Scientists have identified a molecule targeted by dengue virus in mice to bring about the haemorrhagic fever associated with lethal disease. The research, reported online this week in Nature, could help the development of therapeutic agents for this and other viral diseases.

Dengue is mosquito borne and infects at least 50 million people a year, but little is known about how the virus causes disease. Taiwanese researchers show that it hijacks the CLEC5A molecule on immune cells to cause a massive release of potent inflammatory agents known as cytokines. These cytokines are probably responsible for the inappropriate inflammation that causes haemorrhagic fever.

Using antibodies to block the interaction between CLEC5A and dengue virus, the team found that they could prevent inflammation without affecting the normal immune response to virus infection. What's more, 50% of mice treated with these antibodies managed to clear the virus. This ability to control inflammation and simultaneously maintain natural viral immunity makes CLEC5A an exciting prospect for the development of treatment agents, say the authors.

The abstract says (citations omitted):

Dengue haemorrhagic fever and dengue shock syndrome, the most severe responses to dengue virus (DV) infection, are characterized by plasma leakage (due to increased vascular permeability) and low platelet counts. CLEC5A (C-type lectin domain family 5, member A; also known as myeloid DAP12-associating lectin (MDL-1)) contains a C-type lectin-like fold similar to the natural-killer T-cell C-type lectin domains and associates with a 12-kDa DNAX-activating protein (DAP12) on myeloid cells. Here we show that CLEC5A interacts with the dengue virion directly and thereby brings about DAP12 phosphorylation. The CLEC5A– DV interaction does not result in viral entry but stimulates the release of proinflammatory cytokines. Blockade of CLEC5A–DV interaction suppresses the secretion of proinflammatory cytokines without affecting the release of interferon-a, supporting the notion that CLEC5A acts as a signalling receptor for proinflammatory cytokine release. Moreover, anti-CLEC5A monoclonal antibodies inhibit DV-induced plasma leakage, as well as subcutaneous and vital-organ haemorrhaging, and reduce the mortality of DV infection by about 50% in STAT1-deficient mice. Our observation that blockade of CLEC5A-mediated signalling attenuates the production of proinflammatory cytokines by macrophages infected with DV (either alone or complexed with an enhancing antibody) offers a promising strategy for alleviating tissue damage and increasing the survival of patients suffering from dengue haemorrhagic fever and dengue shock syndrome, and possibly even other virus-induced inflammatory diseases.