CD8+ T–cell Exhaustion Phenotype in Human Asymptomatic and Ocular Toxoplasmosis

This work analyzed exhaustion markers in CD8+ T-cell subpopulations in 21 samples of peripheral blood mononuclear cells (PBMCs) from individuals with ocular toxoplasmosis (n = 9), chronic asymptomatic toxoplasmosis (n = 7), and non-infected people (n = 5) by using RT-qPCR and flow cytometry techniques. The study found that gene expression of PD-1 and CD244, but not LAG-3, was higher in individuals with ocular toxoplasmosis versus individuals with asymptomatic infection or uninfected. Expression of PD1 in CD8+ central memory (CM) cells was higher in nine individuals with toxoplasmosis versus five uninfected individuals (p =.003). After ex vivo stimulation, an inverse correlation was found between the exhaustion markers and quantitative clinical characteristics (lesion size, recurrence index, and number of lesions). A total exhaustion phenotype was found in 55.5% (5/9) of individuals with ocular toxoplasmosis. Our results suggest that the CD8+ exhaustion phenotype is involved in the pathogenesis of ocular toxoplasmosis.