Isolation ofTwoGiardia lamblia (WBStrain) Clones withDistinct Surface Protein andAntigenic Profiles andDiffering Infectivity andVirulence

test using apolyclonal rabbit anti-G. lamblia trophozoite serum madeagainst theparent strain. Twoclones were chosen forfurther studies: a highly fluorescent clone, F+,in which more than95%ofthetrophozoites fluoresced, andalow-fluorescence clone, F-,inwhichfewerthan5% fluoresced. Sodiumdodecyl sulfate-polyacrylamide gradient gelelectrophoresis andenzyme-linked immunotransfer blot studies ofthemembranefractions ofthetwoclones andparent strain revealed differences in boththetotal protein andantigenic profiles. A serum cytotoxicity test withthepolyclonal serum showedthat theF+clones were more susceptible toimmobilization andkilling, whilethemajority ofcells oftheF-clones were resistant tosuchkilling. Assessment oftheinfectivity ofthetwoclones intheMongolian gerbil animal modelindicated that theF-clone more readily initiated infections, produced more cysts, hadahigher intestinal trophozoite load, andproduced a more severeclinical syndrome, whiletheF+clone was less phenotypically stable invivoandinsome casestooklonger tobecleared fromtheintestine.