News in Science

Anti-typhoid gene raises vaccine hopes

Protective gene Scientists have found a variant of a gene that confers a near five-fold protection against typhoid fever, which kills millions of people each year.

The discovery, published in the journal Nature Genetics, came from screening the genomes of hundreds of infected people and healthy controls in Vietnam and Nepal.

The study's authors say the findings from the first large-scale search for genes that affect a person's risk of getting typhoid fever may aid the development of better vaccines for this and other invasive bacterial diseases.

"We found that carrying a particular form of the HLA-DRB1 gene provides natural resistance against typhoid fever," says the study's lead author Dr Sarah Dunstan of the University of Melbourne.

People with typhoid fever usually have a high fever, abdominal pain, and headache. Typhoid fever can lead to bowel perforation, shock, and death.

According to the World Health Organization (WHO), about 21 million people are infected with typhoid fever every year, and an estimated 216,000 to 600,000 die.

It is caused by the Salmonella typhi or Salmonella paratyphi bacteria carried in contaminated food or water.

The gene protects against infection by recognising proteins from invading bacteria, thus stimulating an immune response.

Better treatments and vaccines are needed for typhoid fever as the infecting bacteria are getting increasingly more resistant to antibiotic treatment, and the current vaccine is only moderately effective and does not protect against paratyphoid fever, say the authors.

Vaccines against S. typhi do exist, but are not always effective and are not suitable for young children -- the group most at risk.

"Consequently, these vaccines are not widely deployed in the populations with the greatest need.

"Notably, there is currently no licensed vaccine against enteric fever caused by S. Paratyphi pathovars, potentially constituting a huge problem as the incidence of S. Paratyphi A infection is increasing in many countries across Asia," they write.

The international collaboration included scientists from the Genome Institute of Singapore and Oxford University Clinical research units in Vietnam and Nepal.