Jerome Coudert

Influenza remains a global health threat, infecting approximately one billion people annually and causing significant mortality, particularly among older adults. While hemagglutination inhibition (HAI) antibody titers are a standard correlate of immunity against influenza, they do not reliably predict protection in high-risk populations. Using multiomic single-cell profiling, we identified a distinct subset of adaptive-like NK cells that respond to influenza antigen, predominantly in younger females. These TNFSF10+LGALS9+ NK cells exhibit features of adaptive NK cells but lack classical cytomegalovirus-driven markers observed in previous studies. Notably, their increased frequency correlates with high pre-existing HAI titers, suggesting a link between adaptive-like NK responses and humoral immunity. Together, our findings identify an NK subset influenced by age and sex that may contribute to influenza protection, expanding the known diversity of adaptive-like NK cells. These insights could inform future vaccine strategies, particularly for aging populations, by integrating NK responses into assessments of vaccine efficacy.

Inclusion body myositis (IBM) is a late-onset, treatment-resistant inflammatory myopathy. Approximately half of IBM patients develop autoantibodies against cytosolic 5′-nucleotidase 1A (cN1A), but their role in disease pathogenesis remains unclear. This pilot study examined the effects of anti-cN1A-positive IBM serum on human primary myotubes’ transcriptome profile, using anti-cN1A-negative IBM and healthy sera as controls. Exposure to anti-cN1A-positive serum altered the expression of 1126 genes, with upregulation of adaptive immune response genes, notably CTSH and CTSZ, encoding cathepsins H and Z. These findings were validated using a publicly available independent dataset comprising transcriptomes from fresh muscle tissue samples. NT5C1A mRNA, which encodes cN1A, was not detected in cultured myotubes regardless of the presence of autoantibodies. The findings suggest distinct pathological mechanisms in anti-cN1A-positive IBM, independent of direct antibody-target interactions. The role of cathepsins in IBM pathogenesis warrants further investigation.

Parkinson's disease (PD) is a progressive neurodegenerative disorder defined by motor impairments. However, people with PD (PwPD) experience a defined spectrum of non-motor symptoms, with gastrointestinal dysfunction the most common and earliest-presenting. Evidence suggests that PD pathology may originate in the gut, where microbial dysbiosis and immune dysregulation contribute to neuroinflammation, although mechanisms underlying this are unclear. PwPD (n = 31) and healthy controls (n = 28) were evaluated for clinical and gastrointestinal symptoms, faecal and plasma sample metabolomics, and comprehensive blood immunophenotyping. In PwPD, faecal samples exhibited reduced glutamate, succinate, and uracil concentrations, while plasma showed decreased 3-hydroxybutyrate and elevated creatine, succinate, and alanine levels. Immunophenotyping revealed a reduction in T cells, with evidence of altered effector capacity and functionality in CD4, CD8, MAIT and Vδ2 compartments. NK cells were expanded, while B cells were decreased in frequency with an enrichment of memory-like cells. Immune perturbations were correlated with levels of immunomodulatory metabolite succinate. Finally, clustering of blood parameters identified two PD endophenotypes distinguishable by gastrointestinal symptoms and T cell phenotypes associated with gut- and brain-tropism. These findings contribute to the growing understanding of metabolite-associated immune dysregulation in PD and highlight potential targets for early intervention in individuals presenting with gastrointestinal dysfunction.

Autoantibodies targeting cytosolic 5′-nucleotidase 1A (cN1A) are found in several autoimmune diseases, including inclusion body myositis (IBM), Sjögren’s syndrome, and systemic lupus erythematosus. While they have diagnostic relevance for IBM, little is known about the autoreactive B cells that produce these antibodies. To address this, we developed a robust protocol for the expression and site-specific biotinylation of recombinant human cN1A in
Escherichia coli
. The resulting antigen is suitable for generating double-labelled fluorescent baits for the isolation and characterisation of cN1A-specific B cells by flow cytometry. Site-specific biotinylation was achieved using the AviTag and BirA ligase, preserving the protein’s structure and immunoreactivity. Western blot analysis confirmed that the biotinylated cN1A was recognised by both human and rabbit anti-cN1A antibodies. Compared to conventional chemical biotinylation, this strategy minimises structural alterations that may affect antigen recognition. This approach provides a reliable method for producing biotinylated antigens for use in immunological assays. While demonstrated here for cN1A, the protocol can be adapted for other autoantigens to support studies of antigen-specific B cells in autoimmune diseases.

OBJECTIVES:
Inclusion body myositis (IBM) is a complex inflammatory muscle disease in adults over 40, with histological features of autoinflammation, cell stress and autophagic abnormalities, and marked clinically by relentless progression with no effective disease-modifying therapy. Sirolimus (rapamycin) may help maintain function by inhibiting T effector cells, preserving T regulatory cells, inducing autophagy, and improving mitochondrial function. This international trial follows a phase II pilot study.

METHODS:
This phase IIb/III double-blind, randomised, controlled trial (RCT) of sirolimus involves 140 IBM patients randomly assigned with equal allocation to sirolimus (2 mg) or matching placebo. This RCT aims to assess the efficacy of sirolimus compared to placebo in slowing or stabilising IBM progression, as measured by the mean change in patient function using the IBM Functional Rating Scale (IBM-FRS) from Baseline to Week 84. Secondary outcomes will evaluate efficacy and safety to inform future clinical trial design.

RESULTS:
Ethical approval has been granted in Australia (St Vincent’s Hospital Melbourne HREC-D 311/20) and the USA (University of Kansas Medical Center Human Research Protection Program FWA no. 00003411), with European approval pending. The protocol is version 3.0 (02-Dec-2022). Trial registration: ANZCTR: ACTRN12620001226998p, ClinicalTrials.gov: NCT04789070, UTN: U1111-1258-1354, and EU CT 2024-514575-17-00.

CONCLUSIONS:
This phase IIb/III trial builds on prior findings to assess sirolimus’s potential in slowing or halting IBM progression, preserving patient function and independence, and advancing IBM therapeutic strategies and trial design.

Objective
Inclusion body myositis (IBM) is a progressive late-onset muscle disease characterised by preferential weakness of quadriceps femoris and finger flexors, with elusive causes involving immune, degenerative, genetic and age-related factors. Overlapping with normal muscle ageing makes diagnosis and prognosis problematic.

Methods
We characterised peripheral blood leucocytes in 81 IBM patients and 45 healthy controls using flow cytometry. Using a random forest classifier, we identified immune changes in IBM compared to HC. K-means clustering and the random forest one-versus-rest model classified patients into three immunophenotypic clusters. Functional outcome measures including mTUG, 2MWT, IBM-FRS, EAT-10, knee extension and grip strength were assessed across clusters.

Results
The random forest model achieved a 94% AUC ROC with 82.76% specificity and 100% sensitivity. Significant differences were found in IBM patients, including increased CD8+ T-bet+ cells, CD4+ T cells skewed towards a Th1 phenotype and altered γδ T cell repertoire with a reduced proportion of Vγ9+Vδ2+ cells. IBM patients formed three clusters: (i) activated and inflammatory CD8+ and CD4+ T-cell profile and the highest proportion of anti-cN1A-positive patients in cluster 1; (ii) limited inflammation in cluster 2; (iii) highly differentiated, pro-inflammatory T-cell profile in cluster 3. Additionally, no significant differences in patients' age and gender were detected between immunophenotype clusters; however, worsening trends were detected with several functional outcomes.

Conclusion
These findings unveil distinct immune profiles in IBM, shedding light on underlying pathological mechanisms for potential immunoregulatory therapeutic development.

Introduction: Inclusion body myositis (IBM) is a progressive inflammatory myopathy characterised by skeletal muscle infiltration and myofibre invasion by CD8+ T lymphocytes. In some cases, IBM has been reported to be associated with a systemic lymphoproliferative disorder of CD8+ T cells exhibiting a highly differentiated effector phenotype known as T cell Large Granular Lymphocytic Leukemia (T-LGLL).

Methods: We investigated the incidence of a CD8+ T-LGL lymphoproliferative disorder in 85 IBM patients and an aged-matched group of 56 Healthy Controls (HC). Further, we analysed the phenotypical characteristics of the expanded T-LGLs and investigated whether their occurrence was associated with any particular HLA alleles or clinical characteristics.

Results: Blood cell analysis by flow cytometry revealed expansion of T-LGLs in 34 of the 85 (40%) IBM patients. The T cell immunophenotype of T-LGLHIGH patients was characterised by increased expression of surface molecules including CD57 and KLRG1, and to a lesser extent of CD94 and CD56 predominantly in CD8+ T cells, although we also observed modest changes in CD4+ T cells and γδ T cells. Analysis of Ki67 in CD57+ KLRG1+ T cells revealed that only a small proportion of these cells was proliferating. Comparative analysis of CD8+ and CD4+ T cells isolated from matched blood and muscle samples donated by three patients indicated a consistent pattern of more pronounced alterations in muscles, although not significant due to small sample size. In the T-LGLHIGH patient group, we found increased frequencies of perforin-producing CD8+ and CD4+ T cells that were moderately correlated to combined CD57 and KLRG1 expression. Investigation of the HLA haplotypes of 75 IBM patients identified that carriage of the HLA-C*14:02:01 allele was significantly higher in T-LGLHIGH compared to T-LGLLOW individuals. Expansion of T-LGL was not significantly associated with seropositivity patient status for anti-cytosolic 5'-nucleotidase 1A autoantibodies. Clinically, the age at disease onset and disease duration were similar in the T-LGLHIGH and T-LGLLOW patient groups. However, metadata analysis of functional alterations indicated that patients with expanded T-LGL more frequently relied on mobility aids than T-LGLLOW patients indicating greater disease severity.

Conclusion: Altogether, these results suggest that T-LGL expansion occurring in IBM patients is correlated with exacerbated immune dysregulation and increased disease burden.

OBJECTIVES: Inclusion body myositis (IBM) is a progressive inflammatory-degenerative muscle disease of older individuals, with some patients producing anti-cytosolic 5'-nucleotidase 1A (NT5C1A, aka cN1A) antibodies. Human Leukocyte Antigens (HLA) is the highest genetic risk factor for developing IBM. In this study, we aimed to further define the contribution of HLA alleles to IBM and the production of anti-cN1A antibodies.

METHODS: We HLA haplotyped a Western Australian cohort of 113 Caucasian IBM patients and 112 ethnically matched controls using Illumina next-generation sequencing. Allele frequency analysis and amino acid alignments were performed using the Genentech/MiDAS bioinformatics package. Allele frequencies were compared using Fisher's exact test. Age at onset analysis was performed using the ggstatsplot package. All analysis was carried out in RStudio version 1.4.1717.

RESULTS: Our findings validated the independent association of HLA-DRB1*03:01:01 with IBM and attributed the risk to an arginine residue in position 74 within the DRβ1 protein. Conversely, DRB4*01:01:01 and DQA1*01:02:01 were found to have protective effects; the carriers of DRB1*03:01:01 that did not possess these alleles had a fourteenfold increased risk of developing IBM over the general Caucasian population. Furthermore, patients with the abovementioned genotype developed symptoms on average five years earlier than patients without. We did not find any HLA associations with anti-cN1A antibody production.

CONCLUSIONS: High-resolution HLA sequencing more precisely characterised the alleles associated with IBM and defined a haplotype linked to earlier disease onset. Identification of the critical amino acid residue by advanced biostatistical analysis of immunogenetics data offers mechanistic insights and future directions into uncovering IBM aetiopathogenesis.