Watch the Moment HIV Infects New Host: Footage Is Helping Scientists Develop a Vaccine

In first-of-its-kind footage, scientists have captured the moment an HIV-infected T cell passes the virus to a new host. The footage is helping scientists better understand the precise way HIV is transmitted and may lead to better prevention methods and even an eventual HIV vaccine.

The fascinating moment HIV is transmitted to a new host is detailed in a new study published in Cell Reports. The footage shows exactly how HIV is able to cross the genital mucous membranes in a new host in order to reach immune system cells and complete the viral transmission.

The T cell in the video is infected with HIV and highlighted with bright green dye. In the video, we see the T cell come into contact with a reconstructed urethral mucosal tissue found in the urethra. These cells are observed in an in vitro model, meaning it was created from components of living organisms but actually occurred outside of a body, such as in a petri dish.

As the HIV-infected T cell and the urinary tract tissue make contact, they form a pocket called a virological synapse. The contact spurs the infected T cell to create more of the virus, which eventually passes from the T cell to the urinary tract cells thanks to the virological synapse.

However, the urinary tract cells are not the main target and remain uninfected despite this contact. Instead, the HIV virus travels to specialized cells called macrophages, which are waiting nearby. Macrophages are immune system cells meant to attack an impending infection as a way to rid it from the body. The macrophages envelop the virus, but instead of getting rid of it, they keep the virus inside them. The macrophages will produce and shed the virus for 20 days before entering a latent stage where they are still infected but no longer produce the virus.

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A nurse holds a vial of blood to be tested for HIV at the LoveYourself Anglo Center in Manila, the Philippines. Noel Celis/AFP/Getty Images

According to the study, the entire process takes one to two hours, with the process ending after the infected T cell breaks contact with the urinary tract tissue.

The footage left the researchers stunned. "We had this global idea of how HIV infects this tissue, but following something live is completely different. The precise sequence of events can be defined, and we were very surprised by them," said senior researcher Morgane Bomsel, a molecular biologist at the Institut Cochin in Paris, in a statement.

The footage and corresponding research revealed a known behavior of HIV infections. The virus purposely sought out uninfected cells in the potential new host that were within close proximity to macrophages. This finding suggests there is some sort of relationship or communication between the tissue lining of the urinary tract and these immune system cells.

"We couldn't have imagined that before this kind of imaging," said Bomsel in the statement.

The research also shows how early HIV enters macrophages and forms reservoirs of the virus—a term used to describe infected macrophages in the latent, or non-virus-producing, stage. This suggests that an HIV vaccine would need to target the mucous membrane in the genital tract.

The team is working on just that and said these important findings will help it reach its goal.