| Summary: | 碩士 === 國立臺灣大學 === 免疫學研究所 === 89 === His 62 is a glycoprotein isolated from the cell wall and cell membrane fraction of the yeast cells of the pathogenic fungus Histoplasma capsulatum. Spleen cells from mice infected with viable H. capsulatum yeast cells or immunized with native His 62 protein proliferate in response to His 62 stimulation in vitro. In addition, mice immunized with His 62 confer protection against lethal challenge of H. capsulatum yeast cells. In this study, we sought to determine the protective effect of recombinant His 62 (rHis 62). C57BL/6 and C3H/HeJ mice were injected with rHis 62 emulsified in complete Frend's adjuvant. Lymph node cells from these mice were stimulated with rHis 62 in vitro. In response to stimulation, lymph node cells proliferated and produced IFN-g. In addition, specific IgG2a was detected in the sera of these animals. However, our data show that C57BL/6 mice injected with rHis 62 suspended in MPL+TDM+CWS adjuvant did not reduce mortality upon challenge with a lethal dose, nor did it reduce fungal burden after challenge with a sublethal dose of the fungus. Moreover, rHis 62 injection did not increase the level of IFN-g in animals after sublethal infection. Possible causes for why rHis 62 failed to confer protection were discussed.
We went on to identify immunogens from H. capsulatum yeast cell lysate. Yeast cells were disrupted by glass beads to obtain lysate. By use of immunoprecipition and Western blotting, we found that a 80 KDa protein was recognized by pooled immune mouse sera. Immune T cells from infected mice proliferated and produced IFN-g in response to stimulation by yeast cell lysate in a dose-dependent manner. These data demonstrate that yeast cell lysate contains both B-cell and T cell-immunogens. Further study is warranted to identify specific immunogens in the yeast cell lystate.
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