The VL data alone is not sufficient to identify the dominant mechanism of immune response: here we primarily worked with a model where the immune response restricts viral production, but other models where the immune response increases the rate of clearance of infected cells, reduces the infectivity of the virus, or protects target cells from infection are all also statistically supported above the target cell limited model, although do not give as good a fit to the observed data as the model with reduction in viral production. The gene discussed is MLC1; the disease is infection.