The Canadian Society for Immunology's 34th annual meeting 2022: symposia minireview

Abstract

The Canadian Society for Immunology 2022 Annual Meeting (June 17–20, 2022) brought together immunologists from across the country to discuss current topics and cutting-edge research in immunology. Here we highlight the published work presented during three thematic symposia (1) Immune Development and Layered Immunity; (2) Primary Immune Deficiencies from Thymic Developmental Defects to Dysregulation and Inflammation; and (3) Opposing Inflammatory and Suppressive Regulation of Anti-Tumor Immunity.

1 Introduction

The Canadian Society for Immunology 2022 Annual Meeting was held June 17–20, 2022 in Halifax, Nova Scotia. Symposia, poster sessions, and workshops afforded many opportunities for researchers and trainees to describe their ongoing work, much of it unpublished. Here, we report on the presented published data from the symposia, which featured invited speakers from Canada and abroad, with a focus on connecting common themes between speakers. The symposia featured three thematic sessions: (1) Immune Development and Layered Immunity; (2) Primary Immune Deficiencies from Thymic Developmental Defects to Dysregulation and Inflammation; and (3) Opposing Inflammatory and Suppressive Regulation of Anti-Tumor Immunity.

2 Immune development and layered immunity

The prenatal and neonatal periods are critical for calibrating immune function for life. In this symposium, researchers discussed recent advances in immune development facilitated by modern technological advances.

Hematopoiesis is generally well understood, but nuances and definition of differentiation decision points lack clarity. Dr. Ana Cvejic (Biotech Innovation and Research Centre, Denmark) described single-cell RNA sequencing (scRNA-seq) and a single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) on hematopoietic cells isolated from the human fetal liver, femur, and hip from donors aged between 17 and 22 wk postconception.¹ Their analysis showed that hematopoietic stem and progenitor cells (HSC/MPPs) in the bone marrow differentiate into three distinct oligopotent progenitor populations. Interestingly, changes in gene motif accessibility in HSCs precede activation of lineage-specific transcriptional programs and their cell fate choice. Finally, this work redefined parameters for fetal HSC identification, which might improve their isolation, study, and use.

Beyond hematopoiesis, the immune system is shaped and polarized by its interactions with microbes, even in utero. Dr. Kathy McCoy (University of Calgary, Canada) used an axenic/gnotobiotic system to explore how the maternal microbiome might impact the fetus. An auxotrophic Escherichia coli HA107 mutant allowed transient colonization, so that the timing of exposure could be controlled.² Previous results showed that when colonization with E. coli occurred only during pregnancy, a B-cell-dependent increase in NKp46+ type 3 innate lymphoid cells (ILC3s) and CD11b+ mononuclear cells occurred in the offspring in the intestine, even after the microbe was eliminated.³ Microbial metabolites, likely captured by maternal immunoglobulin G (IgG), were thought to cross the placenta with impacts on fetal immune development. The McCoy group is now studying the role of the neonatal Fc receptor in trans-placental transfer.

Immediately after birth, neonates rapidly accumulate microbes, and their immune system must adjust for sensitivity and tolerance.⁴Petter Brodin (Imperial College London and Karolinska Institute, Sweden) described observations of monocyte expansion, increased levels of interferon-gamma (IFN-γ) production (mucosal-specific memory CD4+ T cells), and high levels of endogenous interleukin (IL)-1 regulators present after birth.⁵ With a systems-level approach to characterize the microbiome, the Brodin lab found that immune cell proportions differ between preterm and full-term babies with convergence around 100 d after birth.⁶ Epidemiologic studies have demonstrated that environmental exposures and selective pressures during this time critically impact health later in adulthood, so it may be important to intervene and support healthy immune development at this time.^6–8 At birth, the expansion of Bifidobacterium is highly variable, but supplementation with Bifidobacterium infantis, a bacteria shown to be efficient at utilizing human breastmilk oligosaccharides, reduced intestinal inflammation in infants by lowering Th2 and Th17 cytokines.

Does early immune polarization impact disease susceptibility and progression? Dr. Padmaja Subbarao (University of Toronto) focused on asthma and followed children from pregnancy until at least age 5, as part of the Canadian Healthy Infant Longitudinal Development (CHILD) study. With a wealth of biologic samples including cord blood and serial samples of peripheral blood, breast milk, urine, nasal swabs, and stool samples, they identified associations between recently identified phenotypic disease trajectories⁹ with atopy symptoms and a higher number of eosinophils in the blood, suggesting that a divergence between Th1 or Th2 responses are established in infancy, with impacts on susceptibility to allergic asthma.

Calibration of allergy and immune function is likely influenced by many factors. Dr. James Gern (University of Wisconsin School, USA) described a meta-analysis to explore childhood asthma epidemiology using the Environmental influences on Child Health Outcomes (ECHO) database, a collection of longitudinal cohorts that study the impact of early environmental exposures on health. Family history, especially in the youngest children,¹⁰ and African American heritage were among the strongest predictors for asthma. Analyses revealed chromosome 17q12-21 variants to be associated with disease presentation in childhood;¹¹ with RNA sequencing, two loci within it were identified to be associated with asthma risk: rs2305480 and rs8076131. Quantitative trait locus analysis from nasal epithelial cells demonstrated that these two asthma-related SNPs regulate expression of GSDMB (gasdermin B), implicating regulation of this candidate gene in susceptibility to childhood asthma.

In sum, the immune development and layered immunity symposium featured novel insights and opened questions into fetal and neonatal health, demonstrating how the intersections of genetics and environmental/microbial exposure shape immunity into the future, possibly providing opportunities for early intervention and future health.

3 Primary immune deficiencies from thymic developmental defects to dysregulation and inflammation

A functioning immune system requires careful synchronization of tissue and cellular interactions. Within this system, congenital alterations in genes controlling immune cell or structural development can lead to primary immune deficiencies that manifest as recurrent infections or augmented inflammatory conditions.^12,13 These changes unveil complexities in the immune system, and with increasing capacity for genome sequencing and analysis, the genetic underpinnings for these conditions can be defined.

Dr. Georg Holländer (University of Oxford, England) and the Holländer team used scRNA-seq to characterize the complexity of the thymus epithelial cell (TEC) scaffold and how aging impacts this stromal compartment. They found a higher heterogeneity of TEC subtypes than previously appreciated and showed significant changes in the individual cells’ relative representation across the life course.¹⁴ FOXN1 is a transcription factor that regulates TEC differentiation, maintenance, and function, and it is indispensable for the fate commitment of these cells.^15,16 A complete loss of FOXN1 function prevents thymic tissue growth and is one of the causes of severe combined immunodeficiency (SCID). Altered FOXN1 expression can lead to transient hypoplasia and premature thymic involution.^17,18 Dr. Hollander's team reported on patients heterozygous for a novel FOXN1 mutation characterized by a shortened C-terminus containing a novel amino acid sequence secondary to a frame shift.¹⁹ Designated Δ550 FOXN1, this mutation was unable to form multimolecular nuclear condensates, which are essential for transcription to occur.¹⁹ In addition, the Δ550 FOXN1 variant displaces wild-type FOXN1 molecules from nuclear aggregates and thus acts as a dominant negative mutant.¹⁹ Physiologically higher levels of FOXN1 expression during early development grant heterozygous Δ550 FOXN1 patients the ability to generate a peripheral T cell pool, albeit compromised in size and diversity. As the fetus ages, wild-type FOXN1 expression and function fall below a critical threshold and are thus unable to counteract the dominant negative effect of Δ550 FOXN. Consequently, TEC differentiation and maintenance are impaired, and these patients are born without a thymus.¹⁹

T cell dysfunction could occur because of exhaustion, and Dr. Hélène Decaluwe (University of Montréal, Canada) discussed how this occurs in children treated with allogeneic hematopoietic cell transplantation (HCT) for the treatment of children born with SCID. Approximately 30% of patients with SCID do not achieve complete immune reconstitution and present with low T cell counts after HCT.²⁰ The Decaluwe laboratory found that these patients have low naïve CD4⁺ and CD8⁺ T cell counts, a reduction in recent thymic emigrants, and the presence of T cell receptor excision circles. In patients with low T cell counts, T cells consistently exhibited a phenotype consistent with exhaustion: increased expression of inhibitory receptors and perforin; this was especially prominent among those who did not receive preconditioning prior to HCT,²⁰ representing potentially persistent defects in immunity among these patients and highlighting the importance of preconditioning for HCT.

Dr. Emilia Liana Falcone (IRCM and University of Montréal, Canada) described another primary immune deficiency: chronic granulomatous disease (CGD), which is caused by mutations in the phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 complex (NOX2).^21,22 NOX2 plays a role in generating reactive oxygen species (ROS) in eosinophils, macrophages, neutrophils, and dendritic cells (DCs), which are important for antimicrobial host defense and regulating tissue homeostasis.^21,22 Resulting inflammatory dysregulations cause 50% of patients with CGD to develop inflammatory bowel diseases (IBD).²³ IBD can cause severe dehydration, skin, eye, and joint inflammation, and colon cancer.²⁴ Although patients with CGD-associated IBD are treated with the same immune modulators used to treat conventional IBD,²⁵ these agents may lead to additional infectious complications in patients with pre-existing immune deficiencies such as those with CGD.²⁶ Among many other questions, Dr. Falcone and team are studying the impact of NOX2 defects at the intestinal barrier, how the microbiome contributes to intestinal inflammation in patients with CGD, and which mutations are associated with the development of colitis. Uncovering these mechanisms could help develop precise treatments and therapeutics for patients suffering from CGD.

Genetic mutations in genes central to immune function can have systemic effects. Dr. Aleixo Muise (SickKids Research Institute, Canada) and team identified a monoallelic mutation in the spleen tyrosine kinase (SYK) gene in a patient that presented with multiorgan inflammatory disease at 2 weeks of age.²⁷ The SYK mutation analyzed here led to spontaneous phosphorylation of the Y525.526, an important amino acid for SYK autophosphorylation and activation, which led to its constitutive activation.²⁷ To determine whether this could be sufficient to cause the disease presented, they generated the equivalent mutation in a mouse model. Heterozygous SYK^S544Y animals developed arthritis, neuroinflammation at the tail, increased SYK phosphorylation in intestinal epithelial cells and bone-marrow-derived DCs, and higher levels of serum inflammatory cytokines.²⁷ Using bone marrow chimera models, the researchers demonstrated that immune features were the main drivers of the inflammation observed in SYK^mut animals,²⁷ providing a clue toward the precise treatment of patients with this mutation. Supporting this conclusion, treatment with SYK inhibitor, R406, ameliorated arthritis symptoms, further supporting its central role in this disease.

The potential of precision medicine for treating genetically informed diseases extends further. For example, Dr. Stuart Turvey's group (University of British Columbia, Canada) reported on a patient with a complete NFAT1 deficiency, who presented with joint contractures, osteochondromas, and recurrent B cell lymphoma.^28–30 Within this patient's PBMCs, scRNA-seq revealed pro-lymphomagenesis signals, resulting in an aberrant lymphocyte population including changes in naïve B, CD4+ T, CD8+ T, and follicular T cells.

With increasingly sensitive technology and precise, genetics-informed therapy, it is now possible to treat patients with primary immunodeficiency in a very directed manner. Further, studying, modeling, and, ultimately, applying precise approaches to correct defects is highlighting features and functions of the immune system. While rarer mutations leading to immune dysfunction may only impact a single patient, such patients provide a unique opportunity to understand immunity, potentially aiding in developing new treatment strategies for diseases, including and beyond primary immunodeficiencies.

4 Opposing inflammatory and suppressive regulation of antitumor immunity

A transformed and growing tumor simultaneously avoids immune-mediated eradication while co-opting immune inflammatory and regulatory mechanisms to facilitate its growth. In this symposium, speakers explored the roles of immune cells in cancer and immunosurveillance. Targeting immune cells within the tumor microenvironment may be key to precision cancer treatment, and understanding their unique roles, products, and interaction may highlight new avenues to treatment.

Dr. David Brooks’ (University of Toronto, Canada) group is investigating the role of interferon regulatory factor-2 (IRF2) and type I interferons (IFN-I).³¹ In the context of cancer, increased IRF2 expression is associated with tumor progression and adaptive immune evasion.³² Interestingly, Dr. Brooks’ team showed that type I interferon (IFN-I) can negatively regulate T cell responsiveness within the tumor microenvironment (TME) through chronic IFN-I signaling, increasing T cell programmed cell death ligand-1 (PD-1) expression and exhaustion after therapeutic intervention.³³ Using an IFN-I response score, they demonstrate that patients who responded less strongly to IFN-I prior to anti-PD-1 therapy had prolonged survival, suggesting that IFN-I response may be an important biomarker to predict therapeutic outcomes.

Features of the tumor microenvironment may impact T cell function. Dr. Thorsten Mempel's group (Massachusetts General Hospital, USA) used scRNAseq to probe the interactions between DCs and T cells within the TME, focusing on chemokine receptor expression. They report that loss of TCF-1 enabled maximal CXCR6 expression on cytotoxic effector T cells, which facilitated their accumulation in the TME.³⁴ Dr. Mempel's team further showed that engineered CXCR6 expression could improve the efficacy of chimeric antigen receptor (CAR)-T cell therapy in solid tumors.³⁵ Targeting the CARMA1/Bcl10/MALT1 (CBM) complex, which is involved in T regulatory (Treg) cell development, enabled reprogramming of Treg cells to become effector T cells; conditional deletion of CARMA1 in mature Treg cells caused them to produce IFN-γ within the TME.³⁶ Similarly, inhibiting MALT1 during anti-PD-1 therapy acted synergistically in reduced murine tumor growth. In a phase 1 clinical study, 5 out of 11 patients with solid tumors exhibited disease stabilization already in response to MALT1 inhibitor monotherapy and showed an increase in intratumoral T cells. This demonstrates that multipronged treatment approaches are a promising strategy to alter the TME of solid tumors to improve efficacy of existing approaches.

Dr. Brent Johnston's group (Dalhousie University, Canada) similarly approaches cancer therapy from multiple angles, and described how his team combines natural killer T (NKT) cell immunotherapy (stimulation of lipid-reactive NKT cells via adoptive transfer of α-galactosylceramide-loaded dendritic cells) with oncolytic vesicular stomatitis virus (VSV).³⁷ In metastatic 4T1 breast cancer and ID8 ovarian peritoneal cancer mouse models, combination therapy enhanced antitumor immunity to reduce tumor burden and improve survival.³⁸ Iterating this success, the modification of VSV to encode IL-15 (VSV-IL-15) and the addition of anti-PD-1 checkpoint blockade enabled enhanced immune function and tumor control in an ectopic model of pancreatic adenocarcinoma, with clearance in 20% of mice.³⁹ Taken together, Dr. Johnston's work reinforces the conclusion that multifaceted approaches are likely to have the biggest impact in cancer treatment.

Each tumor is complex and reflects many features of the patient. Dr. Daniela Quail (McGill University, Montreal) described the interactions between obesity and metabolism and how adipocyte hypotrophy can lead to the release of damage associated molecular patterns.⁴⁰ Interactions between adipocytes and myeloid cells can also lead to phenotypic changes that contribute to systemic inflammation, disruption of tissue homeostasis, and metabolic syndrome.^41,42 In obese conditions, neutrophilia occurs, coinciding with increased incidence of cancer and its metastasis; often to the lungs or liver.^43,44 In these environments, Dr. Quail's team finds increased infiltrating neutrophils, reactive oxygen species, greater release of MMP9, and neutrophil extracellular trap (NET) formation.⁴⁴ This NET release led to endothelial junction dissociation and metastasis in a murine breast cancer model.⁴³ Weight loss, anti-IL-5 therapy, antioxidants, or NET inhibitors are therefore interesting avenues to explore for the amelioration of neutrophil-driven tumor microenvironments.⁴⁴

There are many unknowns in immuno-oncology; with two complex systems interacting, consideration of its many features will be key to adequate disease control. Our speakers highlighted effective preclinical approaches to treatment and some of the additional barriers and considerations to overcome, inspiring further consideration for the design of future studies and effective cancer therapies.

5 Conclusion

The Canadian Society for Immunology 2022 symposia highlighted how novel techniques at all stages of immunologic research, from single-cell approaches and intricate murine models to systems-level considerations and population studies, allow further understanding of the many roles of the immune system. These symposia highlighted how complex many of these factors are and focused on understanding how the immune system may contribute to or is influenced by dynamic physiologic conditions, including development, aging, cancer, microbiome, and inflammatory disease. Canadian and international researchers are unlocking the secrets of the immune system and defining new opportunities for immunomodulation and immunotherapy.

The next annual meeting of the CSI will be held in Orford, Quebec on June 6–9, 2023, and will undoubtedly showcase more exciting and cutting-edge immunology research!

Acknowledgments

The authors gratefully thank Dr. Nathan Peters for editing and critical appraisal of the manuscript.

Conflict of interest statement. The authors declare that no conflict of interest exists.

References

Author notes