Deltaviruses Use a Trojan Horse Method to Spread via a previously unrecognized transmission mode

Amazing stuff!

"Viruses ... employ different strategies to spread. One approach involves a virus relying on another “helper” virus to infect. A classic example is hepatitis delta virus (HDV), which hijacks hepatitis B virus surface glycoproteins to enter cells.

In recent years, scientists have discovered many HDV-like deltaviruses in animals. While helper viral glycoproteins play a role in infectivity, the broader nature of deltavirus–helper virus interactions remained largely unresolved.  ...

Their findings, published in Cell, revealed a previously unrecognized mode of viral transmission. Instead of hitchhiking on the surface of helper virus glycoproteins to enter cells, deltaviruses take a page out of an ancient Greek strategy—the Trojan Horse. Here, deltaviruses can package themselves inside another virus particle as a vehicle to spread and enter other cells. These findings reveal a novel viral transmission route and shed insight into how deltaviruses spread to different tissues. ..."

From the highlights and abstract:

"Highlights

• Deltaviruses hitchhike within helper virus virions, using them as viral Trojan Horses

• The Trojan Horse model is mandatory for productive herpesvirus-deltavirus associations

• This mode of propagation favors deltavirus infectivity

• Trojan Horse model warrants screening for extra-hepatic deltavirus infections in humans

Summary

Hepatitis D-like satellite viruses, known as deltaviruses, have been recently discovered in a wide range of animals. These viruses are thought to expropriate glycoproteins from helper viruses to form infectious particles.

Here, we challenge this paradigm and demonstrate that deltaviruses are packaged within helper virus particles, using them as viral Trojan Horses for cell entry. By leveraging orthogonal electron and optical super-resolution microscopy, we visualize deltaviruses enclosed within virions from rhabdo-, herpes-, and arenavirus families.

We show that this conserved hitchhiking mechanism ensures concomitant deltavirus-helper virus spread, thereby promoting the dissemination of deltaviruses, broadening their host range, and expanding their tropism. Our findings reveal a previously unrecognized mode of viral transmission, providing a framework to investigate overlooked deltavirus infections outside of the human liver."

Deltaviruses Use a Trojan Horse Method to Spread | The Scientist "New research shows that deltaviruses can sneak into cells by hitchhiking inside other viruses, highlighting a previously unrecognized transmission mode."

Deltaviruses spread through a viral Trojan Horse (open access)

Graphical abstract