Scientists image birth of HIV particle for first time

Researchers at Rockefeller University in New York City have figured out a way to image the formation of a human immunodeficiency virus particle in real-time. The novel technique could change the approach to HIV research and lead to the development of new treatments.

Nearly 0.6% of the world's population is HIV-positive, according to the World Health Organization. More than 25 million people have died of acquired immunodeficiency syndrome since the discovery of the retrovirus responsible for AIDS in the early 1980s.

Much is known about HIV and the process leading to AIDS, but questions remain about the genesis of the lethal virus. This is the first time anyone has seen an HIV particle being born, said Paul D. Bieniasz, Ph.D., head of the Laboratory of Retrovirology at Rockefeller and a scientist at the Aaron Diamond AIDS Research Center.

"Not just HIV, any virus," he said.

Conventional microscopes shine light through a whole cell. The new technique, called total internal reflection microscopy, illuminates only the cell's surface, allowing a detailed view of events during HIV's birth, said professor Sandy Simon, Ph.D., head of the Laboratory of Cellular Biophysics at Rockefeller.

"You never even illuminate anything inside of the cell, so you can focus on what you are interested in seeing the moment it is happening," said Simon, who has been developing the imaging technique since 1992.

In the past, scientists ignored how long it took an HIV particle, or "virion," to assemble. Guesses run the gamut from milliseconds to hours. Using the new technique, researchers found out it took from five to six minutes, said lead investigator Nolwenn Jouvenet.

To prove they were watching HIV particles assembling, investigators tagged a major viral protein called the Gag protein that is the only one necessary for assembly. Using the microscopy technique, they found that the Gag molecules traveled from the inside of the cell to its surface, bumping into each other until they bulged outwardly into a budding virion.

The researchers were able to watch the steps of viral assembly from birth to scission. They published their findings in the May 25 online issue of Nature.

"The use of this technique is almost unlimited," Jouvenet said. "Now that we can actually see a virus being born, it gives us the opportunity to answer previously unanswered questions, not only in virology but in biology in general."

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