The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada.|Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada.|The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada.|Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada.|Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada.|Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada.|The J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute and the Department of Physiology and Pharmacology, The University of Western Ontario, London, Ontario, Canada.|Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada.|Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, Canada.|Department of Microbiology and Immunology, The University of Western Ontario, London, Ontario, Canada.