Expression pattern of ARG1 and iNOS genes in macrophages of Rhombomys opimus, BALB/c and C57BL/6 mice exposed to Leishmania major and salivary gland homogenates of Phlebotomus papatasi.

Early interactions between Leishmania-macrophages (MQ) of host and effect of sand fly saliva are central to leishmaniasis outcome. Macrophages are able to kill or act as long-term hosts of parasite depending on host immunity. It proved that immunogenic proteins in sand fly saliva mostly have an exacerbating effect on leishmaniasis by up-regulating cytokines. We have explored expression of Arginase 1 (ARG1) and inducible Nitric Oxide Synthase (iNOS) genes in macrophages of three different rodents, BALB/c (susceptible), C57BL/6 (resistant) and Rhombomys opimus (R. opimus, natural reservoir) in presence of Leishmania major (L. major), salivary gland homogenate (SGH) of Phlebotomus papatasi (Ph. papatasi) and finally L. major + SGH. Stationary phase of promastigotes was used; salivary glands were extracted from female of Ph. papatasi (3-5 day-old/non-blood fed). SGH prepared by sonication. Macrophages harvested from the peritoneal cavity of each rodent and grouped as follow; 1) macrophage (control group), 2) MQ + L.major 3) MQ + SGH 4) MQ + L.major + SGH. After 6 h of incubation, culture medium supernatant collected, RNA extraction and cDNA synthesis performed, expression level of desired genes checked by Real-time PCR. ARG1 expression pattern in MQ + SGH and MQ + L.major group showed the highest and lowest expressions level respectively in BALB/c and C57BL/6. But, in MQ + L.major + SGH, although the highest ARG1 expression happened in BALB/c again, the lowest one observed in R. opimus. On the other hand, iNOS expression showed significant increase in all treated group of C57BL/6 macrophages. Interestingly, iNOS expression showed significant differences in MQ + L.major group of C57BL/6 in comparison to other rodents. Expression of ARG1 and iNOS in macrophages of BALB/c and C57BL/6 and R. opimus are different and can justify their clinical outcome of disease. The difference in gene expression pattern is related to the genetics of host and shows that genetic differences between hosts can affect the immune responses caused by saliva proteins even of the same species of sand fly.