宿主内の抗原進化モデル(<特集>感染症の数理モデル)

概要

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Following infection to a host, some pathogens including human immunodeficiency virus(HIV)and Trypanosoma brucei repeatedly alter their antigen expression, thereby escaping host immune defence (antigenic drift/switching). I here theoretically study intra-host dynamics of pathogen antigenic variants and immune response. In the first model, I assume that antigenicity of a pathogen strain can be indexed in a one-dimensional lattice (the charge-state model) , and analyzes the traveling waves of pathogen antigen variants and specific immune response in antigen-type space. In the second model, I assume that an epitope sequence of a finite length mounts a specific immune response (finite-site model), and focus on the effect of demographic stochasticity and phylogenetic pattern of pathogen variants generated by this escape-and-chase dynamics in sequence space. I found that, 'phylogenetic R_0', the mean number of new escaping mutants generated by a antigen variant before it is wiped out by mounted immune response, gives an accurate predictor for the phylogenetic patterns of antigenic drift.
2004-06-25