The microsporidian species Glugea anomala, G. stephani, G . americanus and Spraguea lophii were compared by using sequence data derived from their small subunit rDNA genes which were amplified by polyrnerase chaln reaction and directly sequenced. These sequence data and published data of G. atherinae were analyzed and were used to infer a phylogenetic tree. The 5 rnicrosporidian fish parasites appeared to be closely related. The higher sequence similarities demonstrated among G. anomala, G. stephani and G. atherinae suggest that these 3 parasites are in fact only 1 species of Glugea. Moreover, the higher sequence similarities between S. lophji and G. americanus support the transfer of the latter Glugea species into the genus Spraguea.

The SSUrDNA and the ITS of different microsporidia from eight fishes, four insects and a shrimp were amplified and digested with restriction enzymes. The generated riboprints suggest a close evolutionary relatioship between Glugea americanus and Spraguea lophii suggesting that Glugea americanus should be renamed Spraguea americanus and that the tissue infected and host origin should be considered of greater taxonomic importance for defining a genus than previously considered. Phylogenetic analysis of the riboprints demonstrates an unidentified microsporidium from a bumper fish (Chloroscombrus chrysurus) is related although not identical to Microgemma ovoidea. a parasite from red band fish. We were also able to distinguish between Glugea anomala and Glugea atherinae and Glugea stephani but were not able to differenciate among the latter two. Insects isolates, Nosema costelytrae, N. hombycis, N. trichoplusiae, Nosema sp. and a shrimp isolate, Agmusoma penaei, are not related to the fish isolates.

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Monoclonal antibodies against spores of Glugea atherinae were obtained after lymphocytic hybridization made from immunized mouse splenocytes. Screening using an indirect enzyme linked immunosorbent assay (ELISA), revealed seven monoclonal antibodies with an intense but variable reaction with the spores of fish microsporidia, and a moderate reaction with those of an insect microsporidium (Nosema sp.). The reaction was weaker with spores of Encephalitozoon intestinalis found in HIV' patients. FITC and Dot Blot confirmed the majority of these results. After biotinylation of the seven antibodies, inhibition tests allowed the localization of two different recognition domains on the spores of Glugea atherinae. The multiple antigenic determinants and their probable polysaccharide nature seem to be in accord with the class IgM of the antibodies produced. This work confirms the potential of these antibodies for microsporidian taxonomy and diagnosis, especially the use of Mabs 12F9 and 12H5 for detection of spores in stools of HIV' patients.

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