André Jean-Baptiste, Gandon Sylvain
Génome, Populations, Interactions, Adaptations, UM2-IFREMER-CNRS UMR 5171, Université des Sciences et Techniques du Languedoc, Montpellier, France.
Evolution. 2006 Jan;60(1):13-23.
We explore the potential consequences of vaccination on parasite epidemiology and evolution. Our model combines a microscopic (within-host dynamics) and a macroscopic (epidemiological dynamics) description of the interaction between the parasite and its host. This approach allows relevant epidemiological traits such as parasite transmission, parasite virulence, and host recovery to emerge from a mechanistic model of acute infection describing the interaction between the parasite and the host immune system. We model the effect of a vaccine as an activator of immunity enhancing the replication rate of lymphocytes, their initial density at infection's initiation, their efficacy to kill the parasite, or their activation delay after infection. We analyze the evolution of the replication rate of parasites and show that vaccination may promote the evolution of faster replicating and, consequently, more virulent strains. We also show that intermediate vaccination coverage may lead to the coexistence of two different parasite strategies (a low-virulence strain adapted to naive hosts, and a high-virulence strain, more generalist, adapted to both naive and vaccinated hosts). We discuss the consequences of various vaccination strategies under different epidemiological situations using several distinct measures to evaluate the cost induced by the parasite on individuals and entire host populations.
我们探讨了疫苗接种对寄生虫流行病学和进化的潜在影响。我们的模型结合了对寄生虫与其宿主之间相互作用的微观（宿主内动态）和宏观（流行病学动态）描述。这种方法使得诸如寄生虫传播、寄生虫毒力和宿主恢复等相关流行病学特征能够从一个描述寄生虫与宿主免疫系统相互作用的急性感染机制模型中显现出来。我们将疫苗的作用建模为一种免疫激活剂，它可提高淋巴细胞的复制率、感染开始时它们的初始密度、它们杀死寄生虫的效力，或者感染后它们的激活延迟。我们分析了寄生虫复制率的进化，并表明疫苗接种可能会促进更快复制且因此更具毒力的菌株的进化。我们还表明，中等疫苗接种覆盖率可能导致两种不同寄生虫策略的共存（一种适应未感染宿主的低毒力菌株，以及一种更具通用性、适应未感染和已接种疫苗宿主的高毒力菌株）。我们使用几种不同的指标来评估寄生虫给个体和整个宿主种群带来的成本，从而讨论了在不同流行病学情况下各种疫苗接种策略的影响。
