Dipeptidylpeptidase 4 inhibition enhances lymphocyte trafficking, improving both naturally occurring tumor immunity and immunotherapy.

The success of antitumor immune responses depends on the infiltration of solid tumors by effector T cells, a process guided by chemokines. Here we show that in vivo post-translational processing of chemokines by dipeptidylpeptidase 4 (DPP4, also known as CD26) limits lymphocyte migration to sites of inflammation and tumors. Inhibition of DPP4 enzymatic activity enhanced tumor rejection by preserving biologically active CXCL10 and increasing trafficking into the tumor by lymphocytes expressing the counter-receptor CXCR3. Furthermore, DPP4 inhibition improved adjuvant-based immunotherapy, adoptive T cell transfer and checkpoint blockade. These findings provide direct in vivo evidence for control of lymphocyte trafficking via CXCL10 cleavage and support the use of DPP4 inhibitors for stabilizing biologically active forms of chemokines as a strategy to enhance tumor immunotherapy.

The Immune System Fails to Mount a Protective Response to Gram-Positive or Gram-Negative Bacterial Prostatitis.

Bacterial prostatitis affects 1% of men, with increased incidence in the elderly. Acute bacterial prostatitis frequently progresses to chronicity, marked by recurrent episodes interspersed with asymptomatic periods of variable duration. Antibiotic treatment is standard of care; however, dissemination of antimicrobially resistant uropathogens threatens therapy efficacy. Thus, development of nonantibiotic-based approaches to treat chronic disease is a priority. Currently, why chronic prostatitis arises is unclear, as the immune response to prostate infection is incompletely understood. As 80% of prostatitis cases are caused by Gram-negative uropathogenic Escherichia coli (UPEC) or Gram-positive Enterococcus faecalis, we used a mouse transurethral instillation model to address the hypothesis that an innate immune response fails to develop following prostate infection with these uropathogens, leading to chronic disease. Surprisingly, infection induced robust proinflammatory cytokine expression and myeloid cell infiltration. Following a second infection, cytokine responses and innate cell infiltration were largely comparable to primary infection. Characteristic of memory responses, more lymphoid cells infiltrated the prostate in a second infection compared with a first, suggesting that adaptive immunity develops to eliminate the pathogens. Unexpectedly, bacterial burden in prostates challenged with either UPEC or E. faecalis was equal or greater than primary infection despite that a protective adaptive response to UPEC infection was evident in the bladder of the same animals. Our findings support that chronic or recurrent prostatitis develops despite strong innate immune responses and may be the result of a failure to develop immune memory to infection, pointing to actionable targets for immunotherapy.

The glycobiology of uropathogenic E. coli infection: the sweet and bitter role of sugars in urinary tract immunity.

Urinary tract infections (UTI) are among the most prevalent infectious diseases and the most common cause of nosocomial infections, worldwide. Uropathogenic E. coli (UPEC) are responsible for approximately 80% of all UTI, which most commonly affect the bladder. UPEC colonize the urinary tract by ascension of the urethra, followed by cell invasion, and proliferation inside and outside urothelial cells, thereby causing symptomatic infections and quiescent intracellular reservoirs that may lead to recurrence. Sugars, or glycans, are key molecules for host-pathogen interactions, and UTI are no exception. Surface glycans regulate many of the events associated with UPEC adhesion and infection, as well as induction of the host immune response. While the bacterial protein FimH binds mannose-containing host glycoproteins to initiate infection and UPEC-secreted polysaccharides block immune mechanisms to favour intracellular replication, host glycans on the urothelial surface and on secreted glycoproteins prevent or limit infection by inhibiting UPEC adhesion. Given the importance of glycans during UTI, here we review the glycobiology of UPEC infection to highlight fundamental sugar-mediated processes of immunological interest for their potential clinical applications. Interdisciplinary approaches incorporating glycomics and infection biology may help to develop novel non-antibiotic-based therapeutic strategies for bacterial infections as the spread of antimicrobial-resistant uropathogens is currently threatening modern healthcare systems.

Bladder cancer, a unique model to understand cancer immunity and develop immunotherapy approaches.

With the mechanistic understanding of immune checkpoints and success in checkpoint blockade using antibodies for the treatment of certain cancers, immunotherapy has become one of the hottest areas in cancer research, with promise of long-lasting therapeutic effect. Currently, however, only a proportion of cancers have a good response to checkpoint inhibition immunotherapy. Better understanding of the cancer response and resistance mechanisms is essential to fully explore the potential of immunotherapy to cure the majority of cancers. Bladder cancer, one of the most common and aggressive malignant diseases, has been successfully treated both at early and advanced stages by different immunotherapeutic approaches, bacillus Calmette-Guérin (BCG) intravesical instillation and anti-PD-1/PD-L1 immune checkpoint blockade, respectively. Therefore, it provides a good model to investigate cancer immune response mechanisms and to improve the efficiency of immunotherapy. Here, we review bladder cancer immunotherapy with equal weight on BCG and anti-PD-1/PD-L1 therapies and demonstrate why and how bladder cancer can be used as a model to study the predictors and mechanisms of cancer immune response and shine light on further development of immunotherapy approaches and response predictive biomarkers to improve immunotherapy of bladder cancer and other malignancies. We review the success of BCG and anti-PD-1/PD-L1 treatment of bladder cancer, the underlying mechanisms and the therapeutic response predictors, including the limits to our knowledge. We then highlight briefly the adaptation of immunotherapy approaches and predictors developed in other cancers for bladder cancer therapy. Finally, we explore the potential of using bladder cancer as a model to investigate cancer immune response mechanisms and new therapeutic approaches, which may be translated into immunotherapy of other human cancers. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

CXCR3/CXCL10 Axis Shapes Tissue Distribution of Memory Phenotype CD8+ T Cells in Nonimmunized Mice.

The preimmune repertoire consists of mature T lymphocytes that have not yet been stimulated in the periphery. Memory phenotype (MP) cells have been reported as part of the preimmune repertoire (i.e., T cells bearing memory markers despite lack of engagement with cognate Ag); however, little is known about their trafficking and function. In this study, we hypothesized that MP cells, naive to TCR stimulation, constitute a transient population that traffics to tissues during development. Using mutant and transgenic animals with a monospecific TCR, we discovered increased numbers of MP CD8+ T cells circulating in nonimmunized Cxcr3-/- and Cxcl10-/- mice compared with wild-type animals. Phenotypic differences included decreased numbers of preimmune MP Ag-specific T cells in the skin and thymus and a distinct pattern of activation upon TCR engagement. Our results show for the first time, to our knowledge, an important role for CXCR3 and CXCL10 in the tissue distribution of preimmune MP cells.

Limited Macrophage Positional Dynamics in Progressing or Regressing Murine Atherosclerotic Plaques-Brief Report.

Objective- Macrophages play important roles in the pathogenesis of atherosclerosis, but their dynamics within plaques remain obscure. We aimed to quantify macrophage positional dynamics within progressing and regressing atherosclerotic plaques. Approach and Results- In a stable intravital preparation, large asymmetrical foamy macrophages in the intima of carotid artery plaques were sessile, but smaller rounded cells nearer plaque margins, possibly newly recruited monocytes, mobilized laterally along plaque borders. Thus, to test macrophage dynamics in plaques over a longer period of time in progressing and regressing disease, we quantified displacement of nondegradable phagocytic particles within macrophages for up to 6 weeks. In progressing plaques, macrophage-associated particles appeared to mobilize to deeper layers in plaque, whereas in regressing plaques, the label was persistently located near the lumen. By measuring the distance of the particles from the floor of the plaque, we discovered that particles remained at the same distance from the floor regardless of plaque progression or regression. The apparent deeper penetration of labeled cells in progressing conditions could be attributed to monocyte recruitment that generated new superficial layers of macrophages over the labeled phagocytes. Conclusions- Although there may be individual exceptions, as a population, newly differentiated macrophages fail to penetrate significantly deeper than the limited depth they reside on initial entry, regardless of plaque progression, or regression. These limited dynamics may prevent macrophages from escaping areas with unfavorable conditions (such as hypoxia) and pose a challenge for newly recruited macrophages to clear debris through efferocytosis deep within plaque.

Bladder resident macrophages: Mucosal sentinels.

Macrophages are instrumental in the response to infectious and noninfectious diseases, however, their role in the bladder is poorly understood. Indeed, the bladder is a mucosal tissue frequently overlooked in research, despite the prevalence of illnesses such as urinary tract infection and bladder cancer. Notably, bladder tissue macrophages are among the most populous resident immune cells in this organ and recent studies support that resident macrophages and infiltrating monocytes play nonredundant roles in response to infection, immunotherapy, and inflammation. Advancing our understanding of macrophage behavior in the bladder is complicated by the difficulty in obtaining tissue-resident cells. Surmounting this challenge, however, for a greater understanding of macrophage ontology, impact on innate and adaptive immunity, and regulation of homeostasis, will ultimately contribute to better therapies for common afflictions of the bladder.

Origin of the lamina propria dendritic cell network.

CX(3)CR1(+) and CD103(+) dendritic cells (DCs) in intestinal lamina propria play a key role in mucosal immunity. However, the origin and the developmental pathways that regulate their differentiation in the lamina propria remain unclear. We showed that monocytes gave rise exclusively to CD103(-)CX(3)CR1(+) lamina propria DCs under the control of macrophage-colony-stimulating factor receptor (M-CSFR) and Fms-like thyrosine kinase 3 (Flt3) ligands. In contrast, common DC progenitors (CDP) and pre-DCs, which give rise to lymphoid organ DCs but not to monocytes, differentiated exclusively into CD103(+)CX(3)CR1(-) lamina propria DCs under the control of Flt3 and granulocyte-macrophage-colony-stimulating factor receptor (GM-CSFR) ligands. CD103(+)CX(3)CR1(-) DCs but not CD103(-)CX(3)CR1(+) DCs in the lamina propria constitutively expressed CCR7 and were the first DCs to transport pathogenic Salmonella from the intestinal tract to the mesenteric lymph nodes. Altogether, these results underline the diverse origin of the lamina propria DC network and identify mucosal DCs that arise from pre-DCs as key sentinels of the gut immune system.

Biology of nonmuscle-invasive bladder cancer: pathology, genomic implications, and immunology.

PURPOSE OF REVIEW: Despite that nearly 75% of bladder cancer patients are diagnosed with nonmuscle-invasive disease, our understanding of the biological landscape in bladder cancer is primarily within the context of muscle-invasive bladder cancer. More recent studies addressing the genomic changes and immunology of nonmuscle-invasive bladder cancer (NMIBC) have helped to extend our understanding of this prevalent disease. RECENT FINDINGS: Genomic studies reveal that NMIBC possesses complexity that can be defined by specific gene expression signatures and has helped to define subsets within this disease. These subsets possess different risk profiles that may impact treatment decisions. In addition, the baseline or posttreatment immunological response to the growing tumor may help to inform whether a specific NMIBC subset is likely to progress. SUMMARY: Findings from studies addressing the molecular landscape of NMIBC may help to establish parameters for stratifying patient risk within this disease as well as establish novel or targeted treatment strategies. Inclusion of information about the immune response within tumors will likely contribute to defining the relative risk and treatment strategy for these patients.

Enterococcus faecalis Promotes Innate Immune Suppression and Polymicrobial Catheter-Associated Urinary Tract Infection.

Enterococcus faecalis, a member of the human gastrointestinal microbiota, is an opportunistic pathogen associated with hospital-acquired wound, bloodstream, and urinary tract infections. E. faecalis can subvert or evade immune-mediated clearance, although the mechanisms are poorly understood. In this study, we examined E. faecalis-mediated subversion of macrophage activation. We observed that E. faecalis actively prevents NF-κB signaling in mouse RAW264.7 macrophages in the presence of Toll-like receptor agonists and during polymicrobial infection with Escherichia coliE. faecalis and E. coli coinfection in a mouse model of catheter-associated urinary tract infection (CAUTI) resulted in a suppressed macrophage transcriptional response in the bladder compared to that with E. coli infection alone. Finally, we demonstrated that coinoculation of E. faecalis with a commensal strain of E. coli into catheterized bladders significantly augmented E. coli CAUTI. Taken together, these results support the hypothesis that E. faecalis suppression of NF-κB-driven responses in macrophages promotes polymicrobial CAUTI pathogenesis, especially during coinfection with less virulent or commensal E. coli strains.

Macrophages Subvert Adaptive Immunity to Urinary Tract Infection.

Urinary tract infection (UTI) is one of the most common bacterial infections with frequent recurrence being a major medical challenge. Development of effective therapies has been impeded by the lack of knowledge of events leading to adaptive immunity. Here, we establish conclusive evidence that an adaptive immune response is generated during UTI, yet this response does not establish sterilizing immunity. To investigate the underlying deficiency, we delineated the naïve bladder immune cell compartment, identifying resident macrophages as the most populous immune cell. To evaluate their impact on the establishment of adaptive immune responses following infection, we measured bacterial clearance in mice depleted of either circulating monocytes, which give rise to macrophages, or bladder resident macrophages. Surprisingly, mice depleted of resident macrophages, prior to primary infection, exhibited a nearly 2-log reduction in bacterial burden following secondary challenge compared to untreated animals. This increased bacterial clearance, in the context of a challenge infection, was dependent on lymphocytes. Macrophages were the predominant antigen presenting cell to acquire bacteria post-infection and in their absence, bacterial uptake by dendritic cells was increased almost 2-fold. These data suggest that bacterial uptake by tissue macrophages impedes development of adaptive immune responses during UTI, revealing a novel target for enhancing host responses to bacterial infection of the bladder.

The impact of macroautophagy on CD8(+) T-cell-mediated antiviral immunity.

Macroautophagy is a catabolic recycling pathway, which can be induced by various stress stimuli. Viruses are able to manipulate autophagy in the cells that they infect. The impact of autophagy on the innate immune response to viruses and its stimulatory role in antigen presentation to CD4(+) T cells are well documented. Herein, we present the impact of autophagy on the activation of cytotoxic T lymphocyte (CTL)-mediated antiviral immune responses, which are required for the eradication or control of multiple viruses. We first discuss the general mechanisms by which viruses can either induce or block autophagy in cells. We then explore the cross-talk between autophagy and innate immune processes, which are both first line defenses against viruses; and constitute crucial steps for the initiation of potent adaptive immune responses. We describe the impact of autophagy on the presentation of viral peptide antigens on class I major histocompatibility complex (MHC I), a prerequisite for the priming of CTL responses. In sum, our review highlights the interplay between viruses and three integrated host response pathways - autophagy, innate and adaptive immunity - providing a framework for future mechanistic and pathogenesis-based research.

Monocyte trafficking in acute and chronic inflammation.

Environmental signals at the site of inflammation mediate rapid monocyte mobilization and dictate differentiation programs whereby these cells give rise to macrophages or dendritic cells. Monocytes participate in tissue healing, clearance of pathogens and dead cells, and initiation of adaptive immunity. However, recruited monocytes can also contribute to the pathogenesis of infection and chronic inflammatory disease, such as atherosclerosis. Here, we explore monocyte trafficking in the context of acute inflammation, relying predominantly on data from microbial infection models. These mechanisms will be compared to monocyte trafficking during chronic inflammation in experimental models of atherosclerosis. Recent developments suggest that monocyte trafficking shares common themes in diverse inflammatory diseases; however, important differences exist between monocyte migratory pathways in acute and chronic inflammation.

Variability in cell division among anatomical sites shapes Escherichia coli antibiotic survival in a urinary tract infection mouse model.

Urinary tract infection (UTI), mainly caused by Escherichia coli, are frequent and have a recurrent nature even after antibiotic treatment. Potential bacterial escape mechanisms include growth defects, but probing bacterial division in vivo and establishing its relation to the antibiotic response remain challenging. Using a synthetic reporter of cell division, we follow the temporal dynamics of cell division for different E. coli clinical strains in a UTI mouse model with and without antibiotics. We show that more bacteria are actively dividing in the kidneys and urine compared with the bladder. Bacteria that survive antibiotic treatment are consistently non-dividing in three sites of infection. Additionally, we demonstrate how both the strain in vitro persistence profile and the microenvironment impact infection and treatment dynamics. Understanding the relative contribution of the host environment, growth heterogeneity, non-dividing bacteria, and antibiotic persistence is crucial to improve therapies for recurrent infections.

CD11b⁺, Ly6G⁺ cells produce type I interferon and exhibit tissue protective properties following peripheral virus infection.

The goal of the innate immune system is containment of a pathogen at the site of infection prior to the initiation of an effective adaptive immune response. However, effector mechanisms must be kept in check to combat the pathogen while simultaneously limiting undesirable destruction of tissue resulting from these actions. Here we demonstrate that innate immune effector cells contain a peripheral poxvirus infection, preventing systemic spread of the virus. These innate immune effector cells are comprised primarily of CD11b⁺Ly6C⁺Ly6G⁻ monocytes that accumulate initially at the site of infection, and are then supplemented and eventually replaced by CD11b⁺Ly6C⁺Ly6G⁺ cells. The phenotype of the CD11b⁺Ly6C⁺Ly6G⁺ cells resembles neutrophils, but the infiltration of neutrophils typically occurs prior to, rather than following, accumulation of monocytes. Indeed, it appears that the CD11b⁺Ly6C⁺Ly6G⁺ cells that infiltrated the site of VACV infection in the ear are phenotypically distinct from the classical description of both neutrophils and monocyte/macrophages. We found that CD11b⁺Ly6C⁺Ly6G⁺ cells produce Type I interferons and large quantities of reactive oxygen species. We also observed that depletion of Ly6G⁺ cells results in a dramatic increase in tissue damage at the site of infection. Tissue damage is also increased in the absence of reactive oxygen species, although reactive oxygen species are typically thought to be damaging to tissue rather than protective. These data indicate the existence of a specialized population of CD11b⁺Ly6C⁺Ly6G⁺ cells that infiltrates a site of virus infection late and protects the infected tissue from immune-mediated damage via production of reactive oxygen species. Regulation of the action of this population of cells may provide an intervention to prevent innate immune-mediated tissue destruction.

Tissue-resident memory T cells mediate mucosal immunity to recurrent urinary tract infection.

Urinary tract infection (UTI) is one of the most prevalent human bacterial infections. New therapeutic approaches, including vaccination and immunotherapy, are urgently needed to combat the rapid global dissemination of multidrug-resistant uropathogens. Development of therapies is impeded by an incomplete understanding of memory development during UTI. Here, we found that reducing bacterial load early in infection, by reducing the inoculum or with antibiotics after infection, completely abrogated the protective memory response. We observed a mixed T helper (TH) cell polarization, composed of TH1, TH2, and TH17 T cells, among T cells infiltrating the bladder during primary infection. Thus, we hypothesized that reducing antigen load altered TH cell polarization, leading to poor memory. Unexpectedly, however, TH cell polarization was unchanged in these scenarios. Instead, we uncovered a population of tissue-resident memory (TRM) T cells that was significantly reduced in the absence of sufficient antigen. Demonstrating that TRM cells are necessary for immune memory, transfer of lymph node- or spleen-derived infection-experienced T cells to naïve animals did not confer protection against infection. Supporting that TRM cells are sufficient to protect against recurrent UTI, animals depleted of systemic T cells, or treated with FTY720 to block memory lymphocyte migration from lymph nodes to infected tissue, were equally protected compared with unmanipulated mice against a second UTI. Thus, we uncovered an unappreciated key role for TRM cells in the memory response to bacterial infection in the bladder mucosa, providing a target for non-antibiotic-based immunotherapy and/or new vaccine strategies to prevent recurrent UTI.

Adaptive Immunity in Genitourinary Cancers.

CONTEXT: While urothelial and renal cell cancers have exhibited modest responses to novel immune checkpoint inhibitors targeting the programmed death ligand 1 and its receptor, response rates in patients with prostate cancer have remained poor. The factors underlying suboptimal outcomes observed in patients treated with novel immunotherapies are still to be resolved. OBJECTIVE: To review the literature and describe the key adaptive immune physiological events associated with cancer progression and therapeutic response in genitourinary (GU) cancers. EVIDENCE ACQUISITION: We performed a nonsystematic, collaborative narrative review to highlight recent advancements leading to the current state of knowledge on the critical mediators of antitumor adaptive immunity to GU cancers. Further, we discuss the findings on the pre- and post-treatment immunological events that either are unique to each of the three cancer types or exhibit overlapping clinical associations. EVIDENCE SYNTHESIS: Aging-associated immune function decline is a major factor underlying poor outcomes observed in patients treated with both conventional and novel immunotherapies. Other cancer immunobiological aspects associated with suboptimal responses in GU cancers include the overall tumor mutational burden, mutations in specific tumor suppressor/DNA damage repair genes (KDM6A, PTEN, STAG2, TP53, ATM, and BRCA2), and abundance of multiple functional states of adaptive immune cells and their spatiotemporal localization within the tumor immune microenvironment. Understanding these mechanisms may potentially lead to the development of prognostic and predictive biomarkers such as immune cell infiltration profiles and tertiary lymphoid structures (TLSs) that associate with variable clinical outcomes depending on the nature of the novel immunotherapeutic approach. Implementation of newer immune-monitoring technologies and improved preclinical modeling systems will augment our understanding of the host and tumor intrinsic factors contributing to the variability of responses to immunotherapies. CONCLUSIONS: Despite the tremendous progress made in the understanding of dynamic and static adaptive immune elements within the tumor immune landscape, several knowledge gaps remain. A comprehensive knowledge thus gained will lead to precision immunotherapy, improved drug sequencing, and a therapeutic response. PATIENT SUMMARY: We performed a collaborative review by a diverse group of experts in the field to examine our understanding of the events and crosstalk between cancer cells and the patient's immune system that are associated with responses to novel immunotherapies. An evolving understanding of tumor-intrinsic and host-related immune alterations, both before and after therapy, will aid in the discovery of promising markers of responses to immunotherapy as well as the development of unique therapeutic approaches for the management of genitourinary cancers.

CD115+ monocytes protect microbially experienced mice against E. coli-induced sepsis.

Uropathogenic E. coli (UPEC) is a primary organism responsible for urinary tract infections and a common cause of sepsis. Microbially experienced laboratory mice, generated by cohousing with pet store mice, exhibit increased morbidity and mortality to polymicrobial sepsis or lipopolysaccharide challenge. By contrast, cohoused mice display significant resistance, compared with specific pathogen-free mice, to a monomicrobial sepsis model using UPEC. CD115+ monocytes mediate protection in the cohoused mice, as depletion of these cells leads to increased mortality and UPEC pathogen burden. Further study of the cohoused mice reveals increased TNF-α production by monocytes, a skewing toward Ly6ChiCD115+ "classical" monocytes, and enhanced egress of Ly6ChiCD115+ monocytes from the bone marrow. Analysis of cohoused bone marrow also finds increased frequency and number of myeloid multipotent progenitor cells. These results show that a history of microbial exposure impacts innate immunity in mice, which can have important implications for the preclinical study of sepsis.

Comparison of gene expression profiles between human and mouse monocyte subsets.

Blood of both humans and mice contains 2 main monocyte subsets. Here, we investigated the extent of their similarity using a microarray approach. Approximately 270 genes in humans and 550 genes in mice were differentially expressed between subsets by 2-fold or more. More than 130 of these gene expression differences were conserved between mouse and human monocyte subsets. We confirmed numerous of these differences at the cell surface protein level. Despite overall conservation, some molecules were conversely expressed between the 2 species' subsets, including CD36, CD9, and TREM-1. Other differences included a prominent peroxisome proliferator-activated receptor gamma (PPARgamma) signature in mouse monocytes, which is absent in humans, and strikingly opposed patterns of receptors involved in uptake of apoptotic cells and other phagocytic cargo between human and mouse monocyte subsets. Thus, whereas human and mouse monocyte subsets are far more broadly conserved than currently recognized, important differences between the species deserve consideration when models of human disease are studied in mice.