Mosquito Saliva: The Hope for a Universal Arbovirus Vaccine?

Arthropod-borne viruses (arboviruses) are taxonomically diverse causes of significant morbidity and mortality. In recent decades, important mosquito-borne viruses such as West Nile, chikungunya, dengue, and Zika have re-emerged and spread widely, in some cases pandemically, to cause serious public health emergencies. There are no licensed vaccines against most of these viruses, and vaccine development and use has been complicated by the number of different viruses to protect against, by subtype and strain variation, and by the inability to predict when and where outbreaks will occur. A new approach to preventing arboviral diseases is suggested by the observation that arthropod saliva facilitates transmission of pathogens, including leishmania parasites, Borrelia burgdorferi, and some arboviruses. Viruses carried within mosquito saliva may more easily initiate host infection by taking advantage of the host's innate and adaptive immune responses to saliva. This provides a rationale for creating vaccines against mosquito salivary proteins, rather than against only the virus proteins contained within the saliva. As proof of principle, immunization with sand fly salivary antigens to prevent leishmania infection has shown promising results in animal models. A similar approach using salivary proteins of important vector mosquitoes, such as Aedes aegypti, might protect against multiple mosquito-borne viral infections.