An In vitro Model for the Study of HIV Infection of Thymocytes

Abstract

The study of human thymocytes requires an appropriate matrix to enable the proper function of thymocytes. Although OP9-DL1 cells have been well established as an ideal co-culture system for the generation of T-cells from their progenitors; their ability to support a mixed population of mature human thymocytes for in vitro HIV infection studies has yet to be established. We assessed the effects of co-culturing a heterogeneous population of mature human thymocytes with a mouse derived cell line (OP9) transduced with the notch ligand delta like 1 (OP9-DL-1) and compared this to standard co-culture with human thymic epithelial cells (TEC). Co-culturing thymocytes with OP9- DL1 cells resulted in higher viability and lower apoptosis when compared to TEC co-cultures. The subset distribution and CD127 expression of thymocytes varied slightly between conditions. Thymocytes co-cultured with OP9-DL1 cells had a lower proportion of CD3+DP cells and higher proportion of SP4 cells compared to TEC co-cultures. The mature CD3+CD4+CD8- (SP4) cells also had lower levels of CD127 expression in OP9-DL1 cultures when compared to TEC. Interleukin-7 stimulation of thymocytes resulted in a decrease in CD127 expression in OP9-DL1 co-cultures, as previously observed with TEC co-cultures. Thymocytes co-cultured with OP9-DL1 tended to have higher levels of IL-7 induced STAT-5 phosphorylation and had higher levels of Interleukin-7 induced Bcl-2 expression. OP9-DL1 cells provide a microenvironment which is permissive to HIV infection in thymocytes in vitro. Co-culturing thymocytes with OP9-DL1 will facilitate the study of human thymocytes and aid in the study of exogenous stimuli or infection on individual thymocyte subsets.