Reading the room: iNKT cells influence B cell responses

α-GalCer sp2-iminoglycolipid analogs as CD1d-dependent iNKT modulators: Evaluation of their immunotherapeutic potential in murine models of asthma and autoimmune hepatitis

Invariant natural killer T (iNKT) cells are a subset of innate T cells displaying powerful immunomodulatory functions. Despite extensive preclinical research on the use of iNKT agonist and antagonist for various diseases, translating these findings into successful clinical applications has proven challenging, leaving no approved treatments to date. Efforts to optimize therapeutic outcomes by developing alternative glycolipids to α-galactosylceramide (α-GalCer or KRN7000), the prototypical iNKT antigen, have shown improved preclinical results. However, significant obstacles remain, including the relatively laborious synthesis of α-glycosides and their vulnerability to degradation by α-glycosidases. To overcome these limitations, we explored the use of sp2-iminosugars, a class of glycomimetics, to replace the carbohydrate moiety in α-GalCer-like glycolipids. This substitution offers enhanced biostability and precise control over α-selectivity in glycosylation reactions. The resulting sp2-iminoglycolipids (sp2-IGLs) were tested for their immunomodulatory effects, demonstrating the ability to bind the α-GalCer binding site on the CD1d protein in antigen-presenting cells (APCs), and functioning as iNKT antagonists in α-GalCer-stimulated splenocytes. Notably, analogs featuring a 4-alkyl-1,2,3-aminotriazol-1-yl segment in place of the C25N-acyl tail in α-GalCer additionally exhibited mild agonistic activity in the absence of α-GalCer stimulation. Computational studies support the formation of stable CD1d- sp2-IGL and CD1d - sp2-IGL - T-cell receptor complexes, with significant differences in the dynamics depending on the glycone nature and lipid tail length. These findings provide a molecular rationale for the observed experimental data. Furthermore, in vivo studies using murine models of asthma and autoimmune hepatitis have identified promising sp2-IGL candidates for further development in immunotherapy.

Unravelling metabolic factors impacting iNKT cell biology in obesity

Obesity and related diseases have reached epidemic proportions and continue to rise. Beyond creating an economical burden, obesity and its co-morbidities are associated with shortened human life expectancy. Despite major advances, the underlying mechanisms of obesity remain not fully elucidated. Recently, several studies have highlighted that various immune cells are metabolically reprogrammed in obesity, thereby profoundly affecting the immune system. This sheds light on a new field of interest: the impact of obesity-related systemic metabolic changes affecting immune system that could lead to immunosurveillance loss. Among immune cells altered by obesity, invariant Natural Killer T (iNKT) cells have recently garnered intense focus due to their ability to recognize lipid antigen. While iNKT cells are well-described to be affected by obesity, how and to what extent immunometabolic factors (e.g., lipids, glucose, cytokines, adipokines, insulin and free fatty acids) can drive iNKT cells alterations remains unclear, but represent an emerging field of research. Here, we review the current knowledge on iNKT cells in obesity and discuss the immunometabolic factors that could modulate their phenotype and activity.

Modulation of myeloid-derived suppressor cell functions by oral inflammatory diseases and important oral pathogens

The oral cavity presents a diverse microbiota in a dynamic balance with the host. Disruption of the microbial community can promote dysregulation of local immune response which could generate oral diseases. Additionally, alterations in host immune system can result in inflammatory disorders. Different microorganisms have been associated with establishment and progression of the oral diseases. Oral cavity pathogens/diseases can modulate components of the inflammatory response. Myeloid-derived suppressor cells (MDSCs) own immunoregulatory functions and have been involved in different inflammatory conditions such as infectious processes, autoimmune diseases, and cancer. The aim of this review is to provide a comprehensive overview of generation, phenotypes, and biological functions of the MDSCs in oral inflammatory diseases. Also, it is addressed the biological aspects of MDSCs in presence of major oral pathogens. MDSCs have been mainly analyzed in periodontal disease and Sjögren's syndrome and could be involved in the outcome of these diseases. Studies including the participation of MDSCs in other important oral diseases are very scarce. Major oral bacterial and fungal pathogens can modulate expansion, subpopulations, recruitment, metabolism, immunosuppressive activity and osteoclastogenic potential of MDSCs. Moreover, MDSC plasticity is exhibited in presence of oral inflammatory diseases/oral pathogens and appears to be relevant in the disease progression and potentially useful in the searching of possible treatments. Further analyses of MDSCs in oral cavity context could allow to understand the contribution of these cells in the fine-tuned balance between host immune system and microorganism of the oral biofilm, as well as their involvement in the development of oral diseases when this balance is altered.

Emerging insights into atypical B cells in pediatric chronic infectious diseases and immune system disorders: T(o)-bet on control of B-cell immune activation

Repetitive or persistent cellular stimulation in vivo has been associated with the development of a heterogeneous B-cell population that exhibits a distinctive phenotype and, in addition to classical B-cell markers, often expresses the transcription factor T-bet and myeloid marker CD11c. Research suggests that this atypical population consists of B cells with distinct B-cell receptor specificities capable of binding the antigens responsible for their development. The expansion of this population occurs in the presence of chronic inflammatory conditions and autoimmune diseases where different nomenclatures have been used to describe them. However, as a result of the diverse contexts in which they have been investigated, these cells have remained largely enigmatic, with much ambiguity remaining regarding their phenotype and function in humoral immune response as well as their role in autoimmunity. Atypical B cells have garnered considerable interest because of their ability to produce specific antibodies and/or autoantibodies and because of their association with key disease manifestations. Although they have been widely described in the context of adults, little information is present for children. Therefore, the aim of this narrative review is to describe the characteristics of this population, suggest their function in pediatric immune-related diseases and chronic infections, and explore their potential therapeutic avenues.

CD1 and iNKT cells mediate immune responses against the GBS hemolytic lipid toxin induced by a non-toxic analog

Although hemolytic lipids have been discovered from many human pathogens including Group B Streptococcus (GBS), strategies that neutralize their function are lacking. GBS is a leading cause of pregnancy-associated neonatal infections, and adult GBS infections are on the rise. The GBS hemolytic lipid toxin or granadaene, is cytotoxic to many immune cells including T and B cells. We previously showed that mice immunized with a synthetic nontoxic analog of granadaene known as R-P4 had reduced bacterial dissemination during systemic infection. However, mechanisms important for R-P4 mediated immune protection was not understood. Here, we show that immune serum from R-P4-immunized mice facilitate GBS opsonophagocytic killing and protect naïve mice from GBS infection. Further, CD4+ T cells isolated from R-P4-immunized mice proliferated in response to R-P4 stimulation in a CD1d- and iNKT cell-dependent manner. Consistent with these observations, R-P4 immunized mice lacking CD1d or CD1d-restricted iNKT cells exhibit elevated bacterial burden. Additionally, adoptive transfer of iNKT cells from R-P4 vaccinated mice significantly reduced GBS dissemination compared to adjuvant controls. Finally, maternal R-P4 vaccination provided protection against ascending GBS infection during pregnancy. These findings are relevant in the development of therapeutic strategies targeting lipid cytotoxins.

Predictive role of blood eosinophils in adult varicella patients

The study aimed to explore the relationship between eosinophils and the prognosis of varicella in adults. We retrospectively reviewed the medical records of patients who were hospitalised in The Fifth People's Hospital of Suzhou with a diagnosis of adult varicella during the period between 1 January 2012 and 31 December 2020. Of the 359 patients, 228 (63.51%) had eosinopenia. The proportion of patients with mild type disease was significantly lower in the eosinopenia group than that in the non-eosinopenia group (50.44% vs. 65.65%, P = 0.006). The proportion of the patients with common type disease was significantly higher in the eosinopenia group than that in the non-eosinopenia group (39.47% vs. 28.24%, P = 0.039). The proportion of the patients with severe type disease was higher in the eosinopenia group, although the difference did not reach statistical significance (10.09% vs. 6.11%, P = 0.243). The rates of high fever (47.81% vs. 32.82%, P = 0.008; relative risk (RR) 1.296, 95% confidence interval (CI) 1.091–1.540), headache (43.42% vs. 22.14%, P < 0.001; RR 1.415, 95% CI 1.233–1.623), anorexia (53.51% vs. 35.88%, P = 0.001; RR 1.367, 95% CI 1.129–1.655) and complications (82.89% vs. 64.12%, P < 0.001; RR 2.106, 95% CI 1.460–3.038) were also significantly higher in the eosinopenia group. Among the complications, the liver injury and skin infection were more serious in the eosinopenia group. The disease course was significantly longer in the eosinopenia group than that in the non-eosinopenia group (9.43 ± 1.89 days vs. 8.73 ± 1.25 days, P < 0.001). The improvement rate of liver injury in the recovery period was lower in the eosinopenia group than that in the non-eosinopenia group (35.38% vs. 50%, P = 0.012). The study found that adult varicella patients with eosinopenia had a more serious condition, a higher morbidity of complications and a slower recovery. Blood eosinophils can be used as a new predictor of the severity of adult varicella.

The Effect of Peripheral Immune Cell Counts on the Risk of Multiple Sclerosis: A Mendelian Randomization Study

Objectives

Multiple sclerosis (MS) is a complex central nervous system (CNS) demyelinating disease, the etiology of which involves the interplay between genetic and environmental factors. We aimed to determine whether genetically predicted peripheral immune cell counts may have a causal effect on MS.

Methods

We used genetic variants strongly associated with cell counts of circulating leukocyte, lymphocyte, monocyte, neutrophil, eosinophil, and basophil, in addition to some subpopulations of T and B lymphocyte, as instrumental variables (IVs) to perform Mendelian randomization (MR) analyses. The effect of immune cell counts on MS risk was measured using the summary statistics from the International Multiple Sclerosis Genetics Consortium (IMSGC) genome-wide association studies (GWAS).

Results

Our findings indicated that higher leucocyte count [odds ratio (OR), 1.24; 95% confidence interval (CI), 1.07 - 1.43; p = 0.0039] and lymphocyte count (OR, 1.17; 95% CI, 1.01 – 1.35; p = 0.0317) were causally associated with MS susceptibility. In addition, we also found that increase of genetically predicted natural killer T (NKT) cell count is also associated with an increase MS risk (OR, 1.24; 95% CI, 1.06 - 1.45; p = 0.0082).

Conclusions

These findings show that the genetic predisposition to higher peripheral immune cell counts can exert a causal effect on MS risk, which confirms the crucial role played by peripheral immunity in MS. Particularly, the causal association between NKT cell count and MS underscores the relevance of exploring the functional roles of NKT cells in disease pathogenesis in future.

NKT and NKT-like Cells in Autoimmune Neuroinflammatory Diseases-Multiple Sclerosis, Myasthenia Gravis and Guillain-Barre Syndrome

NKT cells comprise three subsets-type I (invariant, iNKT), type II, and NKT-like cells, of which iNKT cells are the most studied subset. They are capable of rapid cytokine production after the initial stimulus, thus they may be important for polarisation of Th cells. Due to this, they may be an important cell subset in autoimmune diseases. In the current review, we are summarising results of NKT-oriented studies in major neurological autoimmune diseases-multiple sclerosis, myasthenia gravis, and Guillain-Barre syndrome and their corresponding animal models.

Glycolipid-Containing Nanoparticle Vaccine Engages Invariant NKT Cells to Enhance Humoral Protection against Systemic Bacterial Infection but Abrogates T-Independent Vaccine Responses

CD4⁺ T cells enable the critical B cell humoral immune protection afforded by most effective vaccines. We and others have recently identified an alternative source of help for B cells in mice, invariant NK T (iNKT) cells. iNKT cells are innate glycolipid-specific T cells restricted to the nonpolymorphic Ag-presenting molecule CD1d. As such, iNKT cells respond to glycolipids equally well in all people, making them an appealing adjuvant for universal vaccines. We tested the potential for the iNKT glycolipid agonist, α-galactosylceramide (αGC), to serve as an adjuvant for a known human protective epitope by creating a nanoparticle that delivers αGC plus antigenic polysaccharides from Streptococcus pneumoniae αGC-embedded nanoparticles activate murine iNKT cells and B cells in vitro and in vivo, facilitate significant dose sparing, and avoid iNKT anergy. Nanoparticles containing αGC plus S. pneumoniae polysaccharides elicits robust IgM and IgG in vivo and protect mice against lethal systemic S. pneumoniae However, codelivery of αGC via nanoparticles actually eliminated Ab protection elicited by a T-independent S. pneumoniae vaccine. This is consistent with previous studies demonstrating iNKT cell help for B cells following acute activation, but negative regulation of B cells during chronic inflammation. αGC-containing nanoparticles represent a viable platform for broadly efficacious vaccines against deadly human pathogens, but their potential for eliminating B cells under certain conditions suggests further clarity on iNKT cell interactions with B cells is warranted.