'Sputnik' Virus Orbits, Hijacks Other Viruses

Aug. 13, 2008 -- A virus that takes advantage of other viruses for its own survival has been found by scientists in France.

"This opens up whole new avenues of scientific exploration in terms of how viruses interact," said Curtis Suttle, a scientist at the University of British Columbia who was not involved in the research, which was recently published in the journal Nature.

In 2003 scientists at the Mediterranean Institute of Microbiology in Marseilles, France, found the world's largest virus in a U.K. cooling tower, a behemoth so large scientists initially discarded it as a bacteria. (Bacteria are typically many times larger than viruses.)

The French scientists continued to study the large virus, called mimivirus, and recently found an even larger one, which they named mamavirus.

Then they found something no one had seen before -- a third virus orbiting, and actually parasitizing, the mamavirus. The scientists named it Sputnik.

Viruses are a unique form of life. Unlike most other forms, they don't have the cellular equipment to reproduce. Instead they have to infect other cells, hijacking their equipment to produce thousands of little replicas.

Unfortunately for the infected cells, those copies typically pile up inside and eventually explode. The host cells are typically killed in the process.

Sputnik, in essence, hijacks a hijacker. About 100 times smaller than mimivirus or mamavirus, it can't directly infect the other viruses. Instead, it co-infects the same cells that mimivirus and mamavirus infect, usually amoebas.