Higher late galectin-3 and galectin-9 amid lower cytokine concentrations in DENV-2-exposed PBMC cultures from older versus middle-aged donors

Older adults with dengue have higher risks of adverse outcomes, but the contribution of age-related immune responses remains uncertain. We compared soluble mediators after ex vivo dengue virus serotype 2 (DENV-2) exposure of peripheral blood mononuclear cells (PBMCs) from older and middle-aged volunteer donors. PBMCs from 10 older donors (≥ 65 years; median age, 74.9 years; observed range, 65.8–92.0 years) and 10 middle-aged donors (20–64 years eligible; median age, 39.4 years; observed range, 34.8–49.1 years) were exposed to DENV-2 strain TH-36 at a multiplicity of infection of 5. Supernatants collected before exposure and at 24, 48, and 72 h were assayed for GM-CSF, IFN-γ, IL-6, IL-10, MCP-1, TNF-α, VEGF-A, galectin-3, and galectin-9. Between-group p values at each time point were unadjusted exploratory comparisons. Compared with middle-aged donor cultures, older donor cultures had higher galectin-3 concentrations at 48 and 72 h (median 363.6 versus 197.8 pg/mL, p = 0.0412; 810.1 versus 218.5 pg/mL, p = 0.0011) and higher galectin-9 at 72 h (219.6 versus 92.23 pg/mL, p = 0.0355). Concentrations of the seven other measured mediators were generally lower in older donor cultures at 24–72 h. IFN-γ, IL-10, and TNF-α also differed at baseline. Interpretation of the nominal p values is limited by the small sample and multiple comparisons. After ex vivo DENV-2 exposure, PBMC cultures from older donors had higher galectin-3 and galectin-9 concentrations at selected late time points and generally lower concentrations of the seven other measured mediators than cultures from predominantly middle-aged donors. This contrasting pattern highlights the value of examining galectins alongside other soluble mediators when investigating variation in responses to DENV-2. The small sample and culture model limit causal and clinical inference, and cytokine–galectin associations were not tested. Larger donor-linked experiments and studies in patients with dengue are needed to assess reproducibility and clinical relevance.