Xiao J, Bhondoekhan F, Seaberg EC, et al. - As there is a lack of knowledge concerning clinically useful predictors for fatal toxoplasmosis, researchers here examined the utility of serological assays for antibodies to whole Toxoplasma antigens and to peptide antigens of the Toxoplasma cyst protein MAG1, in predicting incident toxoplasmic encephalitis (TE) in people living with HIV (PLWH). Within the Multicenter AIDS Cohort Study (MACS), a nested case control study was conducted using serum samples collected 2 years prior to diagnosis of TE from 28 cases, and 37 HIV disease-matched Toxoplasma seropositive controls at matched time-points. Two years prior to clinical diagnosis, MAG1_4.2 seropositivity was observed in 68% of TE cases compared with 16% of controls. Findings suggest that in PLWH, antibodies to MAG1 displayed predictive value on the occurrence of TE, and further improvement in the predictive performance was noted by adding the levels of Toxoplasma antibody. They indicate clinical utility of these measures for predicting subsequent diseases in multiple at-risk populations.