Genetic Control of Malaria Parasite Transmission: Threshold Levels for Infection in an Avian Model System

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The discovery and mapping of cis-regulatory elements is important for understanding regulation of gene transcription in mosquito vectors of human diseases. Genome sequence data are available for 3 species, Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus (Diptera: Culicidae), representing 2 subfamilies (Culicinae and Anophelinae) that are estimated to have diverged 145 to 200 million years ago. Comparative genomics tools were used to screen genomic DNA fragments located in the 5 -end flanking regions of orthologous genes. These analyses resulted in the identification of 137 sequences, designated ''mosquito motifs,'' 7 to 9 nucleotides in length, representing 18 families of putative cis-regulatory elements conserved significantly among the 3 species when compared to the fruit fly, Drosophila melanogaster. Forty-one of the motifs were implicated previously in experiments as sites for binding transcription factors or functioning in the regulation of mosquito gene expression. Further analyses revealed associations between specific motifs and expression profiles, particularly in those genes that show increased or decreased mRNA abundance in females following a blood meal, and those accumulating transcription products exclusively or preferentially in the midgut, fat bodies, or ovaries. These results validate the methodology and support a relationship between the discovered motifs and the conservation of hematophagy in mosquitoes.gene expression ͉ hematophagy ͉ Aedes ͉ Anopheles ͉ Culex

Section: Discussionmentioning

confidence: 99%

Comparative genomics allows the discovery of cis -regulatory elements in mosquitoes

Sieglaff

Dunn

Xie

et al. 2009

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“…The target of zero sporozoites in salivary glands was set as the most epidemiologically-relevant phenotype following experiments in an avian malaria model in which few parasites (<10) were needed to infect the vertebrate host (19). The absence of sporozoites in mosquitoes carrying the transgenes tested here, in particular those comprising m1C3 and m2A10, meets this target.…”

Section: Discussionmentioning

confidence: 99%

Transgenic Anopheles stephensi coexpressing single-chain antibodies resist Plasmodium falciparum development

Isaacs

Jasinskiene

Третьяков

et al. 2012

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129

150

Anopheles stephensi mosquitoes expressing m1C3, m4B7, or m2A10 single-chain antibodies (scFvs) have significantly lower levels of infection compared to controls when challenged with Plasmodium falciparum, a human malaria pathogen. These scFvs are derived from antibodies specific to a parasite chitinase, the 25 kDa protein and the circumsporozoite protein, respectively. Transgenes comprising m2A10 in combination with either m1C3 or m4B7 were inserted into previously-characterized mosquito chromosomal "docking" sites using site-specific recombination. Transgene expression was evaluated at four different genomic locations and a docking site that permitted tissue-and sex-specific expression was researched further. Fitness studies of docking site and dual scFv transgene strains detected only one significant fitness cost: adult docking-site males displayed a late-onset reduction in survival. The m4B7/m2A10 mosquitoes challenged with P. falciparum had few or no sporozoites, the parasite stage infective to humans, in three of four experiments. No sporozoites were detected in m1C3/m2A10 mosquitoes in challenge experiments when both genes were induced at developmentally relevant times. These studies support the conclusion that expression of a single copy of a dual scFv transgene can completely inhibit parasite development without imposing a fitness cost on the mosquito.mosquito vector | population replacement | genetic engineering

“…Utilization of transgenesis to generate mosquitoes with altered immunity has been instrumental in deciphering major immune pathways and their role in antipathogen defense (7,(9)(10)(11). Transgenic mosquitoes with antipathogen refractory phenotypes have been developed by utilizing blood meal-activated, tissue-specific promoters, and effector molecules or RNAi-constructs (11)(12)(13)(14)(15). However, complete interruption of pathogen transmission in these transgenic models has not been achieved.…”

mentioning

confidence: 99%

“…However, complete interruption of pathogen transmission in these transgenic models has not been achieved. In the case of malaria parasite, only a few sporozoites present in mosquito salivary glands were sufficient to infect a vertebrate host (15). These transgenic mosquitoes with antipathogen refractory phenotypes have been based on expression of a single type effector molecule in a single organ or tissue.…”

mentioning

confidence: 99%

Blocking of Plasmodium transmission by cooperative action of Cecropin A and Defensin A in transgenic Aedes aegypti mosquitoes

Kokoza

Ahmed

Shin

et al. 2010

133

105

To overcome burden of mosquito-borne diseases, multiple control strategies are needed. Population replacement with genetically modified mosquitoes carrying antipathogen effector genes is one of the possible approaches for controlling disease transmission. However, transgenic mosquitoes with antipathogen phenotypes based on overexpression of a single type effector molecule are not efficient in interrupting pathogen transmission. Here, we show that co-overexpression of two antimicrobial peptides (AMP), Cecropin A, and Defensin A, in transgenic Aedes aegypti mosquitoes results in the cooperative antibacterial and antiPlasmodium action of these AMPs. The transgenic hybrid mosquitoes that overexpressed both Cecropin A and Defensin A under the control of the vitellogenin promoter exhibited an elevated resistance to Pseudomonas aeruginosa infection, indicating that these AMPs acted cooperatively against this pathogenic bacterium. In these mosquitoes infected with P. gallinaceum, the number of oocysts was dramatically reduced in midguts, and no sporozoites were found in their salivary glands when the mosquitoes were fed twice to reactivate transgenic AMP production. Infection experiments using the transgenic hybrid mosquitoes, followed by sequential feeding on naive chicken, and then naive wild-type mosquitoes showed that the Plasmodium transmission was completely blocked. This study suggests an approach in generating transgenic mosquitoes with antiPlasmodium refractory phenotype, which is coexpression of two or more effector molecules with cooperative action on the parasite.vector-borne disease | malaria | immunity | antimicrobial peptide | vitellogenin