Mosquito salivary gland protein preservation in the field for immunological and biochemical analysis

Mosquitoes are responsible for a wide range of important diseases that cause morbidity and mortality in tropical and temperate regions [1,2]. Pathogen transmission occurs during the blood-feeding of infected mosquitoes, concomitant with salivary protein release [3]. Analysis of salivary mosquito contents using transcriptomic and proteomic tools [4-6] have revealed a panel of salivary molecules with anti-hemostatic and immuno-modulatory properties which facilitate blood meals by counteracting host's defences [6,7]. It was repeatedly demonstrated that mosquito salivary proteins could also elicit a host IgG response in natural conditions [8-10]. Thus, the potential use of these antigenic proteins as epidemiological markers for evaluating individual human exposure level to specific mosquito species is a major research area. Additionally, the identification of such vector-borne immunogenic proteins can lead to a panel of promising applications such as the evaluation of anti-mosquito strategies effectiveness, the mapping of new infestation areas, the estimation of disease transmission risk or the development of vaccines protecting the host against the transmission and establishment of pathogens [11,12]. As our aim is to identify biological markers of individual exposure to arthropod bites using correspondent antigenic materials, it was necessary to develop a convenient protocol to collect and preserve biological samples in the field.The most common method used to obtain salivary proteins is salivary gland (SG) dissection [13-15]. Mosquito SGs contain a cocktail of enzymes and active proteins necessary for their blood-feeding that could alter salivary protein integrity [3,16]. To avoid protein degradation, SGs are generally collected on ice and stored at or below -20°C until needed [15,17]. However, maintaining samples in a frozen environment can be hard to achieve in field conditions.Although hundreds of mosquito species have been reared in laboratories, relatively few ha