THEILERIA-ANNULATA SPOROZOITE TARGETS

Bovine peripheral blood mononuclear cells (PBM) infected in vitro with Theileria annulata sporozoites have previously been characterized as MHC class II+ mature macrophages. The ability of T. annulata sporozoit es to infect different subpopulations of MHC class II+ bovine monocyte s was investigated. Cells were labelled with monocyte specific monoclo nal antibodies (MoAb) and isolated using magnetic cell sorting (MACS). Sporozoites infected both immature and mature monocytes, but more rea dily infected the mature population. A potential ligand for sporozoite entry is the elastin receptor which is expressed mainly on the immatu re population of monocytes and not on B cells or T cells. T. annulata sporozoites infected elastin receptor positive and negative cell popul ations equally well. Infected immature cells lost the expression of el astin receptors and the immature marker, subsequently expressing the m ature marker. All monocytes lost the expression of CD14 (the LPS recep tor) upon infection with sporozoites. The infection of specific popula tions and subsequent alterations in phenotype may alter the function o f these cells and play an important role in disease pathogenesis.