The two gag isoforms from putative HERV-K109Pt1 and HERV-K115Pt1, which were isolated from patient-1’s genomic DNA, were examined for their effects on the expression of inflammatory mediators upon overexpression in RAW264.7 cells. Overexpression of HERV-K109Pt1-gag substantially induced various inflammatory mediators, such as IL-1β and IL-6, iNOS, and Ptgs-2 (COX-2) while only a slight increase in IL-1β expression was observed with HERV-K115Pt1-gag. There are three different negative controls: No DNA, pcDNA4 (empty pcDNA4/HisMax plasmid), and (−)K115Pt1-gag (reverse oriented HERV-K115Pt1-gag insert in pcDNA4). K109Pt1-gag (HERV-K109Pt1-gag); K115Pt1-gag (HERV-K115Pt1-gag). *P < 0.05; **P < 0.01; error bar (standard deviation).