DIFFERENCES IN ANTIGEN EXPRESSION WITHIN AND BETWEEN 10 ISOLATES OF GIARDIA-DUODENALIS

In this study indirect immunofluorescence was performed on both live a nd fixed trophozoites to determine the level of variability in surface antigen expression between 14 Giardia duodenalis isolates, using a mo noclonal antibody raised against the Portland 1 isolate (ATCC No. 3088 8). Subsets of antigen positive cells were detected in 13 isolates ran ging in number from < 1% to 50% of the total population. The differenc es in antigen expression between 10 uncloned isolates did not correlat e with genetic differences determined using isoenzyme analysis. Examin ation of four clones of the Portland 1 isolate showed that all of the progeny expressed surface antigen at significantly different levels to the parent.