Understanding the human infectivity in Tyrpanosoma species

2019 Fiscal Year Final Research Report

• Project/Area Number: 17K15366
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Veterinary medical science
• Research Institution: Hokkaido University
• Principal Investigator: Hayashida Kyoko 北海道大学, 人獣共通感染症リサーチセンター, 特任助教 (40615514)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: トリパノソーマ原虫 / 進化 / ゲノム / 人獣共通感染症

Outline of Final Research Achievements

Human had evolved to acquire the natural immunity against Trypanosoma infection, called Trypanolytic factor (TLF) in its serum. On the other hand, two Trypanosome species evolved to acquire the mechanism to combat with human anti-Trypanosome immune system, allowing to infect humans. To better understand of host-parasite interaction of the Trypanozoon parasite, we adapted T. evansi parasite into human-serum added media in vitro. Genome-wide transcription analysis using RNA-seq revealed that, several genes are differentially expressed comparing the original strain in these human-serum resistant parasite clones. Notably, the expression of HpHbR gene, that encodes the parasite receptor of TLF was significantly downregulated. This result provided a possible mechanism of African Trypanosoma to acquire human serum resistance, and proposed the potential risk of animal-infective Trypanosoma to become an potential zoonotic parasite.

Free Research Field

寄生虫学

Academic Significance and Societal Importance of the Research Achievements

ヒトのアフリカ睡眠病を引き起こすTrypanosoma brucei と、家畜の病原体であるT. evansiは近縁関係にあるが後者はヒト血清抵抗性を有さない。本研究ではT. evansiを試験管内でヒト血清へ馴化し網羅的遺伝子解析を行った。結果、ヒトの抗トリパノソーマ因子TLFのレセプターHpHbRの発現が血清抵抗性T. evansiで減少していることを明らかにした。本知見はヒト血清抵抗性の獲得という現象が、Trypanozoon亜属に共通して起こりうる現象であることを示唆する。T. evansiが新たな人獣共通感染症の原因となりうるのか、今後慎重に検討すべき課題であると考えられる。