A novel obligately intracellular bacterium, ileal symbiont intracellularis, which was obtained from the intestines of pigs with proliferative enteropathy disease, was grown in pure cocultures with tissue cultures of rat cells. An examination of the 16s ribosomal DNA gene sequence revealed that the isolates which we obtained are members of the delta subdivision of the Proteobucteriu and that the sequences of these organisms exhibit a level of similarity of 91% with the sequence of Desulfovibrio desulfuricuns ATCC 27774. These isolates were homogeneous and differed in cellular morphology, acid fastness, phenotype, electrophoretic protein profile, and habitat from Desulfovibrio species. On the basis of the results of an integrated study of the phenotype and genotype of a consistent morphological entity found in particular porcine cells and associated with a welldefined clinical condition, we concluded that these bacteria belong to a previously undescribed genus and species, for which we propose the name Luwsoniu intrucelluluris gen. nov., sp. nov. A species-specific recombinant DNA probe was cloned previously, and this probe was used to identify the bacterium in tissue culture cells and in the ileal epithelia of pigs with proliferative enteropathy disease. Coculture of the organism with a rat enterocyte cell line allowed us to designate strain NCTC 12656 the type strain and to describe the new genus and species. The organism which we cultured is pathogenic for pigs and causes proliferative enteropathy lesions in their ilea and colons, and Koch's postulates were fulfilled for this organism.The recently described organism ileal symbiont (IS) intracellularis (5) was given a vernacular name until its taxonomic position could be clarified. Classification of IS intracellularis has been problematic because this organism is an obligately intracellular bacterium, which has been cultured only in established rat enterocyte cell cultures (11). Taxonomic studies of the organism before cultured organisms were available were performed with bacteria purified directly from infected tissues (5, 6, 12). It was found that this intracellular bacterium had novel immunological and DNA probe reactions (6, 12, 13) compared with those of Campylobacter species.A subsequent taxonomic study of IS intracellularis in which the 16s ribosomal DNA (rDNA) was amplified and sequenced clearly revealed that the purified intracellular bacteria were homogeneous and belonged to the delta subdivision of the class Proteobacteria (5). The DNA sequences determined for each purified bacterial preparation were most similar to the sequences of a sulfate-reducing proteobacterium, Desulfovihrio desulfiricans (level of sequence similarity, 91%). There is considerable interest in the taxonomic position of IS intracellularis because of the etiologic role of this organism in proliferative enteropathy, a major disease that affects the economics of pig industries worldwide (14, 19).The natural habitat of IS intracellularis is lying not bound by membranes within the cyto...

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Bovine macrophage-derived tumour necrosis factor-alpha/cachectin (TNF-alpha) was synthesized when peripheral blood mononuclear cells (PBMC) and purified adherent PBMC from naive and Theileria annulata-infected cattle were incubated in vitro with concanavalin A (Con-A) or bovine recombinant interferon gamma (Bo rIFN-gamma). TNF-alpha production was also induced when adherent PBMC were cultured with T. annulata macroschizont-infected cells. In contrast, non-adherent PBMC from sublethally infected cattle produced interferon (IFN) when incubated with Hu rIL-2, Con-A, phytohaemagglutinin (PHA) or T. annulata macroschizont-infected cells growing as cell lines in vitro. Whilst PBMC from lethally infected cattle spontaneously produced IFN-gamma during advanced stages of infection, the sera of such animals contained type 1 IFN (alpha/beta). IFN was also produced by T. annulata macroschizont-infected cell lines maintained in vitro. This work suggests that cytokines serve as crucial links between proliferating Theileira-infected cells and the characteristic clinical symptoms of tropical theileriosis.