# Measles Infection Dose Responses: Insights from Mathematical Modeling

## TL;DR

This study uses mathematical modeling to show how different doses of the measles virus affect infection progression and immune response in monkeys.

## Contribution

The study introduces a new mathematical model to explain how higher measles infection doses lead to earlier immune responses and similar peak viral levels.

## Key findings

- Higher measles infection doses lead to earlier peaks in viremia but similar peak magnitudes.
- Early immune response activation correlates with higher initial viral loads and faster viral clearance.
- Virus-host interactions and immune efficiency determine measles progression and outcomes.

## Abstract

How viral infections develop can change based on the number of viruses initially entering the body. The understanding of the impacts of infection doses remains incomplete, in part due to challenging constraints, and a lack of research. Gaining more insights is crucial regarding the measles virus (MV). The higher the MV infection dose, the earlier the peak of acute viremia, but the magnitude of the peak viremia remains almost constant. Measles is highly contagious, causes immunosuppression such as lymphopenia, and contributes substantially to childhood morbidity and mortality. This work investigated mechanisms underlying the observed wild-type measles infection dose responses in cynomolgus monkeys. We fitted longitudinal data on viremia using maximum likelihood estimation, and used the Akaike Information Criterion (AIC) to evaluate relevant biological hypotheses and their respective model parameterizations. The lowest AIC indicates a linear relationship between the infection dose, the initial viral load, and the initial number of activated MV-specific T cells. Early peak viremia is associated with high initial number of activated MV-specific T cells. Thus, when MV infection dose increases, the initial viremia and associated immune cell stimulation increase, and reduce the time it takes for T cell killing to be sufficient, thereby allowing dose-independent peaks for viremia, MV-specific T cells, and lymphocyte depletion. Together, these results suggest that the development of measles depends on virus-host interactions at the start and the efficiency of viral control by cellular immunity. These relationships are additional motivations for prevention, vaccination, and early treatment for measles.

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\begin{document}$$10^2$$\end{document}102, 10 and 1 TCID50 correspond to red diamonds, blue stars, orange triangles, magenta dots, and green squares respectively. The solid lines represent the trajectories generated by the proposed model parameterization. The shapes represent data. The dark grey dotted dashed line represents the limit of detection < 0.3. Bottom: Cartoon illustrating that when the measles infection dose increases, the stimulation of the measles-specific cellular immune responses increases early on post-infection. This enhanced immune response reduces the time required to clear the infectious viral load and helps maintain similar levels of viral loads and lymphocyte depletion irrespective of the initial dose.

The online version contains supplementary material available at 10.1007/s11538-024-01305-0.