Explore the vast range of titles available.

Myeloid-derived suppressor cells (MDSCs) are major negative regulators of immune responses in cancer and chronic infections. It remains unclear if regulation of MDSC activity in different conditions is controlled by similar mechanisms. We compared MDSCs in mice with cancer and lymphocytic choriomeningitis virus (LCMV) infection. Chronic LCMV infection caused the development of monocytic MDSCs (M-MDSCs) but did not induce polymorphonuclear MDSCs (PMN-MDSCs). In contrast, both MDSC populations were present in cancer models. An acquisition of immune-suppressive activity by PMN-MDSCs in cancer was controlled by IRE1[alpha] and ATF6 pathways of the endoplasmic reticulum (ER) stress response. Abrogation of PMN-MDSC activity by blockade of the ER stress response resulted in an increase in tumor-specific immune response and reduced tumor progression. In contrast, the ER stress response was dispensable for suppressive activity of M-MDSCs in cancer and LCMV infection. Acquisition of immune-suppressive activity by M-MDSCs in spleens was mediated by IFN-[gamma] signaling. However, it was dispensable for suppressive activity of M-MDSCs in tumor tissues. Suppressive activity of M-MDSCs in tumors was retained due to the effect of IL-6 present at high concentrations in the tumor site. These results demonstrate disease- and population-specific mechanisms of MDSC accumulation and the need for targeting different pathways to achieve inactivation of these cells.

Seasonal epidemics of influenza virus result in ∼36,000 deaths annually in the United States. Current vaccines against influenza virus elicit an antibody response specific for the envelope glycoproteins. However, high mutation rates result in the emergence of new viral serotypes, which elude neutralization by preexisting antibodies. T lymphocytes have been reported to be capable of mediating heterosubtypic protection through recognition of internal, more conserved, influenza virus proteins. Here, we demonstrate using a recombinant influenza virus expressing the LCMV GP33-41 epitope that influenza virus-specific CD8+ T cells and virus-specific non-neutralizing antibodies each are relatively ineffective at conferring heterosubtypic protective immunity alone. However, when combined virus-specific CD8 T cells and non-neutralizing antibodies cooperatively elicit robust protective immunity. This synergistic improvement in protective immunity is dependent, at least in part, on alveolar macrophages and/or other lung phagocytes. Overall, our studies suggest that an influenza vaccine capable of eliciting both CD8+ T cells and antibodies specific for highly conserved influenza proteins may be able to provide heterosubtypic protection in humans, and act as the basis for a potential \"universal\" vaccine.

The transcriptional control of T cell exhaustion remains unclear. Wherry and colleagues show that the transcription factor T-bet regulates CD8 + T cell exhaustion and inhibitory receptor expression. T cell exhaustion has a major role in failure to control chronic infection. High expression of inhibitory receptors, including PD-1, and the inability to sustain functional T cell responses contribute to exhaustion. However, the transcriptional control of these processes remains unclear. Here we demonstrate that the transcription factor T-bet regulated the exhaustion of CD8 + T cells and the expression of inhibitory receptors. T-bet directly repressed transcription of the gene encoding PD-1 and resulted in lower expression of other inhibitory receptors. Although a greater abundance of T-bet promoted terminal differentiation after acute infection, high T-bet expression sustained exhausted CD8 + T cells and repressed the expression of inhibitory receptors during chronic viral infection. Persistent antigenic stimulation caused downregulation of T-bet, which resulted in more severe exhaustion of CD8 + T cells. Our observations suggest therapeutic opportunities involving higher T-bet expression during chronic infection.

T cell exhaustion has a major role in failure to control chronic infection. High expression of inhibitory receptors, including PD-1, and the inability to sustain functional T cell responses contribute to exhaustion. However, the transcriptional control of these processes remains unclear. Here we demonstrate that the transcription factor T-bet regulated the exhaustion of [CD8.sup.+] T cells and the expression of inhibitory receptors. T-bet directly repressed transcription of the gene encoding PD-1 and resulted in lower expression of other inhibitory receptors. Although a greater abundance of T-bet promoted terminal differentiation after acute infection, high T-bet expression sustained exhausted [CD8.sup.+] T cells and repressed the expression of inhibitory receptors during chronic viral infection. Persistent antigenic stimulation caused downregulation of T-bet, which resulted in more severe exhaustion of [CD8.sup.+] T cells. Our observations suggest therapeutic opportunities involving higher T-bet expression during chronic infection.

Myeloid-derived suppressor cells (MDSCs) are major negative regulators of immune responses in cancer and chronic infections. It remains unclear if regulation of MDSC activity in different conditions is controlled by similar mechanisms. We compared MDSCs in mice with cancer and lymphocytic choriomeningitis virus (LCMV) infection. Chronic LCMV infection caused the development of monocytic MDSCs (M-MDSCs) but did not induce polymorphonuclear MDSCs (PMN-MDSCs). In contrast, both MDSC populations were present in cancer models. An acquisition of immune-suppressive activity by PMNMDSCs in cancer was controlled by IRE1a and ATF6 pathways of the endoplasmic reticulum (ER) stress response. Abrogation of PMN-MDSC activity by blockade of the ER stress response resulted in an increase in tumor-specific immune response and reduced tumor progression. In contrast, the ER stress response was dispensable for suppressive activity of M-MDSCs in cancer and LCMV infection. Acquisition of immune-suppressive activity by M-MDSCs in spleens was mediated by IFN-γ signaling. However, it was dispensable for suppressive activity of M-MDSCs in tumor tissues. Suppressive activity of M-MDSCs in tumors was retained due to the effect of IL-6 present at high concentrations in the tumor site. These results demonstrate disease- and population-specific mechanisms of MDSC accumulation and the need for targeting different pathways to achieve inactivation of these cells.

Seasonal epidemics of influenza virus result in ~36,000 deaths annually in the United States. Current vaccines against influenza virus elicit an antibody response specific for the envelope glycoproteins. However, high mutation rates result in the emergence of new viral serotypes, which elude neutralization by preexisting antibodies. T lymphocytes have been reported to be capable of mediating heterosubtypic protection through recognition of internal, more conserved, influenza virus proteins. Here, we demonstrate using a recombinant influenza virus expressing the LCMV GP33-41 epitope that influenza virus-specific CD8+ T cells and virus-specific non-neutralizing antibodies each are relatively ineffective at conferring heterosubtypic protective immunity alone. However, when combined virus-specific CD8 T cells and non-neutralizing antibodies cooperatively elicit robust protective immunity. This synergistic improvement in protective immunity is dependent, at least in part, on alveolar macrophages and/or other lung phagocytes. Overall, our studies suggest that an influenza vaccine capable of eliciting both CD8+ T cells and antibodies specific for highly conserved influenza proteins may be able to provide heterosubtypic protection in humans, and act as the basis for a potential \"universal\" vaccine.

T cell exhaustion has a major role in failure to control chronic infection. High expression of inhibitory receptors, including PD-1, and the inability to sustain functional T cell responses contribute to exhaustion. However, the transcriptional control of these processes remains unclear. Here we demonstrate that the transcription factor T-bet regulated the exhaustion of CD8 super(+) T cells and the expression of inhibitory receptors. T-bet directly repressed transcription of the gene encoding PD-1 and resulted in lower expression of other inhibitory receptors. Although a greater abundance of T-bet promoted terminal differentiation after acute infection, high T-bet expression sustained exhausted CD8 super(+) T cells and repressed the expression of inhibitory receptors during chronic viral infection. Persistent antigenic stimulation caused downregulation of T-bet, which resulted in more severe exhaustion of CD8 super(+) T cells. Our observations suggest therapeutic opportunities involving higher T-bet expression during chronic infection.

T cell exhaustion plays a major role in failure to control chronic infections. High expression of inhibitory receptors, including PD-1, and the inability to sustain functional T cell responses contribute to exhaustion. However, the transcriptional control of these processes remains unclear. Here we demonstrate that the transcription factor T-bet regulates CD8+ T cell exhaustion and inhibitory receptor expression. T-bet directly repressed Pdcd1 transcription and decreased the expression of other inhibitory receptors. While elevated T-bet promoted terminal differentiation following acute infection, high T-bet expression sustained exhausted CD8+ T cells and repressed inhibitory receptor expression during chronic viral infection. Persisting antigenic stimulation caused T-bet downregulation, which resulted in more severe exhaustion of CD8+ T cells. These observations suggest therapeutic opportunities involving increasing T-bet expression during chronic infection.

Exhausted CD8 T cells (T EX ) are a distinct state of T cell differentiation associated with failure to clear chronic viruses and cancer. Immunotherapies such as PD-1 blockade can reinvigorate T EX cells, but reinvigoration is not durable. A major unanswered question is whether T EX cells differentiate into functional durable memory T cells (T MEM ) upon antigen clearance. Here, using a mouse model, we found that upon eliminating chronic antigenic stimulation, T EX cells partially (re)acquire phenotypic and transcriptional features of T MEM cells. These ‘recovering’ T EX cells originated from the T cell factor (TCF-1 + ) T EX progenitor subset. Nevertheless, the recall capacity of these recovering T EX cells remained compromised as compared to T MEM cells. Chromatin-accessibility profiling revealed a failure to recover core memory epigenetic circuits and maintenance of a largely exhausted open chromatin landscape. Thus, despite some phenotypic and transcriptional recovery upon antigen clearance, exhaustion leaves durable epigenetic scars constraining future immune responses. These results support epigenetic remodeling interventions for T EX cell–targeted immunotherapies. Wherry and colleagues examine whether exhausted T cells (T EX ) can differentiate into functional memory T cells (T MEM ) when chronic antigen is withdrawn. Using the chronic LCMV infection mouse model, they show that ‘recovering’ T EX cells (REC-T EX ) only partially recover immunophenotypic and functional characteristics of T MEM cells. The epigenomic status of REC-T EX cells more closely resembles that of T EX cells, and, upon rechallenge, the REC-T EX cells were still compromised in their ability to respond to virus.

The transcriptional programs that regulate CD8 T-cell differentiation and function in the context of viral infections or tumor immune surveillance have been extensively studied; yet how long noncoding RNAs (lncRNAs) and the loci that transcribe them contribute to the regulation of CD8 T cells during viral infections remains largely unexplored. Here, we report that transcription of the lncRNA Morrbid is specifically induced by T-cell receptor (TCR) and type I IFN stimulation during the early stages of acute and chronic lymphocytic choriomeningitis virus (LCMV) infection. In response to type I IFN, the Morrbid RNA and its locus control CD8 T cell expansion, survival, and effector function by regulating the expression of the proapoptotic factor, Bcl2l11, and by modulating the strength of the PI3K–AKT signaling pathway. Thus, our results demonstrate that inflammatory cue-responsive lncRNA loci represent fundamental mechanisms by which CD8 T cells are regulated in response to pathogens and potentially cancer.