How the stealth food poisoning bacteria ‘Salmonella’ evades immunity

Cells and surrounding vacuoles divide together, being larger than the lysosomes of immune cells
Self-produced protein SopB prevents immune cells from producing lysosomes
Anticipating infection prevention using small molecule inhibitors or TFEB activators

Food poisoning, which always appears in summer when food is easily spoiled due to high temperature, can be cured with conservative treatment to prevent dehydration, but if it is severe, it can lead to death, so prevention is important Recently, a new study related to Salmonella, the causative agent of food poisoning, has appeared. The study, which revealed how Salmonella evades the body’s immunity, may help fight food poisoning infections in the future.

Person with stomach ache / Photo source – Pripic

According to a paper published in Science Direct by researchers from the Department of Microbiology and Cell Biology (MCB) at the Indian Institute of Science (IISc) in April, Salmonella produces a protein called SopB that reduces the fusion and production of lysosomes in immune cells. , thereby increasing the survival rate.

Salmonella, the causative agent of typhoid fever and food poisoning, is a type of proteobacteria belonging to the genus Salmonella of the family Enterobacteriaceae, and is divided into Salmonella enterica and Salmonella Bongori, and has more than 2600 of serotypes (= types of antigen). is further classified as

Foods to pay attention to in summer sanitation / Photo source - Pripic, editor of Newyddion Chemegol
Foods to pay attention to in summer sanitation / Photo source – Pripic, editor of Newyddion Chemegol

Salmonella mainly causes infection by eating undercooked or undercooked poultry, meat, eggs, fruit and vegetables, including fever, diarrhoea, abdominal cramps and headache. In Korea, there were cases of women in their 20s and men in their 60s who ate gimbap and naengmyeon two years ago and last year from food poisoning.

When Salmonella enters the human body, it exists in a bubble-like structure called a vacuole (SVC). Our body’s immune cells that detect the bacteria produce reactive oxygen species (ROS) and reactive nitrogen species (RNS), and the vacuole and the lysosome fuse with the putrid vacuole to operate the manual to destroy the bacterial cell.

However, Salmonella managed to escape the attack of immune cells with a cunning strategy. When a bacterial cell divides, the vacuole also divides to place a new cell inside the vacuole. This strategy outnumbers the lysosomes that fuse with the vacuole, increasing the survival rate and leading to full proliferation.

Salmonella strategy to avoid host cells / Image source -
Salmonella’s strategy to avoid host cells / Image source – Science X, sciencedirect

The research team discovered that SopB, a protein produced by Salmonella bacteria, not only prevents the fusion of vacuoles and lysosomes, but also prevents the formation of lysosomes, and saw how SopB is involved.

Consequently, SopB was found to inhibit the translocation of host cell transcription factor EB (TFEB) from the cytoplasm to the nucleus. Transcription factors are proteins that act as switches that bind to DNA and control the role of target genes. The research team say this finding is very important because TFEB is responsible for the key regulation of lysosomal production.

“This study is novel as it identifies a second mechanism by which SopB prevents vacuole fusion with lysosomes and increases the ratio of vacuole to lysosome for survival,” said Deepsika Chakraborty, MCB professor and author of the study. For reference, a study that SopB mediates epithelial cell proliferation was published in 2004 by a Canadian research team.

The research team suggested that using small molecule inhibitors of SopB or TFEB activators could help fight Salmonella infection.

Chemical News Reporter Park Chan-seo

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