Toxoplasma gondii (T gondii) is a common parasite that shows affinity to neural tissue and may lead to the formation of
cysts in the brain. Previous epidemiologic studies have suggested an association between
glioma and increased prevalence of T gondii
infection, but prospective studies are lacking. Therefore, we examined the association between prediagnostic T gondii
antibodies and risk of
glioma in two prospective cohorts using a nested case-control study design. Cases and matched controls were selected from the American Cancer Society's
Cancer Prevention Study-II Nutrition Cohort (CPSII-NC) (n = 37 cases and 74 controls) and the Norwegian
Cancer Registry's Janus Serum Bank (Janus) (n = 323 cases and 323 controls). Blood samples collected prior to diagnosis were analyzed for
antibodies to two T gondii
surface antigens (p22 and sag-1), with individuals considered seropositive if
antibodies to either
antigen were detected. Conditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (95% CI) for each cohort. In both cohorts, a suggestive increase in
glioma risk was observed among those infected with T gondii (OR: 2.70; 95% CI: 0.96-7.62 for CPSII-NC; OR: 1.32, 95% CI: 0.85-2.07 for Janus), particularly among participants with high antibody titers specific to the sag-1
antigen (CPSII-NC OR: 3.35, 95% CI: 0.99-11.38; Janus OR: 1.79, 95% CI: 1.02-3.14). Our findings provide the first prospective evidence of an association between T gondii
infection and risk of
glioma. Further studies with larger case numbers are needed to confirm a potential etiologic role for T gondii in
glioma.