Enhancing T cell function to malaria

A means to boost immune responses to malaria-causing parasites is reported this week in Nature Immunology. CD4+ T immune cell function is essential for developing immune responses to blood-borne Plasmodia, the parasites that cause malaria, however the potency of these immune cells decreases during chronic infections. John Harty and colleagues show children endemically infected by the P. falciparum species possess T cells that express the T cell inhibitory receptor PD-1, which suppress T cell function. Similarly CD4+ T cells in mice experimentally infected with another similar species, P. yoelii, have higher expression of PD-1 and related LAG-3 inhibitory molecules. Treating infected mice with monoclonal antibodies designed to block LAG-3 and the PD-1 ligand led to a restoration of T cell function and a rapid decrease in parasitemia. The results suggest that blockade of T cell inhibitory receptors might likewise prove beneficial to human malaria patients.