Figure 1

Schematic diagram and model formulation. The elements of the model consist of cells susceptible to viral infections (activated CD4⁺ cells, in large circles), HIV virions (small circles) and hunter viruses (ovals). The diagram illustrates the dynamics of susceptible cells in healthy condition x _h and the formation of infected cell populations (HIV-infected x _v and double infected x _vw , x _s ) via pathogen or therapeutic viral infection (HIV v, hunter w, and HIV-hunter fused particles s). Dashed arrows indicate the cell population targeted by each type of virus. In the diagram, healthy cells x _h infected by HIV are transferred to the population of HIV-infected cells x _v , and then release HIV virions. Alternatively, healthy cells x _h can be infected by fused particles s to become s-infected cells x _s that release hunters. Hunters w and fused particles s can infect HIV-infected cells and generate double-infected cells x _vw , which release both HIV and hunter virions. The graph also shows the formation of fused particles s. Parameters describe infection rates i, death rates of cells d, removal rates of viruses r, and production rates p. Subscripts denote to which population a particular parameter applies (see parameters in Table 1). Equations (denoted as Eqs. 1 in Model description) describe the change in the number of cells or virions over time t (e.g. x^· _h  = dx _h /dt). The positive and negative terms at the right side of a given equation correspond to incoming and outcoming arrows, respectively, for the relevant population in the diagram.