Troy D. Randall

Checkpoint blockade only works in 10-20% of patients. Consequently, investigators are testing checkpoint inhibitors in combination with drugs like the class I histone deacetylase inhibitor, entinostat (ENT). Unfortunately, the combination of ENT and checkpoint blockade fared poorly in patients with breast or ovarian cancer, despite promising pre-clinical results. Here we show that ENT enhances CD8 ⁺ T cell responses by maintaining a progenitor-like population of CD8 ⁺ T cells that supplies activated effector T cells to tumors for prolonged periods. Surprisingly, the anti-tumor effects of ENT are only experienced when delivered during a narrow window that occurs after T cell activation and before T cell exhaustion—a window that is likely closed in most patients. However, by first “jump-starting” the T cell response using an oncolytic virus, the anti-tumor activity of ENT and PD1 blockade is restored. These data establish a general paradigm, independent of tumor type, to rationally manipulate anti-tumor immunity.

Background/Objectives: The emergence of SARS-CoV-2 variants and breakthrough infections underscores the need for next-generation vaccines capable of protecting from natural infection and/or preventing virus transmission. Intranasal vaccination offers a promising approach by eliciting local immune responses in the nasal mucosa, the primary site of infection and reservoir for transmissible virus. We evaluated two live-attenuated, respiratory syncytial virus-vectored vaccines in which the RSV F and G surface glycoproteins were replaced with a chimeric SARS-CoV-2 Spike protein from the ancestral USA/WA-1/2020 strain (MV-014-212) or the Delta variant (MV-014-212-delta). Methods: K18-hACE2 mice and LVG Syrian hamsters were vaccinated with a single intranasal dose of MV-014-212 or MV-014-212-delta. Systemic and mucosal immunity were assessed following vaccination, and protection was evaluated following Delta SARS-CoV-2 challenge. In vaccinated hamsters, morbidity, viral shedding, and lung inflammation and injury were also assessed following natural exposure to infected cagemates. Results: A single intranasal dose of either vaccine elicited systemic and mucosal immunity in K18-hACE2 mice, including serum neutralizing antibodies, Spike-specific memory B cells and plasmablasts, and Spike-specific CD8⁺ lung-resident memory T cells. Although MV-014-212-delta vaccination provided the best protection against the Delta variant virus challenge, both vaccines decreased viral loads in nasal discharge, lung, and brain, and reduced weight loss and mortality. In naturally acquired infection studies, vaccinated hamsters exposed to infected cagemates exhibited minimal weight loss, limited viral replication within the nasal mucosa, and attenuated lung pathology. Conclusions: Intranasal RSV-vectored vaccines can elicit broad protective respiratory immunity, suggesting that this platform could be leveraged for other respiratory pathogens.

Background/Objectives: Histone deacetylase (HDAC) inhibitors have been shown to prime the response to immunotherapy (IMT) treatment by inducing immune activation and infiltration to target tumor cells. Many studies primarily focus on adaptive immune cells and their expression of pro-inflammatory markers, like somatostatin receptor 2 (SSTR2); however, macrophages are known to help mediate key tumor microenvironment changes. The goal of this study is to evaluate the effects of HDAC inhibitors and IMT on macrophages, their expression of SSTR2, and their impact on the treatment response in triple-negative breast cancer (TNBC). Methods: Cytotoxic effects of HDAC inhibitors on 4T1 mouse mammary carcinoma cells, including suberoylanilide hydroxamic acid (SAHA), were evaluated using flow cytometry. Bone marrow-derived macrophages (BMDMs) were stimulated to M1-like and M2-like phenotypes and treated with SAHA to explore the effects on SSTR2 expression in different macrophage phenotypes. 4T1-tumor-bearing BALB/c mice were used to evaluate the therapy response to four treatments: saline control, SAHA, anti-PD-1 + anti-CTLA-4 checkpoint blockade IMT, or a combination of SAHA + IMT. Additional cohorts of 4T1-tumor-bearing BALB/c mice and NOD SCID mice, which lack adaptive immune cells, were euthanized for early evaluation of tumor-associated macrophage (TAM) populations via flow cytometry and cytokine analysis. One-way independent ANOVAs and log-rank tests were used to compare group differences. Results: SAHA promotes SSTR2 expression on M1-like BMDMs in vitro. SAHA promotes M2-like TAMs in vivo and stimulates pro-inflammatory, anti-tumor cytokine production in combination with IMT. Conclusions: SAHA drives SSTR2 expression and anti-tumor innate immune responses with additive effects in combination with immunotherapy in preclinical TNBC.

The emergence of new SARS-CoV-2 variants and breakthrough infections underscores the need for next-generation vaccines capable of protecting from natural infection and/or preventing virus transmission to others. Intranasal vaccination offers a promising approach by eliciting local immune responses in the nasal mucosa, the primary site of infection and reservoir for transmissible virus. We evaluated two live-attenuated, respiratory syncytial virus vectored vaccines in which the RSV F and G surface glycoproteins were replaced with a chimeric SARS-CoV-2 Spike protein from either the ancestral USA/WA-1/2020 strain (MV-014-212) or the Delta variant (MV-014-212-delta). A single intranasal dose of either vaccine elicited systemic and mucosal immunity in K18-hACE2 mice, including serum neutralizing antibodies, Spike-specific memory B cells and plasmablasts, and Spike-specific CD8⁺ lung-resident memory T cells. Although MV-014-212-delta vaccination provided the best protection against Delta variant virus challenge, both vaccines decreased viral loads in nasal discharge, lung and brain, and reduced weight loss and mortality. In naturally acquired infection studies, vaccinated hamsters exposed to infected cagemates exhibited minimal weight loss, limited viral replication within the nasal mucosa, and attenuated lung pathology. Therefore, intranasal RSV-vectored vaccines can elicit broad protective respiratory immunity, suggesting that this platform could be leveraged for other respiratory pathogens.

SUMMARY: Interferon regulatory factor 1 (IRF1), a transcription factor encoded within the 5q31 locus harboring systemic lupus erythematosus (SLE) associated variants, promotes inflammatory responses by T and myeloid cells. Although IFNγ-activated B cells also express IRF1, its role in B cell biology and SLE is unclear. Here, we use a mouse SLE model, single-cell multiomics, and human B cells to show that IRF1 intrinsically regulates Irf4 gene chromatin accessibility and expression in B cells to control the balance between the antibody secreting cell (ASC) lineage commitment factor, IRF4, and the B cell identity factor, IRF8. We demonstrate that IRF1, through its integration of IFNγ and TLR7 induced transcriptional programs, tips B cells toward a terminal effector inflammatory AC fate at the expense of preserving more stem-like, resting and regulatory B cells that do not elicit autoantibody-associated pathology in SLE. Thus, IRF1 serves as a central node controlling B cell-driven autoimmune disease.

Systemically administered influenza vaccines provide strain-limited protection, while influenza infection of the respiratory epithelium supports development of lung resident memory B and T cells and more broadly reactive antibody responses. To test whether local antigen delivery is critical for establishing broad immunity, we directly compared respiratory tract and systemic delivery of influenza antigens to mice and hamsters using a replication-deficient adenovirus serotype 5 vector (Ad5[E1-,E2b-,E3-]). Both immunization routes elicited antibody responses in the lower respiratory tract and antigen-specific B and T cells in the draining lymph node. However, only intranasal immunization established lung-resident memory B and T cells, induced IgA responses in the upper respiratory tract directly at the site of viral entry and supported generation of IgA and IgG antibodies that bound antigenically drifted and distantly related influenza strains, including those of avian origin. Intranasal immunization accelerated viral clearance following heterologous virus challenge and was associated with limited pulmonary inflammation and fibrosis. Thus, intranasal immunization with the immunologically stealthy Ad5[E1-,E2b-,E3-] platform supports respiratory and systemic immunity to divergent influenza strains in the absence of overt lung immunopathology, suggesting that local antigen delivery may be key to development of more broadly protective “universal” flu vaccines.

Summary: Well known functions of adipose tissue include energy storage, regulation of thermogenesis, and glucose homeostasis—each of which are associated with the metabolic functions of fat. However, adipose tissues also have important immune functions. In this issue of Immunological Reviews, we present a series of articles that highlight the immune functions of adipose tissue, including the roles of specialized adipose‐resident immune cells and fat‐associated lymphoid structures. Importantly, immune cell functions in adipose tissues are often linked to the metabolic functions of adipocytes and vice versa. These reciprocal interactions and how they influence both immune and metabolic functions will be discussed in each article. In the first article, Wang et al.,¹¹discuss adipose‐associated macrophages and how obesity and metabolism impact their phenotype and function. Several articles in this issue discuss T cells as either contributors to, or regulators of, inflammatory responses in adipose tissues. Valentine and Nikolajczyk¹²provide insights into the role of T cells in obesity‐associated inflammation and their contribution to metabolic dysfunction, whereas an article from Kallies and Vasanthakumar¹³and another from Elkins and Li¹⁴describe adipose‐associated Tregs and how they help prevent inflammation and maintain metabolic homeostasis. Articles from Okabe³⁵as well as from Daley and Benezech¹⁵discuss the structure and function of fat‐associated lymphoid clusters (FALCs) that are prevalent in some adipose tissues and support local immune responses to pathogens, gut‐derived microbes and fat‐associated antigens. Finally, an article from Meher and McNamara¹⁶describes how innate‐like B1 cells in adipose tissues regulate cardiometabolic disease. Importantly, these articles highlight the physical and functional attributes of adipose tissues that are different between mice and humans, the metabolic and immune differences between various adipose depots in the body and the differences in immune cells, adipose tissues and metabolic functions between the sexes. At the end of this preface, we highlight how these differences are critically important for our understanding of anti‐tumor immunity to cancers that metastasize to a specific example of visceral adipose tissue, the omentum. Together, these articles identify some unanswered mechanistic questions that will be important to address for a better understanding of immunity in adipose tissues.

Multiple mechanisms restrain inflammation in neonates, most likely to prevent tissue damage caused by overly robust immune responses against newly encountered pathogens. Here, we identify a population of pulmonary dendritic cells (DCs) that express intermediate levels of CD103 (CD103 ^int ) and appear in the lungs and lung-draining lymph nodes of mice between birth and 2 weeks of age. CD103 ^int DCs express XCR1 and CD205 and require expression of the transcription factor BATF3 for development, suggesting that they belong to the cDC1 lineage. In addition, CD103 ^int DCs express CCR7 constitutively and spontaneously migrate to the lung-draining lymph node, where they promote stromal cell maturation and lymph node expansion. CD103 ^int DCs mature independently of microbial exposure and TRIF- or MyD88-dependent signaling and are transcriptionally related to efferocytic and tolerogenic DCs as well as mature, regulatory DCs. Correlating with this, CD103 ^int DCs show limited ability to stimulate proliferation and IFN-γ production by CD8 ⁺ T cells. Moreover, CD103 ^int DCs acquire apoptotic cells efficiently, in a process that is dependent on the expression of the TAM receptor, Mertk, which drives their homeostatic maturation. The appearance of CD103 ^int DCs coincides with a temporal wave of apoptosis in developing lungs and explains, in part, dampened pulmonary immunity in neonatal mice. Together, these data suggest a mechanism by which DCs sense apoptotic cells at sites of noninflammatory tissue remodeling, such as tumors or the developing lungs, and limit local T cell responses.

Supplementary Data from Circulating Tregs Accumulate in Omental Tumors and Acquire Adipose-Resident Features