Dengue is an acute mosquito born viral infections in tropical and subtropical countries, that has been steadily increasing every year. Dengue haemorrhagic fever in Indonesia is caused by all 4 viral serotypes termed as DENV-1, DENV-2, DENV-3, and DENV-4. It is very difficult to treat the disease and there is no effective vaccine to eradicate Dengue virus infections .The aim of this research is to express the antibody fragment gene coding VL and VH of Fab IgG antibody in rat bone marrow mesenchymal stem cells (rat BM-MSCs). The genes were isolated from immunized mice using inactive virus of all dengue serotypes. Then genes were hybridized through ligation and insertion into plasmid pBR322, and transfected into rat BMMSCs. To analytically characterize Fab IgG hybrid binding ability, capacity and specificity, we used immune precipitation, western blotting, neutralization assay, and ELISA. All assays suggested that hybrid Fab IgG antibody have high reactivity and affinity, to efficiently neutralize all Dengue virus serotypes 1,2,3,4. Results of this study show that hybrid Fab IgG antibody can be used as neutralizing agent for the treatment of dengue infections in the future.