Unravelling complex interactions during Toxoplasma, Plasmodium, and Leishmania co-infections in French Guiana.

Toxoplasma gondii, Plasmodium spp., and Leishmania spp. collectively infect billions and cause millions of deaths worldwide. In French Guiana, the geographical coexistence of malaria, acute toxoplasmosis, and cutaneous leishmaniasis may result in sequential or simultaneous infections. This study assesses the seroprevalence of protozoan multi-infections and their impact on host responses compared to individual infections. We analyzed plasma samples and clinical data from patients with these diseases and healthy controls (n = 253) collected at Cayenne Hospital Centre between 2012 and 2022. Seroprevalence for T. gondii, Plasmodium spp. and Leishmania spp. was determined using chemiluminescence and ELISA, and cytokine and chemokine levels were measured via a multiplex assay. Multivariate analysis was utilized to identify distinct biological markers and disease signatures of single and co-infections. About 60% of patients were seropositive for at least two pathogens, with 2.4% having concomitant infections. Significant differences were noted in cytokine profiles, particularly levels of IL-10, IL-17, IL-33, and IFN-α, between single and co-infected patients. These results underline the complex dynamics and high prevalence of co-infections, providing crucial insights for developing effective public health strategies and biomarkers, especially in endemic regions.