Simulating the effect of vaccine-induced immune responses on HIV infection.

The need for anti-HIV-1 vaccines is universally recognized. Although several potential vaccine formulations are being tested in clinical trials, the complexity of the viral system and the length of the experimentation required and its costs makes the goal of obtaining such a vaccine still elusive. We have built a mathematical model for the simulation of HIV-1 infection spreading into the body, which allows us study in silico the effect of hypothetical anti-HIV-1 vaccines having different properties. In particular, vaccines eliciting a cytolytic T-cell response, a humoral response, or both can be simulated. The vaccines considered can be envisaged either as preventive or therapeutic and can have different strength. The kinetic parameters used for solving the model are those of HIV-1 infection obtained from experimental and clinical observations. The vaccines are instead characterized by parameters that can be varied in order to mimic different behaviors: the rate of killing of the single effector cell and the rate of neutralization of the single antibody molecule; and the level of the immune response raised. The model allows us to predict which characteristics of immunogenicity a preventive or therapeutic vaccine should possess to be efficacious, and which are the key factors that most likely will affect its ability to control the spread of the infection. We discuss here the conclusions that can be drawn from a such a model and some of its limitations.