Modeling latently infected cell activation: viral and latent reservoir persistence, and viral blips in HIV-infected patients on potent therapy

Model Status

This CellML model has been built with the differential expressions in Rong and Perelson's 2009 paper for the model with programmed expansion and contraction of latently infected cells upon activation using equation set 4 from the paper (rong_2009b). This file is known to run in OpenCell and COR, and is set to the parameters in Table 1 and figure 3 in the paper. The model requires the use of a Normal and Uniform distribution on the variable f (causing it to occasionally spike randomly), but this feature has not been implemented in this CellML model (since we are still waiting for the publication of the 1.2 specification) and therefore we may need to return to this model later. Instead of a normal distribution, f has been manually set to spike from T_on (at day 50) to T_off only once to replicate one spike, and used to compare against the diagrams in the paper (figure 3) which it has replicated. Boolean mathematics have been used to generate f and thus OpenCell gives a validation warning.

Model Structure

ABSTRACT: Although potent combination therapy is usually able to suppress plasma viral loads in HIV-1 patients to below the detection limit of conventional clinical assays, a low level of viremia frequently can be detected in plasma by more sensitive assays. Additionally, many patients experience transient episodes of viremia above the detection limit, termed viral blips, even after being on highly suppressive therapy for many years. An obstacle to viral eradication is the persistence of a latent reservoir for HIV-1 in resting memory CD4(+) T cells. The mechanisms underlying low viral load persistence, slow decay of the latent reservoir, and intermittent viral blips are not fully characterized. The quantitative contributions of residual viral replication to viral and the latent reservoir persistence remain unclear. In this paper, we probe these issues by developing a mathematical model that considers latently infected cell activation in response to stochastic antigenic stimulation. We demonstrate that programmed expansion and contraction of latently infected cells upon immune activation can generate both low-level persistent viremia and intermittent viral blips. Also, a small fraction of activated T cells revert to latency, providing a potential to replenish the latent reservoir. By this means, occasional activation of latently infected cells can explain the variable decay characteristics of the latent reservoir observed in different clinical studies. Finally, we propose a phenomenological model that includes a logistic term representing homeostatic proliferation of latently infected cells. The model is simple but can robustly generate the multiphasic viral decline seen after initiation of therapy, as well as low-level persistent viremia and intermittent HIV-1 blips. Using these models, we provide a quantitative and integrated prospective into the long-term dynamics of HIV-1 and the latent reservoir in the setting of potent antiretroviral therapy.

Schematic diagram of the model.

The original paper reference is cited below:

Modeling latently infected cell activation: viral and latent reservoir persistence, and viral blips in HIV-infected patients on potent therapy, Rong L, Perelson A, 2009, PLoS Computational Biology, 5(issue 10): e1000533. PubMed ID: 19834532