Immunization with apoptotic phagocytes containing Histoplasma capsulatum activates functional CD8(+) T cells to protect against histoplasmosis

Infect Immun. 2011 Nov;79(11):4493-502. doi: 10.1128/IAI.05350-11. Epub 2011 Sep 12.

Abstract

We have previously revealed the protective role of CD8(+) T cells in host defense against Histoplasma capsulatum in animals with CD4(+) T cell deficiency and demonstrated that sensitized CD8(+) T cells are restimulated in vitro by dendritic cells that have ingested apoptotic macrophage-associated Histoplasma antigen. Here we show that immunization with apoptotic phagocytes containing heat-killed Histoplasma efficiently activated functional CD8(+) T cells whose contribution was equal to that of CD4(+) T cells in protection against Histoplasma challenge. Inhibition of macrophage apoptosis due to inducible nitric oxide synthase (iNOS) deficiency or by caspase inhibitor treatment dampened the CD8(+) T cell but not the CD4(+) T cell response to pulmonary Histoplasma infection. In mice subcutaneously immunized with viable Histoplasma yeasts whose CD8(+) T cells are protective against Histoplasma challenge, there was heavy granulocyte and macrophage infiltration and the infiltrating cells became apoptotic. In mice subcutaneously immunized with carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled apoptotic macrophages containing heat-killed Histoplasma, the CFSE-labeled macrophage material was found to localize within dendritic cells in the draining lymph node. Moreover, depleting dendritic cells in immunized CD11c-DTR mice significantly reduced CD8(+) T cell activation. Taken together, our results revealed that phagocyte apoptosis in the Histoplasma-infected host is associated with CD8(+) T cell activation and that immunization with apoptotic phagocytes containing heat-killed Histoplasma efficiently evokes a protective CD8(+) T cell response. These results suggest that employing apoptotic phagocytes as antigen donor cells is a viable approach for the development of efficacious vaccines to elicit strong CD8(+) T cell as well as CD4(+) T cell responses to Histoplasma infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / physiology*
  • CD11c Antigen / metabolism
  • CD4-Positive T-Lymphocytes / physiology
  • CD8-Positive T-Lymphocytes / immunology*
  • Fungal Vaccines / immunology*
  • Gene Expression Regulation / physiology
  • Histoplasma / immunology*
  • Histoplasmosis / immunology*
  • Histoplasmosis / prevention & control
  • Immunization
  • Mice
  • Mice, Knockout
  • Nitric Oxide Synthase Type II / genetics
  • Nitric Oxide Synthase Type II / metabolism
  • beta 2-Microglobulin / genetics
  • beta 2-Microglobulin / metabolism

Substances

  • CD11c Antigen
  • Fungal Vaccines
  • beta 2-Microglobulin
  • Nitric Oxide Synthase Type II