Evaluation of T cell recognition of Theileria Parva homologs of apicomplexan antigens
Abstract
East Coast fever is a severe lymphoproliferative disease of cattle caused by the intracellular
protozoan Theileriaparva from the family Apicomplexa, CD8+ cytotoxic T lymphocyte (CTL)
mediated destruction of parasite infected lymphocytes constitutes the dominant protective
immune response following exposure to infection or vaccination using a live infection and
treatment protocol. Appropriate delivery of parasite antigens targeted by CTL from T parva
immune cattle has long been proposed as a strategy for the development of a subunit vaccine that
would contribute substantially to a sustainable integrated ECF control program. Gene homologs
encoding antigens from other apicomplexan parasites constitute a source of vaccine candidate
antigens. The aim of this study was to evaluate the recognition of T parva homologs of known
apicomplexan antigens by CD8+ and CD4+ T lymphocytes isolated from cattle immunized by a
live vaccine. Eight T parva homo logs of apicomplexan antigens were sub-cloned into a
eukaryotic expression vector and transiently transfected into bovine antigen presenting cells
(APC). Recognition of transfected APC by T parva specific CD8+ CTL lines was assessed using
an IFN-y ELISpot assay but none of the 7 CTL lines tested recognized any of the homologs. A
recombinant protein was generated representing atruncated version of one T parva protein
designated X9-3 (a homolog of T Complex Protein-I zeta subunit in Babesia microti) and tested
in immunoassays for recognition by T cells from immune cattle. Peripheral blood mononuclear
cells from 3112cattle and a T parva specific polyclonal CD4+ T cell line from immune cattle
BW014 responded to the X9-3 protein. The results suggest that none of the eight homolog genes
are CTL target antigens but X9-3 is a candidate T-helper cell target antigen and should be
considered for inclusion in a subunit vaccine against ECF
Citation
M.Sc (Biochemistry)Sponsorhip
University of NairobiPublisher
School of Medicine, University of Nairobi
Description
Master of Science Thesis