Highways for HIV

What am I looking at?

This is an image of HIV particles moving from a T cell, part of the immune system, to an astrocyte, a cell in the nervous system, along a bridge of so-called filopodia. The HIV particles are red and white (1), the T cell is gold (2), and the astrocyte is blue (3). And the long, thin structures that the HIV particles are riding on are filopodia (4) – filaments in some kinds of cells, including nerve cells.

Biology in the background

HIV is a virus that mainly infects cells of the immune system known as T cells and kills them, decreasing the immune system’s ability to fight other infections.

While the death of T cells is a hallmark of an HIV infection, studies have shown that the virus can also infect other types of cells – including other immune system cells, as well as nervous system cells like the astrocyte seen here. The consequences of a secondary infection of nervous system cells are not well understood, but figuring out how and why HIV infects these secondary cell populations could provide valuable insights into the mechanisms behind the virus’s spread.

T cells can grow to be 10 micrometers across, or roughly 7.5 times smaller than the width of a human hair. Astrocytes are larger; they can be up to 75 micrometers across, or roughly the same size as the width of a human hair. But HIV particles are much smaller than even T cells – only about 115 nanometers across, or roughly 650 times smaller than the width of a human hair.

Technique

This image was created using focused ion beam scanning electron microscopy.