HIV-Infected T Cells Help Transport the Virus Throughout the Body

ScienceDaily (Aug. 1, 2012) — A new study has discovered one more way the human immunodeficiency virus (HIV) exploits the immune system. Not only does HIV infect and destroy CD4-positive helper T cells -- which normally direct and support the infection-fighting activities of other immune cells -- the virus also appears to use those cells to travel through the body and infect other CD4 T cells. The study from Massachusetts General Hospital (MGH) investigators, which will appear in the journal Nature and has received advance online release, is the first to visualize the behavior of HIV-infected human T cells within a lymph node of a live animal, using a recently developed "humanized" mouse model of HIV infection.

• HIV disseminates in the body of an infected individual by 'hitching a ride' on the T cells it infects: Infected T cells continue doing what they usually do, migrating within and between tissues such as lymph nodes, and in doing so they carry HIV to remote locations that free virus could not reach as easily. 
• When HIV is introduced into blood or tissues, the virus binds to CD4 molecules on the surface of helper T cells, injecting its contents into cells and setting off a process that leads to the assembly and release of new virus particles.早期以為是病毒隨體液/血液傳播
• lymph nodes -- known to be important sites of HIV replication 
• the researchers injected the animals with HIV engineered to express green fluorescent protein (GFP), allowing them to track the movement of infected cells within living animals using a method called intravital microscopy. 

T cell

T cells or T lymphocytes belong to a group of white blood cells known aslymphocytes, and play a central role in cell-mediated immunity. 
T helper cell (T_H cells) assist other white blood cells in immunologic processes, including maturation of B cells into plasma cellsand memory B cells, and activation of cytotoxic T cells and macrophages. These cells are also known as CD4⁺ T cells because they express the CD4 protein on their surface.

Journal Reference:

1. Thomas T. Murooka, Maud Deruaz, Francesco Marangoni, Vladimir D. Vrbanac, Edward Seung, Ulrich H. von Andrian, Andrew M. Tager, Andrew D. Luster, Thorsten R. Mempel.HIV-infected T cells are migratory vehicles for viral dissemination. Nature, 2012; DOI: 10.1038/nature11398