Scientists from the University of Texas have successfully used a therapeutic virus to block the spread of a lethal one. The researchers hope their technique will one day be adapted to treat chronic HIV infections.

Integrative biologist Matthew Paff and his colleagues infected colonies of E. coli bacteria with two viruses: one that swiftly kills infected hosts and another that establishes a permanent infection, but does not kill, its hosts. They then closely observed the E. coli populations.

When the therapeutic virus was introduced first, it rapidly spread to infect the bacterial populations. An hour later, the researchers introduced the lethal virus into some of the colonies. In colonies infected with the therapeutic virus, host populations remained fairly stable, while host populations without the therapeutic virus saw their numbers dwindle by two orders of magnitude (see D in the figure below).

The intervention was not as successful when the lethal virus was introduced first, as the bacterial population declined rapidly before the therapeutic virus could impart protection.

The therapeutic virus, succinctly dubbed "f1", blocks subsequent viral infection by damaging or modifying the pilus of its bacterial host. The pilus is a hairlike appendage which bacteria use to transfer genetic information, and which many viruses co-opt to infect bacterial cells.

With their aptly named "virus wars" system demonstrated in a bacterial host, the authors mused on applying the technique to humans.

"It is too early to identify the actual agents that might be used in an application against a human chronic infection such as HIV, and even if such transmissible agents were known, regulatory issues might thwart implementation in the near future. Our suggested approach is thus futuristic, but it is only a few steps from current practices."

The authors suggest that therapeutic viruses could one day be designed to prevent viral infections or even to destroy malicious viruses upon entry.

The new research was published to the open-access journal PeerJ.

Source: Paff ML, Nuismer SL, Ellington A, Molineux IJ, Bull JJ. (2016) Virus wars: using one virus to block the spread of another. PeerJ 4:e2166 https://doi.org/10.7717/peerj.2166

(Image: Reconfirming the Traditional Model of HIV Particle Assembly. Gross L, PLoS Biology Vol. 4/12/2006, e445.)