Why do Pullorum disease and Fowl typhoid occur only in avian hosts?

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K08029
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Veterinary medical science
• Research Institution: Kitasato University
• Principal Investigator: Okamura Masashi 北里大学, 獣医学部, 准教授 (70374775)
• Co-Investigator(Kenkyū-buntansha): 羽田 健 北里大学, 薬学部, 講師 (00348591)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 家禽チフス / サルモネラ / 鳥類 / 全身感染 / IVIAT / 病原性遺伝子

Outline of Final Research Achievements

Salmonella Gallinarum biovar Gallinarum (SG) is the causative agent of fowl typhoid, which is a lethal, systemic infection only in avian hosts, and the mechanism of its pathogenesis is still unclear. We applied an immunoscreening method, in vivo-induced antigen technology (IVIAT), to identify in vivo-induced genes during chicken infection by SG. An inducible expression library of genomic proteins was constructed from sequenced SG 287/91 and was then screened using adsorbed, pooled chicken sera obtained from experimentally intravenously infected chickens. We successfully identified 28 unique genes expressed in vivo. At least 8 of 28 SG single gene deletion mutants showed lower lethality in 20-day old layer chickens compared with SG wild type. These proteins were implicated in amino acid transport, iron ion transport, outer membrane integrity, and catalysis of redox, most of which were newly found as SG pathogenic factors in this study.

Free Research Field

鳥類疾病学、人獣共通感染症学

Academic Significance and Societal Importance of the Research Achievements

家禽チフスは日本国内では発生していないが、主に家禽生産・輸出国でいまだ常在している。大規模な発生があると、世界的に生産量及び貿易額の増加している鶏肉の供給に重大な影響を及ぼし、その経済被害は甚大となる。使用されているワクチンの予防効果は不完全であり、まだ撲滅には至っていない。本研究で明らかにした遺伝子群は、家禽チフスの新規ワクチンや診断法の開発、そしてこれを標的とした治療薬の開発に応用できるため、感染制御・予防において有用である。また、獣医学領域のみならず、ヒトの腸チフスやパラチフスにも適用範囲を広げれば、途上国での本病の制御にも寄与することが期待される。