Hormonal and Immunological Biomarkers (Testosterone, Oxytocin, and IL-5) Associated with Toxoplasma gondii Infection in Relation to Autism Spectrum Disorder

Abstract

Background: Toxoplasma gondii is an intracellular protozoan parasite capable of crossing the placental barrier and influencing fetal neurodevelopment. Increasing evidence suggests that maternal toxoplasmosis may contribute to the development of Autism Spectrum Disorder (ASD) through hormonal and immunological alterations.
Objective: This study aimed to investigate the association between maternal Toxoplasma gondii infection and serum levels of testosterone, oxytocin (OXT), and interleukin-5 (IL-5), and to evaluate their possible relationship with Autism Spectrum Disorder.
Methods; A case–control study was conducted between January and October 2025. A total of 180 peripheral blood samples were collected from 60 families, including mothers of children with ASD, affected children, and their siblings. Maternal T. gondii infection was determined by detecting anti-T. gondii IgG and IgM antibodies using a TORCH rapid cassette test. Serum testosterone, oxytocin, and IL-5 levels were measured using commercially available enzyme-linked immunosorbent assay (ELISA) kits according to the manufacturers' instructions. Results: Maternal Toxoplasma gondii infection was associated with a markedly higher frequency of Autism Spectrum Disorder (ASD) among offspring (76.2%, 96/126) compared with non-infected mothers (13.4%, 54/404). Infected mothers exhibited significantly higher serum testosterone levels than non-infected mothers (0.69 ± 0.00 vs. 0.65 ± 0.00 ng/mL, P = 0.001) and significantly elevated serum IL-5 concentrations (1.991 ± 0.010 vs. 1.480 ± 0.011 pg/mL, P = 0.001). In contrast, serum oxytocin levels were significantly lower in infected mothers compared with non-infected mothers (0.90 ± 0.00 vs. 2.35 ± 0.02 pg/mL, P = 0.001).
Conclusion: Maternal Toxoplasma gondii infection was associated with significant changes in serum testosterone, oxytocin, and IL-5 levels. These alterations may contribute to the biological mechanisms linking maternal toxoplasmosis with Autism Spectrum Disorder and could serve as potential biomarkers for evaluating the impact of maternal infection on neurodevelopment.