Anti-PD-1/PD-L1 therapy for infectious diseases: learning from the cancer paradigm

Dual blockade of IL-10 and PD-1 leads to control of SIV viral rebound following analytical treatment interruption

Human immunodeficiency virus (HIV) persistence during antiretroviral therapy (ART) is associated with heightened plasma interleukin-10 (IL-10) levels and PD-1 expression. We hypothesized that IL-10 and PD-1 blockade would lead to control of viral rebound following analytical treatment interruption (ATI). Twenty-eight ART-treated, simian immunodeficiency virus (SIV)mac239-infected rhesus macaques (RMs) were treated with anti-IL-10, anti-IL-10 plus anti-PD-1 (combo) or vehicle. ART was interrupted 12 weeks after introduction of immunotherapy. Durable control of viral rebound was observed in nine out of ten combo-treated RMs for >24 weeks post-ATI. Induction of inflammatory cytokines, proliferation of effector CD8+ T cells in lymph nodes and reduced expression of BCL-2 in CD4+ T cells pre-ATI predicted control of viral rebound. Twenty-four weeks post-ATI, lower viral load was associated with higher frequencies of memory T cells expressing TCF-1 and of SIV-specific CD4+ and CD8+ T cells in blood and lymph nodes of combo-treated RMs. These results map a path to achieve long-lasting control of HIV and/or SIV following discontinuation of ART.

Bivalent chromatin accommodates survivin and BRG1/SWI complex to activate DNA damage response in CD4+ cells

BACKGROUND

Bivalent regions of chromatin (BvCR) are characterized by trimethylated lysine 4 (H3K4me3) and lysine 27 on histone H3 (H3K27me3) deposition which aid gene expression control during cell differentiation. The role of BvCR in post-transcriptional DNA damage response remains unidentified. Oncoprotein survivin binds chromatin and mediates IFNγ effects in CD4+ cells. In this study, we explored the role of BvCR in DNA damage response of autoimmune CD4+ cells in rheumatoid arthritis (RA).

METHODS

We performed deep sequencing of the chromatin bound to survivin, H3K4me3, H3K27me3, and H3K27ac, in human CD4+ cells and identified BvCR, which possessed all three histone H3 modifications. Protein partners of survivin on chromatin were predicted by integration of motif enrichment analysis, computational machine-learning, and structural modeling, and validated experimentally by mass spectrometry and peptide binding array. Survivin-dependent change in BvCR and transcription of genes controlled by the BvCR was studied in CD4+ cells treated with survivin inhibitor, which revealed survivin-dependent biological processes. Finally, the survivin-dependent processes were mapped to the transcriptome of CD4+ cells in blood and in synovial tissue of RA patients and the effect of modern immunomodulating drugs on these processes was explored.

RESULTS

We identified that BvCR dominated by H3K4me3 (H3K4me3-BvCR) accommodated survivin within cis-regulatory elements of the genes controlling DNA damage. Inhibition of survivin or JAK-STAT signaling enhanced H3K4me3-BvCR dominance, which improved DNA damage recognition and arrested cell cycle progression in cultured CD4+ cells. Specifically, BvCR accommodating survivin aided sequence-specific anchoring of the BRG1/SWI chromatin-remodeling complex coordinating DNA damage response. Mapping survivin interactome to BRG1/SWI complex demonstrated interaction of survivin with the subunits anchoring the complex to chromatin. Co-expression of BRG1, survivin and IFNγ in CD4+ cells rendered complete deregulation of DNA damage response in RA. Such cells possessed strong ability of homing to RA joints. Immunomodulating drugs inhibited the anchoring subunits of BRG1/SWI complex, which affected arthritogenic profile of CD4+ cells.

CONCLUSIONS

BvCR execute DNA damage control to maintain genome fidelity in IFN-activated CD4+ cells. Survivin anchors the BRG1/SWI complex to BvCR to repress DNA damage response. These results offer a platform for therapeutic interventions targeting survivin and BRG1/SWI complex in autoimmunity.

Targeted delivery of Fc-fused PD-L1 for effective management of acute and chronic colitis

The PD-1/PD-L1 pathway in mucosal immunity is currently actively explored and considered as a target for inflammatory bowel disease (IBD) treatment. However, systemic PD-L1 administration may cause unpredictable adverse effects due to immunosuppression. Here we show that reactive oxygen species (ROS)-responsive nanoparticles enhance the efficacy and safety of PD-L1 in a mouse colitis model. The nanoparticles control the accumulation and release of PD-L1 fused to Fc (PD-L1-Fc) at inflammatory sites in the colon. The nanotherapeutics shows superiority in alleviating inflammatory symptoms over systemic PD-L1-Fc administration and mitigates the adverse effects of PD-L1-Fc administration. The nanoparticles-formulated PD-L1-Fc affects production of proinflammatory and anti-inflammatory cytokines, attenuates the infiltration of macrophages, neutrophils, and dendritic cells, increases the frequencies of Treg, Th1 and Tfh cells, reshapes the gut microbiota composition; and increases short-chain fatty acid production. In summary, PD-L1-Fc-decorated nanoparticles may provide an effective and safe strategy for the targeted treatment of IBD.

Pooled prevalence of lymphopenia in all-cause hospitalisations and association with infection: a systematic review and meta-analysis

BACKGROUND

Lymphopenia is defined as a decrease below normal value (often 1.0 x 109 cells/L) of blood circulating lymphocyte count. In the general population, lymphopenia is associated with an increased risk of hospitalisation secondary to infection, independent of traditional clinical risk factors. In hospital, lymphopenia is associated with increased risk of healthcare-associated infection and mortality. By summarising lymphopenia's prevalence and impact on clinical outcomes, we can identify an at-risk population and inform future studies of immune dysfunction following severe illness.

METHODS

Peer-reviewed search strategy was performed on three databases. Primary objective was to summarise the pooled prevalence of lymphopenia. Primary outcome was infection including pre-existing lymphopenia as a risk factor for admission with infection and as an in-hospital risk factor for healthcare-associated infection. Secondary outcomes were length of stay and mortality. Mortality data extracted included in-hospital, 28/30-day ('early'), and 90-day/1-year ('late') mortality. Meta-analysis was carried out using random-effects models for each outcome measure. Heterogeneity was assessed using I2 statistic. Joanna Briggs Institute checklist for cohort studies was used to assess risk of bias. The protocol was published on PROSPERO.

RESULTS

Fifteen observational studies were included. The pooled prevalence of lymphopenia in all-cause hospitalisations was 38% (CI 0.34-0.42, I2= 97%, p< 0.01). Lymphopenia was not associated with an infection diagnosis at hospital admission and healthcare associated infection (RR 1.03; 95% CI 0.26-3.99, p=0.97, I2 = 55% and RR 1.31; 95% CI 0.78-2.20, p=0.31, I2=97%, respectively), but was associated with septic shock (RR 2.72; 95% CI 1.02-7.21, p=0.04, I2 =98%). Lymphopenia was associated with higher in-hospital mortality and higher 'early' mortality rates (RR 2.44; 95% CI 1.71-3.47, p < 0.00001, I2 = 89% and RR 2.05; 95% CI 1.64-2.56, p < 0.00001, I2 = 29%, respectively). Lymphopenia was associated with higher 'late' mortality (RR 1.59; 1.33-1.90, p < 0.00001, I2 = 0%).

CONCLUSIONS

This meta-analysis demonstrates the high prevalence of lymphopenia across all-cause hospitalisations and associated increased risk of septic shock, early and late mortality. Lymphopenia is a readily available marker that may identify immune dysfunctional patients. Greater understanding of immune trajectories following survival may provide insights into longer-term poor clinical outcomes.

Harnessing the druggability at orthosteric and allosteric sites of PD-1 for small molecule discovery by an integrated in silico pipeline

The PD-1/PD-L1 interaction is a promising target for small molecule inhibitors in cancer immunotherapy, but targeting this interface has been challenging. While efforts have been made to identify compounds that target the orthosteric sites, no reports have explored the potential of small molecules to target the allosteric region of PD-1. Therefore, our study aims to establish a pipeline to identify small molecules that can effectively bind to either the orthosteric or allosteric pockets of PD-1. We categorized the PD-1 interface into two hot-spot zones (P-and N-zones) based on extensive analysis of its structural, dynamical, and energetic properties. These zones correspond to the orthosteric and allosteric PPI sites, respectively, targeted by monoclonal antibodies. We used a guided virtual screening workflow to identify hits from ∼7 million compounds library, which were then clustered based on structural similarity and assessed by interaction fingerprinting. The selective and diverse chemical representatives were subjected to MD simulations and binding energetics calculations to filter out false positives and identify actual binders. Binding poses metadynamics calculations confirmed the stability of the final hits in the pocket. This study emphasizes the need for an integrated pipeline that uses molecular dynamics simulations and binding energetics to identify potential binders for the dynamic PD-1/PD-L1 interface, due to the lack of small molecule co-crystals. Only a few potential binders were discovered from a large pool of molecules targeting both the allosteric and orthosteric zones. Our results suggest that the allosteric site has more potential than the orthosteric site for inhibitor design. The identified "computational hits" hold potential as starting points for in vitro evaluations followed by hit-to-lead optimization. Overall, this study represents an effort to establish a computational pipeline for exploring and enriching both the allosteric and orthosteric sites of PPI interfaces, "a tough but indispensable nut to crack".

From immunology to artificial intelligence: revolutionizing latent tuberculosis infection diagnosis with machine learning

Latent tuberculosis infection (LTBI) has become a major source of active tuberculosis (ATB). Although the tuberculin skin test and interferon-gamma release assay can be used to diagnose LTBI, these methods can only differentiate infected individuals from healthy ones but cannot discriminate between LTBI and ATB. Thus, the diagnosis of LTBI faces many challenges, such as the lack of effective biomarkers from Mycobacterium tuberculosis (MTB) for distinguishing LTBI, the low diagnostic efficacy of biomarkers derived from the human host, and the absence of a gold standard to differentiate between LTBI and ATB. Sputum culture, as the gold standard for diagnosing tuberculosis, is time-consuming and cannot distinguish between ATB and LTBI. In this article, we review the pathogenesis of MTB and the immune mechanisms of the host in LTBI, including the innate and adaptive immune responses, multiple immune evasion mechanisms of MTB, and epigenetic regulation. Based on this knowledge, we summarize the current status and challenges in diagnosing LTBI and present the application of machine learning (ML) in LTBI diagnosis, as well as the advantages and limitations of ML in this context. Finally, we discuss the future development directions of ML applied to LTBI diagnosis.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.

Fatal acute-on-chronic liver failure following camrelizumab for hepatocellular carcinoma with HBsAg seroclearance: a case report and literature review

In the last few years, immune checkpoint inhibitors (ICIs) have become major therapeutic agents for the treatment of advanced hepatocellular carcinoma (HCC). However, immunotherapy can activate hepatitis B virus (HBV), and immune clearance may lead to liver failure and even life-threatening conditions. Here we report a case of HCC with HBV-related cirrhosis that caused severe liver injury and rapidly progressed to fatal acute-on-chronic liver failure (ACLF) after only once application of camrelizumab; the patient underwent serological conversion of hepatitis B surface antigen (HBsAg) with liver injury. The patient's condition progressed rapidly. We added corticosteroids and applied plasma dialysis, along with tenofovir alafenamide (TAF) to control HBV. However, the patient eventually died of liver failure. To our knowledge, there are few reports of HBsAg clearance due to ICIs accompanied by fatal acute-on-chronic liver failure shortly after ICIs initiation. These results suggest that ICIs can cause fatal liver injury in a short term; in patients with chronic HBV infection, ICIs use may promote serological conversion of HBsAg.

Forsythiaside A prevents zymosan A-induced cell migration in neutrophil-differentiated HL-60 cells via PD-1/PD-L1 pathway

Neutrophils, which account for more than 80% of leukocyte, play an important role in resolution of inflammation. Immune checkpoint molecules could be potential biomarkers in immunosuppression. Forsythiaside A (FTA), a main constituent of Forsythia suspensa (Thunb.) Vahl, provides a very significant anti-inflammatory activity. Here we defined the immunological mechanisms of FTA by taking programmed cell death-1 (PD-1)/programmed cell death-Ligand 1 (PD-L1) pathway into consideration. FTA could inhibited cell migration in HL-60-derived neutrophils in vitro, and this action appeared to be mediated via PD-1/PD-L1 depended JNK and p38 MAPK pathways. In vivo, FTA prevented PD-L1⁺ neutrophils infiltration and reduced the levels of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1) and interferon-gamma (IFN-γ) after zymosan A-induced peritonitis. PD-1/PD-L1 inhibitor could abolish the suppression of FTA. The expression of inflammatory cytokines and chemokines were positively correlated with PD-L1. Molecular docking showed that FTA could bind to PD-L1. Taken together, FTA might prevent neutrophils infiltration to exert inflammation resolution through PD-1/PD-L1 pathway.

Diesel exhaust particle exposure accelerates oxidative DNA damage and cytotoxicity in normal human bronchial epithelial cells through PD-L1

Diesel exhaust particles (DEPs) are a major cause of cancer progression as well as a variety of acute and chronic diseases. It is well-known that programmed death-ligand 1 (PD-L1) is an immune checkpoint molecule that can induce immune escape in tumor cells. However, the function of PD-L1 in bronchial epithelial cells or how PD-L1 relates to cellular oxidation under DEPs-mediated oxidative stress is not well known. In this study, we investigated how PD-L1 affected DEPs-induced oxidative stress and cytotoxicity in human bronchial epithelial (HBE) cells, Beas-2B. DEPs not only induced intracellular reactive oxygen species (ROS) production, but also increased PD-L1 expression in HBE cells. Beas-2B cells overexpressing PD-L1 showed higher levels of ROS production, DNA damage, and apoptosis after DEPs treatment compared to control cells. In particular, the expression of an antioxidant enzyme heme-oxygenase-1 (HO-1) and nuclear translocation and transcriptional activity of Nrf2, a major regulator of HO-1, were lower in Beas-2B overexpressing PD-L1 cells than in control cells. DEPs-induced ROS generation, DNA damage and apoptosis in Beas-2B cells overexpressing PD-L1 were significantly restored by overexpressing HO-1. Collectively, our results suggest that DEPs can increase the expression of PD-L1 in HBE cells and that overexpressing PD-L1 might eventually promote DEPs-induced oxidative DNA damage and apoptosis.

Repurposing BCL-2 and Jak 1/2 inhibitors: Cure and treatment of HIV-1 and other viral infections

B cell lymphoma 2 (BCL-2) family proteins are involved in the mitochondrial apoptotic pathway and are key modulators of cellular lifespan, which is dysregulated during human immunodeficiency virus type 1 (HIV-1) and other viral infections, thereby increasing the lifespan of cells harboring virus, including the latent HIV-1 reservoir. Long-lived cells harboring integrated HIV-1 DNA is a major barrier to eradication. Strategies reducing the lifespan of reservoir cells could significantly impact the field of cure research, while also providing insight into immunomodulatory strategies that can crosstalk to other viral infections. Venetoclax is a first-in-class orally bioavailable BCL-2 homology 3 (BH3) mimetic that recently received Food and Drug Administration (FDA) approval for treatment in myeloid and lymphocytic leukemia. Venetoclax has been recently investigated in HIV-1 and demonstrated anti-HIV-1 effects including a reduction in reservoir size. Another immunomodulatory strategy towards reduction in the lifespan of the reservoir is Jak 1/2 inhibition. The Jak STAT pathway has been implicated in BCL-2 and interleukin 10 (IL-10) expression, leading to a downstream effect of cellular senescence. Ruxolitinib and baricitinib are FDA-approved, orally bioavailable Jak 1/2 inhibitors that have been shown to indirectly decay the HIV-1 latent reservoir, and down-regulate markers of HIV-1 persistence, immune dysregulation and reservoir lifespan in vitro and ex vivo. Ruxolitinib recently demonstrated a significant decrease in BCL-2 expression in a human study of virally suppressed people living with HIV (PWH), and baricitinib recently received emergency use approval for the indication of coronavirus disease 2019 (COVID-19), underscoring their safety and efficacy in the viral infection setting. BCL-2 and Jak 1/2 inhibitors could be repurposed as immunomodulators for not only HIV-1 and COVID-19, but other viruses that upregulate BCL-2 anti-apoptotic proteins. This review examines potential routes for BCL-2 and Jak 1/2 inhibitors as immunomodulators for treatment and cure of HIV-1 and other viral infections.

NK cell dysfunction is linked with disease severity in SARS-CoV-2 patients

SARS-CoV-2 first raised from Wuhan City, Hubei Province in November 2019. The respiratory disorder, cough, weakness, fever are the main clinical symptoms of coronavirus disease 2019 (COVID-19) patients. Natural Killer (NK) cells as a first defense barrier of innate immune system have an essential role in early defense against pulmonary virus. They kill the infected cells by inducing apoptosis or the degranulation of perforin and granzymes. Collectively, NK cells function are coordinated by the transmitted signals from activating and inhibitory receptors. It is clear that the cytotoxic function of NK cells is disrupted in COVID-19 patients due to the dysregulation of activating and inhibitory receptors. Therefore, better understanding of the activating and inhibitory receptors mechanism could facilitate the treatment strategy in clinic. To improve the efficacy of immunotherapy in COVID-19 patients, the functional detail of NK cell and manipulation of their key checkpoints are gathered in current review.

Viral Delivery of IL-7 Is a Potent Immunotherapy Stimulating Innate and Adaptive Immunity and Confers Survival in Sepsis Models

Persistence of an immunosuppressive state plays a role in septic patient morbidity and late mortality. Both innate and adaptive pathways are impaired, pointing toward the need for immune interventions targeting both arms of the immune system. We developed a virotherapy using the nonpropagative modified vaccinia virus Ankara (MVA), which harbors the intrinsic capacity to stimulate innate immunity, to deliver IL-7, a potent activator of adaptive immunity. The rMVA-human IL-7 (hIL-7)-Fc encoding the hIL-7 fused to the human IgG2-Fc was engineered and shown to express a dimeric, glycosylated, and biologically active cytokine. Following a single i.v. injection in naive mice, the MVA-hIL-7-Fc increased the number of total and activated B, T, and NK cells but also myeloid subpopulations (Ly6C^high, Ly6C^int, and Ly6C^neg cells) in both lung and spleen. It triggered differentiation of T cells in central memory, effector memory, and acute effector phenotypes and enhanced polyfunctionality of T cells, notably the number of IFN-γ-producing cells. The MVA vector contributed significantly to immune cell activation, particularly of NK cells. The MVA-hIL-7-Fc conferred a significant survival advantage in the cecal ligation and puncture (CLP) and Candida albicans sepsis models. It significantly increased cell numbers and activation in both spleen and lung of CLP mice. Comparatively, in naive and CLP mice, the rhIL-7-Fc soluble counterpart overall induced less vigorous, shorter lasting, and narrower immune activities than did the MVA-hIL-7-Fc and favored TNF-α-producing cells. The MVA-hIL-7-Fc represents a novel class of immunotherapeutic with clinical potential for treatment of septic patients.

Role of the PD-1/PD-L1 Pathway in Experimental Trypanosoma cruzi Infection and Potential Therapeutic Options

Chagas disease (CD) is a neglected chronic infection caused by the protozoan parasite Trypanosoma cruzi (T. cruzi). A significant portion of infected people develops cardiac or digestive alterations over a lifetime. Since several chronic infections associated with antigen persistence and inflammation have been shown to lead to T cell exhaustion, new therapies targeting co-inhibitory receptors to regain T cell activity are under consideration. This study explored immune therapeutic approaches targeting the inhibitory PD-1/PD-L pathway in an experimental model for CD. Infected PD-L1 knockout mice (PD-L1 KO) showed increased systemic parasitemia in blood although no significant differences in parasite load were observed in different organs. Furthermore, we found no significant differences in the frequency of activated T cells or proinflammatory cytokine production when compared to WT counterparts. PD-L1 deficiency led to the production of IL-10 by CD8+ T cells and an upregulation of Tim-3 and CD244 (2B4). Unexpectedly, the lack of PD-L1 did not contribute to a significantly improved T cell response to infection. Single blockade and combined blockade of PD-1 and Tim-3 using monoclonal antibodies confirmed the results observed in infected. PD-L1 KO mice. Our results describe for the first time that the interruption of the PD-1/PD-L1 axis during acute T. cruzi infection does not necessarily enhance the immune response against this parasite. Its interruption favors increased levels of parasitemia and sustained upregulation of other co-inhibitory receptors as well as the production of regulatory cytokines. These results suggest that the clinical application of immune therapeutic approaches targeting the PD-1/PD-L1 axis in CD might be risky and associated with adverse events. It highlights that more research is urgently needed to better understand the immune regulation of T cells in CD before designing immune therapeutic approaches for a clinical context.

Rational design of synthetically tractable HDAC6/HSP90 dual inhibitors to destroy immune-suppressive tumor microenvironment

INTRODUCTION

The tumor microenvironment is mainly flooded with immunosuppressive cells and inhibitory cytokines, resulting in the inability of effective immune cells to infiltrate and recognize tumors and even the loss of anti-cancer ability.

OBJECTIVES

We propose a novel HDAC6/HSP90 dual inhibitory strategy as well as a chemoimmunotherapeutic agent that does not only kill tumor cells but also destroys the tumor microenvironment and enhances anti-cancer immunity.

METHODS

A hybrid scaffold construction approach was leveraged to furnish a series of rationally designed resorcinol-based hydroxamates as dual selective HDAC6/HSP90 inhibitors. The drug design campaign commenced with a fragment recruitment process to pinpoint validated structural units to inhibit HDAC6 and HSP90, followed by their installation in flexible HDAC inhibitory templates via an efficient and facile multistep synthetic route. Subsequent evaluations identified a strikingly potent selective HDAC6/HSP90 dual inhibitor (compound 17) via molecular and biological analysis in vitro and in vivo.

RESULTS

Compound 17 exhibited not only direct cytotoxicity to cancer cells but also downregulated immune checkpoints (PD-L1 and IDO) expression in tumors via the inhibition of STAT1 pathway and degradation of oncogene proteins (Src, AKT, Rb, and FAK), leading to in vivo tumor growth inhibition. These multiple effects enabled the effector T cells to largely infiltrate into the tumor region and release granzyme B to kill cancer cells. In addition, compound 17 also decreased TGF-β secretion from normal cells, resulting in the systemic reduction of immunosuppressive regulatory T cells. Delightfully, a cocktail treatment of compound 17 and anti-PD-1 antibodies demonstrated synergistic efficacy to eliminate solid tumors with 83.9% of tumor growth inhibition.

CONCLUSION

In summary, the impressive activity profile of compound 17, as an effective anticancer agent and a potential immunosensitizer, forecasts the application of HDAC6/HSP90 dual inhibitory strategy to overcome the immunosuppressive tumor microenvironment.

IL-10 Producing Regulatory B Cells Mediated Protection against Murine Malaria Pathogenesis

Simple Summary

The immunomodulatory role of B cell subset called regulatory B cells was evaluated during Plasmodium infection to study their role in susceptibility or resistance during infection. The expansion of regulatory B cells during Plasmodium infection indicated their important role in regulating the immune response. Adoptive transfer of regulatory B cells following infection with a lethal parasite resulted in enhanced survival of mice and inhibited growth of the Plasmodium parasite. Moreover, by inhibiting the production of the pro-inflammatory cytokine, IFN-γ, and stimulating anti-inflammatory IL-10 production, regulatory B cells may serve as an important contributor to protective immune response.

Abstract

Various immune cells are known to participate in combating infection. Regulatory B cells represent a subset of B cells that take part in immunomodulation and control inflammation. The immunoregulatory function of regulatory B cells has been shown in various murine models of several disorders. In this study, a comparable IL-10 competent B-10 cell subset (regulatory B cells) was characterized during lethal and non-lethal infection with malaria parasites using the mouse model. We observed that infection of Balb/c mice with P. yoelii I 7XL was lethal, and a rapid increase in dynamics of IL-10 producing B220⁺CD5⁺CD1d⁺ regulatory B cells over the course of infection was observed. However, animals infected with a less virulent strain of the parasite P. yoelii I7XNL attained complete resistance. It was observed that there is an increase in the population of regulatory B cells with an increase of parasitemia; however, a sudden drop in the frequency of these cells was observed with parasite clearance. Adoptive transfer of regulatory B cells to naïve mice followed by infection results in slow parasite growth and enhancement of survival in P. yoelii 17XL (lethal) infected animals. Adoptively transferred regulatory B cells also resulted in decreased production of pro-inflammatory cytokine (IFN-γ) and enhanced production of anti-inflammatory cytokine (IL-10). It infers that these regulatory B cells may contribute in immune protection by preventing the inflammation associated with disease and inhibiting the parasite growth.

Traversing through the Dynamic Protein-Protein Interaction Landscape and Conformational Plasticity of PD-1 for Small-Molecule Discovery

Monoclonal antibodies (mAbs) blocking the PD-1/PD-L1 interface have shown remarkable success in treating malignancies, but they may also initiate lethal immune-related adverse events. Small molecules may circumvent the mAb limitations; however, none has entered clinical trials targeting PD-1. Its complex protein-protein interaction interfaces necessitate an atomic-level understanding of recognition and binding mechanisms. Hence, we have aimed to highlight the PD-1's sequence-structure-dynamic-function link with its cognate ligands and diversely reported inhibitors. We focus primarily on the anti-PD-1 mAbs, their mode of actions, and interactions with PD-1 epitopes. The comparison of co-crystals showed that these ligands/inhibitors harness the PD-1's conformational plasticity and structural determinants differentially. The relationship between modulator binding patterns and biological activity is demonstrated using interaction fingerprinting of all reported human PD-1 co-crystals. The significant dynamical events and hot-spot residues underpinned from crystallographic wealth and computational studies have been highlighted to expedite small-molecule discovery.

Risk of Hepatitis B Virus Reactivation in Patients Treated With Immunotherapy for Anti-cancer Treatment

BACKGROUND & AIMS

Hepatitis B virus (HBV) reactivation is a well-known complication in patients with chronic hepatitis B treated with cytotoxic chemotherapy. However, the risk of HBV reactivation through use of immune checkpoint inhibitors (ICIs) is not well understood. Therefore, we aimed to evaluate the risk of HBV reactivation and hepatic adverse events in patients with cancer receiving ICIs according to cancer type and virologic serology.

METHODS

This historical cohort study included 3465 patients with cancer treated with ICIs between January 2015 and September 2020. The primary outcome was the occurrence of HBV reactivation, and the secondary outcome was presence of hepatic adverse events during ICI treatment.

RESULTS

The mean patient age was 62.2 years, and 68.8% of patients were men. Of the 3465 eligible patients, 511 (14.7%) showed hepatitis B surface antigen (HBsAg) positivity. The incidence rates of HBV reactivation of the total patients, HBsAg-positive patients, and HBsAg-negative patients were 0.14% (5/3465), 1.0% (5/511), and 0.0% (0/2954), respectively. Among HBsAg-positive patients, HBV reactivation occurred at a rate of 0.5% (2/409) and 2.9% (3/102) in patients with and without hepatocellular carcinoma, respectively. The HBV reactivation rates were 0.4% (2/464) and 6.4% (3/47) in patients with and without antiviral prophylaxis, respectively. Grade 3-4 hepatitis occurred in 23 (4.5%) HBsAg-positive, and 218 (7.4%) HBsAg-negative patients. No HBV-related fatality occurred. Only 2 patients (0.4%) experienced HBsAg seroclearance after ICI treatment among HBsAg-positive patients.

CONCLUSIONS

In general, HBV reactivation was rarely observed in patients with antiviral prophylaxis while undergoing ICI treatment. However, HBV reactivation may occur in HBsAg-positive patients without antiviral prophylaxis or noncompliant with antiviral prophylaxis.

CD84 is a Suppressor of T and B Cell Activation during Mycobacterium tuberculosis Pathogenesis

Interest in host-directed therapies as alternatives/adjuncts to antibiotic treatment has resurged with the increasing prevalence of antibiotic-resistant tuberculosis (TB). Immunotherapies that reinvigorate immune responses by targeting immune checkpoints like PD-1/PD-L1 have proved successful in cancer therapy. Immune cell inhibitory receptors that trigger Mycobacterium tuberculosis-specific immunosuppression, however, are unknown. Here, we show that the levels of CD84, a SLAM family receptor, increase in T and B cells in lung tissues from M. tuberculosis-infected C57BL/6 mice and in peripheral blood mononuclear cells (PBMCs) from pulmonary TB patients. M. tuberculosis challenge experiments using CD84-deficient C57BL/6 mice suggest that CD84 expression likely leads to T and B cell immunosuppression during M. tuberculosis pathogenesis and also plays an inhibitory role in B cell activation. Importantly, CD84-deficient mice showed improved M. tuberculosis clearance and longer survival than M. tuberculosis-infected wild-type (WT) mice. That CD84 is a putative M. tuberculosis infection-specific inhibitory receptor suggests it may be a suitable target for the development of TB-specific checkpoint immunotherapies. IMPORTANCE Immune checkpoint therapies, such as targeting checkpoints like PD-1/PD-L1, have proved successful in cancer therapy and can reinvigorate immune responses. The potential of this approach for treating chronic infectious diseases like TB has been recognized, but a lack of suitable immunotherapeutic targets, i.e., immune cell inhibitory receptors that trigger immunosuppression specifically during Mycobacterium tuberculosis pathogenesis, has limited the application of this strategy in the development of new TB therapies. Our focus in this study was to address this gap and search for an M. tuberculosis-specific checkpoint target. Our results suggest that CD84 is a putative inhibitory receptor that may be a suitable target for the development of TB-specific checkpoint immunotherapies.

Soluble Immune Checkpoints Are Dysregulated in COVID-19 and Heavy Alcohol Users With HIV Infection

Immune checkpoints (ICPs) consist of paired receptor-ligand molecules that exert inhibitory or stimulatory effects on immune defense, surveillance, regulation, and self-tolerance. ICPs exist in both membrane and soluble forms in vivo and in vitro. Imbalances between inhibitory and stimulatory membrane-bound ICPs (mICPs) in malignant cells and immune cells in the tumor immune microenvironment (TIME) have been well documented. Blockades of inhibitory mICPs have emerged as an immense breakthrough in cancer therapeutics. However, the origin, structure, production regulation, and biological significance of soluble ICPs (sICPs) in health and disease largely remains elusive. Soluble ICPs can be generated through either alternative mRNA splicing and secretion or protease-mediated shedding from mICPs. Since sICPs are found in the bloodstream, they likely form a circulating immune regulatory system. In fact, there is increasing evidence that sICPs exhibit biological functions including (1) regulation of antibacterial immunity, (2) interaction with their mICP compartments to positively or negatively regulate immune responses, and (3) competition with their mICP compartments for binding to the ICP blocking antibodies, thereby reducing the efficacy of ICP blockade therapies. Here, we summarize current data of sICPs in cancer and infectious diseases. We particularly focus on sICPs in COVID-19 and HIV infection as they are the two ongoing global pandemics and have created the world's most serious public health challenges. A "storm" of sICPs occurs in the peripheral circulation of COVID-19 patients and is associated with the severity of COVID-19. Similarly, sICPs are highly dysregulated in people living with HIV (PLHIV) and some sICPs remain dysregulated in PLHIV on antiretroviral therapy (ART), indicating these sICPs may serve as biomarkers of incomplete immune reconstitution in PLHIV on ART. We reveal that HIV infection in the setting of alcohol misuse exacerbates sICP dysregulation as PLHIV with heavy alcohol consumption have significantly elevated plasma levels of many sICPs. Thus, both stimulatory and inhibitory sICPs are present in the bloodstream of healthy people and their balance can be disrupted under pathophysiological conditions such as cancer, COVID-19, HIV infection, and alcohol misuse. There is an urgent need to study the role of sICPs in immune regulation in health and disease.

PD-L1 signaling in reactive astrocytes counteracts neuroinflammation and ameliorates neuronal damage after traumatic brain injury

BACKGROUND

Tissue damage and cellular destruction are the major events in traumatic brain injury (TBI), which trigger sterile neuroimmune and neuroinflammatory responses in the brain. While appropriate acute and transient neuroimmune and neuroinflammatory responses facilitate the repair and adaptation of injured brain tissues, prolonged and excessive neuroimmune and neuroinflammatory responses exacerbate brain damage. The mechanisms that control the intensity and duration of neuroimmune and neuroinflammatory responses in TBI largely remain elusive.

METHODS

We used the controlled cortical impact (CCI) model of TBI to study the role of immune checkpoints (ICPs), key regulators of immune homeostasis, in the regulation of neuroimmune and neuroinflammatory responses in the brain in vivo.

RESULTS

We found that de novo expression of PD-L1, a potent inhibitory ICP, was robustly and transiently induced in reactive astrocytes, but not in microglia, neurons, or oligodendrocyte progenitor cells (OPCs). These PD-L1⁺ reactive astrocytes were highly enriched to form a dense zone around the TBI lesion. Blockade of PD-L1 signaling enlarged brain tissue cavity size, increased infiltration of inflammatory Ly-6C^High monocytes/macrophages (M/Mɸ) but not tissue-repairing Ly-6C^LowF4/80⁺ M/Mɸ, and worsened TBI outcomes in mice. PD-L1 gene knockout enhanced production of CCL2 that is best known for its ability to interact with its cognate receptor CCR2 on Ly-6C^High M/Mϕ to chemotactically recruit these cells into inflammatory sites. Mechanically, PD-L1 signaling in astrocytes likely exhibits dual inhibitory activities for the prevention of excessive neuroimmune and neuroinflammatory responses to TBI through (1) the PD-1/PD-L1 axis to suppress the activity of brain-infiltrating PD-1⁺ immune cells, such as PD-1⁺ T cells, and (2) PD-L1 intrinsic signaling to regulate the timing and intensity of astrocyte reactions to TBI.

CONCLUSIONS

PD-L1⁺ astrocytes act as a gatekeeper to the brain to control TBI-related neuroimmune and neuroinflammatory responses, thereby opening a novel avenue to study the role of ICP-neuroimmune axes in the pathophysiology of TBI and other neurological disorders.

Soluble programmed cell death-1 predicts hepatocellular carcinoma development during nucleoside analogue treatment

Soluble immune checkpoint molecules are emerging novel mediators of immune regulation. However, it is unclear whether soluble immune checkpoint proteins affect the development of hepatocellular carcinoma (HCC) during nucleos(t)ide analogue (NA) treatment in patients with chronic hepatitis B virus infection. This study included 122 NA-naïve patients who received NA therapy. We assessed the associations of clinical factors, including soluble immune checkpoint proteins, with HCC development during NA treatment. The baseline serum concentrations of 16 soluble immune checkpoint proteins were measured using multiplexed fluorescent bead-based immunoassay. In total, 13 patients developed HCC during the follow-up period (median duration, 4.3 years). Of the 16 proteins, soluble inducible T-cell co-stimulator (≥ 164.71 pg/mL; p = 0.014), soluble programmed cell death-1 (sPD-1) (≤ 447.27 pg/mL; p = 0.031), soluble CD40 (≤ 493.68 pg/mL; p = 0.032), and soluble herpes virus entry mediator (≤ 2470.83 pg/mL; p = 0.038) were significantly associated with HCC development (log-rank test). In multivariate analysis, an sPD-1 level ≤ 447.27 pg/mL (p = 0.014; hazard ratio [HR], 4.537) and α-fetoprotein level ≥ 6.4 ng/mL (p = 0.040; HR, 5.524) were independently and significantly associated with HCC development. Pre-treatment sPD-1 is a novel predictive biomarker for HCC development during NA treatment.

Mycobacterium avium complex lung disease in a patient treated with an immune checkpoint inhibitor: A case report

Immune checkpoint inhibitors (ICIs) are becoming widely used for the treatment of various types of cancer. However, characteristic side effects, which are referred to as immune-related adverse events, may appear, and they have important clinical implications for the management of patients treated with ICIs. The development of mycobacterial infections has also been reported, but they have mostly been seen in cases with tuberculosis, and only a few cases involved non-tuberculous mycobacteriosis. We herein present the case of an 82-year-old man who was treated with nivolumab for gastric cancer. After the 22nd course of the treatment, the patient experienced loss of appetite for 1 week, and infiltration shadows were observed in the lower lobe of the left lung. Treatment for bacterial pneumonia was ineffective, and the lung field shadow gradually worsened. Mycobacterium intracellulare was detected in two consecutive sputum cultures. Thus, the patient was diagnosed with Mycobacterium avium complex (MAC) lung disease, and treatment for MAC infection was thus initiated, with subsequent improvement of the patient's condition and infiltration shadows. At 7 months after the start of treatment, the sputum cultures became negative for acid-fast bacilli. Since MAC lung disease may develop acutely during immunotherapy with ICIs, clinicians should include it in the differential diagnoses for pneumonia during immunotherapy with ICIs.

The role of AI technology in prediction, diagnosis and treatment of colorectal cancer

Artificial intelligence (AI) is a fascinating new technology that incorporates machine learning and neural networks to improve existing technology or create new ones. Potential applications of AI are introduced to aid in the fight against colorectal cancer (CRC). This includes how AI will affect the epidemiology of colorectal cancer and the new methods of mass information gathering like GeoAI, digital epidemiology and real-time information collection. Meanwhile, this review also examines existing tools for diagnosing disease like CT/MRI, endoscopes, genetics, and pathological assessments also benefitted greatly from implementation of deep learning. Finally, how treatment and treatment approaches to CRC can be enhanced when applying AI is under discussion. The power of AI regarding the therapeutic recommendation in colorectal cancer demonstrates much promise in clinical and translational field of oncology, which means better and personalized treatments for those in need.

T-Cell Exhaustion in Mycobacterium tuberculosis and Nontuberculous Mycobacteria Infection: Pathophysiology and Therapeutic Perspectives

Immune exhaustion is a condition associated with chronic infections and cancers, characterized by the inability of antigen-specific T cells to eliminate the cognate antigen. Exhausted T cells display a peculiar phenotypic profile and exclusive functional characteristics. Immune exhaustion has been described in patients with Mycobacterium tuberculosis infection, and cases of tuberculosis reactivation have been reported in those treated with immune checkpoint inhibitors, drugs able to re-establish T-cells’ function. Exhausted T CD8⁺ cells’ profile has also been described in patients with infection due to nontuberculous mycobacteria. In this review, we initially provide an overview of the mechanisms leading to immune exhaustion in patients infected by Mycobacterium tuberculosis and nontuberculous mycobacteria. We then dissect the therapeutic perspectives related to immune checkpoint blockade in patients with these infections.

PDL1 expression on monocytes is associated with plasma cytokines in Tuberculosis and HIV

Introduction

PDL1 and its interaction with PD1 is implicated in immune dysfunction in TB and HIV. The expression of PDL1 on multiple subsets of monocytes as well as their associations with cytokines and microbial products have not been well studied.

Method

HIV (TB-HIV+), TB (TB+HIV-) and TB/HIV co-infected (TB+HIV+) patients as well as apparently healthy controls (TB-HIV-) were recruited. TB and HIV patients were treatment naïve while TB/HIV patients were both ART naïve and experienced but not yet started TB therapy. Monocyte subsets were evaluated for PDL1 expression by flow cytometry; plasma TNFα, IL6, IP10, IFNγ and IL10 were measured by Luminex; and cytokine mRNA from purified monocytes quantitated by qPCR. The association of PDL1 with cytokines, clinical and microbial indices, including HIV viral load, TB smear microscopy and TB urinary lipoarabinomannan (LAM) were assessed.

Results

Monocyte expression of PDL1 was significantly higher in TB, HIV and TB/HIV co-infected patients compared with healthy controls (p = 0.0001), with the highest levels in TB/HIV co-infected patients. The highest expression of PDL1 was on intermediate (CD14+CD16+) monocytes in all participant groups. PDL1 strongly correlated with HIV viral load in TB/HIV while weakly correlated in HIV. PDL1 levels moderately correlated with plasma TNFα, IL6, IP10, IFNγ and IL10 level in TB subjects whereas weakly correlated with TNFα and IP10 in HIV patients. However, cytokine mRNA from purified monocytes showed no association with either plasma cytokines or monocyte PDL1 expression, implying that if cytokines modulate PDL1, they are likely not originating from circulating monocytes themselves. These results underscore the importance of further characterization of multiple monocyte subsets and their phenotypic and functional differences in different disease states.

Emerging glyco-based strategies to steer immune responses

Glycan structures are common posttranslational modifications of proteins, which serve multiple important structural roles (for instance in protein folding), but also are crucial participants in cell-cell communications and in the regulation of immune responses. Through the interaction with glycan-binding receptors, glycans are able to affect the activation status of antigen-presenting cells, leading either to induction of pro-inflammatory responses or to suppression of immunity and instigation of immune tolerance. This unique feature of glycans has attracted the interest and spurred collaborations of glyco-chemists and glyco-immunologists to develop glycan-based tools as potential therapeutic approaches in the fight against diseases such as cancer and autoimmune conditions. In this review, we highlight emerging advances in this field, and in particular, we discuss on how glycan-modified conjugates or glycoengineered cells can be employed as targeting devices to direct tumor antigens to lectin receptors on antigen-presenting cells, like dendritic cells. In addition, we address how glycan-based nanoparticles can act as delivery platforms to enhance immune responses. Finally, we discuss some of the latest developments in glycan-based therapies, including chimeric antigen receptor (CAR)-T cells to achieve targeting of tumor-associated glycan-specific epitopes, as well as the use of glycan moieties to suppress ongoing immune responses, especially in the context of autoimmunity.

Immunotherapy use outside clinical trial populations: never say never?

BACKGROUND

Based on favourable outcomes in clinical trials, immune checkpoint inhibitors (ICIs), most notably programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte antigen-4 (CTLA-4) inhibitors, are now widely used across multiple cancer types. However, due to their strict inclusion and exclusion criteria, clinical studies often do not address challenges presented by non-trial populations.

DESIGN

This review summarises available data on the efficacy and safety of ICIs in trial-ineligible patients, including those with autoimmune disease, chronic viral infections, organ transplants, organ dysfunction, poor performance status, and brain metastases, as well as the elderly, children, and those who are pregnant. In addition, we review data concerning other real-world challenges with ICIs, including timing of therapy switch, relationships to radiotherapy or surgery, re-treatment after an immune-related toxicity, vaccinations in patients on ICIs, and current experience around ICI and coronavirus disease-19. Where possible, we provide recommendations to aid the often-difficult decision-making process in those settings.

CONCLUSIONS

Data suggest that ICIs are often active and have an acceptable safety profile in the populations described above, with the exception of PD-1 inhibitors in solid organ transplant recipients. Decisions about whether to treat with ICIs should be personalised and require multidisciplinary input and careful counselling of patients with respect to potential risks and benefits. Clinical judgements need to be carefully weighed, considering factors such as underlying cancer type, feasibility of alternative treatment options, or activity in trial-eligible patients.

Incidence of tuberculosis in advanced lung cancer patients treated with immune checkpoint inhibitors - A nationwide population-based cohort study

OBJECTIVES

The aim of this study was to investigate the risk of TB in advanced non-small cell lung cancer (NSCLC) patients treated with Immune checkpoint inhibitors (ICI) after a platinum-based chemotherapy.

MATERIALS AND METHODS

A nationwide population-based retrospective cohort study using National health insurance dataset was designed. Patients who were diagnosed as lung cancer between September 1st, 2017 and August 31st, 2018 in South Korea were selected. Among them, those with NSCLC who initiated a platinum-based chemotherapy within 3 months were finally included and followed up until December 31st, 2018. Patients who received nivolumab, pembrolizumab, and atezolizumab within study period were classified as the ICI group. Cox proportional hazard model with time-varying covariates was used to determine effects of the duration of conventional chemotherapy, ICI, and consecutive use of systemic steroid on TB.

RESULTS

A total of 6335 patients were enrolled with 3568.7 years of total follow-up period. Among them, 899 patients underwent ICI treatment. Within the follow-up period, 15 TB cases were identified in the ICI group (incidence: 2582.5 per 100,000 person-years) and 63 TB cases were found in the conventional chemotherapy group (incidence: 2108.5 per 100,000 person-years). In a multivariable Cox proportional hazard model, treatment with ICI was not a significant risk factor for TB development (hazard ratio (HR): 1.21, 95 % confidence interval (CI): 0.45-3.26,p =  0.700). Instead, prolonged use of steroid was associated with an increased TB risk (HR: 1.91, 95 %CI: 0.89-4.08, p =  0.095), although its statistical significance was dependent on the operational definition of the effect duration. Previous TB history and older age were independent risk factors for TB disease.

CONCLUSION

In this real-world study, additional treatment with ICI did not increase the risk of TB in advanced NSCLC patients who underwent a cytotoxic chemotherapy. However, TB incidence in these patients was high regardless of ICI treatment.

CLASSIFICATIONS

Systemic Treatments.

Mechanisms of PD-L1 Regulation in Malignant and Virus-Infected Cells

Programmed cell death protein 1 (PD-1), a receptor on T cells, and its ligand, PD-L1, have been a topic of much interest in cancer research. Both tumour and virus-infected cells can upregulate PD-L1 to suppress cytotoxic T-cell killing. Research on the PD-1/PD-L1 axis has led to the development of anti-PD-1/PD-L1 immune checkpoint blockades (ICBs) as promising cancer therapies. Although effective in some cancer patients, for many, this form of treatment is ineffective due to a lack of immunogenicity in the tumour microenvironment (TME). Despite the development of therapies targeting the PD-1/PD-L1 axis, the mechanisms and pathways through which these proteins are regulated are not completely understood. In this review, we discuss the latest research on molecules of inflammation and innate immunity that regulate PD-L1 expression, how its expression is regulated during viral infection, and how it is modulated by different cancer therapies. We also highlight existing research on the development of different combination therapies with anti-PD-1/PD-L1 antibodies. This information can be used to develop better cancer immunotherapies that take into consideration the pathways involved in the PD-1/PD-L1 axis, so these molecules do not reduce their efficacy, which is currently seen with some cancer therapies. This review will also assist in understanding how the TME changes during treatment, which will provide further rationale for combination therapies.

PD-1 Blockade Modulates Functional Activities of Exhausted-Like T Cell in Patients With Cutaneous Leishmaniasis

Patients infected by Leishmania braziliensis develop debilitating skin lesions. The role of inhibitory checkpoint receptors (ICRs) that induce T cell exhaustion during this disease is not known. Transcriptional profiling identified increased expression of ICRs including PD-1, PDL-1, PDL-2, TIM-3, and CTLA-4 in skin lesions of patients that was confirmed by immunohistology where there was increased expression of PD-1, TIM-3, and CTLA-4 in both CD4⁺ and CD8⁺ T cell subsets. Moreover, PDL-1/PDL-2 ligands were increased on skin macrophages compared to healthy controls. The proportions PD1⁺, but not TIM-3 or CTLA-4 expressing T cells in the circulation were positively correlated with those in the lesions of the same patients, suggesting that PD-1 may regulate T cell function equally in both compartments. Blocking PD-1 signaling in circulating T cells enhanced their proliferative capacity and IFN-γ production, but not TNF-α secretion in response to L. braziliensis recall antigen challenge in vitro. While we previously showed a significant correlation between the accumulation of senescent CD8⁺CD45RA⁺CD27^- T cells in the circulation and skin lesion size in the patients, there was no such correlation between the extent of PD-1 expression by circulating on T cells and the magnitude of skin lesions suggesting that exhausted-like T cells may not contribute to the cutaneous immunopathology. Nevertheless, we identified exhausted-like T cells in both skin lesions and in the blood. Targeting this population by PD-1 blockade may improve T cell function and thus accelerate parasite clearance that would reduce the cutaneous pathology in cutaneous leishmaniasis.

Immunological Aspects of Diagnosis and Management of Childhood Tuberculosis

The diagnosis of tuberculosis (TB) in children is difficult because of the low sensitivity and specificity of traditional microbiology techniques in this age group. Whereas in adults the culture of Mycobacterium tuberculosis (M. tuberculosis), the gold standard test, detects 80% of positive cases, it only detects around 30-40% of cases in children. The new methods based on the immune response to M. tuberculosis infection could be affected by many factors. It is necessary to evaluate the medical record, clinical features, presence of drug-resistant M. tuberculosis strains, comorbidities, and BCG vaccination history for the diagnosis in children. There is no ideal biomarker for all TB cases in children. A new strategy based on personalized diagnosis could be used to evaluate specific molecules produced by the host immune response and make therapeutic decisions in each child, thereby changing standard immunological signatures to personalized signatures in TB. In this way, immune diagnosis, prognosis, and the use of potential immunomodulators as adjunct TB treatments will meet personalized treatment.

PD-L1 siRNA Theranostics With a Dextran Nanoparticle Highlights the Importance of Nanoparticle Delivery for Effective Tumor PD-L1 Downregulation

Purpose

The inhibition of immune checkpoints such as programmed cell death ligand-1 (PD-L1/CD274) with antibodies is providing novel opportunities to expose cancer cells to the immune system. Antibody based checkpoint blockade can, however, result in serious autoimmune complications because normal tissues also express immune checkpoints. As sequence-specific gene-silencing agents, the availability of siRNA has significantly expanded the specificity and range of “druggable” targets making them promising agents for precision medicine in cancer. Here, we have demonstrated the ability of a novel biodegradable dextran based theranostic nanoparticle (NP) to deliver siRNA downregulating PD-L1 in tumors. Optical imaging highlighted the importance of NP delivery and accumulation in tumors to achieve effective downregulation with siRNA NPs, and demonstrated low delivery and accumulation in several PD-L1 expressing normal tissues.

Methods

The dextran scaffold was functionalized with small molecules containing amine groups through acetal bonds. The NP was decorated with a Cy5.5 NIR probe allowing visualization of NP delivery, accumulation, and biodistribution. MDA-MB-231 triple negative human breast cancer cells were inoculated orthotopically or subcutaneously to achieve differences in vascular delivery in the tumors. Molecular characterization of PD-L1 mRNA and protein expression in cancer cells and tumors was performed with qRT-PCR and immunoblot analysis.

Results

The PD-L1 siRNA dextran NPs effectively downregulated PD-L1 in MDA-MB-231 cells. We identified a significant correlation between NP delivery and accumulation, and the extent of PD-L1 downregulation, with in vivo imaging. The size of the NP of ~ 20 nm allowed delivery through leaky tumor vasculature but not through the vasculature of high PD-L1 expressing normal tissue such as the spleen and lungs.

Conclusions

Here we have demonstrated, for the first time, the feasibility of downregulating PD-L1 in tumors using siRNA delivered with a biodegradable dextran polymer that was decorated with an imaging reporter. Our data demonstrate the importance of tumor NP delivery and accumulation in achieving effective downregulation, highlighting the importance of imaging in siRNA NP delivery. Effective delivery of these siRNA carrying NPs in the tumor but not in normal tissues may mitigate some of the side-effects of immune checkpoint inhibitors by sparing PD-L1 inhibition in these tissues.

Distinct Immunophenotypes of T Cells in Bronchoalveolar Lavage Fluid From Leukemia Patients With Immune Checkpoint Inhibitors-Related Pulmonary Complications

Patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) treated with immune checkpoint inhibitors (ICIs) are at risk of pneumonitis as well as pneumonia (combined henceforth as ICI-related pulmonary complications). Little is known about the cellular and molecular mechanisms underlying ICI-related pulmonary complications. We characterized lymphocytes from bronchoalveolar lavage (BAL) fluid and peripheral blood from seven AML/MDS patients with pulmonary symptoms after ICI-based therapy (ICI group) and four ICI-naïve AML/MDS patients with extracellular bacterial or fungal pneumonias (controls). BAL T cells in the ICI group were clonally expanded, and BAL IFNγ+ IL-17- CD8+ T and CXCR3+ CCR6+ Th17/Th1 cells were enriched in the ICI group. Our data suggest that these cells may play a critical role in the pathophysiology of ICI-related pulmonary complications. Understanding of these cell populations may also provide predictive and diagnostic biomarkers of ICI-related pulmonary complications, eventually enabling differentiation of pneumonitis from pneumonia in AML/MDS patients receiving ICI-based therapies.

PD-1 blockade exacerbates Mycobacterium tuberculosis infection in rhesus macaques

Boosting immune cell function by targeting the coinhibitory receptor PD-1 may have applications in the treatment of chronic infections. Here, we examine the role of PD-1 during Mycobacterium tuberculosis (Mtb) infection of rhesus macaques. Animals treated with anti-PD-1 monoclonal antibody developed worse disease and higher granuloma bacterial loads compared with isotype control-treated monkeys. PD-1 blockade increased the number and functionality of granuloma Mtb-specific CD8 T cells. In contrast, Mtb-specific CD4 T cells in anti-PD-1-treated macaques were not increased in number or function in granulomas, expressed increased levels of CTLA-4, and exhibited reduced intralesional trafficking in live imaging studies. In granulomas of anti-PD-1-treated animals, multiple proinflammatory cytokines were elevated, and more cytokines correlated with bacterial loads, leading to the identification of a role for caspase 1 in the exacerbation of tuberculosis after PD-1 blockade. Last, increased Mtb bacterial loads after PD-1 blockade were found to associate with the composition of the intestinal microbiota before infection in individual macaques. Therefore, PD-1-mediated coinhibition is required for control of Mtb infection in macaques, perhaps because of its role in dampening detrimental inflammation and allowing for normal CD4 T cell responses.

Impact of PD-1 gene polymorphism and its interaction with tea drinking on susceptibility to tuberculosis

The aim of this study was to explore the impact of polymorphism of PD-1 gene and its interaction with tea drinking on susceptibility to tuberculosis (TB). A total of 503 patients with TB and 494 controls were enrolled in this case–control study. Three single-nucleotide polymorphisms of PD-1 (rs7568402, rs2227982 and rs36084323) were genotyped and unconditional logistic regression analysis was used to identify the association between PD-1 polymorphism and TB, while marginal structural linear odds models were used to estimate the interactions. Genotypes GA (OR 1.434), AA (OR 1.891) and GA + AA (OR 1.493) at rs7568402 were more prevalent in the TB patients than in the controls (P < 0.05). The relative excess risk of interaction (RERI) between rs7568402 of PD-1 genes and tea drinking was −0.3856 (95% confidence interval −0.7920 to −0.0209, P < 0.05), which showed a negative interaction. However, the RERIs between tea drinking and both rs2227982 and rs36084323 of PD-1 genes were not statistically significant. Our data demonstrate that rs7568402 of PD-1 genes was associated with susceptibility to TB, and there was a significant negative interaction between rs7568402 and tea drinking. Therefore, preventive measures through promoting the consumption of tea should be emphasised in the high-risk populations.

Modulating the wayward T cell: New horizons with immune checkpoint inhibitor treatments in autoimmunity, transplant, and cancer

The T-cell response is regulated by the balance between costimulatory and coinhibitory signals. Immune checkpoints are essential for efficient T-cell activation, but also for maintaining self-tolerance and protecting tissues from damage caused by the immune system, and for providing protective immunity. Modulating immune checkpoints can serve diametric goals, such that blocking a coinhibitory molecule can unleash anti-cancer immunity whereas stimulating the same molecule can reduce an over-reaction in autoimmune disease. The purpose of this review is to examine the regulation of T-cell costimulation and coinhibition, which is central to the processes underpinning autoimmunity, transplant rejection and immune evasion in cancer. We will focus on the immunomodulation agents that regulate these unwanted over- and under-reactions. The use of such agents has led to control of symptoms and slowing of progression in patients with rheumatoid arthritis, reduced rejection rates in transplant patients, and prolonged survival in patients with cancer. The management of immune checkpoint inhibitor treatment in certain challenging patient populations, including patients with pre-existing autoimmune conditions or transplant patients who develop cancer, as well as the management of immune-related adverse events in patients receiving antitumor therapy, is examined. Finally, the future of immune checkpoint inhibitors, including examples of emerging targets that are currently in development, as well as recent insights gained using new molecular techniques, is discussed. T-cell costimulation and coinhibition play vital roles in these diverse therapeutic areas. Targeting immune checkpoints continues to be a powerful avenue for the development of agents suitable for treating autoimmune diseases and cancers and for improving transplant outcomes. Enhanced collaboration between therapy area specialists to share learnings across disciplines will improve our understanding of the opposing effects of treatments for autoimmune disease/transplant rejection versus cancer on immune checkpoints, which has the potential to lead to improved patient outcomes.

Immunopathogenesis of COVID-19: Summary and Possible Interventions

Since the onset of the COVID-19 pandemic in the fall of 2019 over 4 million people have been infected and over 280,000 have died (1). Information about the SARS-CoV2 virus is evolving rapidly. At this time there are no interventions proven to be effective for cases infected with SARS-CoV2. Current knowledge about the clinical and laboratory manifestations of COVID-19 infection is reviewed and combined with knowledge about the immunopathogenic mechanisms of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV1) and Middle East Respiratory Syndrome (MERS) to formulate theories and suggest possible therapeutic interventions. SARS-CoV2 immunopathogenic mechanisms vary from immunosuppression that initially enables viral escape to a hyperinflammatory immune response. Ultimately therapeutic intervention will be phase dependent.

Programmed death-1 expression and regulatory T cells increase in the Intestinal mucosa of cytomegalovirus colitis in patients with HIV/AIDS

BACKGROUND

Cytomegalovirus (CMV) is among the most common opportunistic infections identified in patients with HIV/AIDS. CMV often targets the colon in such patients. However, the role of regulatory T cells (T_regs) and Programmed death-1 (PD-1) in intestinal CMV infection is unclear. In this study, we evaluate the expression of programmed death -1 (PD-1) and its association with regulatory T cells (T_regs) in patients with HIV/AIDS having CMV colitis.

METHODS

CMV was detected in the intestinal mucosal biopsy samples via nucleic acid in situ hybridization. PD-1, CD4, CD8, and T_reg-specific marker as well as the winged-helix transcription factor and forkhead box P3 (FoxP3) were detected by immunohistochemical methods.

RESULTS

Intestinal CMV diease was identified in 20 out of 195 patients with HIV/AIDS enrolled in our study. CMV was diagnosed microscopically by the presence of giant cell inclusion bodies in epithelial cells, histiocytes, and fibroblasts. Levels of immunoreactive PD-1 detected in mucosal biopsies from patients with HIV/AIDS having CMV colitis were significantly higher than CMV-negative control group (p = 0.023). FoxP3⁺ cells were detected in the CMV colitis group slight more than that in the control group. CD4⁺ T lymphocyte counts in the peripheral blood and intestinal mucosal biopsies from CMV colitis group were all notably decreased compared with those with control group (p < 0.001 for both). PD-1 had a significant negative correlation with CD4 counts in intestinal mucosa (p = 0.016). CD8⁺T lymphocyte counts in peripheral blood and intestinal mucosa were slightly lower than those in the control group, although the differences were not statistically significant.

CONCLUSIONS

CMV colitis with HIV/AIDS is associated with significant changes in T lymphocyte populations. These findings may have important implications for disease pathogenesis and progression.

Inhibitory Immune Checkpoint Molecule Expression in Clinical Sepsis Studies: A Systematic Review

OBJECTIVES

Checkpoint inhibitors have been proposed for sepsis following reports of increased checkpoint molecule expression in septic patients. To determine whether clinical studies investigating checkpoint molecule expression provide strong evidence supporting trials of checkpoint inhibitors for sepsis.

DATA SOURCES

PubMed, EMBASE, Scopus, Web of Science, inception through October 2019.

STUDY SELECTION

Studies comparing checkpoint molecule expression in septic patients versus healthy controls or critically ill nonseptic patients or in sepsis nonsurvivors versus survivors.

DATA EXTRACTION

Two investigators extracted data and evaluated study quality.

DATA SYNTHESIS

Thirty-six studies were retrieved. Across 26 studies, compared with healthy controls, septic patients had significantly (p ≤ 0.05) increased CD4+ lymphocyte programmed death-1 and monocyte programmed death-ligand-1 expression in most studies. Other checkpoint molecule expressions were variable and studied less frequently. Across 11 studies, compared with critically ill nonseptic, septic patients had significantly increased checkpoint molecule expression in three or fewer studies. Septic patients had higher severity of illness scores, comorbidities, and mortality in three studies providing analysis. Across 12 studies, compared with septic survivors, nonsurvivors had significantly increased expression of any checkpoint molecule on any cell type in five or fewer studies. Of all 36 studies, none adjusted for nonseptic covariates reported to increase checkpoint molecule expression.

CONCLUSIONS

Although sepsis may increase some checkpoint molecule expression compared with healthy controls, the data are limited and inconsistent. Further, data from the more informative patient comparisons are potentially confounded by severity of illness. These clinical checkpoint molecule expression studies do not yet provide a strong rationale for trials of checkpoint inhibitor therapy for sepsis.

Landmark clinical observations and immunopathogenesis pathways linked to HIV and Cryptococcus fatal central nervous system co-infection

Cryptococcal meningitis remains one of the leading causes of death among HIV-infected adults in the fourth decade of HIV era in sub-Saharan Africa, contributing to 10%-20% of global HIV-related deaths. Despite widespread use and early induction of ART among HIV-infected adults, incidence of cryptococcosis remains significant in those with advanced HIV disease. Cryptococcus species that causes fatal infection follows systemic spread from initial environmental acquired infection in lungs to antigenaemia and fungaemia in circulation prior to establishment of often fatal disease, cryptococcal meningitis in the CNS. Cryptococcus person-to-person transmission is uncommon, and deaths related to blood infection without CNS involvement are rare. Keen to the persistent high mortality associated with HIV-cryptococcal meningitis, seizures are common among a third of the patients, altered mental status is frequent, anaemia is prevalent with ensuing brain hypoxia and at autopsy, brain fibrosis and infarction are evident. In addition, fungal burden is 3-to-4-fold higher in those with seizures. And high immune activation together with exacerbated inflammation and elevated PD-1/PD-L immune checkpoint expression is immunomodulated phenotypes elevated in CSF relative to blood. Lastly, though multiple Cryptococcus species cause disease in this setting, observations are mostly generalised to cryptococcal infection/meningitis or regional dominant species (C neoformans or gattii complex) that may limit our understanding of interspecies differences in infection, progression, treatment or recovery outcome. Together, these factors and underlying mechanisms are hypotheses generating for research to find targets to prevent infection or adequate therapy to prevent persistent high mortality with current optimal therapy.

Severe pulmonary infections complicating nivolumab treatment for lung cancer: a report of two cases

BACKGROUND

Immunotherapy represents a recent milestone in the treatment of lung cancer, particularly with the rapidly expanding development of monoclonal antibodies targeting checkpoint inhibitors in the programmed cell death-1 (PD-1) pathway, such as nivolumab and pembrolizumab. Classical auto-immune side effects of these treatments, often called immune-related adverse events (irAEs), can affect multiple organs, including the lungs in which potentially life-threatening pneumonitis may require rapid treatment with high doses of corticosteroids. Nevertheless, the occurrence of severe infections in cancer patients treated with nivolumab, outside the context of immunosuppressive therapy, is a complication that has rarely been reported in the literature.

CLINICAL CASES

We report two cases of severe pulmonary infection with unusual microbes, Mycobacterium tuberculosis and Aspergillus fumigatus, in patients treated with nivolumab for non-small cell lung cancer.

CONCLUSION

Ruling out pulmonary infections may require extensive investigation, as these may have an atypical presentation due to immunomodulation. Furthermore, treating the patient with corticosteroids for immune-related pneumonia could lead to a fatal outcome in this context. This report highlights the importance of excluding the presence of opportunistic infections and tuberculosis before considering immune-related pulmonary toxicity with or without a history of prior corticosteroid use. These cases also emphasize the potential value of tuberculosis screening in patients treated with PD-1 checkpoint inhibitors.

On the use of immune checkpoint inhibitors in patients with viral infections including COVID-19

The present review summarizes up-to-date evidence addressing the frequently discussed clinical controversies regarding the use of immune checkpoint inhibitors (ICIs) in cancer patients with viral infections, including AIDS, hepatitis B and C, progressive multifocal leukoencephalopathy, influenza, and COVID-19. In detail, we provide available information on (1) safety regarding the risk of new infections, (2) effects on the outcome of pre-existing infections, (3) whether immunosuppressive drugs used to treat ICI-related adverse events affect the risk of infection or virulence of pre-existing infections, (4) whether the use of vaccines in ICI-treated patients is considered safe, and (5) whether there are beneficial effects of ICIs that even qualify them as a therapeutic approach for these viral infections.

[Anti-PD1 immunotherapy followed by tuberculosis infection or reactivation]

INTRODUCTION

Immunotherapy is now a standard of care in oncology. There is a need to improve our knowledge about immune-related adverse events, especially infectious diseases.

CASE REPORT

We describe the case of a 49-year old male who received anti-PD1 therapy, to treat metastatic melanoma with pulmonary metastasis. After 3 cycles of nivolumab, computed tomography scanning showed a decrease of the pulmonary metastasis in the upper left lobe, but revealed new pulmonary lesions such as tree-in-bud and a lung cavity in the same lobe. This was diagnosed as pulmonary tuberculosis with no antibiotic resistance identified. The patient continued the immunotherapy and was initiated onto a standard anti-tuberculosis therapy. In the absence of an initial positive IFN-γ release assay (Quantiferon) test, but as there might have been a history of primary infection during childhood, a reactivation of tuberculosis was considered to be likely.

CONCLUSIONS

This is the ninth case of tuberculosis infection under immunotherapy and it underlines the need to consider infection risks in patients undergoing immunotherapy. An INF-γ release assay screening test should be considered an essential part of the pre-treatment work-up.

Early Activation of Myeloid-Derived Suppressor Cells Participate in Sepsis-Induced Immune Suppression via PD-L1/PD-1 Axis

Background: Myeloid derived suppressor cells (MDSCs) have been reported to keep elevating during sepsis. The current study was performed to investigate the immunosuppressive effect of MDSCs and their subsets with the underlying mechanisms. Methods: The immunosuppressive status was manifested by the apoptosis of splenocytes, quantity of T cells and PD-1 expression. The dynamics of quantity and PD-L1 level of MDSCs and the subsets were determined over time. The subset of MDSCs with high PD-L1 level was co-cultured with T cells to observe the suppressive effect. Results: Abdominal abscess was observed after 7 days post-sepsis. Five biomarkers related to organ functions were all significantly higher in the CLP group. The survival rate was consistent with the middle grade severity of sepsis model. Apoptosis of splenocytes increased over time during sepsis; CD4 + T cell decreased from day 1 post-sepsis; CD8+ T cells significantly reduced at day 7. The PD-1 expression in spleen was upregulated from an early stage of sepsis, and negatively related with the quantity of T cells. MDSCs were low at day 1 post-sepsis, but increased to a high level later; the dynamics of PMN-MDSC was similar to MDSCs. PD-L1 on MDSCs was highest at day 1 post-sepsis; PMN-MDSC was the main subset expressing PD-L1. The PMN-MDSC with high PD-L1 expression level extracted on day 1 after surgery from CLP mice significantly inhibited the proliferation of T cells. Conclusions: Sepsis-induced immunosuppression is initiated from a very early stage, a high expression level of PD-L1 on MDSCs and the main subset, PMN-MDSC might play a critical role suppressive role on T cells through PD-L1/PD-1 axis.

Consideration of Severe Coronavirus Disease 2019 As Viral Sepsis and Potential Use of Immune Checkpoint Inhibitors

Taking into consideration the multisystemic clinical and autopsy findings in “severe” coronavirus disease 2019 patients, viral sepsis would be a more accurate term to describe the whole clinical picture. The most significant pathophysiological components of this picture are intense cytokine release, prolonged inflammation, immunosuppression with T cell exhaustion, and the development of organ dysfunctions. Currently, the optimal treatment for severe coronavirus disease 2019 is uncertain. Supportive treatment and immunomodulators have a critical place in the treatment of severe patients until effective antivirals are developed. Interleukin-6 antagonists, one of the immunomodulating agents, appears to be effective in the treatment of cytokine storm, but some patients continue to have severe lymphopenia and immunosuppression. We believe it can be useful as immunomodulator therapy in critical coronavirus disease 2019 patients because of the benefits of immune checkpoint inhibitors in cancer and sepsis patients.

The unleashing of the immune system in COVID-19 and sepsis: the calm before the storm?

The novel coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is sorely testing health care systems and economies around the world and is rightly considered as the major health emergency in a century. Despite the course of the disease appearing to be mild in many cases, a significant proportion of symptomatic patients develop pneumonia requiring hospitalisation or progress to manifest respiratory complications leading to intensive care treatment. Potential interventions for SARS-CoV2-associated pneumonia are being tested, some of which holding promise, but as of today none of these has yet demonstrated outstanding efficacy in treating COVID-19. In this article, we discuss fresh perspectives and insights into the potential role of immune dysregulation in COVID-19 as well as similarities with systemic inflammatory response in sepsis and the rationale for exploring novel treatment options affecting host immune response.

Immune checkpoint inhibition for non-small cell lung cancer in patients with pulmonary tuberculosis or Hepatitis B: Experience from a single Asian centre

BACKGROUND

The importance of immune-checkpoint inhibitors (ICI) can no longer be understated since its move to front-line treatment in non-small cell lung cancer (NSCLC) in recent years. However, the safety and efficacy of ICI in special populations such as those with infections like tuberculosis (TB) and hepatitis B (HBV) remain unknown as they are routinely excluded from clinical trials.

METHODS

Records of patients with advanced NSCLC who were treated with ICI from January 2014 to June 2019 at a single Asian centre were reviewed. Those with a history of HBV and/or TB were selected. In this group, safety and treatment outcomes including overall survival (OS), progression-free survival (PFS) and response rate were reported and compared against control.

RESULTS

191 patients received ICI, 47 (24.6%) had a history of TB/HBV. The median PFS in those with a history of TB/HBV was 5.7 months (95% CI 3.9-7.6), compared to 3.1 months (95% CI 2.4-3.8) in control (HR 0.61, 95% CI 0.39-0.93, p = 0.021). Median OS was 15.6 months (95% CI 10.2-21.0) compared to 11.1 months (95% CI 7.6-14.7 months) in the control group (HR 0.58, 95% CI 0.34-0.99, p = 0.046). Adverse events of any grade (G) were similar in both groups; slightly more patients with TB/HBV experienced G3 or higher adverse events. Four patients developed TB after initiation of ICI, none with previously documented TB experienced reactivation. Of the 42 patients with a history of HBV, eight had inactive chronic HBV and six had detectable viral load. None of the 34 patients who were previously exposed to HBV had reactivation.

CONCLUSION

The use of ICI appears to be safe and efficacious in patients with TB/HBV infection. Prospective studies are required to identify those at risk in order to optimise care to these groups of patients.