A new, three–dimensional snapshot of HIV demonstrates the radical structural transformations that enable the virus to recognize and infect host cells, according to a new study led by scientists at The Scripps Research Institute (TSRI).

The atomic–scale close–up image reveals an intricate dance between different parts of a key HIV protein complex, known as the envelope (Env) trimer, that takes place just moments before the virus would normally fuse itself to an immune cell’s plasma membrane.

“One could consider this a ‘missing link’ between HIV’s previously known prefusion and the post–fusion states,” said Andrew Ward, an associate professor at TSRI who led the study.

The image also gives scientists their clearest glimpse yet at the plastic nature of Env, which constantly shifts between different configurations before latching on to human cells.

“Several other studies have shown evidence of trimer ‘breathing,’ and here we are able to capture two different conformational states of Env at high resolution,” said study co–first author Gabriel Ozorowski, a senior research associate at TSRI.

Findings from the study, published online on July 12 in the journal Nature, could provide new potential targets for HIV vaccine designs.

“By understanding the molecular details of this fusion intermediate state, we can infer how the trimer transitions between states and engineer mutations or molecules to block those transitions,” Ward said. The article is titled, “Open and Closed Structures Reveal Allostery and Pliability in the HIV–1 Envelope Spike.”