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Identification and characterization of three Encephalitozoon cuniculi strains
E S Didier1, C R Vossbrinck, M D Baker
1Department of Microbiology, Tulane Regional Primate Research Center, Covington, LA 70433, USA.
Abstract:
Microsporidia are increasingly recognized as causing opportunistic infections in immunocompromised individuals. Encephalitozoon cuniculi is probably the most studied mammalian microsporidian that infects insects and mammals, including man. In this study, 8 E. cuniculi isolates were compared and were found to fall into 3 strains. Strain type I includes the rabbit type isolate, as well as isolates from an additional rabbit, a dwarf rabbit, and a mouse. Strain type II includes 2 murine isolates and strain type III includes 2 isolates obtained from domestic dogs. By SDS-PAGE, the 3 strains differ primarily in the molecular weight range of 54-59 kDa where strain type I displays an apparent broad singlet at 57 kDa, strain type II displays an apparent doublet at 54 and 58 kDa, and strain type III displays an apparent broad band at 59 kDa. Antigenic differences were detected in the molecular weight regions of 54-58 kDa as well as 28-40 kDa by Western blot immunodetection using murine antisera raised against E. cuniculi, Encephalitozoon hellem, and the Encephalitozoon-like Septata intestinalis. Polymerase chain reaction (PCR) products containing only small subunit rDNA sequences from the different E. cuniculi isolates formed homoduplexes whereas PCR products containing intergenic rRNA gene sequences formed heteroduplexes in mobility shift analyses. Fok I digestion of the PCR products containing the intergenic rRNA gene region resulted in unique restriction fragment length polymorphism patterns, and DNA sequencing demonstrated that in the intergenic spacer region, the sequence 5'-GTTT-3' was repeated 3 times in strain type I, twice in strain type II, and 4 times in strain type III. This study indicates that there exist at least 3 E. cuniculi strains which may become important in the epidemiology of human E. cuniculi infections. Furthermore, as additional E. cuniculi isolates are characterized, these strains will be named or reclassified once the criteria for taxonomy and phylogenetic tree construction for microsporidia become better defined.
Insights
Three distinct strains of Encephalitozoon cuniculi were identified using molecular and antigenic methods. These Encephalitozoon cuniculi strains have implications for understanding opportunistic infections in humans.
Area of Science:
- Medical Mycology
- Parasitology
- Molecular Biology
Background:
- Microsporidia are opportunistic pathogens, with Encephalitozoon cuniculi being a significant mammalian-infecting species.
- E. cuniculi infections pose risks to immunocompromised individuals, necessitating a deeper understanding of its diversity.
Purpose of the Study:
- To differentiate and characterize various isolates of Encephalitozoon cuniculi.
- To investigate the genetic and antigenic variations among E. cuniculi strains.
Main Methods:
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) to analyze protein profiles.
- Western blot immunodetection to assess antigenic differences.
- Polymerase chain reaction (PCR) with subsequent heteroduplex analysis, restriction fragment length polymorphism (RFLP), and DNA sequencing of rRNA gene regions.
Main Results:
- Identified three distinct strains (Type I, II, and III) of E. cuniculi based on SDS-PAGE protein profiles (54-59 kDa region).
- Detected antigenic variations in the 54-58 kDa and 28-40 kDa regions using Western blot.
- PCR and DNA sequencing revealed strain-specific repeat patterns (5'-GTTT-3') in the intergenic spacer region of rRNA genes.
Conclusions:
- At least three distinct strains of Encephalitozoon cuniculi exist, with potential epidemiological significance in human infections.
- Strain characterization is crucial for understanding the transmission and pathogenesis of E. cuniculi.
- Further taxonomic and phylogenetic refinement is needed for microsporidia classification.