How Does the Dengue Virus Infect People?

Each year, about 100 million people get infected with the dengue virus, usually because of getting bitten by an infected mosquito, according to the Centers for Disease Control and Prevention (CDC). However, little is known on how the virus infects human cells, until now.

Researchers have recently found how the dengue virus infects cells of people. The finding, which appeared on the October 7, 2010, issue of PLoS Pathogens, provides new researchers a background, which paves the way for the creation and testing of new drugs that can prevent or treat dengue infection.

The virus that causes the disease is commonly transmitted by the dengue-carrying mosquito -- the Aedes aegypti. Once infected, the person usually starts to have fever after a few days. It can be accompanied by severe headache, joint pains, nausea, and rashes.

Sometimes, the virus can cause dengue hemorrhagic fever DHF) -- a more severe form of dengue fever -- that can cause damage to blood and lymph vessels. DHF can cause difficulty breathing, bleeding in the nose or gums, bruising, and, if left untreated, will cause death. The World Health Organization (WHO) says that DHF takes the life of about 22, 000 people each year, most of them children.

How Dengue Virus Infect Cells

Once inside the body, the dengue virus attaches to the surface of the cell, called the cell membrane -- the material that envelopes the entire cell. The cell membrane will form a pouch-like structure -- called endosome -- that surrounds the virus, allowing entry into the cell. As the endosome travels deep into the cell, the membrane of the virus fuses with the endosomal membrane forming an opening. The virus releases its own genetic material, infecting the cell. The infected cell is now forced to replicate itself, producing more infected cells.

The Study

Led by Dr. Leonid V. Chernomordik of the Section on Membrane Biology at the NIH's Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the researchers used fluorescent probes on the dengue virus and human cell membranes. The probes glow when the membrane of the virus fuses with the normal human cell membrane.

The researchers found that two components should be present for the fusion of the membranes to occur. One component is that there is an acidic environment and the other is having 'negatively charged lipids in the endosome membrane.' The scientists say that the 'negativity of charges' would only occur if the endosome is in the right place, deep within the cell.

Dr. Chernomordik says, "We spent several years trying to understand how the dengue virus fuses with its target membrane." He added, "The findings will now enable us to test new ways to disrupt the fusion process and prevent infection."

The study was funded the NICHD and the National Institute of Allergy and Infectious Diseases (NIAID).

Sources:

Centers for Disease Control and Prevention (CDC). Dengue. Accessed on October 30, 2010.

National Institutes of Health (NIH) Research Matters. How Dengue Virus Infects Cells. Accessed on October 30, 2010.

NIH News. NIH scientists discover how dengue virus infects cells: Discovery essential for testing potential treatments. Accessed on October 30, 2010.

World Health Organization (WHO). Impact of Dengue. Accessed on October 30, 2010.