Characteristic analysis of antibodies against mosquito salivary proteins in dengue patients

Dengue fever is a major international public health concern. The interplay between dengue virus, Aedes mosquitoes, and human hosts is crucial for the spread of disease. It has been reported that mosquito salivary proteins were composed of anti-haemostatic, anti-inflammatory, and immunomodulatory agents which contribute to the success of blood meal. Some of these molecules might involve in the transmission and establishment of pathogens in the hosts. In this study, dengue virus was first demonstrated able to bind to the salivary glands of Aedes aegypti at the proximal-lateral lobes by immunofluorescence assay. The affinity was further detected by antibodies against mosquito saliva after probing viral proteins with mosquito salivary gland extract. A band with similar molecular weight of structural protein E (60 kDa) was observed. Since mosquito saliva was injected into the hosts along with pathogens, antibodies were elicited against mosquito salivary proteins as well as virus. The influence of antibodies against mosquito salivary proteins on dengue virus infection is worth to investigate. In 2013, a small scale of indigenous dengue outbreak occurred in Taipei, where only Ae. albopictus thrives. Human antibody responses against Ae. aegypti and Ae. albopictus revealed a significant pattern that most patients were with stronger immune responses against Ae. albopictus than Ae. aegypti, with only one exception of the first case. The result confirmed the transmission route regardless of any mention of travel history. Nevertheless, cross-reactions were observed in most sera. A modified method of Western blot was therefore applied to examine the species-specific immunogens of Aedes mosquitoes. Less than 10 immunogens appeared in the mosquito salivary proteins. After pre-treating serum with salivary gland extracts of Ae. aegypti, bands with molecular weights about 290-, 68-, 44-, 36-, 35-, 29-, and 15-kDa were remained against Ae. albopictus. The potential applications of these immunogenic salivary proteins as biomarkers for exposure to dengue vector mosquitoes will be discussed.