title: Increased CD8+ T cell memory to concurrent infection at the expense of increased erosion of pre-existing memory: the paradoxical role of IL-15.
abstract: The use of cytokines during vaccination, particularly IL-15, is being considered due to the unique ability of IL-15 to enhance the proliferation of memory CD8(+) T cells. However, as homeostatic mechanisms limit excessive lymphocyte expansion, we addressed the consequences of this enhancement of T cell memory by IL-15. Infection of mice with either recombinant Mycobacterium bovis (BCG) expressing IL-15 (BCG-IL-15) or BCG and purified IL-15 resulted in an increased CD44, IL-2Rbeta expression and increased frequency of IFN-gamma-secreting CD8(+) T cells. Surprisingly, the enhancement of memory to concurrent infection by IL-15 exacerbated the attrition of pre-existing memory. Infection of mice with Listeria monocytogenes expressing OVA resulted in potent OVA(257-264)-specific CD8(+) T cell memory, and a challenge of these mice with either BCG-IL-15 or BCG and purified IL-15 resulted in an increased erosion of OVA(257-264)-specific CD8(+) T cell memory, relative to BCG. Enhancement in the erosion of OVA-specific CD8(+) T cell memory by BCG-IL-15 resulted in a consequently greater impairment in protection against a challenge with OVA-expressing tumor cells. We thus raise important questions regarding vaccinations that are aimed at maximizing T cell memory without considering the impact on pre-existing T cell memory.
authors: Laboratory of Cellular Immunology, Institute for Biological Sciences, National Research Council of Canada, Ontario, Canada.
authors: Yvan
authors: Y
authors: Chapdelaine
authors: Dean K
authors: DK
authors: Smith
authors: Joao A
authors: JA
authors: Pedras-Vasconcelos
authors: Lakshmi
authors: L
authors: Krishnan
authors: Subash
authors: S
authors: Sad
mesh_terms: D000276:Adjuvants, Immunologic / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000378:metabolism* / Q000382:microbiology; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D005260:Female; D007111:Immunity, Cellular / Q000235:genetics; D007117:Immunization, Secondary; D007156:Immunologic Memory / Q000235:genetics; D019409:Interleukin-15 / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008088:Listeriosis / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009163:Mycobacterium bovis / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D010047:Ovalbumin / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D010446:Peptide Fragments / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D010957:Plasmids / Q000378:metabolism; D014376:Tuberculosis / Q000235:genetics / Q000276:immunology; D015854:Up-Regulation / Q000235:genetics / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D019409:Interleukin-15; C110366:OVA-8; D010446:Peptide Fragments; D010047:Ovalbumin