Research in Medicine

Background: Leishmania major (L.major) is a causative agent of leishmaniasis. The disease has now become
a public health problem. Modulation of the immune responses to inhibit the infection or the proliferation
of the parasite is an effective way to overcome the leishmaniosis. Leishmania parasite secretory-excretory
antigens are responsible for immune system modulation; therefore, they are used in vaccine design and
immunotherapy. Nanoparticles have been considered in recent years due to the features that stimulate
the immune system. The purpose of the present study was to produce a combination of nanoparticles and
secretory-excretory antigens to induce immune responses.
Materials and methods: L.major secretory-excretory antigens were isolated from supernatant of parasite
culture using ultracentrifugation and protein molecular weight and concentration were determined using
SDS-PAGE and Bradford methods. The chitosan nanoparticle were loaded with antigens which confirmed
by FTIR. MTT test was performed to determine the cytotoxic effect of nanoparticles on macrophages. Five
groups of female BALB/c mice were sensitized with nanoparticles and nanoparticles loaded with the protein
on days 0.10 and 21. The macrophages were isolated from the mice and infected with L.major for one hour.
After 72 hours of incubation, NO production and inhibition of parasite growth were measured in response
to L.major.
Result: In the present study, the excretory-secretory antigens of the L.major were in the range of 75-110
kDa, and loaded with chitosan nanoparticle by %76 efficacy. The results showed that the excretory-secretory
antigens of the L.major parasites significantly increased the production of nitric oxide in the macrophages
and the presence of chitosan induced this increase (P<0.01). In addition, the group that received chitosan
loaded with the excretory secretory antigens of the L.major showed the least proliferation of the parasites
(P<0.05).
Conclusion: If chitosan nanoparticles loaded with L.major excretory-secretory antigens can increase
the activity of macrophage killing function by increasing nitric oxide production; therefore, they can be
nominated as candidates for vaccine development and disease improvement.