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Dengue virus exposure may amplify Zika infection

Previous exposure to the dengue virus may increase the potency of Zika infection, according to research from Imperial College London.

The early-stage laboratory findings, published in the journal Nature Immunology, suggests the recent explosive outbreak of Zika may have been driven in part by previous exposure to the dengue virus.

The study, which included scientists from Institut Pasteur in Paris and Mahidol University in Bangkok, suggests the Zika virus uses the body’s own defences as a ‘Trojan horse’, allowing it to enter a human cell undetected. Once inside the cell, it replicates rapidly.

Professor Gavin Screaton, senior author of the research and Dean of the Faculty of Medicine at Imperial, said: “Although this work is at a very early stage, it suggests previous exposure to dengue virus may enhance Zika infection. This may be why the current outbreak has been so severe, and why it has been in areas where dengue is prevalent. We now need further studies to confirm these findings, and to progress towards a vaccine.”

A second study by the same team, published in Nature, suggests an antibody that works against the dengue virus may also neutralise Zika – providing a potential target for a vaccine.

Dengue fever has risen dramatically over recent decades and the virus is thought to cause around 390 million infections each year – with 40 per cent of the world’s population living in areas of risk.

The dengue virus is similar to the Zika virus – they belong to the same viral family, called the Flaviviridae, and both are transmitted by the Aedes mosquito.

In the new Nature Immunology paper, supported by the Wellcome Trust and the Medical Research Council, the researchers used antibodies that recognise the dengue virus collected from individuals who had been infected with dengue. The team, who were also supported by the National Institute for Health Research Imperial Biomedical Research Centre, added them to human cell cultures, together with the Zika virus.

Their results suggest dengue antibodies can recognise and bind to Zika, due to the similarities between the viruses. Crucially, they also suggest that pre-existing dengue antibodies can amplify a Zika infection through a phenomenon called antibody-dependent enhancement (ADE).

This has been previously identified in dengue fever, and is thought to be why a second infection with dengue is often more serious than the first.

When dengue first infects the body, the immune system makes antibodies against the virus. Antibodies are large proteins that latch onto invading bacteria or viruses, neutralising them and enabling the immune system to destroy the pathogens. The antibodies are then primed to recognise the same invaders should another attack occur.