Immunological inter-strain crossreactivity correlated to 18S rDNA sequencetypes in Acanthamoeba spp.

Various species of the genus Acanthamoeba have been described as potential pathogens; however, differentiation of acanthamoebae remains problematic. T he genus has been divided into 12 18S rDNA sequence types, most keratitis c ausing strains exhibiting sequence type T4. We recently isolated a keratiti s causing Acanthamoeba strain showing sequence type T6, but being morpholog ically identical to a T4 strain. The aim of our study was to find out, whet her the 18S rDNA sequence based identification correlates to immunological differentiation. The protein and antigen profiles of the T6 isolate and thr ee reference Acanthamoeba strains were investigated using two sera from Aca nthamoeba keratitis patients and one serum from an asymptomatic individual. It was shown, that the T6 strain produces a distinctly different immunolog ical pattern, while patterns within T4 were identical. Affinity purified an tibodies were used to further explore immunological cross-reactivity betwee n sequence types. Altogether, the results of our study support the Acantham oeba 18S rDNA sequence type classification in the investigated strains. (C) 2001 Australian Society for Parasitology Inc. Published by Elsevier Scienc e Ltd. All rights reserved.