Leishmania major strains isolated from distinct endemic areas show diverse cytokine mRNA expression levels in C57BL/6 mice: Toward selecting an ideal strain for the vaccine studies.

Leishmania major, the causative agent of zoonotic cutaneous leishmaniasis shows heterogeneity and diverse clinical manifestations in different areas of infection and experimental models. Such polymorphism may cause difficulties in selection of reliable strains for development of prophylaxes. Hence, the aim of this study was to identify an ideal strain of L. major, capable of inducing protective and long-lasting Th1 responses in an animal model that mimics the human response to L. major infection. The isolates were from patients residing in 4 endemic areas of L. major in Iran, namely Damghan (north), Kashan (center), Dehloran (west) and Shiraz (south) which their heterogeneity had been previously confirmed in BALB/c mice. In this study, the same isolates as well as the Iranian reference strain of L. major were inoculated to C57BL/6 mice to evaluate their pathogenicity and changes in expression of key cytokine genes from lymph nodes of the mice in different time points, in order to evaluate their ability to control leishmaniasis by development of Th1 responses. Our results showed the lowest and highest parasite burden in lymph nodes of mice infected with all strains at weeks 3 and 8 post-infection, respectively. However, the Damghan strain (DA39) showed comparatively lower number of viable parasite than other strains at week 8 post-infection. Furthermore, DA39 showed higher expression of Ifng and Il12 mRNA at week 8 post-infection while the ratio of its Ifng/Il4 mRNA expressions was higher than other strains. In conclusion, DA39 among the studied strains appears to induce strong and lasting Th1 cytokine gene expressions with minimum virulence, making it a suitable candidate strain for vaccine studies in leishmaniasis.

Naloxone Diminishes the Virulence and Modifies the Cellular Immune Responses of BALB/c Mice Infected with Leishmania major.

PURPOSE: Leishmania major-infected BALB/c mice display strong susceptibility to the infection due to the induction of Th2 response. The aim of this study was to assess the effects of naloxone on virulence of L. major in BALB/c mice and the ensued cellular immune response. METHODS: The effects of injection of a single dose of naloxone in the footpad of L. major-infected BALB/c mice were investigated by evaluating the lesion sizes, the parasite burden, cell proliferation, secreted cytokines (IFN-γ, IL-4, IL-10 and IL-12) and their genes expressions due to naloxone treatment while the untreated mice were used as a control. RESULTS: Significantly lower lesion sizes and less parasite burden were measured in the treated mice. Significantly decreased productions of IFN-γ, IL-12, IL-4, and IL-10 were also observed in the treated mice at week 4 post-infection while the production IL-10 remained significantly hindered till 8 weeks post-infection. CONCLUSION: Our data indicated that although the treatment of L. major-infected BALB/c mice with a single dose of naloxone was unable to improve the cellular immune response, it led to lower virulence, confirmed by significantly reduced lesions and parasite load.