Leishmaniasis and various immunotherapeutic approaches.

Leishmaniasis is a vector-borne infectious disease caused by multiple Leishmania (L.) species with diverse clinical manifestations. There is currently no vaccine against any form of the disease approved in humans, and chemotherapy is the sole approach for treatment. Unfortunately, treatment options are limited to a small number of drugs, partly due to high cost and significant adverse effects. The other obstacle in leishmaniasis treatment is the potential for drug resistance, which has been observed in multiple endemic countries. Immunotherapy maybe another important avenue for controlling leishmaniasis and could help patients control the disease. There are different approaches for immunotherapy in different infectious diseases, generally with low-cost, limited side-effects and no possibility to developing resistance. In this paper, different immunotherapy approaches as alternatives to routine drug treatment will be reviewed against leishmaniasis.

Leishmania tarentolae expressing CXCL-10 as an efficient immunotherapy approach against Leishmania major-infected BALB/c mice.

Recent findings have demonstrated the suitability of interferon-gamma-induced protein 10 (IP-10) or CXCL-10 as an immunotherapy tool in treatment of leishmaniasis. This chemokine can overcome Leishmania (L.) infection through inducing nitric oxide (NO) production for parasite elimination. This study was undertaken to investigate the therapeutic effects of recombinant Leishmania tarentolae expressing CXCL-10 and an expression vector encoding CXCL-10 (pcDNA-CXCL-10-EGFP) in a model of BALB/c mice susceptible to infection by Leishmania major. The outcome of intervention was examined at 3 weeks post-treatment by evaluating the parameters of parasite burden (PB), arginase activity, NO and various cytokines such as IFN-γ, IL-4, IL-6 and IL-10. The results have shown that despite the efficacy of CXCL-10 expression vector as gene therapy, the live therapy strategy using L. tarentolae expressing CXCL-10 was more effective in terms of decreasing PB. Nitric oxide production increased, especially in the live therapy approaches. Arginase activity also decreased in all regimens, which demonstrates the potency of the treatment. The overall cytokine production shifted in favour of Th1 responses in the treated mice. Altogether, recombinant L. tarentolae expressing CXCL-10 represents a promising therapeutic strategy to improve treatment of cutaneous leishmaniasis.

Comparing acute and chronic human cutaneous leishmaniasis caused by Leishmania major and Leishmania tropica focusing on arginase activity.

BACKGROUND: Cutaneous leishmaniasis (CL) in Iran is mainly caused by Leishmania major (L. major) and L. tropica. Arginase mediated L-arginine metabolism is an important issue in Leishmania parasite propagation. Arginase activity in human CL due to L. major and L. tropica have not been studied up to now. OBJECTIVES: We aimed to compare the clinical and laboratory aspects of acute and chronic CL, focussing on arginase activity. METHODS: In this case-control study, 30 patients with acute CL (duration ≤ 1 year), 13 patients with chronic CL (duration ≥ 2 year) and 11 healthy controls were recruited. Arginase activity was measured in skin biopsies of lesions, peripheral blood polymorphonuclear cells (PMNs), peripheral blood mononuclear cells (PBMCs) and plasma by standard methods. RESULTS: The median of arginase activity in the acute lesions was higher than in chronic samples and significantly higher than in healthy controls (P = 0.008). PMNs of both acute and chronic patients showed higher levels of arginase activity as compared to the levels in PBMCs and plasma. The median of arginase activity in the PMNs of patients with chronic CL was higher than that of patients with acute CL and significantly higher than that of the healthy controls (P = 0.010). CONCLUSION: The level of arginase activity in lesions of patients with acute and chronic CL was higher than the skin of healthy controls. The highest level of arginase activity was observed in PMNs from patients with chronic CL. This suggests that the high level of arginase activity in PMNs of patients with chronic CL may contribute to the chronicity.

Cationic solid-lipid nanoparticles are as efficient as electroporation in DNA vaccination against visceral leishmaniasis in mice.

The use of an appropriate delivery system has recently emerged as a promising approach for the development of effective vaccination against visceral leishmaniasis (VL). Here, we compare two vaccine delivery systems, namely electroporation and cationic solid-lipid nanoparticle (cSLN) formulation, to administer a DNA vaccine harbouring the L. donovani A2 antigen along with L. infantum cysteine proteinases [CPA and CPB without its unusual C-terminal extension (CPB(-CTE) )] and evaluate their potential against L. infantum challenge. Prime-boost administration of the pcDNA-A2-CPA-CPB(-CTE) delivered by either electroporation or cSLN formulation protects BALB/c mice against L. infantum challenge and that protective immunity is associated with high levels of IFN-γ and lower levels of IL-10 production, leading to a strong Th1 immune response. At all time points, the ratio of IFN-γ: IL-10 induced upon restimulation with rA2-rCPA-rCPB and F/T antigens was significantly higher in vaccinated animals. Moreover, Th2-efficient protection was elicited through a high humoral immune response. Nitric oxide production, parasite burden and histopathological analysis were also in concordance with other findings. Overall, these data indicate that similar to the electroporation delivery system, cSLNs as a nanoscale vehicle of Leishmania antigens could improve immune response, hence indicating the promise of these strategies against visceral leishmaniasis.

The contribution of NT-gp96 as an adjuvant for increasing HPV16 E7-specific immunity in C57BL /6 mouse model.

To control cervical cancer, efficient vaccination against human papillomavirus (HPV) is highly required. Despite the advantages and safety of the protein vaccines, additional strategies to enhance their immunogenicity are needed. E7 is a transforming protein which represents a perfect target antigen for vaccines or immunotherapies. Heat shock proteins (HSPs) facilitate cellular immune responses to antigenic peptides or proteins bound to them. Regarding to previous studies, vaccination with purified HSP/antigen complexes efficiently elicit antigen-specific immune responses in mice model. The N-terminal of glycoprotein 96 (NT-gp96) has adjuvant effect and can induce effective cumulative immune response against clinical disorders, especially cancers. In this study, the recombinant HPV16 E7 and E7 linked to NT-gp96 (E7-NT-gp96) proteins were generated in prokaryotic expression system. Mice were vaccinated twice with this recombinant proteins and the immunogenicity of the fusion protein was determined. The preventive efficacy of E7-NT-gp96 fusion protein was also evaluated and compared to E7 protein after challenging with cancerous TC-1 cell line. In vitro re-stimulated splenocytes of mice vaccinated with rE7-NT-gp96 protein induced higher IFN-γ response in comparison with E7 protein immunization. Moreover, immunization with E7-NT-gp96 protein displayed low but stable humoral responses at post-challenge time. The data showed that vaccination with fused E7-NT-gp96 protein delayed the tumour occurrence and growth as compared to protein E7 alone. These results suggest that fused adjuvant-free E7-NT-gp96 protein vaccination could direct the immune responses towards Th1 immunity. Furthermore, the linkage of NT-gp96 to E7 could enhance protective anti-tumour immunity.

Cysteine proteinase type I, encapsulated in solid lipid nanoparticles induces substantial protection against Leishmania major infection in C57BL/6 mice.

Appropriate adjuvant, proper antigen(s) and a suitable formulation are required to develop stable, safe and immunogenic vaccines. Leishmanial cysteine proteinase type I (CPB) is a promising vaccine candidate; nevertheless, it requires a delivery system to induce a potent immune response. Herein, solid lipid nanoparticles (SLN) have been applied for CPB [with and without C-terminal extension (CTE)] formulation to utilize as a vaccine against Leishmania major infection in C57BL/6 mice. Therefore, SLN-CPB and SLN-CPB(-CTE) formulations were prepared from cetyl palmitate and cholesterol, using melt emulsification method. After intraperitoneal vaccination and subsequent L. major challenge, a strong antigen-specific T-helper type 1 (Th1) immune response was induced compared to control groups. Lymph node cells from immunized mice displayed lower parasite burden, higher IFN-γ, IgG2a and lower IL-4 production, indicating that robust Th1 immune response had been induced. Our results revealed that CTE is not necessary for inducing protective responses against L. major infection as the IFN-γ/IL-4 ratio was significantly higher, whereas IgG1 responses were lower in the SLN-CPB(-CTE) vaccinated group, post-challenge. Thus, SLN-CPB(-CTE) was shown to induce specific Th1 immune responses to control L. major infection, through effective antigen delivery to the peritoneal antigen presenting cells.

Leishmania tarentolae secreting the sand fly salivary antigen PpSP15 confers protection against Leishmania major infection in a susceptible BALB/c mice model.

Cutaneous leishmaniasis is a zoonotic, vector-borne disease causing a major health problem in several countries. No vaccine is available and there are limitations associated with the current therapeutic regimens. Immune responses to sand fly saliva have been shown to protect against Leishmania infection. A cellular immune response to PpSP15, a protein from the sand fly Phlebotomus papatasi, was sufficient to control Leishmania major infection in mice. This work presents data supporting the vaccine potency of recombinant live non-pathogenic Leishmania (L.) tarentolae secreting PpSP15 in mice and its potential as a new vaccine strategy against L. major. We generated a recombinant L. tarentolae-PpSP15 strain delivered in the presence of CpG ODN and evaluated its immunogenicity and protective immunity against L. major infection in BALB/c mice. In parallel, different vaccination modalities using PpSP15 as the target antigen were compared. Humoral and cellular immune responses were evaluated before and at three and eight weeks after challenge. Footpad swelling and parasite load were assessed at eight and eleven weeks post-challenge. Our results show that vaccination with L. tarentolae-PpSP15 in combination with CpG as a prime-boost modality confers strong protection against L. major infection that was superior to other vaccination modalities used in this study. This approach represents a novel and promising vaccination strategy against Old World cutaneous leishmaniasis.