The major surface antigen SAG1 was a consistent hit in CRISPR screens for parasite genes needed in interferon-γ-stimulated cells. In Infection and Immunity we show with a SAG1 knockout that the protein is important for fitness specifically under interferon-γ.
Host surface sialic acids are important for attachment, especially in interferon-γ-treated cells, and SAG1-deficient parasites attach less efficiently, a defect that worsens under immune pressure.
Read the paper: Surface antigen SAG1 mediates Toxoplasma gondii fitness and host cell attachment in IFNγ-stimulated cells. Infect Immun 2025.