating that this population needs additional signals to develop into Th1 cells. In contrast, effector cells isolated from immune mice produced IFN-gamma in vitro or in vivo in the absence of IL-12. In addition, we found that when central memory CD4(+) T cells were adoptively transferred into IL-12-deficient hosts, many of the cells became IL-4 producers. These studies indicate that the central memory CD4(+) T cell population generated during L. major infection is capable of developing into either Th1 or Th2 effectors. Thus, continued IL-12 production may be required to ensure the development of Th1 cells from this central memory T cell pool, a finding that has direct relevance to the design of vaccines dependent upon central memory CD4(+) T cells.
The Journal of Immunology 06/2008; 180(12):8299-305. · 5.79 Impact Factor
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ABSTRACT: A forkhead transcription factor gene, fktf-1, which we propose to be orthologous to the Caenorhabditis elegans dauer-regulatory gene daf-16 has been discovered in the parasitic nematode Strongyloides stercoralis. Genomic and cDNA sequences from both species predict alternately spliced a and b message isoforms. In contrast to C. elegans, where two a isoforms, daf-16a1 and daf-16a2, are found, a single fktf-1a isoform is found in S. stercoralis. Five of the 10 introns found in the C. elegans gene are found in the proposed S. stercoralis ortholog. Functional motifs common to DAF-16 and several mammalian forkhead transcription factors are conserved in FKTF-1. These include the forkhead DNA binding domain, four Akt/protein kinase B phosphorylation sites and a C-terminal domain that may associate with factors such as the steroid receptor coactivator and other factors necessary for transcriptional regulation. An N-terminal serine-rich domain found in DAF-16A is greatly expanded in FKTF-1A. This domain is missing in DAF-16B, FKTF-1B and all mammalian orthologs. FKTF-1 shows the closest phylogenetic relationship to DAF-16 among all known mammalian and nematode forkhead transcription factors. Like its proposed Caenorhabditis ortholog, the fktf-1 message is expressed at all stages of the life cycle examined thus far. Discovery of fktf-1 indicates the presence of an insulin-like signalling pathway in S. stercoralis similar to that known to regulate dauer development in C. elegans. This pathway is a likely candidate to control infective larval arrest and reactivation as well as regulation of the switch between parasitic and free-living development in the parasite.
International Journal for Parasitology 12/2003; 33(13):1537-44. · 3.39 Impact Factor
