1996 Fiscal Year Final Research Report Summary
Studies on the roles of the virulence-associated proteins which are coded by virulence plasmids of Rhodococcus equi in the infection and immunity
| Project/Area Number |
06454119
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied animal science
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| Research Institution | Kitasato University |
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Principal Investigator |
TAKAI Shinji Kitasato University, Faculty of Veterinary Medicine, Associate Professor, 獣医畜産学部, 助教授 (80137900)
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| Co-Investigator(Kenkyū-buntansha) |
MADARAME Hiroo Kitasato University, Faculty of Veterinary Medicine, Lecturer, 獣医畜産学部, 講師 (20173768)
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| Project Period (FY) |
1994 – 1996
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| Keywords | Rhodococcus equi / pathogeincity / plasmid / antigens / horse / infection / virulence / mouse |
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| Research Abstract |
Rhodococcus equi is a well-known pathogen in domestic animals, especially horses, horses, which causes uppurative bronchopneumonia with high mortality in foals aged 1 to 3 months. In the present study, we obtained the following evidence : 1) virulent and avirulent strains exist in R.equi isolates from horses and their environment ; 2) virulent R.equi expresses 15- to 17-kDa antigens and are virulent in mice (LD_<50>=10^6) ; 3) virulent R.equi strains contain an 85- or a 90-kb virulence plasmid and curing of the plasmidattenuates the virulence ; 4) virulence plasmids encode a 15- to 17-kDaantigen gene ; 5) a plasmid-cured mutant does not induce thedisease in foals ; 6) only virulent R.equi strains are isolated from lesions of naturally infectedfoals ; 7) horse-breeding farms with endemicinfection are contaminated heavily with virulent R.equi ; 8) virulence-associated antigens are expressed on the cell surface and regulated by temperature ; 9) expression of virulence-associated antigens
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is regulated by pH ; 10) virulence-associated antigens are expressed within foal macrophages ; 11) the nucleotide sequence of the gene encoding 15- to 17-kDa antigens, located on plasmid pREAT701, has been determined, and the gene encodes a 19-kDa protein of 189 amino acids having an Alanine-rich leader signal sequence. At least five SS peptidase cleavage sites were found in this region, suggesting that the molecular diversity of 15- to 17-kDa antigens may be attributed to the multiple SS peptidase cleavage sites ; 12) the PCR was applied for identifying virulent R.equi rapidly by amplification of gene sequences unique to virulence plasmids, and its usefulness in the detection and identification of virulent R.equi in clinical specimens has been shown ; 13) endogeneous IFN-g and TNF-a play an essential role in the host defense against virulent R.equi infection in mice model.
Further studies are needed to define the roles of the virulence-associated antigens involved in the pathogenesis and immunity of R.equi infection. Less
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