Immune Continuum Research Articles

Abstract 11966: Translational Cardioinformatics: Neutrophil-Derived Translocator Protein as a Novel Regulator of Myocarditis and Coronary Artery Aneurysm in Kawasaki Disease and Multisystem Inflammatory Syndrome in Children

Introduction: Cardiovascular disease (CVD) in Kawasaki disease (KD) and multisystem inflammatory syndrome in children (MIS-C) lead to increased mortality through myocardial infarction. Hypothesis: Since KD and MIS-C are shaped by the same immune continuum, the cardiac pathologies and lethal complications may be averted by targeting a key regulator controlling both diseases; however, the pathogenic drivers are largely undefined. Methods: Through integrated, multi-cohort, single-cell meta-analysis of KD and MIS-C PBMC scRNA-seq profiles, we investigated the immunological drivers associated with systemic damage and cardiac pathologies, compared with other pediatric diseases, and validated across independent cohorts of KD, MIS-C, and myocardial infarction. Via cheminformatics approaches, we identified FDA-approved drugs for repurposing. Results: We found the expansion and hyperactivation of CD177 + neutrophils in KD and MIS-C, but not in other pediatric diseases. CD177 + neutrophils overexpressed markers and causal mediators of CVD development, supported by activation of prognostic CVD gene signatures (acute CVD, major adverse cardiovascular and limb events, and myocardial infarction). CD177 + neutrophils’ overactivated effector repertoire may mediate systemic inflammation and molecular damage via a vascular homing mechanism. We identified a dysfunctional SPI1-dependent regulatory network shared by KD and MIS-C during neutrophil hyperactivation, as well as key regulators which may induce cardiac disorders. Importantly, we found that TSPO is associated with myocarditis and coronary artery aneurysm, disease severity, IVIG treatment, and patient recovery. Via independent cohorts analyses, we validated TSPO as a prime target against KD and MIS-C pathologies. Murine myocardial infarction model confirmed the cardiac hyper-infiltration of hyperactivated CD177 + neutrophils. Lastly, we identified FDA-approved drugs against KD and MIS-C neutrophil hyperactivation. Conclusions: Collectively, CD177 + neutrophils have a pivotal role in KD/MIS-C systemic pathologies, clinical severity, and prognosis. We suggest drugs that can be developed as a single therapeutic strategy against either KD or MIS-C for clinical translation.

Dissecting Platelet's Role in Viral Infection: A Double-Edged Effector of the Immune System.

Platelets play a major role in the processes of primary hemostasis and pathological inflammation-induced thrombosis. In the mid-2000s, several studies expanded the role of these particular cells, placing them in the "immune continuum" and thus changing the understanding of their function in both innate and adaptive immune responses. Among the many receptors they express on their surface, platelets express Toll-Like Receptors (TLRs), key receptors in the inflammatory cell-cell reaction and in the interaction between innate and adaptive immunity. In response to an infectious stimulus, platelets will become differentially activated. Platelet activation is variable depending on whether platelets are activated by a hemostatic or pathogen stimulus. This review highlights the role that platelets play in platelet modulation count and adaptative immune response during viral infection.

Spatially variant immune infiltration scoring in human cancer tissues

The Immunoscore is a method to quantify the immune cell infiltration within cancers to predict the disease prognosis. Previous immune profiling approaches relied on limited immune markers to establish patients’ tumor immunity. However, immune cells exhibit a higher-level complexity that is typically not obtained by the conventional immunohistochemistry methods. Herein, we present a spatially variant immune infiltration score, termed as SpatialVizScore, to quantify immune cells infiltration within lung tumor samples using multiplex protein imaging data. Imaging mass cytometry (IMC) was used to target 26 markers in tumors to identify stromal, immune, and cancer cell states within 26 human tissues from lung cancer patients. Unsupervised clustering methods dissected the spatial infiltration of cells in tissue using the high-dimensional analysis of 16 immune markers and other cancer and stroma enriched labels to profile alterations in the tumors’ immune infiltration patterns. Spatially resolved maps of distinct tumors determined the spatial proximity and neighborhoods of immune-cancer cell pairs. These SpatialVizScore maps provided a ranking of patients’ tumors consisting of immune inflamed, immune suppressed, and immune cold states, demonstrating the tumor’s immune continuum assigned to three distinct infiltration score ranges. Several inflammatory and suppressive immune markers were used to establish the cell-based scoring schemes at the single-cell and pixel-level, depicting the cellular spectra in diverse lung tissues. Thus, SpatialVizScore is an emerging quantitative method to deeply study tumor immunology in cancer tissues.

Oral Versus Gastrointestinal Mucosal Immune Niches in Homeostasis and Allostasis

Different body systems (epidermis, respiratory tract, cornea, oral cavity, and gastrointestinal tract) are in continuous direct contact with innocuous and/or potentially harmful external agents, exhibiting dynamic and highly selective interaction throughout the epithelia, which function as both a physical and chemical protective barrier. Resident immune cells in the epithelia are constantly challenged and must distinguish among antigens that must be either tolerated or those to which a response must be mounted for. When such a decision begins to take place in lymphoid foci and/or mucosa-associated lymphoid tissues, the epithelia network of immune surveillance actively dominates both oral and gastrointestinal compartments, which are thought to operate in the same immune continuum. However, anatomical variations clearly differentiate immune processes in both the mouth and gastrointestinal tract that demonstrate a wide array of independent immune responses. From single vs. multiple epithelia cell layers, widespread cell-to-cell junction types, microbial-associated recognition receptors, dendritic cell function as well as related signaling, the objective of this review is to specifically contrast the current knowledge of oral versus gut immune niches in the context of epithelia/lymphoid foci/MALT local immunity and systemic output. Related differences in 1) anatomy 2) cell-to-cell communication 3) antigen capture/processing/presentation 4) signaling in regulatory vs. proinflammatory responses and 5) systemic output consequences and its relations to disease pathogenesis are discussed.

The Coronavirus SARS-Cov-2: the Complexity of Infection Pathogenesis, the Search of Vaccines and Possible Future Pandemics

Relevance . The vaccine against the SARS-Cov-2 coronavirus is considered as the most promising approach to curb (tame) a current pandemic and prevent new one. Among difficulties in vaccine creating is a right choice of immunodominant antigens providing the effectiveness and safety of vaccines. Aim is to show the usefulness of application of the global immune epitope continuum protein relationship concept in the search of vaccines against SARS-Cov-2 and discuss the possible nature of future pandemics. Materials and method . For the computer analysis of peptide (immune epitope) relationship amongst the SARS-Cov-2 structural proteins, human proteins and proteins of other viruses, the search of homologous sequences was made. All protein sequences sequences were used from databases available on the INTERNET. Results. In the SARS-Cov-2 structural proteins, especially in S-protein, there are a large number of peptide sequences homologous to human and viral proteins that may be the cause of autoimmune complications and/or heterologous immunity. Conclusion : The concept of the global immune epitope continuum of protein relationship is of value in the search of immune epitopes for the vaccines against SARS-Cov-2 and allows us to predict the possible risks in vaccines. The coronavirus breaks and pandemics may be more often than the influenza pandemics.

The Coronavirus SARS-Cov-2: the Characteristics of Structural Proteins, Contagiousness, and Possible Immune Collisions

Relevance. Coronavirus SARS-Cov-2 is a novel virus demonstrating the ability to be trans¬mitted from human-to-human, via respiratory droplets or close contact, and cause the severe acute respiratory syndrome (SARS). The role of its structural proteins in the SARS pathogenesis is unknown.Aim is to characterize the features of the SARS-Cov-2 structural proteins and their changes associated with acquiring other way of transmission and analyze the possibility of heterologous immunity emergence in its infection. Materials and method. For the computer analysis and alignment, the gene sequences of SARS-Cov-2 , SARS-CoV , MERS-CoV и bat CoV HKU3 reference strains were used from the Internet. From the primary structure of their genes it were translated their structural proteins: spike (S), envelope (E),membrane (M), and nucleocapsid (N). The genetic code of structural proteins was also defined. The search of homologous sequences in the SARS-Cov-2 S-protein, surface proteins of other viruses, and human proteins was made to find immune epitope continuum of protein relationships.Results. In the SARS-Cov-2 structural proteins amino acid sequences of M, E, and N-proteins are conservative. The S1 subunit of the S-protein contains some large insertions, significant changes of the amino acid content with the predominance of arginine and lysine which is typical for the surface glycoproteins in the viruses possessing high contagiousness. The S2 subunit is rather conservative and retain negative polarity. The S-protein exhibits the immune epitope relationships with many proteins of viruses and human which may be associated with immune collisions.Conclusion: The SARSCov-2 features are determined by marked changes of the S1 subunit structure in the S-protein which may be responsible for its contagiousness and many immune collisions aggravating infection process.

Understanding Platelets in Infectious and Allergic Lung Diseases.

Emerging evidence suggests that platelets, cytoplasmic fragments derived from megakaryocytes, can no longer be considered just as mediators in hemostasis and coagulation processes, but as key modulators of immunity. Platelets have received increasing attention as the emergence of new methodologies has allowed the characterization of their components and functions in the immune continuum. Platelet activation in infectious and allergic lung diseases has been well documented and associated with bacterial infections reproduced in several animal models of pulmonary bacterial infections. Direct interactions between platelets and bacteria have been associated with increased pulmonary platelet accumulation, whereas bacterial-derived toxins have also been reported to modulate platelet function. Recently, platelets have been found extravascular in the lungs of patients with asthma, and in animal models of allergic lung inflammation. Their ability to interact with immune and endothelial cells and secrete immune mediators makes them one attractive target for biomarker identification that will help characterize their contribution to lung diseases. Here, we present an original review of the last advances in the platelet field with a focus on the contribution of platelets to respiratory infections and allergic-mediated diseases.

Obstructive Sleep Apnea: From Intermittent Hypoxia to Cardiovascular Complications via Blood Platelets.

Obstructive sleep apnea is a chronic condition characterized by recurrent episodes of apneas or hypopneas during sleep leading to intermittent hypoxemia and arousals. The prevalence of the sleep disordered breathing is estimated that almost 50% of men and 24% of women suffer from moderate to severe form of the disorder. Snoring, collapse of upper airways and intermittent hypoxia are main causes of smoldering systemic inflammation in patients suffering from obstructive sleep apnea. The systematic inflammation is considered one of the key mechanisms leading to significant cardiovascular complications. Blood platelets, formerly not even recognized as cells, are currently gaining attention as crucial players in the immune continuum. Platelet surface is endowed with receptors characteristic for cells classically belonging to the immune system, which enables them to recognize pathogens, immune complexes, and interact in a homo- and heterotypic aggregates. Platelets participate in the process of transcellular production of bioactive lipids by delivering both specific enzymes and substrate molecules. Despite their lack of nucleus, platelets synthetize proteins in a stimuli-dependent manner. Atherosclerosis and consequent cardiovascular complications result from disruption in homeostasis of both of the platelet roles: blood coagulation and inflammatory processes modulation. Platelet parameters, routinely evaluated as a part of complete blood count test, were proposed as markers of cardiovascular comorbidity in patients with obstructive sleep apnea. Platelets were found to be excessively activated in this group of patients, especially in obese subjects. Persistent activation results in enhanced spontaneous aggregability and change in cytokine production. Platelet-lymphocyte ratio was suggested as an independent marker for cardiovascular disease in obstructive sleep apnea syndrome and continuous positive air pressure therapy was found to have an impact on platelet parameters and phenotype. In this literature review we summarize the current knowledge on the subject of platelets involvement in obstructive sleep apnea syndrome and consider the possible pathways in which they contribute to cardiovascular comorbidity.

Amicus or Adversary Revisited: Platelets in Acute Lung Injury and Acute Respiratory Distress Syndrome.

Platelets are essential cellular effectors of hemostasis and contribute to disease as circulating effectors of pathologic thrombosis. These are their most widely known biologic activities. Nevertheless, recent observations demonstrate that platelets have a much more intricate repertoire beyond these traditional functions and that they are specialized for contributions to vascular barrier integrity, organ repair, antimicrobial host defense, inflammation, and activities across the immune continuum. Paradoxically, on the basis of clinical investigations and animal models of disease, some of these newly discovered activities of platelets appear to contribute to tissue injury. Studies in the last decade indicate unique interactions of platelets and their precursor, the megakaryocyte, in the lung and implicate platelets as essential effectors in experimental acute lung injury and clinical acute respiratory distress syndrome. Additional discoveries derived from evolving work will be required to precisely define the contributions of platelets to complex subphenotypes of acute lung injury and to determine if these remarkable and versatile blood cells are therapeutic targets in acute respiratory distress syndrome.

Platelets in Pulmonary Immune Responses and Inflammatory Lung Diseases.

Platelets are essential for physiological hemostasis and are central in pathological thrombosis. These are their traditional and best known activities in health and disease. In addition, however, platelets have specializations that broaden their functional repertoire considerably. These functional capabilities, some of which are recently discovered, include the ability to sense and respond to infectious and immune signals and to act as inflammatory effector cells. Human platelets and platelets from mice and other experimental animals can link the innate and adaptive limbs of the immune system and act across the immune continuum, often also linking immune and hemostatic functions. Traditional and newly recognized facets of the biology of platelets are relevant to defensive, physiological immune responses of the lungs and to inflammatory lung diseases. The emerging view of platelets as blood cells that are much more diverse and versatile than previously thought further predicts that additional features of the biology of platelets and of megakaryocytes, the precursors of platelets, will be discovered and that some of these will also influence pulmonary immune defenses and inflammatory injury.

Emerging evidence for platelets as immune and inflammatory effector cells.

While traditionally recognized for their roles in hemostatic pathways, emerging evidence demonstrates that platelets have previously unrecognized, dynamic roles that span the immune continuum. These newly recognized platelet functions, including the secretion of immune mediators, interactions with endothelial cells, monocytes, and neutrophils, toll-like receptor (TLR) mediated responses, and induction of neutrophil extracellular trap formation, bridge thrombotic and inflammatory pathways and contribute to host defense mechanisms against invading pathogens. In this focused review, we highlight several of these emerging aspects of platelet biology and their implications in clinical infectious syndromes.

The Platelet Glycoprotein Ib-IX Axis In Murine Polymicrobial Sepsis

The platelet glycoprotein (GP) Ib-IX receptor complex is expressed exclusively on the surface of platelets and is well characterized as a primary adhesion receptor supporting normal hemostasis and pathologic thrombosis. Beyond hemostasis and thrombosis, platelets can also participate in the innate immune response and inflammation. While the platelet as a contributor to the immune continuum is recognized, many aspects of the molecular mechanisms whereby platelets influence the immune response are still undefined. Here, we report studies using a murine model of GP Ib-IX deficiency linking GP Ib-IX to the immune response associated with polymicrobial sepsis, as modeled by cecal ligation and puncture (CLP). In the CLP model, genetic absence of the major GP Ib-IX hemostatic ligand, von Willebrand factor (VWF), improves survival following CLP when compared to control wild-type animals (p= 0.003, Logrank analysis). This suggests a VWF role in thrombosis contributes to survival outcome following CLP. In contrast, genetic absence of the VWF platelet receptor, GP Ib-IX, does not improve survival with no statistical difference comparing wild-type animals to GPIb-IX deficient animals. The molecular basis to explain improved survival in VWF-deficient (ligand deficient) but not GPIb-IX deficient (receptor deficient) animals was pursued. We tested the hypothesis GPIb-IX has normal physiologic and pathophysiologic functions beyond platelet adhesion influencing infection and an inflammatory response. Indeed, GPIb-IX influencing the innate immune response is not completely unexpected since a hallmark structural feature of each subunit of the GPIb-IX receptor is leucine rich repeats, the common motif to all members of the toll like receptor family (TLRs). Whether structural similarities are a consequence of ancestral origins for GPIb-IX and TLRs is unknown. We first documented in the absence of murine platelet GP Ib-IX there are reduced platelet-neutrophil and platelet-monocyte interactions under normal conditions and following CLP in whole blood. Whether there are physiologic consequences for disrupting a platelet/monocyte and/or platelet/neutrophil axis was determined via multianalyte profiling of circulating cytokine levels on a Luminex analyzer following CLP. In the absence of GP Ib-IX there is a robust and statistically significant increase 24 hrs following CLP in some of the major proinflammatory cytokines produced by monocytes and macrophages, including TNFα, MCP-1, MIP-β, IL-6, and IL-15. Increases in cytokines, such as IL-5 and IL-13, associated with other immune cells were also observed. These results highlight a coagulation/inflammation interface where the platelet, and specifically GP Ib-IX, contributes to the pathophysiology of CLP. On the one hand, absence of platelet GPIb-IX reduces thrombotic potential, but it occurs at the expense of upregulation of inflammatory cytokine release leading to a reduced survival in CLP. Clearly, survival outcomes in CLP reflect a complex dysregulation of coagulation and inflammation where platelet GPIb-IX likely contributes to both processes with physiologic consequences. Understanding dysregulation of the coagulation/ inflammation interface and identifying a platelet receptor (GPIb-IX) critical to both adds new information to this complex set of pathophysiologic events Sharing the common structural motifs, leucine rich repeats, with the well characterized family of toll-like receptors, platelet GPIb-IX should now be considered an active participant in the inflammatory cascade. Disclosures:No relevant conflicts of interest to declare.

Bench-to-bedside review: Platelets and active immune functions - new clues for immunopathology?

Platelets display a number of properties besides the crucial function of repairing damaged vascular endothelium and stopping bleeding; these are exploited to benefit patients receiving platelet component transfusions, which might categorize them as innate immune cells. For example, platelets specialize in pro-inflammatory activities, and can secrete a large number of molecules, many of which display biological response modifier functions. Platelets also express receptors for non-self-infectious and possibly non-infectious danger signals, and can engage infectious pathogens by mechanisms barely explained beyond observation. This relationship with infectious pathogens may involve other innate immune cells, especially neutrophils. The sophisticated interplay of platelets with bacteria may culminate in sepsis, a severe pathology characterized by significant reductions in platelet count and platelet dysfunction. How this occurs is still not fully understood. Recent findings from in-depth platelet signaling studies reveal the complexity of platelets and some of the ways they evolve along the immune continuum, from beneficial functions exemplified in endothelium repair to deleterious immunopathology as in systemic inflammatory response syndrome and acute vascular diseases. This review discusses the extended role of platelets as immune cells to emphasize their interactions with infectious pathogens sensed as potentially dangerous.

Novel Functions of Therapeutic Platelets as “Immune Cells”

Platelet components are commonly transfused to bleeding in patients in the absence of a suitable alternative. If one exempts granulocyte concentrates, this labile blood component is associated with the most common infectious and immune-related hazards. Though infection can be prevented, immune-related reactions are more difficult to combat because the physiopathology is not fully understood. Recent research has placed platelets in the immune continuum as cells fully licensed for innate immunity and inflammation, possibly bridging innate and adaptive immunity. This novel paradigm provides clues for understanding how platelets can mediate immunerelated side effects when transfused to a patient in need, and to address prevention strategies. The present paper discusses novel functions associated with platelets and their potential response upon encounters with a recipient’s cells during transfusion.

Platelets: versatile effector cells in hemostasis, inflammation, and the immune continuum

Platelets are chief effector cells in hemostasis. In addition, however, their specializations include activities and intercellular interactions that make them key effectors in inflammation and in the continuum of innate and adaptive immunity. This review focuses on the immune features of human platelets and platelets from experimental animals and on interactions between inflammatory, immune, and hemostatic activities of these anucleate but complex and versatile cells. The experimental findings and evidence for physiologic immune functions include previously unrecognized biologic characteristics of platelets and are paralleled by new evidence for unique roles of platelets in inflammatory, immune, and thrombotic diseases.

Platelets and the immune continuum

Platelets are anucleate cells that are crucial mediators of haemostasis. Most immunologists probably don't think about platelets every day, and may even consider these cells to be 'nuisances' in certain in vitro studies. However, it is becoming increasingly clear that platelets have inflammatory functions and can influence both innate and adaptive immune responses. Here, we discuss the mechanisms by which platelets contribute to immunity: these small cells are more immunologically savvy than we once thought.

Fever and sickness behaviour vary among congeneric rodents

Summary 1. Fever and sickness behaviour are immune defences that most organisms engage to control bacterial and viral infections. Although generally beneficial, these defences can be energetically expensive, which may lead to variation within and among species. Here, we asked whether fever and sickness behaviour differ among five species of mice in the genus, Peromyscus . 2. This comparison was motivated by our previous discovery of extensive, but systematic, immunological variation among many of these same rodent species. Some species were adept at controlling gram-negative bacteria whereas others were proficient at generating antibodies; no species was strongly capable of both. Such discrete variation suggested a continuum of immune defence strategies. We therefore predicted that variation in fever and sickness behaviour would mirror variation in bacterial killing capacity, as these defences are mediated by some of the same molecular pathways. 3. To test this hypothesis, we characterized responses to lipopolysaccharide (LPS), a component of gram-negative bacteria that activates febrile responses without causing infection. Peromyscus species that showed little sickness behaviour post-LPS engaged fever; species that engaged sickness behaviour, however, either did not mount fevers or became hypothermic post-LPS. As predicted, species that were adept at killing bacteria in vitro mounted the largest fevers; species that were not as proficient at killing bacteria did not engage fever. 4. These results further indicate a continuum of immunological strategies among Peromyscus species, which we expect applies to other taxa. We propose a few possible reasons for why species occupy specific points along an immune continuum; life-history orientation appears the most viable alternative at present.