Abstract
BackgroundMalaria transmission occurs during the blood feeding of infected anopheline mosquitoes concomitant with a saliva injection into the vertebrate host. In sub-Saharan Africa, most malaria transmission is due to Anopheles funestus s.s and to Anopheles gambiae s.l. (mainly Anopheles gambiae s.s. and Anopheles arabiensis). Several studies have demonstrated that the immune response against salivary antigens could be used to evaluate individual exposure to mosquito bites. The aim of this study was to assess the use of secreted salivary proteins as specific biomarkers of exposure to An. gambiae and/or An. funestus bites.MethodsFor this purpose, salivary gland proteins 6 (SG6) and 5′nucleotidases (5′nuc) from An. gambiae (gSG6 and g-5′nuc) and An. funestus (fSG6 and f-5′nuc) were selected and produced in recombinant form. The specificity of the IgG response against these salivary proteins was tested using an ELISA with sera from individuals living in three Senegalese villages (NDiop, n = 50; Dielmo, n = 38; and Diama, n = 46) that had been exposed to distinct densities and proportions of the Anopheles species. Individuals who had not been exposed to these tropical mosquitoes were used as controls (Marseille, n = 45).ResultsThe IgG responses against SG6 recombinant proteins from these two Anopheles species and against g-5′nucleotidase from An. gambiae, were significantly higher in Senegalese individuals compared with controls who were not exposed to specific Anopheles species. Conversely, an association was observed between the level of An. funestus exposure and the serological immune response levels against the f-5′nucleotidase protein.ConclusionThis study revealed an Anopheles salivary antigenic protein that could be considered to be a promising antigenic marker to distinguish malaria vector exposure at the species level. The epidemiological interest of such species-specific antigenic markers is discussed.
Highlights
Malaria transmission occurs during the blood feeding of infected anopheline mosquitoes concomitant with a saliva injection into the vertebrate host
These enzymes are known to facilitate the acquisition of blood meals by removing and degrading pharmacologically active nucleotides (i.e., ATP/ADP) that are important for platelet aggregation at the site of the injury [43]
Understanding the complexity of the Anopheles species behavior is of major importance in vector control interventions to protect human populations against malaria
Summary
Malaria transmission occurs during the blood feeding of infected anopheline mosquitoes concomitant with a saliva injection into the vertebrate host. Several strategies could be used to protect individuals from mosquito bites, either by using personal antivectorial devices, like impregnated bed nets, repellents, and long-sleeved clothes [6], or by controlling vector populations at both the adult and larval stages [7,8] The effectiveness of these anti-vectorial devices is generally evaluated with parasitological and entomological methods [9,10,11]. These methods have demonstrated their capacity to estimate human exposure to malaria vectors and Anopheles densities, these tools lack important logistics and present limited efficiency in the context of lowlevel exposure to Anopheles bites. The development of new indicators and methods to evaluate the effectiveness of anti-vectorial strategies at the individual level is necessary
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