Molecular and immunological detection of Toxoplasma gondii in forensic human brain tissue from suicide, traffic accident and homicide decedents with CD45R0 tissue expression analysis.

BACKGROUND

Studies have linked toxoplasmosis to neuropsychiatric disorders. However, no previous reports exist on parasite tissue cyst frequency in suicide or violent death autopsies, or its variation among brain behavior-associated regions (amygdala or hippocampus).

METHODS

Amygdala, hippocampus, prefrontal, and occipital areas from forensic brain tissues were examined using real-time PCR with T. gondii RE sequence and indirect immunofluorescence antibody test (IFAT) on brain tissue using anti-BAG1 monoclonal antibodies. CD45R0 was analyzed by immunohistochemistry. Serum postmortem samples were analyzed using ELFA assay.

RESULTS

T. gondii was detected in 30% of brain tissue samples (PCR-positive in 29.3% [17/57]; IFAT-positive in 30% [6/20]). Serum IgG antibodies were positive in 45.2% (19/42), with all IgM negative, indicating chronic infection. PCR positivity was higher in the hippocampus of homicide victims (18.6%) than other causes (2.4%). The hippocampus showed highest parasite loads (lowest mean Ct values: 14.7) and density (approximately 470 cysts/gram), indicating regional tropism. CD45RO expression was significantly higher in the hippocampus of Toxoplasma-seropositive decedents than seronegative individuals (p = 0.002, effect size r = 0.97), with no significant difference in the amygdala. A positive correlation existed between hippocampal CD45RO expression and cyst count (Spearman's ρ = 0.721, p = 0.001).

CONCLUSIONS

This study provides molecular and immunological evidence of chronic T. gondii infection in 30% of forensic brain samples, with tropism and higher parasite load in the hippocampus. Toxoplasma brain infection is strongly associated with elevated CD45RO expression specifically in the hippocampus, suggesting localized neuroinflammatory response that may underline neuropsychiatric associations.