Maternal Passive Immunity and Dengue Hemorrhagic Fever in Infants
Résumé
To understand the role of maternal dengue-specific antibodies in the development of primary Dengue Hemorrhagic Fever (DHF) in infants, we investigated a mathematical model based on a system of nonlinear ordinary differential equations. In this model, we considered the exponential decay of maternal antibodies, the interactions between susceptible and infected target cells, the virus, and maternal antibodies. The neutralization and enhancement activities of maternal antibodies against the virus are represented by a function derived from experimental data and knowledge from medical literature. The analytic study of the model shows the existence of two equilibriums, a disease-free equilibrium and an endemic one. We performed the asymptotic stability analysis for the two equilibriums. The local asymptotic stability of the endemic steady state corresponds to the occurrence of DHF. Numerical results are also presented in order to illustrate the mathematical analysis performed, highlighting the most important parameters that drives the model dynamics. We defined the age at which DHF occurs as the time when the infection takeoff , that means at the inflection point of the infected cell population. We showed that this age corresponds to the age at which maximum enhancing activity for dengue infection appears. This critical time for the occurrence of DHF is calculated from the model to be approximately 2 months after the time for maternal dengue neutralizing antibodies to degrade below a protective level, which correspond to what was observed in the experimental data from the literature.
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