Polymorphism of SPAG-1, a candidate antigen for inclusion in a sub-unit vaccine against Theileria annulata.
SPAG-1, a Theileria annulata sporozoite surface antigen, is a vaccine candidate. Data is presented, based on the clonal segregation of SPAG-1 associated RFLPs, showing that this antigen is encoded by a single copy gene. We have cloned and sequenced a full-length genomic copy of the SPAG-1 gene and a comparison of this with a previously published SPAG-1 cDNA sequence demonstrates a high degree of polymorphism. We infer that these sequences represent two distinct allelic SPAG-1 variants. The deduced polypeptides show an overall identity of 92% with the most variable stretch (60% identity) occurring towards the middle of the molecule. The N and C termini are more conserved with identities of 92% and 97% respectively. The elastin receptor ligand, VGVAPG, present 3 times in the protein sequence derived from the cDNA is not found in that deduced from the genomic copy. Evidence for 2 further SPAG-1 alleles was obtained from PCR based sequences using macroschizont clones containing different SPAG-1 associated RFLPs. In summary we have shown the existence of at least 4 highly polymorphic SPAG-1 alleles. The implications of such polymorphism between and within distinct geographical isolates for the development of a SPAG-1 based subunit vaccine is discussed.
Department of Biology, University of York, UK.
F
F
Katzer
M
M
Carrington
P
P
Knight
S
S
Williamson
A
A
Tait
I W
IW
Morrison
R
R
Hall
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics*; D000954:Antigens, Surface / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D016054:DNA, Protozoan / Q000235:genetics; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000235:genetics*; D016052:Protozoan Vaccines / Q000302:isolation & purification*; D016796:Theileria annulata / Q000235:genetics* / Q000254:growth & development / Q000276:immunology*; D014614:Vaccines, Synthetic / Q000302:isolation & purification
D000953:Antigens, Protozoan; D000954:Antigens, Surface; D016054:DNA, Protozoan; D015800:Protozoan Proteins; D016052:Protozoan Vaccines; D014614:Vaccines, Synthetic; C091729:SPAG-1 antigen, Theileria annulata