In vivo imaging of CD8⁺ T cell-mediated elimination of malaria liver stages

• Published in: Proceedings of the National Academy of Sciences - PNAS 2013-05, Vol.110 (22), p.9090-9095
• Main Authors: Cockburn, Ian A., Amino, Rogerio, Kelemen, Reka K., Kuo, Scot C., Tse, Sze-Wah, Radtke, Andrea, Mac-Daniel, Laura, Ganusov, Vitaly V., Zavala, Fidel, Ménard, Robert
• Format: Article
• Language: English
• Subjects: Adaptive immunology; Adoptive Transfer; Animals; Antigens; Biological Sciences; CD8-Positive T-Lymphocytes - immunology; CD8-Positive T-Lymphocytes - ultrastructure; Cell Line; Epitopes, T-Lymphocyte - metabolism; Glycoproteins; Green Fluorescent Proteins - metabolism; Hepatocytes; Imaging; Immunity; Immunology; Infections; Life Sciences; Liver; Liver - immunology; Liver - parasitology; Malaria; Malaria - immunology; Malaria - parasitology; Mathematical models; Mice; Mice, Inbred BALB C; Mice, Transgenic; Microscopy, Confocal - methods; Models, Immunological; Parasite Load; Parasites; Plasmodium - immunology; Receptors, Antigen, T-Cell - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Sporozoites; T cell receptors; T lymphocytes; Time-Lapse Imaging - methods
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1303858110

CD8 ⁺ T cells are specialized cells of the adaptive immune system capable of finding and eliminating pathogen-infected cells. To date it has not been possible to observe the destruction of any pathogen by CD8 ⁺ T cells in vivo. Here we demonstrate a technique for imaging the killing of liver-stage malaria parasites by CD8 ⁺ T cells bearing a transgenic T cell receptor specific for a parasite epitope. We report several features that have not been described by in vitro analysis of the process, chiefly the formation of large clusters of effector CD8 ⁺ T cells around infected hepatocytes. The formation of clusters requires antigen-specific CD8 ⁺ T cells and signaling by G protein-coupled receptors, although CD8 ⁺ T cells of unrelated specificity are also recruited to clusters. By combining mathematical modeling and data analysis, we suggest that formation of clusters is mainly driven by enhanced recruitment of T cells into larger clusters. We further show various death phenotypes of the parasite, which typically follow prolonged interactions between infected hepatocytes and CD8 ⁺ T cells. These findings stress the need for intravital imaging for dissecting the fine mechanisms of pathogen recognition and killing by CD8 ⁺ T cells.