Molecular and in vitro growth comparisons of Encephalitozoon hellem isolates from human and bird hosts

Molecular and in vitro comparisons were performed using two isolates of Encephalitozoon hellem, one from an avian host and one from a human host, and one isolate of Encephalitozoon cuniculi from a rabbit. The molecular comparisons were performed by amplifying and sequencing the gene coding for a zinc metallo-aminopeptidase from cDNA and gDNA obtained from each of the isolates. The E. hellem sequences shared >99 % identity between each other and 70% identity with the E. cuniculi sequences. Conserved HEXXH and GXMEN motifs located within the sequences classify the protein as an aminopeptidase of the M1 family, with at least one zinc atom required for catalytic activity.
In vitro growth comparisons of the isolates described above were performed under simulated "mammalian and avian conditions". The models utilized mammalian and avian cell lines and sera at incubation temperatures of 37 ?C and 40 ?C, respectively. Three separate experiments were performed. E. cuniculi grew best under the mammalian model and significantly better than both E. hellem isolates under this model. The E. hellem isolates were able to infect and replicate under both the mammalian and avian models, which reflects the zoonotic potential of these isolates.