Immunogenicity and protection effects of cationic liposome containing imiquimod adjuvant on leishmaniasis in BALB/c mice.

OBJECTIVES: Protection against leishmaniasis, in the murine model, is dependent on developing a potent CD4+ mediated Th1 type response. Liposomes can be applied as immunoadjuvants to stimulate immune responses to different antigens. In the present study, it was investigated whether DOTAP liposomes having SLA and imiquimod adjuvant, can induce a Th1 response and protect against Leishmania major challenge in BALB/c mice. MATERIALS AND METHODS: Liposomes were provided applying the lipid film procedure. BALB/C mice were subcutaneously immunized, three times with 2-week intervals, with various formulations. Assessment of lesion development and parasite burden in the foot and spleen after challenge with L. major, assessment of Th1 cytokine (IFN-γ), and titration of IgG isotypes assessed the type of generated immune reaction and the protection extent. RESULTS: The mice immunized with Liposome DOTAP+imiquimod+SLA showed smaller footpad swelling which was meaningfully different (P<0.05) compared with other groups. The highest level of IgG2a was observed with Lip DOTAP+imiquimod+SLA more than the control (P<0.001). Mice immunized with Lip DOTAP+SLA+imiquimod demonstrated the least number of live parasites in the footpad and spleen. Cytokine assay showed that the greatest IFN- γ secretion was seen in the splenocytes of mice immunized with all formulations as compared to the control group (P<0.0001). In contrast, the lowest IL-4 production was detectable in Lip+imiquimod+SLA spleen, which was not significantly different compared with other groups. CONCLUSION: The results of this study show that liposome DOTAP+SLA+imiquimod formulation generates a cellular immune response that is protective against challenge against L. major.

Evaluation of Immune Response against Leishmaniasis in BALB/c Mice Immunized with Cationic DOTAP/DOPE/CHOL Liposomes Containing Soluble Leishmania major Antigens.

BACKGROUND: Whole killed Leishmania vaccine reached phase III clinical trials but failed to display significant efficacy in human mainly due to limited Th1 inducer adjuvant. Liposomes consisting of 1, 2-dioleoyl-3trimethylammonium-propane (DOTAP) bearing an inherent adjuvanticity and 1, 2-dioleoyl-L-α-glycero-3-phosphatidylethanolamine (DOPE) is well known to intensify the efficacy of positively charged liposomes. METHODS: Soluble Leishmania major antigens (SLA) encapsulated in cationic liposomes using lipid film method in 2016). BALB/c mice were immunized subcutaneously (SC), three times in a 2-wk interval, with Lip (DOTAP)-SLA+, Lip (DOTAP/DOPE)-SLA+, Lip (DOTAP/DOPE/CHO)-SLA+, Lip (DOTAP/DOPE/CHO), Lip (DOPE/CHO), SLA or HEPES buffer. At week 2 after the last booster injection, immunized mice have challenged SC in the footpad with L. major parasites. To investigate the rate of protection and the type of immune response generated in mice, lesions development was assessed, IL-4 and IFN-γ levels with the ratio of IgG2a/IgG1 isotype were studied to describe the type of generated immune response. RESULTS: Mice immunized with all liposomal form of SLA showed smaller footpad swelling and lower parasite burden in the spleen and footpad compared to the group of mice received buffer. However, these formulations did not show protection against leishmaniosis because of a generated mixed Th1/Th2 response in mice characterized by high production of IFN-γ and IL4 and a high titer of IgG1 and IgG2a antibody. CONCLUSION: Immunization with Lip (DOTAP/DOPE/CHO)-SLA+ was not an appropriate strategy to protect mice against leishmaniosis.

Chitosan Nanoparticles Loaded with Whole and Soluble Leishmania Antigens, and Evaluation of Their Immunogenecity in a Mouse Model of Leishmaniasis.

BACKGROUND: Although there have been numerous attempts to develop vaccines for Leishmaniasis, no vaccine can be found against Leishmania in routine use for an effective global vaccination. It seems that one of the reasons for the low efficacy of such vaccines is the lack of a suitable adjuvant. OBJECTIVE: To evaluate the effects of chitosan nanoparticles containing whole Leishmania lysate antigen (WLL) and soluble leishmania antigens (SLA), a first generation Leishmania vaccine, on the type of immune response generated in BALB/c in a murine model of leishmaniasis. METHODS: The optimum coating ratio between the polymer and antigens was determined according to their physico-chemical properties such as particle size and zeta potential. Chitosan nanoparticles were loaded with antigens via ionic gelation method. BALB/c mice were immunized subcutaneously three times with various nanoparticulate and free antigens with 2-week intervals. RESULTS: There was no significant (P > 0.05) difference concerning the footpad thickness of mice immunized with nanoparticulate formulations containing either SLA or WLL during the experiment period; these formulations induced a strong mixed Th1/Th2 type immune response characterized by the production of IFN-γ and IL-4, and high levels of IgG2a IgG1 anti-Leishmania antibody. CONCLUSION: Nanoparticulate formulations (CHT: SLA and CHT: WLL) are not suitable candidates for preferential induction of a pure Th1-type immune response and immunization against Leishmania infection. However, it might be a good strategy in other infectious diseases where a mixed Th1/Th2 immune response is required.

The role of MPL and imiquimod adjuvants in enhancement of immune response and protection in BALB/c mice immunized with soluble Leishmania antigen (SLA) encapsulated in nanoliposome.

Adjuvants play an essential role in the induction of immunity against leishmaniasis. In this study, monophosphoryl lipid A (MPL) and imiquimod (IMQ) were used as TLR ligands adjuvants to enhance immunogenicity and rate of protection against leishmaniasis. Nanoliposomes containing soluble Leishmania antigens (SLA) and adjuvants were consisted of DSPC, DSPG and Chol prepared by using lipid film method followed by bath sonication. The size of nanoliposomes was around 95 nm and their zeta potential was negative. BALB/c mice were immunized by liposomal formulations of lip/SLA, lip/MPL/SLA, lip/IMQ/SLA, lip/MPL/IMQ/SLA, lip/SLA + lip/IMQ, lip/SLA + lip/MPL, lip/SLA + lip/MPL/IMQ and five controls of SLA, lip/MPL, lip/IMQ, lip/MPL/IMQ and buffer by subcutaneously (SC) injections, three times in 2 weeks intervals. The synergic effect of two adjuvants when they are used in one formulation showed significantly (p < .001) smaller footpad swelling and the lowest parasite burden in lymph node and foot after the challenge. IgG2a in these groups showed the higher titre compared to control groups, which is compatible with the high IFN-γ production and lowest IL-4. Taken together the results indicated that co-delivery of MPL and IMQ adjuvants and antigen in nanoliposome carrier could be an appropriate delivery system to induce cellular immunity pathway against leishmaniasis.

The role of ISCOMATRIX bilayer composition to induce a cell mediated immunity and protection against leishmaniasis in BALB/c mice.

OBJECTIVES: Development of new generation of vaccines against leishmaniasis is possible because long-term protection is usually seen after recovery from cutaneous leishmaniasis. ISCOMATRIX is particulate antigen delivery system composed of antigen, cholesterol, phospholipid and saponin. In this study, the role of ISCOMATRIX bilayer composition made by different phase transition temperature (Tc) to induce a type of immune response and protection against leishmaniasis was assessed. MATERIALS AND METHODS: ISCOMATRIX formulations with different bilayer compositions consisting of EPC (Tc <0 °C), DMPC (Tc 23 °C) and DSPC (Tc 54 °C) were prepared. Different ISCOMATRIX formulations were mixed with soluble Leishmania antigens (SLA). BALB/c mice were immunized subcutaneously, three times with 2-week intervals. As criteria for protection, footpads swelling, parasite burden, determination of IgG isotypes and the level of IFN-γ and IL-4 were assessed. RESULTS: Although the groups of mice immunized with ISCOMATRIX DMPC or ISCOMATRIX DSPC showed the smallest footpad swelling and least parasite burden compared with the buffer group, the difference was not significant. Moreover, the highest level of IFN- γ and IL-4 was observed in the splenocytes of mice immunized with ISCOMATRIX DMPC or ISCOMATRIX DSPC, respectively. After challenge, the mice immunized with ISCOMATRIX DSPC showed the highest elevation of IgG, IgG1 and IgG2a antibodies (P<0.01) compared with control group. However, our results indicated that ISCOMATRIX EPC, DMPC or DSPC generated a mixed Th1/Th2 response that was not protective. CONCLUSION: Our results showed that the adjuvanticity of prepared ISCOMATRIX doesn't influence with different phospholipids at least in our mice model.

Cationic Immune Stimulating Complexes Containing Soluble Leishmania Antigens: Preparation, Characterization and in Vivo Immune Response Evaluation.

BACKGROUND: Cationic immune stimulating complexes (PLUSCOMs) are particulate antigen delivery systems. PLUSCOMs consist of cationic immunostimulatory complexes (ISCOMs) derivatives and are able to elicit in vivo T cell responses against an antigen. OBJECTIVE: To evaluate the effects of PLUSCOMs containing Leishmania major antigens (SLA) on the type of immune response generated in the murine model of leishmaniasis. METHODS: PLUSCOMs consisting of 1, 2-dioleoyl-3-trimethylammonium-propane (DOTAP) were used as antigen delivery system/immunoadjuvants for soluble SLA. BALB/c mice were immunized subcutaneously, three times in 2-week intervals. Footpads swellings at the site of challenge and parasite loads were assessed as a measure of protection. The immune responses were also evaluated by determination of IgG subclasses and the level of IFN-γ and IL-4 in cultured splenocytes. RESULTS: There was no significant difference (p<0.05) between the sizes of lesions in mice immunized with different formulations. Also, there was no significant difference in the number of parasites in the footpad or spleen of all groups compared with the control group. The highest level of IFN-γ secretion was observed in the splenocytes of mice immunized with PLUSCOM/SLA (p<0.001) and lower amounts of IL-4 was observed in PLUSCOM group (p<0.001) as compared to negative control. CONCLUSION: Our results indicated that SLA in different formulations generated an immune response with mixed Th1/Th2 response that was not protective enough despite the activation of CD4+ T cells with secreting IFN-γ in groups which received PLUSCOM with antigen.