Evaluation of the long-term immune responses following leishmanization
using a live- Lizard Leishmania mixed with chitin
Abstract
Background: Leishmanization using non-pathogenic to human
Leishmania spp. is considered a reliable approach to immunize
subjects against Leishmania infection. Objectives: Here,
we evaluated the long-term immune responses (14 weeks) after
immunization with either live- or killed-Iranian Lizard Leishmania (ILL)
mixed with chitin microparticles (CMPs) against L. major
infection in BALB/c mice. Methods: In total, nine groups of
mice were included in the study. To evaluate short-term immunity, mice
were immunized with live-ILL and three weeks later were challenged with
L. majorEGFP. To evaluate the long-term
immunity, mice were immunized with either live- or killed-ILL, and 14
weeks after immunization were challenged with L.
majorEGFP. A group of healthy mice who received no
injection was also included in the study. Eight weeks after the
challenge with L. majorEGFP all subjects were
sacrificed and the parasite burden (quantitative real-time PCR),
cytokines levels (IFN-γ, IL-4, and IL-10), Leishmania-specific
antibody concentration, and total levels of IgG1 and IgG2a were
measured. In addition, nitric oxide concentration, and arginase activity
were evaluated. Results: In mice that were immunized using
live-ILL+CMP, the induced proactive immune response lasted at least 14
weeks since, when they were challenged with L. major
EGFP at the 14 th-week
post-immunization, no open lesion was formed during 8 weeks follow-up,
and the footpad swelling was significantly lower than controls. As well,
they showed a significant reduction in the parasite burden in
splenocytes, in comparison to the control groups including the group
that received killed-ILL+CMP. The observed protection was associated
with a higher IFN-γ and a lower IL-10 production by splenocytes.
Additionally, the results demonstrated that arginase activity was
decreased in the ILL+CpG group compared to other groups.
Conclusion: The long-term response against L. major
infection induced by Live-ILL+CMP was more competent than the response
elicited by killed-ILL+CMP to protect mice against infection with
L. major EGFP.