The particles of the human T-cell leukemia virus type 1 (HTLV-1), a human retrovirus closely related to HIV, are known to be non-infectious. They don’t cause much damage alone. But when those particles invade other cells, the virus becomes highly infectious, and can cause leukemia. About 5 percent of people who contract HTLV-1 will develop adult t-cell leukemia.
University of Minnesota researchers recently captured 3-D images of HTLV-1 through advanced electron imaging, a technology that enabled them to study the virus particles in more detail than ever before. Their finding, recently published in The Journal of Virology, could provide insight into why some particles are more infectious than others.
“We wanted to see if there were any structural features that explained why some leukemia viruses prove more infectious,” said lead researcher Louis Mansky, Ph.D., director of the Institute for Molecular Virology and professor in the University of Minnesota School of Dentistry. “We found that a lot of the particles did not have a fully-matured core structure.”
Mansky and collaborator Wei Zhang, Ph.D., research assistant professor in the School of Dentistry, hypothesize that the unformed core structure could be a factor as to why some particles are more infectious than others (pictured below).

“Understanding how the core structure matures could provide important insights into the creation of particle infectivity, and disrupting this process could be a tremendous opportunity for developing therapeutic interventions,” Mansky said.
The research team studied the particles that tend to be somewhat non-infectious.  They flash-froze virus samples in liquid ethane, and took tens of thousands of pictures of the frozen sample through a transmission electron microscope. The technique, called cryoelectron tomography, provides researchers with a high resolution, 3-D image.
“We need to continue to research the particles to better understand the correlation between underdeveloped cores and increased infectivity,” Mansky said. “From there we can explore ways to implement possible interventions.”
The ultimate aim is to bring researchers one-step closer to developing potential leukemia treatment and prevention methods for cases caused by HTLV-1.