Tissue distribution of DNA-Hsp65/TDM-loaded PLGA microspheres and uptake by phagocytic cells

This study aimed to demonstrate that microspheres, used as delivery vehicle of DNA-Hsp65/TDM [plasmid DNA encoding heat shock protein 65 (Hsp65) coencapsulated with trehalose dimycolate (TDM) into PLGA microspheres], are widely spread among several organs after intramuscular administration in BALB/c mice. In general, we showed that these particles were phagocytosed by antigen presenting cells, such as macrophages and dendritic cells. Besides, it was demonstrated herein that draining lymph node cells presented a significant increase in the number of cells expressing costimulatory molecules (CD80 and CD86) and MHC class II, and also that the administration of the DNA-Hsp65/TDM and vector/TDM formulations resulted in the up-regulation of CD80, CD86 and MHC class II expression when compared to control formulations (vector/TDM and empty). Regarding the intracellular trafficking we observed that following phagocytosis, the microspheres were not found in the late endosomes and/or lysosomes, until 15 days after internalization, and we suggest that these constructions were hydrolysed in early compartments. Overall, these data expand our knowledge on PLGA [poly (lactic-co- glycolic acid)] microspheres as gene carriers in vaccination strategies, as well as open perspectives for their potential use in clinical practice.

We thank Ms. Izaíra T. Brandão, Ms. Ana Paula Masson, Ms. Ana Flávia Gembre, Ms. Patrícia V.P. Palma, Maria Tereza P. Maglia and Ms. Márcia S.Z. Graeff for excellent technical assistance during the course of the studies. This study was supported by FAPESP and CNPq grants.

We thank Ms. Izaíra T. Brandão, Ms. Ana Paula Masson, Ms. Ana Flávia Gembre, Ms. Patrícia V.P. Palma, Maria Tereza P. Maglia and Ms. Márcia S.Z. Graeff for excellent technical assistance during the course of the studies. This study was supported by FAPESP and CNPq grants.