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Cloning and characterization of a 150 kDa microsphere antigen of Theileria parva that is immunologically cross-reactive with the polymorphic immunodominant molecule (PIM)

Published online by Cambridge University Press:  01 October 1998

R. A. SKILTON
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
R. P. BISHOP
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
C. W. WELLS
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
P. R. SPOONER
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
E. GOBRIGHT
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
C. NKONGE
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
A. J. MUSOKE
Affiliation:
International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
M. MACKLIN
Affiliation:
Agracetus Corporation, 8520 University Green, Middletown, WI 53562, USA
K. P. IAMS
Affiliation:
Department of Biochemistry, University of Zimbabwe, P.O. Box MP167, Harare, Zimbabwe

Abstract

To identify the genes encoding novel immunodominant antigens of Theileria parva a λgt11 library of piroplasm genomic DNA was immunoscreened with bovine recovery serum and a gene encoding a 150 kDa antigen (p150) was identified. The predicted polypeptide contains an N-terminal secretory signal sequence and a proline-rich region of repeated amino acid motifs. The repeat region is polymorphic between stocks of T. parva in both copy number and sequence, and analysis of the repeat region from 10 stocks of T. parva revealed 5 p150 variants. A monoclonal antibody (mAb) against the T. parva polymorphic immunodominant molecule (PIM) cross-reacted with the recombinant p150. The p150 has sequence homology with a PIM peptide sequence containing the anti-PIM mAb epitope. Immunoelectron microscopy demonstrated that the p150 antigen, like PIM, is located in the microspheres of the sporozoites and is exocytosed following sporozoite invasion of the host lymphocyte. By immunoelectron microscopy p150 was subsequently transiently detectable on the sporozoite surface and in the lymphocyte cytosol. Immunoblotting showed that p150 is also expressed by the schizont stage, but at much lower levels compared to the sporozoite. These results suggest a major role for p150 in the early events of host–sporozoite interaction.

Type
Research Article
Copyright
1998 Cambridge University Press

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