Abstract: AIM:To analyse the gene encoding a 90 k Da variant- specific- surface protein (CRISP90 ) expressed by a Giardia isolate,02-4 A1in comparison to the variant- specific- surface protein(VSP) gene.METHODS:The polymerase chain reaction(PCR) ,the cloning PCR product and the sequencing of the inserted gene fragment were used.RESUL TS:The near- full length CRISP90 gene was found to be 2019bp long,encode a 654 amino acid polypeptide and contained a single open reading frame (ORF) .The deduced polypeptide sequence is rich in cysteine (11.8 mol% ) , most of which occur within 26 copies of the 42 amino acid CXXC motif. This polypeptide is also rich in threonine (11.3 mol% ) , glycine (1019 mo l% ) and alanine (1011 mo l% ) and includes two NXS consensus N-linked glycosylation sites. CONCLUSION: Like other previously identified VSPs, it contains a highy conserved hydrophobic C-terminal region. The gene sequence showed 56% homology with the CRP 72

Key words: Giardia lamblia, variant- specific surface antigen, gene cloning, polymerase chain reaction, sequence