Intravenous BCG immunization drives naive CD4+ T cell to Th1 differentiation via CD4+ T cell epigenetic reprogramming

Abstract

Intravenous (IV) administration of live Bacille Calmette-Guerin (BCG) boosts potent immunity through coordinated interactions of innate immune response and adaptive immune response for BCG antiviral activity. The underlying mechanisms by which BCG initiates CD4+ T response remain incompletely understood. Here, we show that IV administration of BCG drives naive CD4+ T cell differentiation to Th1 cell through epigenetic reprogramming. Single-cell transcriptomic and epigenomic analyses revealed that IV BCG immunization induced metabolic reprogramming in monocytes and increased the proportion of T cells. The immunization induced chromatin openness for transcription factors regulating naive CD4+ T cells differentiation into Th1 cells. Importantly, we observed increases in Stat1, Irf1 and interferon-stimulated genes such as Igtp in Th1 cells, leading to upregulation of interferon related gene expression for antiviral response by BCG immunization. Activated transcription factors like Irf1 in CD4+ T cells promotes Il12rb1 expression to facilitate IL-12 signaling and drive naive CD4+ T cells differentiation into Th1 cells. We showed that BCG immunization reduced respiratory syncytial virus (RSV) infection. Thus, transcription regulation through epigenetic reprogramming plays a critical role in BCG-induced CD4+ T cell differentiation and to the broad antiviral activity. SignificanceBacille Calmette-Guerin (BCG) vaccination confers nonspecific protection against heterologous pathogens. Recent work demonstrated that coordinated interactions of innate immune and persistent CD4+ T cell response plays a critical role in BCG induced antiviral activity. In our study, we investigated BCG immunization on epigenetic reprogramming of CD4+ T cells and found that BCG immunization elicited antiviral activity by provoking T cell proliferation. We observed chromatin openness favoring naive T cell differentiation to Th1 response. Importantly, we observed STAT1 and interferon regulatory factor-1 (Irf1) activation. These findings provide mechanistic insights into BCG-induced Th1 response through epigenetic reprogramming and highlight the potential of BCG in offering a long-term protection against emerging and reemerging pathogens. Graphic abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=181 SRC="FIGDIR/small/655674v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1c3cb94org.highwire.dtl.DTLVardef@16a8e8forg.highwire.dtl.DTLVardef@b58b88org.highwire.dtl.DTLVardef@dbc994_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIIntravenous BCG immunization drives naive CD4+ T cell differentiation to Th1 response; C_LIO_LIBCG alters chromatin accessibility for transcriptional factor expression favoring Th1 response through a Irf1-Il12rb1-IL12 feedback loop; C_LIO_LIThe immunization elicits antiviral activity against RSV infection; C_LI