Sigma class GSTs, unlike Mu Class GSTs, have been characterized as GSH-dependent hematopoietic prostaglandin synthases responsible for the production of prostaglandins in both mammals and parasitic worms [13] [14] [15] [16] [17] [18] . Prostaglandins have been extensively studied in mammals and are shown to be involved in a range of physiological and pathological responses [19] [20] [21] [22] [23] . Parasite-produced prostaglandins may be involved in parasite development and reproduction as well as the modulation of host immunity, allergy and inflammation during establishment and maintenance of a host infection [16, [24] [25] [26] [27] [28] ]. The host protection success of Sigma GST based vaccinations in schistosomiasis may therefore be related to neutralising specific functions in host-parasite interplay, such as prostaglandin synthase activity.