Use of nucleotide sequence data to identify a microsporidian pathogen of Pieris rapae (Lepidoptera, Pieridae).

Nucleotide sequence was determined for a portion of genomic DNA which spans the V4 variable region of the small subunit ribosomal RNA gene of an unidentified microsporidium from the cabbage white butterfly, Pieris rapae (174 base pairs). Comparison with equivalent sequence data obtained here for two other microsporidian species, Nosema bombycis (240 base pairs) and Nosema bombi (200 base pairs), and from the GenBank database for 11 other microsporidian species suggests that the unidentified species from P. rapae is most closely related to some Vairimorpha species. Light and electron microscopic observations of the developmental stages of this parasite were in accord with this. Infection experiments conducted at 20 and 26 degrees C demonstrated temperature-dependent dimorphism, with the production of both binucleate free spores (mean dimensions: 3.8 x 1.8 microns; 10-13 polar filament coils) and membrane-bound uninucleate octospores (mean dimensions: 3.1 x 1.9 microns). Macrospores (mean dimensions 8.0 x 2.1 microns) were also observed. Sites of infection were the gut epithelium, the Malpighian tubules, the salivary glands, and the fat body. Infections were found in all insect life stages, including the egg. This microsporidium was found to be indistinguishable from both Nosema mesnili (Paillot) and Microsporidium (Thelohania) mesnili (Paillot) and we propose that these species be combined and transferred to the genus Vairimorpha Pilley.

DNA probes for two Microsporidia, Nosema bombycis and Nosema costelytrae.

Two DNA fragments which hybridize specifically with DNA of Nosema bombycis and Nosema costelytrae, respectively, were obtained from genomic DNA of each microsporidian species and sequenced. Neither fragment hybridized with genomic DNA from four other microsporidian isolates tested: Nosema apis, Vairimorpha sp. from cabbage white butterfly (Pieris rapae), and two isolates of Vavraia oncoperae, one from New Zealand grass grubs, Costelytrae zealandica, and another from porina caterpillars, Wiseana spp. The probe for N. bombycis did not hybridize with genomic DNA from N. costelytrae or with DNA from silkworms (Bombyx mori), the primary insect host of this microsporidium. Likewise, the probe for N. costelytrae did not hybridize with genomic DNA from N. bombycis or with DNA from grass grubs (C. zealandica). Both fragments were AT-rich (59 and 79% of total bases, respectively), had G+C/A+T ratios of 0.70 and 0.25, respectively, and represented repeated sequences dispersed throughout the genome.

Fibrosing cholestatic hepatitis and HBV after bone marrow transplantation.

Liver failure caused by reactivation of hepatitis B virus (HBV) is an uncommon complication of bone marrow transplantation. Fibrosing cholestatic hepatitis is a recently described liver lesion that develops in some patients undergoing liver transplantation for chronic HBV infection. The lesion is characterised by peri portal fibrosis, ballooning degeneration of hepatocytes, prominent cholestasis and paucity of inflammation. Recent data suggests it is a cytopathic effect of the pre-core mutant form of HBV with over-expression of viral antigens. Although only one case has so far been described associated with bone marrow transplantation (BMT) it is likely that increasing use of BMT in people with chronic HBV infection will lead to further patients being recognised.