Immunological reprogramming during natural helminth–protozoan coinfections: a cross-sectional population-based study in rural Nigeria

Abstract Background Concurrent parasitic infections are common in tropical regions and can lead to significant immune modulation. However, the immunological consequences of natural helminth–protozoan remain underexplored in rural African populations. Objective This study investigated immune profiles and environmental correlates of coinfection with helminths and protozoa in a rural Nigerian setting. Methods A total of 400 individuals aged 2–60 years were enrolled in a cross-sectional study in Okeogun, Nigeria. Parasitological assessments identified species of intestinal helminths and protozoa. Circulating cytokines (Th1, Th2, regulatory) were measured using ELISA, and Treg activity was inferred from IL-10 and TGF-β levels. Results Helminth-only, protozoan-only, and mixed infections occurred in 45.3%, 20.8%, and 14.5% of participants, respectively. Coinfected individuals exhibited significantly elevated IL-4, IL-5, IL-10, and TGF-β ( p < 0.001), with concurrent reductions in IFN-γ and IL-12. This cytokine profile suggests immune skewing toward regulatory and Th2 responses. Predictors of this shift included younger age, poor sanitation, and barefoot walking. Conclusion Helminth–protozoan coinfection induces immune reprogramming marked by heightened immunoregulatory activity and suppressed Th1 responses. These findings have implications for disease control, vaccine response, and public health planning in polyparasitic settings.