How does antigenic evolvability scale up to parasite community dynamics and global diversity? Integrated lab, field, and comparative studies

How do parasite abilities to escape the host's immune response scale up to epidemiological dynamics?

Despite the effectiveness of animal immune systems, parasites are often able to reinfect previously infected individuals, evolve in ways that allow them to infect new species, and persist within individuals, populations, and communities. This proposal aims to explore the way that contingency loci, a genetic mechanism that parasites can use to rapidly diversify the expression of their proteins, allows parasites to escape a host’s immune response and how this is reflected in parasite dynamics. The project focuses on a natural system in the Israeli Negev Dunes where a collection of species and strains of Bartonella bacteria are remarkably prevalent in multiple rodent hosts despite an efficient immune response of the hosts against them. By combining field and laboratory experiments and a comparative approach, we will test how differences in contingency loci lead to (i) variation in host immune responses and repeated infections within a host’s lifetime, (ii) parasite turnover and diversity within and among multiple host individuals and species, and (iii) the remarkable global diversity of Bartonella. Understanding how a genetic mechanism that evolves in the genomes of these bacteria and other parasites to make them capable of escaping host immune responses influences parasite dynamics from local to global biological scales has broad implications for predicting outbreak emergence and guiding parasite control strategies.