Special MIG Seminar – Qixin He – Wednesday 11th July, 2018
Agent-based simulations and network analyses reveal the strain structure of falciparum malaria.
The parasite Plasmodium falciparum is the causative agent of malaria, a major human health burden in sub-Saharan Africa. In endemic areas of high transmission, tens of thousands of genes encode for the major antigen of the parasite, resulting in an exorbitant number of distinct parasite strains, which cause chronic malaria infections. Human hosts gain specific immunity towards the different antigens they have been exposed to. This population memory gives an advantage to rare gene variants and a disadvantage to common ones. It is unclear, however, whether such immune selection acts as a dominant force in structuring parasites' enormous diversity, especially given the opposing mixing effect of high recombination rates. We propose the combination of network analyses of genetic similarity with agent-based models that track immunememory in each host, to identify signatures of dominant processes underlying strain structure. We test our theoretical predictions using empirical molecular data from Ghana, unique in their depth of population sampling. We find that networks of repertoire similarity show distinctive signatures of immune selection when compared to networks obtained with neutral models. Application of these network analyses to empirical isolates from asymptomatic infections from local populations in Ghana provides unequivocal evidence for an important role of immune selection at both static and temporal levels.
Qixin He, University of Chicago
University of Chicago
Qixin is an evolutionary biologist, passionate about building theoretical models and applying them empirically to understand the evolution and structuring of population diversities in spacetime. Qixin is a postdoctoral researcher in the group of Prof. Mercedes Pascual at the University of Chicago, having completed a Ph.D. with Prof. L. Lacey Knowles at the University of Michigan, Ann Arbor.