Evaluation of the Genetic Association Between IL-12B (+1188 A/C) Polymorphism and Serum IL-12 Levels in Patients with Toxoplasma gondii Infection

Abstract

Background: Human genetic uniqueness and the opportunistic, neurotropic nature of Toxoplasma gondii drive significant variability in infection outcomes. Given the critical role of interleukin-12 (IL-12B) in the pathogenesis of toxoplasmosis, this study aimed to investigate the association between the IL-12B gene polymorphism (A/C at +1186 of the 3′ UTR) and susceptibility to toxoplasmosis within the Iraqi population. Methods: This study involved 150 women, aged 10 to 70 years, recruited between October 2025 and January 2026 from various urban and rural areas in AL-Najaf and AL-Wasit provinces, Iraq. All participants were screened for T. gondii IgG and IgM antibodies using a rapid immunochromatographic test. The infected cases were further categorized into subgroups: pregnant women, women who had experienced abortion, and non-pregnant women. Results: The mean concentrations of serum IL-12B were significantly higher in patients compared to the healthy group (3.631 ± 0.171 vs. 1.939 ± 0.124, P < 0.0001). Regading the genetic analysis of the IL-12B C/A promoter variant, the A/A was shown to be more common in toxoplasmosis group compared to controls (23% vs. 4%, OR = 7.168, P = 0.0095), whereas the CC genotype was less common in toxoplasmosis patients (42% vs. 60%). The AC genotype was similar between the two groups. In terms of allele frequency, the A allele was more frequent in toxoplasmotic group (44%) compared to healthy (34%), whereas the C allele frequency was higher in controls (66%) compared to toxoplasmosis patients (56%). Conclusion: This study suggests that gene polymorphism of IL-12B -1186 is significantly associated with the risk of developing toxoplasmosis. Patients with toxoplasmosis exhibit elevated serum levels of IL-12B and a higher frequency of the AA genotype, indicating an increased susceptibility to the infection when carrying the A allele and AA genotype. Conversely, the C allele may have a protective influence against toxoplasmosis development within the Iraqi population.