A combination approach to vaccination against tick-borne bacterial infections, using antigens from the tick vector and the bacterial pathogen, and evaluating the elicited immune responses

Summary

Ticks transmit an array of bacteria e.g. Anaplasma, viruses and protozoa to their human/animal hosts, causing tick-borne diseases (TBDs) in humans and animals, high morbidity, and a huge economic cost to livestock farmers. The consequences are especially severe in lower and middle-income countries as the host, vector and pathogen occur in close proximity.  In Africa, ticks are expanding their geographical range, TBD incidence in livestock is increasing and tick resistance to acaricides is leading to greater antibiotic use. In Iran, antibiotic resistance genes in Anaplasma from TBD-infected animals has been reported.

Effective vaccines would prevent TBDs and the emergence of antimicrobial resistance.  Currently there are no vaccines approved for tick-borne bacterial infections in humans, and the few commercially available veterinary vaccines only offer partial protection.   This indicates the urgent need for more efficacious vaccines, and for novel approaches to vaccination. 

Existing vaccines target either the tick vector or the tick-borne pathogen. We propose a different approach.  We hypothesise that combining antigens from the vector and the pathogen in one vaccine formulation would: (i) reduce tick infestation and pathogen transmission among hosts, and (ii) enhance the ability of the host immune response(s) to protect against infection.  

The aim of this project is to test a part of this hypothesis in a murine model, using Anaplasma and Ixodes tick antigens. Animals will be immunised against either the tick antigens, or the pathogen antigens, or a combination of tick and pathogen antigens, and the Th1/Th2 immune responses elicited will be measured.