Complete Cure of Experimental Visceral Leishmaniasis with Amphotericin B in Stearylamine-Bearing Cationic Liposomes Involves Down-Regulation of IL-10 and Favorable T Cell Responses

Abstract

Visceral leishmaniasis caused by Leishmania donovani is a life-threatening disease involving uncontrolled parasitization of liver, spleen, and bone marrow. Most available drugs are toxic. Moreover, relapse after seemingly successful therapy remains a chronic problem. In this study, we evaluated a new therapeutic approach based on combination of a low dose of amphotericin B (AmB) in association with suboptimum dose of stearylamine (SA)-bearing cationic liposomes, itself having leishmanicidal activity. We demonstrate that a single-shot therapy with this formulation caused clearance of parasites from liver and spleen below the level of detection in the selected piece of the organs of BALB/c mice. The combination was superior to free AmB and AmBisome for therapy, as well as for prevention of relapse and reinfection. Besides having better killing activity, AmB in SA liposomes, in contrast to AmBisome, maintained the immunomodulatory effect of free AmB on CD4+ and CD8+ T cells for IFN-γ production, at the same time reducing the toxic effects of the drug, reflected through decline in TNF-α. In addition, IL-10 was down-regulated to almost negligible levels, most efficiently through therapy with SA-bearing cationic liposomes-AmB. This IL-10-deficient environment of IFN-γ-secreting T cells probably up-regulated the enhanced IL-12 and NO production observed in splenic culture supernatants of these mice, correlating with prolonged disease suppression better than free AmB and AmBisome. The ability of the formulation to elicit protective immunity was reconfirmed in a prophylactic model. Our results emphasize the requirement of effective immune stimulation, additionally, by antileishmanials for persistent disease protection, demonstrated by this liposomal AmB formulation.

Combination Therapy with Paromomycin-Associated Stearylamine-Bearing Liposomes Cures Experimental Visceral Leishmaniasis through Th1-Biased Immunomodulation

“…This combination regimen was also found to be effective against established L. major infection, further inhibiting disease relapse in susceptible mice (16). The present study showed that PC-SA at a molar ratio of 7:2 significantly enhanced the levels of IL-12, IFN-␥, and NO and reduced significantly not only IL-10 but also TGF-␤, corroborating our previous observations (7). Maximum induction of IL-12, IFN-␥, and NO was observed with PC-SA-PM treatment in normal mice.…”

“…Previously we showed the antileishmanial activity of PC-SA as monotherapy (2,14) as well as combination therapy (7,38). Here, the efficacy of these leishmanicidal liposomes was determined as a delivery tool, as well as in combination with PM.…”

“…PC-SA in combination with other antileishmanial drugs, such as SAG and AmB, not only reduced the toxicity of the drugs but also enhanced the parasite clearance in the BALB/c model to a great extent (7,38). Moreover, beneficial immunomodulatory activities of AmB were augmented in combination with PC-SA liposomes (7).…”

“…Earlier we established the leishmanicidal activity and mechanism of the cationic liposome, composed of phosphatidylcholine (PC) and stearylamine (SA), as a monotherapy (2,6,14). PC-SA in combination with other antileishmanial drugs, such as SAG and AmB, not only reduced the toxicity of the drugs but also enhanced the parasite clearance in the BALB/c model to a great extent (7,38). Moreover, beneficial immunomodulatory activities of AmB were augmented in combination with PC-SA liposomes (7).…”

Designing Therapies against Experimental Visceral Leishmaniasis by Modulating the Membrane Fluidity of Antigen-Presenting Cells

“…donovani-infected mouse model (5), lending credence to the notion that the cholesterol liposomes have therapeutic ability.…”