Etudiante en Master

Laboratoire d'écologie et évolution des parasites
Institut de biologie
Rue Emile-Argand 11
2000 Neuchâtel

yating.li@unine.ch

Background: Borrelia afzelii is a tick-borne bacterial pathogen, which causes Lyme disease in humans ( ).The main vector of B. afzelii is the hard tick Ixodes ricinus. The bank vole, Myodes glareolus, is an important natural host for both I. ricinus and B. afzeli ( ). Previous work has shown that M. glareolus can develop acquired resistance against larval I. ricinus ticks when it is repeatedly infested ( ). Studies on B. burgdorferi sensu stricto infections have shown that this pathogen immunosuppresses acquired immunity in the rodent host ( , ). Specifically, infection with Borrelia pathogens reduces the ability of the vertebrate host to develop and/or maintain long-term protective antibodies against other antigens. These observations suggest that B. afzelii might suppress acquired immunity in M. glareolus for the benefit of its tick vector, I. ricinus.  

Experimental design: My Master thesis project will test whether infection with B. afzelii suppresses acquired immunity in bank voles and the ability to develop antibody responses to other antigens. I will experimentally infect one group of bank voles with B. afzelii via nymphal tick bite and one control group of bank voles will be infested with uninfected nymphal ticks. Each group of bank voles will be infested with I. ricinus larval ticks on three separate occasions. We will measure the following tick fitness components: engorged larval body weight, larva-to-nymph molting success, and nymphal body weight. Between the first and second larval infestation, we will also immunize the voles with two immunodominant antigens: ovalbumin (OVA) and keyhole limpet hemocyanin (KLH). We will take blood samples to measure how the immune response to OVA, KLH, and tick salivary gland antigens changes over time.

Predictions: My predictions are as follows. First, if B. afzelii suppresses acquired immunity in bank voles, the larvae that fed on the infected group would have higher
fitness (e.g. larger larval engorgement weight, higher molting success, and larger nymphal weight) than the larvae that fed on the control group. Second, if B. afzelii reduces the ability of bank voles to develop antibody responses against other antigens, the antibody level of the infected group against OVA and KLH would increase less rapidly than control group over the immunization schedule