Researchers have uncovered a key mechanism behind the human-specific pathogenicity of Salmonella Typhi, the bacterium that causes typhoid fever. This discovery could lead to new strategies for preventing and treating typhoid fever, a life-threatening disease that affects millions of people worldwide.

Typhoid fever is characterized by high fever, abdominal pain, and diarrhea. The disease is transmitted through contaminated food or water and is most common in developing countries with poor sanitation and hygiene.

Salmonella Typhi is closely related to other Salmonella species that cause food poisoning. However, unlike these other Salmonellae, S. Typhi has evolved to target only humans. The reasons for this human-specific pathogenicity have not been fully understood.

In a new study published in the journal Nature Microbiology, researchers from the Wellcome Sanger Institute and their collaborators identified a key factor that enables Salmonella Typhi to invade and replicate inside human cells. This factor is a protein called SopE2, which is located on the surface of S. Typhi bacteria.

SopE2 binds to a receptor protein called CD18 on human cells. This binding allows S. Typhi bacteria to enter the cells and replicate, causing disease. Other Salmonellae lack SopE2 and therefore cannot bind to CD18 or invade human cells.

"Our study reveals how S. Typhi exploits a specific human receptor to establish infection," said Dr. Akhilesh Pandey, a lead author of the study from the Wellcome Sanger Institute. "This understanding could lead to the development of new therapies that block the interaction between SopE2 and CD18, potentially preventing or treating typhoid fever."

Typhoid fever is a major public health problem, causing an estimated 11-21 million cases and over 150,000 deaths each year. The disease is particularly prevalent in South Asia and sub-Saharan Africa, where access to clean water and sanitation is limited.

Current vaccines against typhoid fever are moderately effective, but they do not provide complete protection and can be expensive. New drugs are needed to treat typhoid fever, particularly in regions where antibiotic resistance is becoming more common.

The discovery of the role of SopE2 in S. Typhi infection could lead to the development of new vaccines and drugs that target this protein and prevent or treat typhoid fever.