The present study has been carried out at College of Veterinary Medicine, Al- Qadisiya University, Iraq for diagnosed the visceral leishmaniasis by qPCRreaction and to investigate the effect of treatment with Pentostam ™ (100 mg /ml) on mRNA expression level of A2 gene in bloodand bone marrow samples of female rats using Reverse Transcriptase –Polymerase Chain Reaction .Blood samples were collected from children infected by visceral leishmaniasis, then injected in the peritoneal cavity ofFourtyWistarfemale rats (weighted 250 ± 2 g.) were assigned into two groups; control group(10rats) and treated group (30 rats). After 8-10 days blood samples collected directly from the heart for diagnosis the infection using quantitative Polymerase Chain Reaction , also collected blood and bone marrow samples from control group to detect A2gene expression byReverse Transcriptase –Polymerase Chain Reaction. The second group was treated with pentostam at dose 25 mg / kg for 30 days and divided into four weeks, and in each week collected blood and bone marrow samples to check the effect of treatment on mRNA expression level of A2 gene. In all of the experimental blood samples, all the results were positive when diagnosed byquantitative Polymerase Chain Reaction . Reverse Transcriptase – Polymerase Chain Reaction results which relied on the relative quantification of A2 gene expression normalized by gene expression levels of housekeeping gene (Glyceraldhyde 3-phosphate dehydrogenase(GAPDH)),The relative quantification results detected the fold changes in A2gene levels of blood and bone marrow samples of rats treated with pentostam. The level of A2gene expression of blood samples was in the first week 0.24 fold, in the second week 0.08 fold , in the third week 0.02 fold and in the fourth week 0.006 fold ,all of that was lower than control sample. Whilein bone marrow samples level of A2gene expression was in the second week 0.09 fold , in the third week 0.04 fold and in fourth week 0.03 fold, all of that lower than control sample. It can be concluded that the pentostam has active effect on virulence factor (A2gene) ,also the parasite remains dormant in bone marrow samples even after treatmentand possiblyreturn to virulencein the case of any immune inhibition .
