• Computational approaches to parameter estimation and model selection in immunology

      Baker, Christopher T. H.; Bocharov, Gennady; Ford, Judith M.; Lumb, Patricia M.; Norton, Stewart J.; Paul, C. A. H.; Junt, Tobias; Krebs, Philippe; Ludewig, Burkhard (Elsevier, 2005-12-01)
      This article seeks to illustrate the computational implementation of an information-theoretic approach (associated with a maximum likelihood treatment) to modelling in immunology.
    • Determining control parameters for dendritic cell-cytotoxic T lymphocyte interaction

      Ludewig, Burkhard; Krebs, Philippe; Junt, Tobias; Metters, Helen; Ford, Neville J.; Anderson, Roy M.; Bocharov, Gennady; University of Zürich ; University of Zürich ; University of Zürich ; University of Zürich ; University College Chester ; Imperial College, University of London ; Institute of Numerical Mathematics, Russian Academy of Sciences (WILEY-VCH Verlag GmbH & Co. KGaA, 2004-08-05)
      Dendritic cells (DC) are potent immunostimulatory cells facilitating antigen transport to lymphoid tissues and providing efficient stimulation of T cells. A series of experimental studies in mice demonstrated that cytotoxic T lymphocytes (CTL) can be efficiently induced by adoptive transfer of antigen-presenting DC. However, the success of DC-based immunotherapeutic treatment of human cancer, for example, is still limited because the details of the regulation and kinetics of the DC-CTL interaction are not yet completely understood. Using a combination of experimental mouse studies, mathematical modeling, and nonlinear parameter estimation, we analyzed the population dynamics of DC-induced CTL responses. The model integrates a predator-prey-type interaction of DC and CTL with the non-linear compartmental dynamics of T cells. We found that T cell receptor avidity, the half-life of DC, and the rate of CTL-mediated DC-elimination are the major control parameters for optimal DC-induced CTL responses. For induction of high avidity CTL, the number of adoptively transferred DC was of minor importance once a minimal threshold of approximately 200 cells per spleen had been reached. Taken together, our study indicates that the availability of high avidity T cells in the recipient in combination with the optimal application regimen is of prime importance for successful DC-based immunotherapy.
    • Underwhelming the immune response: Effect of slow virus growth on CD8+-T-lymphocyte responses

      Bocharov, Gennady; Burkhard, Ludewig; Bertoletti, Antonio; Klenerman, Paul; Junt, Tobias; Krebs, Philippe; Luzyanina, Tatyana; Fraser, Cristophe; Anderson, Roy M.; University of London/Institute of Numerical Mathematics, Russian Academy of Sciences ; University of Zurich ; University College London ; Oxford University ; University of Zurich ; University of Zurich ; Leuven University ; University of London ; University of London (American Society for Microbiology, 2004-02-12)
      The speed of virus replication has typically been seen as an advantage for a virus in overcoming the ability of the immune system to control its population growth. Under some circumstances, the converse may also be true: more slowly replicating viruses may evoke weaker cellular immune responses and therefore enhance their likelihood of persistence. Using the model of lymphocytic choriomeningitis virus (LCMV) infection in mice, we provide evidence that slowly replicating strains induce weaker cytotoxic-T-lymphocyte (CTL) responses than a more rapidly replicating strain. Conceptually, we show a "bell-shaped" relationship between the LCMV growth rate and the peak CTL response. Quantitative analysis of human hepatitis C virus infections suggests that a reduction in virus growth rate between patients during the incubation period is associated with a spectrum of disease outcomes, from fulminant hepatitis at the highest rate of viral replication through acute resolving to chronic persistence at the lowest rate. A mathematical model for virus-CTL population dynamics (analogous to predator [CTL]-prey [virus] interactions) is applied in the clinical data-driven analysis of acute hepatitis B virus infection. The speed of viral replication, through its stimulus of host CTL responses, represents an important factor influencing the pathogenesis and duration of virus persistence within the human host. Viruses with lower growth rates may persist in the host because they "sneak through" immune surveillance.