(RxWiki News) UCLA School of Medicine researchers have discovered that a sugar-binding protein may play a part in HIV infection by making individuals more susceptible to the disease.
Certain types of "helper" T cells that are critical to functioning immune systems contain an enzyme called PDI (protein disulfide isomerase) that affects how proteins fold into specific shapes, influencing how the T cells behave. In HIV infection, PDI helps change the shape of the surface envelope protein of the virus, which enables the virus' prime interaction with receptors on the T cells.
"T cells play a key role in cell-mediated immunity."
It was previously known that PDI inhibitors could prevent HIV infection, but how remained unclear. It was also known that PDI, which usually lives inside the cell could become trapped on the surface, but it wasn't certain how that occurred either.
However, UCLA researchers have found that a sugar-binding protein called galectin-9 traps PDI on T-cells' surface, making them more susceptible to HIV infection. This discovery could potentially lead to a new target for anti-HIV therapeutics, such as therapies to inhibit PDI or galectin-9.
Researcher Dr. Linda G Baum, professor and vice chair of the Department of Pathology and Laboratory Medicine at UCLA School of Medicine, said that the in vitro research was conducted using human and mouse T cells.
Researchers discovered that the T cells made and secreted galectin-9 so they isolated T cell surface receptors that bound galectin-9, and identified PDI as one of the receptors. It was determined that galectin-9 retained PDI on the T cell surface, and evidence suggested increased PDI enzyme activity on the cell surface.
"We found that galectin-9 mediated increase in PDI activity on the surface of T cells had two important effects – it enhanced T cell migration and it enhanced susceptibility of human T cells to infection with HIV in vitro," Baum said.