Scientists have discovered how the immune system fights Toxoplasma gondii, a parasite that causes the disease toxoplasmosis in humans, according to a paper online this week in Nature Immunology.
Immune cells called CD8+ T lymphocytes are required to fight T. gondii, which can cause severe disease in humans with weak immune systems. These cells recognize parasite-derived protein fragments displayed on the surface of infected cells. Nilabh Shastri and colleagues show that a fragment of the T. gondii protein called GRA6 is a target of CD8+ T lymphocytes and induces a protective immune response in mice.
They also showed that the host cell protein ERAAP, which acts as a scissor to ‘clip’ proteins into fragments, is required for the production of this protective GRA6 fragment. This is the first time ERAAP has been shown to have a specific and protective role in the immune response to pathogens.