Preprint
Keywords: rheumatic fever, T cell dysregulation, CXCR3, immune-modulating therapy, CCL5, IgG3
Abstract:
Background: The pathogenesis of Acute Rheumatic Fever (ARF) is poorly understood, limiting development of immune-modulating therapies to treat ARF and prevent progression to Rheumatic Heart Disease (RHD). This prospective cohort study, which recruited participants with definite ARF in Australia and Aotearoa New Zealand, profiled circulating immune molecules and cells to inform disease mechanisms and future druggable pathways.
Methods: ARF was compared to four matched control groups (serious streptococcal infections, other inflammatory conditions, RHD, and healthy). Concentrations of 20 cytokines, chemokines, immunoglobulin subclass IgG3, and C-reactive protein were measured. The frequency of all major immune cell populations and expression of activation markers and chemokine receptors were evaluated by spectral flow cytometry.
Findings: While ARF shared some immunological similarities with other inflammatory conditions, including elevated IL-6 and increased CD4+ T cells, disease specific features provided new insight. Elevation of the chemokine CCL5 and IgG3 and a dramatic reduction of CXCR3 chemokine receptor expression across multiple T cell populations distinguished ARF from all other groups. In ARF the CXCR3+ T cells were uncoupled from a cognate chemokine which, together with reduced T regulatory cells, underscore a perturbed T cell compartment in pathogenesis.
Interpretation: Altered T cell migration mediated by CXCR3 within a circulatory environment characterised by elevated CCL5 and IgG3 contribute to ARF immunopathology. This, in conjunction with the broadly inflammatory nature of ARF, provides rationale for exploring currently available immune-modulating therapies to treat ARF.