Research Article

Alpha 2 giardin is an assemblage A-specific protein of human infective Giardia duodenalis

R. F. L. STEUARTa1 c1, R. O'HANDLEYa1, R. J. LIPSCOMBEa2, R. A. LOCKa2 and R. C. A. THOMPSONa1

a1 WHO Collaborating Centre for the Molecular Epidemiology of Parasitic Infection and Environmental Biotechnology CRC, School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, 6150, Western Australia

a2 Proteomics International Pty Ltd, PO Box 6064, East Perth 6892, Western Australia


Of the 7 genetic assemblages of the parasite Giardia duodenalis only 2 (A and B) are known to cause infections in humans. These assemblages have been characterized in detail at the genomic level but few studies have examined differences in the proteins expressed. Employing one and two-dimensional PAGE we have identified an assemblage A-specific protein of human infective G. duodenalis; alpha 2 giardin. The protein difference was evident using both electrophoretic techniques. Alpha 2 giardin is known to be a structural protein and associates with the caudal flagella and the plasma membrane; however, its exact function is unknown. Although several proteins unique to assemblage B were also observed, we were unable to identify these proteins due to a lack of genomic data available for assemblage B isolates. Together, these proteins represent distinct phenotypic differences between the human infective assemblages of G. duodenalis and support the need to revise the taxonomy of this parasite.

(Received May 21 2008)

(Revised July 07 2008)

(Revised August 11 2008)

(Accepted August 11 2008)

(Online publication October 22 2008)


c1 Corresponding author: School of Veterinary and Biomedical Science, Murdoch University, Murdoch, 6150, Western Australia. Tel: +61 8 9360 2690. E-mail: