• Date: Tuesday, October 3
• Time: 14:00-14:45
• Speaker: Akira Sasaki, Professor, Research Institute for Integrative Evolutionary Science, The Graduate University for Advanced Studies, SOKENDAI, Japan
• Zoom: https://oist.zoom.us/j/91519901846pwd=ZHlDa3J1OC8rVk9ibWtmSk51N1N6UT09 (Meeting ID: 915 1990 1846 / Passcode: 013804)

Title: Mathematical Models Describing Evolutionary Immune Escapes of Pathogens

Abstract: 

Despite the propensity for complex and non-equilibrium dynamics in nature, eco-evolutionary analytical theory typically assumes that populations are at equilibria. In particular, pathogens often show antigenic escape from host immune defenses, leading to repeated epidemics, fluctuating selection, and diversification. We model the evolutionary chase and escape of pathogen antigenicity and host immune system by using a reaction-diffusion system in antigenicity space. The system describes the pathogen immune escape as coupled traveling waves of pathogen antigenicity and host immunity. Our analysis predicts how the speed of antigenic escape of pathogen (traveling wave speed) depends on epidemiological and genetic parameters, as well as the condition under which a stable traveling wave becomes destabilized, resulting in periodic bursts of pathogen outbreaks both in time and antigenicity space. Our model also predicts how this antigenic escape impacts the evolution of transmission and virulence of a pathogen. An extended model incorporating the effect of heterogeneity in host immune competence is also analyzed, showing that the presence of immunocompetent hosts sensitively speeds up the evolutionary rate of antigenic escape. 

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Biography: 

Akira Sasaki joined the Department of Evolutionary Studies of Biosystems at SOKENDAI in July 2007 as a Professor of Mathematical Biology. He is working on the stochastic theory of population genetics, host-parasite coevolution, species packing theory, spatially explicit models of ecology and epidemiology, intrahost dynamics of pathogen and immune system, bet-hedging in changing environment, evolution of cooperation, evolution of mutability in fitness landscapes, restriction avoidance and the evolution of word frequency in phage genome, spatial mosaic formation in Müllerian mimicry system, epidemiology and evolution of virulence in small worlds networks, and on other problems in theoretical population biology. Dr. Sasaki received his bachelor degree in biology from Kyoto University and his master's degree and Ph.D. in mathematical biology from Kyushu University. He has worked as assistant professor and associate professor of mathematical biology at Kyushu University. He has been a visiting research fellow at North Carolina State University, the University of Utrecht, University College London Silwood Park, and Oxford University. He has been a member of the Institute for Advanced Study, Princeton, a visiting professor at Harvard University, a research associate at the International Institute for Applied Systems Analysis, Austria, and a Japan Science and Technology Agency PRESTO researcher.