Old world monkey species including African green monkey (AGM) are resistant to HIV-1. Although the virus can gain entry into the susceptible cells of these monkeys, virus replication is blocked prior to viral genome integration by the restriction factors. HIV-1 Tat are the first viral protein that are produced after viral genome integration and they are essential for the production of other viral proteins. According to our preliminary results, AGM CV-1 cells that are known to be resistant to HIV-1 were transfected with HIV-1 regulatory tat. Then, protein profiles of Tat and empty vector expressing AGM CV-1 were compared by 2D-PAGE and that way observed to be induced in cells expressivity tat was identified to be SLPI by mass spectrometry analysis. Based on our literature reviews, SLPI is found to be an anti-bacterial, anti-fungal and anti-inflammatory protein. SLPI also has an extracellular anti-HIV-1 effect. Our study aims to measure SLPI expression level in AGM and human cells in presence of HIV-1 tat and to research effect of SLPI on NF-kB and HIV LTR promoter. In our research, expression level of SLPI gene is measured by QRT-PCR method. SLPI protein was screened by Western Blot method. SLPI’s effect on NF-kB and HIV-LTR promoter was researched through the luciferase experiment. While SLPI gene shows increase in AGM cells in presence of HIV-1 tat, no such increase was observed in human cells. Furthermore, it has been shown that SLPI gene decreases luciferase expression dependent on NF-kB promoter and HIV-LTR. In other words, SLPI suppresses NF-kB promoter and HIV-LTR.