Anopheles gambiae salivary protein expression modulated by wild Plasmodium falciparum infection: highlighting of new antigenic peptides as candidates of An. gambiae bites

Abstract

BackgroundMalaria is the major parasitic disease worldwide caused by Plasmodium infection. The objective of integrated malaria control programs is to decrease malaria transmission, which needs specific tools to be accurately assessed. In areas where the transmission is low or has been substantially reduced, new complementary tools have to be developed to improve surveillance. A recent approach, based on the human antibody response to Anopheles salivary proteins, has been shown to be efficient in evaluating human exposure to Anopheles bites. The aim of the present study was to identify new An. gambiae salivary proteins as potential candidate biomarkers of human exposure to P. falciparum-infective bites.MethodsExperimental infections of An. gambiae by wild P. falciparum were carried out in semi-field conditions. Then a proteomic approach, combining 2D-DIGE and mass spectrometry, was used to identify the overexpressed salivary proteins in infected salivary glands compared to uninfected An. gambiae controls. Subsequently, a peptide design of each potential candidate was performed in silico and their antigenicity was tested by an epitope-mapping technique using blood from individuals exposed to Anopheles bites.ResultsFive salivary proteins (gSG6, gSG1b, TRIO, SG5 and long form D7) were overexpressed in the infected salivary glands. Eighteen peptides were designed from these proteins and were found antigenic in children exposed to the Anopheles bites. Moreover, the results showed that the presence of wild P. falciparum in salivary glands modulates the expression of several salivary proteins and also appeared to induce post-translational modifications.ConclusionsThis study is, to our knowledge, the first that compares the sialome of An. gambiae both infected and not infected by wild P. falciparum, making it possible to mimic the natural conditions of infection. This is a first step toward a better understanding of the close interactions between the parasite and the salivary gland of mosquitoes. In addition, these results open the way to define biomarkers of infective bites of Anopheles, which could, in the future, improve the estimation of malaria transmission and the evaluation of malaria vector control tools.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-014-0599-y) contains supplementary material, which is available to authorized users.

Detection of immunogenic proteins from Anopheles sundaicussalivary glands in the human serum

“…TRIO protein is one of several antigenic proteins, in addition to gSG6, gSG1b, SG5, and long form D7, that are over expressed in salivary glands infected with Plasmodium falciparum. Therefore, TRIO proteins may be involved in malaria transmission and may represent a new candidate biomarker for infected Anopheles bites (25) .…”

Immunization with AgTRIO, a Protein in Anopheles Saliva, Contributes to Protection against Plasmodium Infection in Mice

“…Consistent with this, we detected AgTRIO protein in the salivary glands (Figure 2B). The presence of P. berghei sporozoites in the salivary glands augmented the expression of AgTRIO (Figure 2C) (Marie et al, 2014; Zocevic et al, 2013) and the production of AgTRIO protein (Figure 2D). In addition, AgTRIO was secreted into saliva, as confirmed by a western blot with AgTRIO antiserum (Figure 2E).…”

“…We now call it A. gambiae TRIO (AgTRIO) to reflect that it is from A. gambiae , although functional domains required for Rho GTPase activity are lacking. AgTRIO was previously reported to be expressed in the salivary glands of female anopheline mosquitoes (Arca et al, 2005; Marie et al, 2014). We also found that AgTRIO was expressed only in salivary glands and not in other organs (Figure 2A).…”

Impact of insect salivary proteins in blood feeding, host immunity, disease, and in the development of biomarkers for vector exposure

“…The invasion of vector's salivary gland by pathogens causes disturbances in the cells homeostasis, leading to not only activation of the tissue remodeling machinery [22,23], but also modulations in the expression of salivary proteins [20,22–26]. The later can have a significant impact in the pathogen transmission.…”

“…Whereas Plasmodium falciparum invasion of the mosquito An. gambiae salivary glands leads to up-regulation in the expression of the gSG6 salivary protein [26], P. berghei invasion in the same vector leads to reduction in the expression of gSG6 and other three secreted proteins (apyrase, D7-related 1, and AEDA), and up-regulation of the protein gVAG [20]. Although infection with DENV-2 virus does not seem to induce differential expression in salivary gland genes encoding secreted proteins in the mosquitoes Ae.…”