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Gene profiling of P. falciparum and A. gambiae: an assessment of parasite maturation and of host response to infection

ABSTRACT: Simultaneous analysis of Plasmodium falciparum and Anopheles gambiae gene expression: an assessment of parasite maturation and of the mosquito response to infection. Malaria is probably the most lethal and most prevalent parasitic disease in the world, causing more than one million deaths per year. In spite of intensive research, no vaccine exists and good vaccine candidates are still a necessity. Plasmodium sporozoites from mosquito midguts are not as infective as those from salivary glands, presenting a different type of motility which is presumably associated with their invasive capacity. It is assumed that these differences are due to maturation of sporozoites, which happens either in the salivary glands or somewhere along the way from the midgut to the glands. Indeed, the invasion of the salivary gland is considered to be an essential step for malaria transmission to the host and it is known to causes expression of multiple genes in the parasite and activation of some immune-response genes in the insect. Here we compared the gene expression profile of P. falciparum parasites from midgut and salivary glands in order to search for genes involved in parasite maturation; on the assumption that any differentially expressed genes found under this condition could be potentially related to the higher infectivity of the salivary gland derived sporozoites and therefore would be potentially good vaccine candidates. Also, because very little is known about mosquito genes involved in the response to Plasmodium, we compared the gene expression profile of infected and uninfected midguts and salivary glands. Our results demonstrate that, upon infection, at least 13 genes are differentially expressed in the mosquito midgut and 43 in the salivary gland. Gene ontology enrichment analysis showed that among other things, in mosquito salivary glands, infection causes multiple genes related to chitin metabolism to be differentially expressed. Also and more importantly, at least 54 genes were differentially expressed in P. falciparum from salivary glands in comparison to midgut (19 down-regulated and 35 up-regulated). Last, we show for the first time that P. falciparum causes multiple genes in the salivary gland to be regulated and that some of those genes could be potentially beneficial to the parasite.

ORGANISM(S): Plasmodium falciparum Anopheles gambiae

PROVIDER: GSE18780 | GEO | 2014/10/01

SECONDARY ACCESSION(S): PRJNA121249

REPOSITORIES: GEO

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Project description:The mosquito Anopheles gambiae uses its innate immune system to control bacterial and Plasmodium infection of its midgut tissue. The activation of potent IMD pathway-mediated anti-Plasmodium falciparum defenses is dependent on the presence of the midgut microbiota, which activate this defense system upon parasite infection through a peptidoglycan recognition protein, PGRPLC. We employed transcriptomic and reverse genetic analyses to compare the P. falciparum infection-responsive transcriptomes of septic and aseptic mosquitoes and to determine whether bacteria-independent anti-Plasmodium defenses exist. To examine the impact of P. falciparum infection on the mosquito midgut and carcass transcriptomes in the presence or absence of midgut bacteria, we used A. gambiae whole genome microarrays to compare the mRNA abundance of P. falciparum-infected and -naÃ¯ve mosquitoes of antibiotic- and non-antibiotic treated cohorts. P. falciparum infection induced changes in the abundance of as many as 2,183 and 2,429 transcripts in whole mosquitoes belonging to a variety of functional groups in aseptic and septic mosquitoes. Ultimately, we were interested in identifying the genes involved in bacteria-independent anti-Plasmodium responses, and therefore we focused on transcripts displaying increased abundance in the parasite-infected aseptic midguts, placing a particular emphasis on those with predicted immune functions. Because of the central role of serine protease cascades in regulating insect immune defenses, we focused the remainder of our analysis on a clip-domain serine protease C2 (CLIPC2, AGAP004317) and a serine protease inhibitor 7 (SRPN7, AGAP007693) that were specifically upregulated in the parasite-infected, aseptic mosquito midgut. We showed that SRPN7 negatively and CLIPC2 positively regulate the anti-Plasmodium defense, independently of the midgut-associated bacteria. Co-silencing assays suggested that these two genes may function together in a signaling cascade. Neither gene was regulated, nor modulated, by infection with the rodent malaria parasite Plasmodium berghei, suggesting that SRPN7 and CLIPC2 are components of a defense system with preferential activity towards P. falciparum. Further analysis using RNA interference determined that these genes do not regulate the anti-Plasmodium defense mediated by the IMD pathway, and both factors act as agonists of the endogenous midgut microbiota, further demonstrating the lack of functional relatedness between these genes and the bacteria-dependent activation of the IMD pathway. This is the first study confirming the existence of a bacteria-independent, anti-P. falciparum defense. Aseptic and septic midguts and carcasses from P. falciparum-infected A. gambiae vs aseptic and septic midguts and carcasses from uninfected, blood-fed A. gambiae. 3 biological replicates and 1 pseudo-replicate per each array.

Project description:The mosquito Anopheles gambiae uses its innate immune system to control bacterial and Plasmodium infection of its midgut tissue. The activation of potent IMD pathway-mediated anti-Plasmodium falciparum defenses is dependent on the presence of the midgut microbiota, which activate this defense system upon parasite infection through a peptidoglycan recognition protein, PGRPLC. We employed transcriptomic and reverse genetic analyses to compare the P. falciparum infection-responsive transcriptomes of septic and aseptic mosquitoes and to determine whether bacteria-independent anti-Plasmodium defenses exist. To examine the impact of P. falciparum infection on the mosquito midgut and carcass transcriptomes in the presence or absence of midgut bacteria, we used A. gambiae whole genome microarrays to compare the mRNA abundance of P. falciparum-infected and -naïve mosquitoes of antibiotic- and non-antibiotic treated cohorts. P. falciparum infection induced changes in the abundance of as many as 2,183 and 2,429 transcripts in whole mosquitoes belonging to a variety of functional groups in aseptic and septic mosquitoes. Ultimately, we were interested in identifying the genes involved in bacteria-independent anti-Plasmodium responses, and therefore we focused on transcripts displaying increased abundance in the parasite-infected aseptic midguts, placing a particular emphasis on those with predicted immune functions. Because of the central role of serine protease cascades in regulating insect immune defenses, we focused the remainder of our analysis on a clip-domain serine protease C2 (CLIPC2, AGAP004317) and a serine protease inhibitor 7 (SRPN7, AGAP007693) that were specifically upregulated in the parasite-infected, aseptic mosquito midgut. We showed that SRPN7 negatively and CLIPC2 positively regulate the anti-Plasmodium defense, independently of the midgut-associated bacteria. Co-silencing assays suggested that these two genes may function together in a signaling cascade. Neither gene was regulated, nor modulated, by infection with the rodent malaria parasite Plasmodium berghei, suggesting that SRPN7 and CLIPC2 are components of a defense system with preferential activity towards P. falciparum. Further analysis using RNA interference determined that these genes do not regulate the anti-Plasmodium defense mediated by the IMD pathway, and both factors act as agonists of the endogenous midgut microbiota, further demonstrating the lack of functional relatedness between these genes and the bacteria-dependent activation of the IMD pathway. This is the first study confirming the existence of a bacteria-independent, anti-P. falciparum defense.

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Gene profiling of P. falciparum and A. gambiae: an assessment of parasite maturation and of host response to infection

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