Naegleria fowleri, a ubiquitous pathogenic freeliving amoeba, is the most virulent species and causes primary amoebic meningoencephalitis in laboratory animals and humans. The parasite secretes various inducing molecules as biological responses, which are thought to be involved in pathophysiological and immunological events during infection. To investigate what molecules of N. fowleri excretory-secretory proteins (ESPs) are related with amoebic pathogenicity, N. fowleri ESPs fractionated by two-dimensional electrophoresis were reacted with N. fowleri infection or immune sera. To identify immunodominant ESPs, six major protein spots were selected and analyzed by N-terminal sequencing. Finally, six proteins, 58, 40, 24, 21, 18, and 16 kDa of molecular weight, were partially cloned and matched with reference proteins as follow: 58 kDa of exendin-3 precursor, 40 kDa of secretory lipase, 24 kDa of cathepsin B-like proteases and cysteine protease, 21 kDa of cathepsin B, 18 kDa of peroxiredoxin, and 16 kDa of thrombin receptor, respectively. These results suggest that N. fowleri ESPs contained important proteins, which may play an important role in the pathogenicity of N. fowleri.

Abstract. Retinoid X receptor-· (RXR·) fragments are known to be produced in some cancer cells by proteolytic cleavage. Previous finding that ligand binding domain (LBD) fragment of RXR· specifically inhibits retinoic acid receptor-Á (RARÁ) activity led us to investigate the functional role of RXR· LBD fragment in radiosensitization by retinoic acid (RA). Ectopic expression of RXR· LBD fragment in cells that do not have a detectable endogenous RXR· LBD fragment, blocked synergistic radiosensitizing action of RA, as determined by growth inhibition, cell death and colony formation assays. However, H460 cell, which has an endogenous RXR· LBD fragment, was not radiosensitized by RA regardless of the ectopic RXR· LBD fragment expression. These results were paralleled with the pattern of p21 induction by the treatment of RA in combination with ionizing radiation (IR). Taken together, we hypothesize that the RXR· LBD fragment may act as a negative regulator of radiosensitizing effect of RA by restricting the RARÁ-mediated biological response to RA.

Ginsan, polysaccharide isolated from the root of Panax ginseng C.A. Meyer, has been shown to be a potent immunomodulator, producing several cytokines and stimulating lymphoid cells to proliferate. In this study, ginsan was orally inoculated into BALB/c mice up to 39 days and the activity of immune cells containing macrophages and T cells was analyzed. Moreover, the production of cytokines, e.g., tumor necrotic factor-α (TNF-α), interferon-γ (IFN-γ), GM-CSF and IL-12 was also analyzed. In results, the phagocytosis of macrophages was increased. About 13% cytotoxicity of NK cells was observed in 22 days and 29 days of administration. But, oral administration did not highly affect the proliferation of T cells. In cytokine analysis, 150 mg/kg and 300 mg/kg at 22 days and 29 days showed three times more increase in TNF-α than the controls. IFN-γ showed 1.07 and 1.16 times more increase at 150 mg/kg and 300 mg/kg over 22 days, respectively more than the controls. 32 days of 150 mg/kg and 300 mg/kg induced GM-CSF of about 1.3 times more than the controls. IL-12 was not induced in samples more than the controls. Ginsan could be a potential immunostimulator. Therefore, our study suggests that it can be adapted as an immunostimulator that requires a relatively short oral administration.