Immunohistochemical detection of parasite antigens in Theileria parva infected bovine lymphocytes

Theileria parva is the causal agent of East Coast fever (ECF), a fatal dise ase of cattle characterized by pyrexia, transient lymphadenopathy and panle ukopenia. We have evaluated monoclonal antibodies (mAb) against three disti nct antigens (p67, PIM and p32) of the parasite as immunohistological reage nts for monitoring the kinetics of infection in cattle. Bovine lymphocytes were stained with the mAb at various intervals after infection in vitro and in vivo. The p67 sporozoite surface antigen was detected in only a small p ercentage of both, in vitro and in vivo infected cells. In contrast, expres sion of the polymorphic immunodominant molecule (PIM) of the parasite prove d a useful indicator of infection and staining was correlated with the resu lts of Giemsa analysis. PIM was detected from day 3 in in vitro-infected ce lls, but was not detected until day 5 in vivo after challenge with a 70% le thal dose of stabilized sporozoite. The p32 antigen was expressed only late in infection in vivo and its expression was associated with the developmen t of merozoites. Less than 20% of in vitro-infected cells expressed p32. Th e immunohistochemical staining with anti-PIM mAb was found to be a useful t ool for analysis of T. parva infection kinetics in cattle. (C) 1998 Elsevie r Science B.V. All rights reserved.