Researchers at the University of Massachusetts Medical School have stumbled upon a new stage in the life cycle with a new method taking images of infected cells that are "intact".
They've shown that this phase of infection, dubbed intra-nuclear migration, by principal investigator Abraham L. Brass, MD, PhD, relies on the human protein CPSF6 to guide the virus through the host cell's nucleus and position it at active genes where it prefers to make its home. Details of HIV's intra-nuclear migration and the imaging techniques used to find it were published in Cell Reports.
‘Using the images produced by ViewHIV, scientists can track the virus and its capsid as it moves through the cytoplasm, across the nuclear membrane and finally into the nucleus.’
This is the intra-nuclear migration phase depending on the human protein CPSF6 in order to guide it through the host cell's nucleus. It would reach the genes in order to house itself.
"This study reveals an important stage and mechanism in HIV infection that was previously unappreciated," said Dr. Brass, assistant professor of microbiology & physiological systems. "It's important to know more about these early infection events so we can come up with ways to stop the virus from becoming part of our DNA and infecting us for life."
The key to learning about HIV's intra-nuclear migration came thanks to a new technique, ViewHIV, which was developed by Brass and his colleagues, Jill Perreira and Chris Chin, both research associates at UMMS; and Eric Feeley, a PhD candidate at Duke University.
ViewHIV can create images of the viral genome and protein capsid at the same time, even as they are within the infected host cell. It enables them to look at the movement of the viral capsid, DNA and RNA within the cell, helping them to get a view into the disease.
Up to this point, scientists have been unable to generate good images of HIV inside the nucleus using standard techniques. Because of this limitation, most insights into HIV's transit across the nuclear membrane have been gained through indirect molecular biology and biochemistry methods that evaluate large cell populations.
This technique allows scientists to visualize the movement and fate of the viral capsid, DNA and RNA inside the cell. Standard confocal microscopy is then used to take both horizontal and vertical photos of the cell that are re-assembled into detailed three-dimensional images of the cell.
These findings point to a previously undescribed state in HIV's life cycle taking place between the time the virus enters the nucleus and the time its DNA is integrated into our genome, which was only discovered thanks to the development of ViewHIV.
"We believe ViewHIV is going to be a great tool for unlocking the mechanisms that govern the early state of HIV's life cycle," said Brass. "With our technique we can better determine how HIV establishes itself into our DNA and develop new ways to stop that from happening."