Growth Characteristics of Rickettsia Species LON Strains Closely Related to Rickettsia japonica Isolated from Haemaphysalis longicornis Ticks in Mouse Derived L929 and Human-Derived THP-1 Host Cell Lines

Non-pathogenic Rickettsia species LON strains closely related to an agent of Japanese spotted fever (JSF), R. japonica, were isolated in Japan from Haemaphysalis longicornis ticks in 2001. However, the biological properties of LONs in mammalian host cells are poorly understood. In this study, micros...

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Published inJapanese Journal of Infectious Diseases Vol. 74; no. 2; pp. 102 - 109
Main Authors Tai, Hitoshi, Su, Hongru, Takamoto, Naoya, Fujita, Hiromi, Takano, Ai, Oishi, Saori, Abe, Fuyuki, Ando, Shuji, Ohashi, Norio
Format Journal Article
LanguageEnglish
Published Japan National Institute of Infectious Diseases, Japanese Journal of Infectious Diseases Editorial Committee 31.03.2021
Japan Science and Technology Agency
Subjects
Biological properties
Biotechnology
Cell lines
Deoxyribonucleic acid
DNA
Fever
generation time
growth curve
Growth kinetics
Haemaphysalis longicornis
L929
Mammalian cells
Mammals
Microscopic analysis
Rickettsia
Rickettsia LON
THP-1
Ticks
growth curve
THP-1
generation time
Rickettsia LON
L929
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Summary:Non-pathogenic Rickettsia species LON strains closely related to an agent of Japanese spotted fever (JSF), R. japonica, were isolated in Japan from Haemaphysalis longicornis ticks in 2001. However, the biological properties of LONs in mammalian host cells are poorly understood. In this study, microscopic analysis showed that LONs in a mouse-derived L929 host cell line were rod shaped with sizes of 0.3–0.5 × 0.5–2.0 μm. Molecular analysis revealed the existence of a LON-specific disrupted open reading frame in R. japonica-related group-specific DNA regions. Growth kinetics of LON-2 and LON-13 strains analyzed by a quantitative real-time PCR showed 100-fold or more increment of LONs cultured in L929 host cells at 30°C and slightly less increment at 33°C, and 25-fold increment in human-derived THP-1 host cells at 35°C on day 7 (168 h) post infection. The generation times of the two LON strains cultured in L929 and THP-1 were estimated to be 9.4–12.9 h and 9.6–10.9 h, respectively. To our knowledge, this is the first report on the biological characteristics of Rickettsia sp. LON strains in mammalian cells, which may provide significant information for the experimental approaches for other rickettsiae.
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ISSN:1344-6304
1884-2836
DOI:10.7883/yoken.JJID.2020.444