Comparative virulence analysis of seven diverse strains of Orientia tsutsugamushi reveals a multifaceted and complex interplay of virulence factors responsible for disease
Issued Date
2025-06-01
Resource Type
ISSN
15537366
eISSN
15537374
Scopus ID
2-s2.0-105009514277
Journal Title
Plos Pathogens
Volume
21
Issue
6 June
Rights Holder(s)
SCOPUS
Bibliographic Citation
Plos Pathogens Vol.21 No.6 June (2025)
Suggested Citation
Chaichana P., Satapoomin N., Kullapanich C., Chuenklin S., Mohammad A., Inthawong M., Ball E.E., Burke T.P., Sunyakumthorn P., Salje J. Comparative virulence analysis of seven diverse strains of Orientia tsutsugamushi reveals a multifaceted and complex interplay of virulence factors responsible for disease. Plos Pathogens Vol.21 No.6 June (2025). doi:10.1371/journal.ppat.1012833 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/111149
Title
Comparative virulence analysis of seven diverse strains of Orientia tsutsugamushi reveals a multifaceted and complex interplay of virulence factors responsible for disease
Corresponding Author(s)
Other Contributor(s)
Abstract
Orientia tsutsugamushi is an obligate intracellular bacterium found in Leptotrombidium mites that causes the human disease scrub typhus. A distinguishing feature of O. tsutsugamushi is its extensive strain diversity, yet differences in virulence between strains are not well defined nor well understood. We sought to determine the bacterial drivers of pathogenicity by comparing seven strains using murine infections combined with epidemiological human data to rank each strain in terms of relative virulence. Murine cytokine expression data revealed that the two most virulent strains, Ikeda and Kato, induced higher levels of IL-6, IL-10, IFN-γ and MCP-1 than other strains, consistent with increased levels of these cytokines in patients with severe scrub typhus. We sought to identify the mechanistic basis of the observed differential virulence between strains by comparing their genomes, in vitro growth properties and cytokine/chemokine induction in host cells. We found that there was no single gene or gene group that correlated with virulence, and no clear pattern of in vitro growth rate that predicted disease. However, microscopy-based analysis of the intracellular infection cycle revealed that the only fully avirulent strain in our study, TA686, differed from all the virulent strains in its subcellular localisation and expression of its surface protein ScaC. This leads us to a model whereby drivers of pathogenicity in Orientia tsutsugamushi are distributed throughout the genome, likely in the large and varying arsenal of effector proteins encoded by different strains, and that these interact in complex ways to induce differing immune responses and thus differing disease outcomes in mammalian hosts.