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Size heterogeneity among antigenically related Giardia lamblia variant-specific surface proteins is due to
M R Mowatt1, B Y Nguyen, J T Conrad
1Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892.
Abstract:
Giardia lamblia undergoes antigenic variation by modulating the expression of the different genes that comprise the trophozoite's variant-specific surface protein (VSP) repertoire. We studied an epitope that is conserved among VSPs expressed by cloned trophozoite lines derived from the independent G. lamblia isolates WB, G3M, Be-2, and CAT. The epitope recognized by monoclonal antibody 6E7 lies entirely within the region of tandemly repeated 65-amino-acid units that is characteristic of these size-variant VSPs. Northern (RNA) hybridization, cDNA cloning, and DNA sequence analysis indicate that size heterogeneity among these VSPs is due to differences in the number of repetitive units.