Immunotherapy of Murine Visceral Leishmaniasis with Murine Recombinant Interferon-γ and MTP-PE Encapsulated in Liposomes

Abstract

The efficiency of immunotherapy with murine recombinant interferon-gamma (rIFN-gamma) in mouse visceral leishmaniasis caused by Leishmania donovani was examined. To avoid the side effects encountered after the in vivo administration of high dosages of free IFN-gamma, this lymphokine and muramyltripeptide (MTP-PE) were encapsulated into multilamellar liposomes. We established that a combination of 5 X 10(3) U of IFN-gamma and 6 micrograms of MTP-PE, encapsulated in liposomes and given i.v. in C56BL/6 and BALB/c mice activates macrophages from spleen and liver in vivo to kill L. donovani in vitro. Neither empty liposomes nor the same concentration of free IFN-gamma and/or MTP-PE injected i.v. resulted in a leishmanicidal activity of these macrophage populations. For verification of these results in an in vivo infection model, susceptible mice were infected with L. donovani and were treated with IFN-gamma and MTP-PE encapsulated in multilamellar vesicles. Treatment consisted of multiple i.v. injections beginning 4 and 2 days before infection (prophylactic), either simultaneously with the infection or at various times of the exacerbation and remission phases of visceral leishmaniasis. These mouse strains treated with IFN-gamma and MTP-PE in liposomes had significantly fewer splenic parasites than untreated mice or control animals treated with free drugs or empty liposomes. The targetting of multilamellar vesicles to liver and spleen make them particularly suited for the delivery of macrophage-activating substances used for treatment of visceral L. donovani infection.

Clinical and Experimental Advances in Treatment of Visceral Leishmaniasis

“…In addition to Sb (32), paromomycin (aminosidine) (186), atovaquone (35), and IFN-␥ (59, 78), which are agents currently in use or previously studied as free drug in human kala-azar (123), have been tested in encapsulated form. Liposomes have also been used to deliver other drugs alone (89,98,105) or in combination (59,78). In virtually all instances, encapsulated drug is appreciably more active in vivo than free drug, usually by more than 5-fold and sometimes by more than 100-fold.…”

“…Of perhaps more physiologic interest, however, are interventions which induce (in the inert host) or free up (in the actively suppressed host) expression of the basic Th1-cell antileishmanial immune response, thus producing a broader range of effector mechanisms, including macrophage activation. The notion that immunoenhancement might stand alone as treatment in human visceral infection, as it can experimentally (1,78,107,112,114,116,117), remains appealing and provides a rationale for defining the effects of immunoactivating agents used by themselves. However, from a practical standpoint, clinical experience with the only cytokine well-studied in kala-azar, IFN-␥ (123), suggests that such experimental testing should also be carried out in combination with chemotherapy.…”

Selective Regulation of Human Immunodeficiency Virus-Infected CD4+Lymphocytes by a Synthetic Immunomodulator Leads to Potent Virus Suppression In Vitro and in hu-PBL-SCID Mice

“…However, in the last few years, potent immunomodulating activities for some of these synthetic molecules have been reported, including the suppression of antigen-specific IgE responses (3) and the inhibition of tissue IL-4 and tumor necrosis factor alpha mRNA expression (34,77). The availability of safe MDP analogues, retaining selected biological activities without associated prohibiting toxicity, has prompted the investigation of their potential use as immunomodulators in combination with antibiotics (43), with antivirals (23), and with therapeutic cytokines (6,7,30). One selected and safe derivative, Murabutide, has been shown to retain the capacity of inhibiting IgE responses (3), of down-regulating inflammatory reactions (5, 7), and of inducing colony-stimulating and antiviral activities (22,49,74).…”

Designing of ‘intelligent’ liposomes for efficient delivery of drugs

“…Also, good results in the treatment of infections in mice were obtained by incorporating immunomodulators (i.e. cytokines) in liposomes [60].…”