DIFFERENCES IN THE INTERACTIONS OF NOCARDIA-ASTEROIDES WITH MACROPHAGE, ENDOTHELIAL, AND ASTROCYTOMA CELL-LINES

An in vitro model for studying host cell interactions with Nocardia as teroides was developed. Thus, macrophage cell lines J774A.1 and P388D1 , pulmonary artery endothelium cell line CPAE, rat glial tumor cell li ne C6, and human astrocytoma cell lines CCF-STTG1 and U-373 MG were in fected with either log- or stationary-phase cells of N. asteroides GUH -2, and the host cell-nocardia interactions were determined by light m icroscopy and electron microscopy. Polyclonal antinocardial antibody d id not enhance uptake of nocardiae by any of these cell lines; however , log-phase cells of GUH-2 infected a higher percentage of J774A.1 and P388D1 than did stationary-phase organisms. When cells infected with stationary-phase GUH-2 were incubated for 6 h, filaments developed, wh ich indicated that nocardial growth had occurred. In J774A.1 and P388D 1, only 31 to 57% of the total stationary-phase coccobacillary cells t hat were phagocytized formed filaments within 6 h. This indicated that there was some inhibition of growth of the phagocytized nocardiae wit hin these macrophage cell lines; however, the nocardiae grew within th e endothelial (>87% filaments) and astrocytoma (100% filaments) cell l ines. Microfilament inhibitor cytochalasin B inhibited uptake of GUH-2 by macrophages and other cell lines, except that there was no effect on uptake of nocardial cells by astrocytoma cell line U-373 MG. Scanni ng and transmission electron microscopy showed phagocytosis of GUH-2 b y the different cell lines. In cytochalasin B-treated cells, nocardiae were shown to penetrate through the cell surface and become internali zed in a manner distinct from typical phagocytosis, suggesting that fi lamentous forms of this organism have a phagocytosis-independent invas ion factor. The extent of this cytochalasin-resistant cellular penetra tion by the nocardiae differed in the different cell lines.