Circumsporozoite protein (CS) is a leading vaccine antigen for falciparum malaria. but is highly polymorphic in natural parasite populations. The factors driving this diversity are unclear. but non-random assortment of the T cell epitopes TH2 and TH3 has been observed in a Kenyan parasite population. https://www.roneverhart.com/Sigma-Phi-Lambda-Lil-Big-Sister-Tee-Discontinued/