Salmonella Enteritidis activates inflammatory storm via SPI-1 and SPI-2 to promote intracellular proliferation and bacterial virulence

Dan Xiong; Li Song; Yushan Chen; Xinan Jiao; Zhiming Pan

doi:10.3389/fcimb.2023.1158888

Salmonella Enteritidis activates inflammatory storm via SPI-1 and SPI-2 to promote intracellular proliferation and bacterial virulence

Front Cell Infect Microbiol. 2023 May 30:13:1158888. doi: 10.3389/fcimb.2023.1158888. eCollection 2023.

Authors

Dan Xiong^{1

2

3}, Li Song^{1

2

3}, Yushan Chen^{1

2

3}, Xinan Jiao^{1

2

3}, Zhiming Pan^{1

2

3}

Affiliations

¹ Jiangsu Key Laboratory of Zoonosis, Yangzhou University, Yangzhou, China.
² Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, China.
³ Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, Ministry of Agriculture and Rural Affairs, Yangzhou University, Yangzhou, China.

Abstract

Salmonella Enteritidis is an important intracellular pathogen, which can cause gastroenteritis in humans and animals and threaten life and health. S. Enteritidis proliferates in host macrophages to establish systemic infection. In this study, we evaluated the effects of Salmonella pathogenicity island-1 (SPI-1) and SPI-2 to S. Enteritidis virulence in vitro and in vivo, as well as the host inflammatory pathways affected by SPI-1 and SPI-2. Our results show that S. Enteritidis SPI-1 and SPI-2 contributed to bacterial invasion and proliferation in RAW264.7 macrophages, and induced cytotoxicity and cellular apoptosis of these cells. S. Enteritidis infection induced multiple inflammatory responses, including mitogen-activated protein kinase (ERK-mediated) and Janus kinase-signal transducer and activator of transcript (STAT) (STAT2-mediated) pathways. Both SPI-1 and SPI-2 were necessary to induce robust inflammatory responses and ERK/STAT2 phosphorylation in macrophages. In a mouse infection model, both SPIs, especially SPI-2, resulted in significant production of inflammatory cytokines and various interferon-stimulated genes in the liver and spleen. Activation of the ERK- and STAT2-mediated cytokine storm was largely affected by SPI-2. S. Enteritidis ΔSPI-1-infected mice displayed moderate histopathological damage and drastically reduced bacterial loads in tissues, whereas only slight damage and no bacteria were observed in ΔSPI-2- and ΔSPI-1/SPI-2-infected mice. A survival assay showed that ΔSPI-1 mutant mice maintained a medium level of virulence, while SPI-2 plays a decisive role in bacterial virulence. Collectively, our findings indicate that both SPIs, especially SPI-2, profoundly contributed to S. Enteritidis intracellular localization and virulence by activating multiple inflammatory pathways.

Keywords: Inflammatory pathway; Salmonella Pathogenicity Island; bacterial colonization; macrophage; mouse infection model.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Bacterial Proteins / genetics
Bacterial Proteins / metabolism
Cell Proliferation
Disease Models, Animal
Genomic Islands*
Humans
Mice
Salmonella enteritidis* / genetics
Virulence

Substances

Bacterial Proteins
lambda Spi-1

Grants and funding

This work was funded by the National Natural Science Foundation of China (32102669, 31972685, 31920103015 and 32102679), the Natural Science Foundation of Jiangsu Province (BK20210802), the China Postdoctoral Science Foundation (2020M681748), the Postdoctoral Science Foundation of Jiangsu Province (2021K095A), the 111 Project (D18007), and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).