New Delhi, Dec 19 : A team of researchers has found evidence that people who quietly clear the dengue virus without ever developing symptoms may hold important clues to developing new vaccines for the mosquito-borne disease.

While such patients remain difficult to examine directly, the team from Mahidol University in Thailand and the Wellcome Sanger Institute in the UK provided a uniquely detailed single-cell map based on a five-year household surveillance study that followed close contacts of confirmed dengue patients.

The first single-cell immune atlas of asymptomatic dengue, published in Science Translational Medicine, offers a rare look at how the immune system can defeat the virus without triggering illness.

The work could help guide the design of safer and more effective dengue vaccines.

"The detailed cell-level data revealed sharp differences between immune responses in those who became sick and those who did not," said Dr. Waradon Sungnak, an immunologist and computational biologist at Mahidol University.

"Those without symptoms showed distinct patterns in key immune cell types, including CD8 T cells, natural killer cells, and antibody-producing cells such as those making IgA, which set them apart from symptomatic cases," Sungnak added.

Asymptomatic dengue is practically invisible to medical systems: People feel perfectly healthy, rarely seek care, and the window of detectable viruses in the blood is short.

In the five year-survey, only eight true asymptomatic dengue infections were captured while the virus was still in the blood.

"These cases are incredibly rare and valuable. Without them, we might not understand why some people clear dengue without any symptoms."

These eight cases, along with others with mild and severe symptoms, became the foundation for a high-resolution immune map built from over 134,000 individual immune cells, profiled using single-cell RNA sequencing and immune receptor sequencing. said Assoc. Prof. Ponpan Matangkasombut, an immunologist at Mahidol University.

Symptomatic dengue, by contrast, displayed immune hallmarks associated with more harmful processes. The features present in asymptomatic cases were largely absent in symptomatic dengue, which instead showed signs of antibody-mediated viral uptake and inflammation, the researchers said.

Other biological signals helped distinguish asymptomatic cases from more severe diseases.

In addition, cytokine-related signals were also found to be more pronounced in symptomatic dengue, offering clues to why some infections escalate while others resolve.

The findings collectively paint a clearer picture of the push-and-pull between protective antiviral responses and inflammatory pathways that drive symptoms.

/IANS