Mam. Santos et al., THE IDENTIFICATION AND MOLECULAR CHARACTERIZATION OF TRYPANOSOMA-CRUZI AMASTIGOTE SURFACE PROTEIN-1, A MEMBER OF THE TRANS-SIALIDASE GENE SUPER-FAMILY, Molecular and biochemical parasitology, 86(1), 1997, pp. 1-11
An accumulating body of evidence suggests that T. cruzi-infected host
cells are recognized and destroyed by class I major histocompatibility
complex (MHC) restricted CD8(+) T-cells thus contributing to immune c
ontrol of the infection [1-6]. However, to date, only a few amastigote
proteins which could be the target of this response have been describ
ed and gene sequence information is available only for the amastins [7
]. In order to identify amastigote proteins which could contribute to
immune detection of infected host cells, a panel of monoclonal antibod
ies specific for amastigote proteins was produced and screened. Three
mAbs (IIIC4, VIIC1 and IIID4) were identified which recognized amastig
ote surface proteins of 78, 26 and 53 kDa, respectively. Screening of
an amastigote cDNA expression library with mAb IIIC4 resulted in the i
solation of a 2.8 Kb clone, pSI2. The derived amino acid sequence indi
cates that the pSI2 clone encodes an amastigote surface protein belong
ing to the T. cruzi trans-sialidase super-family. Based on its prefere
ntial expression in the amastigote stage we have named this protein am
astigote surface protein-1 (ASP-1). ASP-1 contains the third and fourt
h Asp block motifs, SxDxGxTW and the fibronectin type III-like domain,
VTVxNVxLYNR, thus placing it in family II of the T. cruzi trans-siali
dases [8]. ASP-1 is the first trans-sialidase family member shown to b
e preferentially expressed in the amastigote stage of the T. cruzi lif
e cycle. This expression of ASP-I on parasites in infected cells and i
ts apparent membrane attachment by a glycosylphosphatidylinositol (GPI
)-anchor makes it a prime candidate to enter the class I MHC processin
g and presentation pathway. (C) 1997 Elsevier Science B.V.