title: Intracellular targeting specificity of novel phthalocyanines assessed in a host-parasite model for developing potential photodynamic medicine.
abstract: Photodynamic therapy, unlikely to elicit drug-resistance, deserves attention as a strategy to counter this outstanding problem common to the chemotherapy of all diseases. Previously, we have broadened the applicability of this modality to photodynamic vaccination by exploiting the unusual properties of the trypanosomatid protozoa, Leishmania, i.e., their innate ability of homing to the phagolysosomes of the antigen-presenting cells and their selective photolysis therein, using transgenic mutants endogenously inducible for porphyrin accumulation. Here, we extended the utility of this host-parasite model for in vitro photodynamic therapy and vaccination by exploring exogenously supplied photosensitizers. Seventeen novel phthalocyanines (Pcs) were screened in vitro for their photolytic activity against cultured Leishmania. Pcs rendered cationic and soluble (csPcs) for cellular uptake were phototoxic to both parasite and host cells, i.e., macrophages and dendritic cells. The csPcs that targeted to mitochondria were more photolytic than those restricted to the endocytic compartments. Treatment of infected cells with endocytic csPcs resulted in their accumulation in Leishmania-containing phagolysosomes, indicative of reaching their target for photodynamic therapy, although their parasite versus host specificity is limited to a narrow range of csPc concentrations. In contrast, Leishmania pre-loaded with csPc were selectively photolyzed intracellularly, leaving host cells viable. Pre-illumination of such csPc-loaded Leishmania did not hinder their infectivity, but ensured their intracellular lysis. Ovalbumin (OVA) so delivered by photo-inactivated OVA transfectants to mouse macrophages and dendritic cells were co-presented with MHC Class I molecules by these antigen presenting cells to activate OVA epitope-specific CD8+T cells. The in vitro evidence presented here demonstrates for the first time not only the potential of endocytic csPcs for effective photodynamic therapy against Leishmania but also their utility in photo-inactivation of Leishmania to produce a safe carrier to express and deliver a defined antigen with enhanced cell-mediated immunity.
authors.affiliation: Department of Microbiology/Immunology, Chicago Medical School/Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, United States of America. sujoy.dutta@rosalindfranklin.edu
authors.forename: Sujoy
authors.initials: S
authors.lastname: Dutta
authors.forename: Benson G
authors.initials: BG
authors.lastname: Ongarora
authors.forename: Hairong
authors.initials: H
authors.lastname: Li
authors.forename: Maria da Graca H
authors.initials: Mda G
authors.lastname: Vicente
authors.forename: Bala K
authors.initials: BK
authors.lastname: Kolli
authors.forename: Kwang Poo
authors.initials: KP
authors.lastname: Chang
mesh_terms: D000818:Animals; D017951:Antigen Presentation / Q000187:drug effects / Q000528:radiation effects; D018414:CD8-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000469:parasitology / Q000528:radiation effects; D002460:Cell Line; D003713:Dendritic Cells / Q000187:drug effects / Q000276:immunology / Q000469:parasitology / Q000528:radiation effects; D055808:Drug Discovery; D004705:Endocytosis / Q000187:drug effects / Q000528:radiation effects; D006680:HLA Antigens / Q000276:immunology; D006790:Host-Parasite Interactions; D007211:Indoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D054833:Isoindoles; D007891:Leishmania / Q000187:drug effects / Q000469:parasitology* / Q000502:physiology*; D008027:Light; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000469:parasitology / Q000528:radiation effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D010047:Ovalbumin / Q000276:immunology; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism / Q000469:parasitology / Q000528:radiation effects; D010778:Photochemotherapy / Q000379:methods*; D010782:Photolysis / Q000187:drug effects / Q000528:radiation effects; D012995:Solubility; D013379:Substrate Specificity
chemical_list: D006680:HLA Antigens; D007211:Indoles; D054833:Isoindoles; D010047:Ovalbumin; C013647:phthalocyanine