Dengue fever : why patients do not have all of the symptoms

mrfiza/epictura

Published the 25.09.2017 at 16h44

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denguesystème immunitaireInstitut Pastor

The ESSENTIAL

Each year, 50 to 100 million new dengue cases are reported.
500 000 cases are severe, and 2.5 % are fatal.
Half of the world’s population lives in an area at risk.
18 French departments are affected, including some in the metropolis.

Dengue is a silent infection. At least three out of four cases do not cause symptoms. Why ? The researchers of the Institut Pasteur – Paris and Cambodia – may be the answer and engage in Science Translational Medicine. They noticed that the immune system is activated differently in asymptomatic patients.

Understand the mechanisms of infection by the dengue virus presents the main challenge of the research. It is, indeed, an essential step in the development of a preventive vaccine to be effective. To better understand the immune response to the virus, biologists at the Pasteur Institute have taken the serum plasma levels of 85 children living in Cambodia.

Some of these young patients have presented symptoms of the infection, others do not. And these latter have a reaction to very specific. Their body produces more of the protein, indicating the antigen – which allows you to attack the virus. But immune activation is extremely controlled. T lymphocytes and antibodies are reduced to their strict minimum.

A more effective vaccine

To the extent that the magnitude of the immune response determines the severity of the symptoms, their absence, therefore, seems logical. But for the director of the Genetics unit of functional of infectious diseases, these results lead further.

“Exploring patients who are infected but asymptomatic, this study helps to understand the mechanisms that make it possible to not develop the symptoms following an infection,” explains Anavaj Sakuntabhai in a press release. And, why not, lead to the implementation of a preventive vaccine more effective.

At the present time, such a product is available, but it remains partially effective. Its impact is limited on certain serotypes of the dengue – and there are four different. In addition, act on the immune response could lead to the development of a specific treatment. For the time being, only the appearance of symptomatic disease is focused.