Background
The transcription factor T cell factor 1 (TCF-1) plays a critical role in maintaining functional memory CD8+ T cells and regulation of their proliferation capacity. TCF-1 expression in HIV-specific CD8+ T cells has been associated with viral control and may be important for promoting the functional activity of HIV-specific CD8+ T cells. Glycogen synthase kinase-3 (GSK-3) inhibitors prevent the degradation of β-catenin, which promotes TCF-1 expression and its transcriptional activity. In this study, we asked whether GSK-3 inhibitors can be used to induce TCF-1 expression in antiviral CD8+ T cells.
Methods
TCF-1 expression in SIV-specific CD8+ T cells from 5 SIV-infected rhesus macaques (RM) with pVL between 1,700-170,000 SIV RNA copies/mL and 7 SIV controllers (pVL < 15 SIV RNA copies/mL) were assessed by flow cytometry. CD8+ T cells from humans (n=13) and RM (n=21) were treated with 5 different GSK-3 inhibitors (BIO, CHIR99021, TWS119, Li2CO3, and LY2090314) for 16 hours to evaluate their potential to induce TCF-1 expression. PBMC from 5 SIV-infected RM on ART were treated with LY2090314 for 16 hours, followed by culture with IL-7 (50ng/mL) for 6 days to assess expansion of Mamu*A01 immunodominant Gag-CM9- and Tat-SL8-specific CD8+ T cells.
Results
TCF-1 expression was significantly higher in SIV-specific CD8+ T cells of controller RM compared with viremic RM (p=0.04), confirming data from human studies. Among the five GSK-3 inhibitors tested, LY2090314 induced the highest expression of TCF-1 in CD8+ T cells from humans (Figure 1A) and RM after overnight exposure. LY2090314 also induced TCF-1 expression in SIV-specific CD8+ T cells compared with DMSO control (p=0.004). To determine whether TCF-1 induction by LY2090314 can enhance the expansion of antigen-specific CD8+ T cells, PBMCs from SIV-infected RM on ART were cultured with IL-7 after LY2090314 exposure. After 6 days of culture, we observed an enrichment of total CD8+ central memory (TCM) (p=0.008) and Gag-CM9- and Tat-SL8-specific CD8+ TCM (p=0.008) (Figure 1B) compared with DMSO+IL-7 alone.
Conclusions
These data suggest that GSK-3 inhibitors can be used to induce TCF-1 in CD8+ T cells in both human and RM. In addition, LY2090314 was able to induce TCF-1 expression in SIV-specific CD8+ T cells of RM on ART. These data support the further evaluation of LY2090314 in SIV-infected RM on ART to determine whether TCF-1 induction can enhance the functional activity of CD8+ T cells and promote durable virologic control.