Biodegradable microspheres containing leukotriene B4 and cell-free antigens from Histoplasma capsulatum activate murine bone marrow-derived macrophages

Because of the potential protective role of leukotrienes (LTs) in histoplasmosis and the therapeutic and prophylactic effects of cell-free antigens from Histoplasma capsulatum (CFAgs), the aim of this study was to develop and characterise biodegradable LTB4/CFAgs-loaded microspheres (MS) that could promote cellular activation for future immunisation purposes. LTB4/CFAgs-loaded MS that were developed through a double emulsion/extraction process were characterised according to their size, zeta potential, morphology, entrapment efficiency and in vitro release kinetics. We evaluated the uptake of LTB4/CFAgs-loaded MS by bone marrow derived-macrophages (BMDM). The TNF-alpha and chemokines, and nitrite production, in the supernatant of BMDM cultures were analysed by enzyme-linked immunosorbent assay (ELISA) and Griess reaction, respectively. We found an instantaneous release of CFAgs and a prolonged release of LTB4 from the poly-(D,L-lactide-co-glycolide) (PLGA) MS. The microencapsulation process did not alter the zeta potential nor the spherical morphology of the MS. The appropriate size of the LTB4/CFAgs-loaded MS (smaller than 10 mu m) enabled the efficient uptake by BMDM and also induced TNF-alpha, CXCL1/KC, CCL2/MCP-1. CCL5/RANTES and nitrite oxide release by these cells. In conclusion, the biodegradable LTB4/CFAgs-loaded MS were able to efficiently activate murine BMDM and thereby have the potential to be used in an effective vaccine against H. capsulatum infection. (C) 2011 Elsevier B.V. All rights reserved.