Transmission-Blocking Vaccines: Focus on Anti-Vector Vaccines against Tick-Borne Diseases

Abstract

Tick-borne diseases are a potential threat that account for significant morbidity and mortality in human population worldwide. Vaccines are not available to treat several of the tick-borne diseases. With the emergence and resurgence of several tick-borne diseases, emphasis on the development of transmission-blocking vaccines remains increasing. In this review, we provide a snap shot on some of the potential candidates for the development of anti-vector vaccines (a form of transmission-blocking vaccines) against wide range of hard and soft ticks that include Ixodes, Haemaphysalis, Dermacentor, Amblyomma, Rhipicephalus and Ornithodoros species.

Fig. 1

Anti-vector vaccines. Schematic representation of the proposed strategy on the effect of anti-tick vaccination in humans is shown. Larval ticks become infected by feeding on infected vertebrate hosts and molt into nymphs. Nymphs transmit pathogens to humans. Several scenarios might be envisioned with regard to the effect of anti-tick vaccine administration in natural human population. Non-vaccinated humans bitten by infected ticks may become infected and develop disease symptoms or remain uninfected by natural resistance. On the other hand, vaccinated individuals might be protected from infection or may still become infected due to poor responsiveness to the vaccine. As shown in the illustration, three types of vaccine strategies can be considered. First, anti-vector vaccine can be designed to degrade pathogens inside ticks. Second, anti-vector vaccine can be designed to target vector molecules to prevent pathogen transmission. Third, anti-vector vaccine can be designed to target vector molecules to degrade or affect physiology and survival of ticks