Our study supports this dualistic role of T. gondii: the HIV-positive patients that lacked the ‘guardian’ in their brains (T. gondii-seronegative) developed CNS cryptococcosis at a higher CD4 count (around 50 cells/mm3) than the patients that possessed the ‘guardian’ (T. gondii-seropositive), that kept the barrier up even at around 30 cells/mm3 CD4 count. This evidence concerns the gene CD4 and cryptococcosis.