Macrophage-Mediated Resistance to Intracellular Infection Induced by Poly-L-Glutamic Acid¹

The ability of poly-L-glutamic acid (PLGA) to induce resistance to infection with an intracellular bacteria was examined. PLGA conferred significant protection in mice against subsequent challenge with an ordinarily lethal inoculum of Listeria monocytogenes. Enhanced resistance, as manifest by a decrease in overall mortality and prolongation of time to death, could be demonstrated for time periods up to 44 days after PLGA treatment. Peritoneal macrophages from PLGA-treated animals were resistant to in vitro challenge with Listeria. Such resistance could be demonstrated for time periods up to 60 days after PLGA treatment. These findings suggest that “activated” macrophages are the effector cells in the PLGA-induced resistance observed.