Have you ever wondered if a virus can get sick? Well, it turns out that viruses can indeed get sick, and their assailants are other viruses. When a virus enters a cell, it can either go dormant or start replicating. During replication, the virus takes over the cell’s molecular factory to produce copies of itself, which are then released from the cell.
Sometimes, a virus enters a cell only to find that another dormant virus already resides there. This leads to a battle for control of the cell. However, in some cases, a virus may encounter a surprise—an existing virus specifically waiting to prey on incoming viruses.
Biologists have long been aware of the existence of viruses that prey on other viruses, known as viral “satellites.” These satellites are viruses that infect other viruses. Researchers studying bacteriophage P2, a virus that infects gut bacterium Escherichia coli, found in 1973 that the infection can lead to the emergence of two different types of viruses from the cell: phage P2 and phage P4.
Phage P4 is a temperate virus that integrates into the chromosome of its host cell and lies dormant. When P2 infects a cell that already has P4, P4 quickly wakes up and reproduces using the genetic material of P2. This relationship between P4 and P2 is referred to as a satellite-helper system.
Similar satellite-helper systems have been observed in various bacterial species. However, viral satellites are not limited to bacteria. Satellite viruses have also been discovered in plants, lurking in plant cells and waiting for other viruses while affecting crop health.
The satellite-helper viral systems play an essential role in an evolutionary arms race. Satellite viruses constantly evolve new ways to exploit helper viruses, and helpers develop countermeasures to defend against the satellites. These systems have become hotbeds for the evolution of antiviral mechanisms.
Recent research indicates that many antiviral systems found in bacteria may have originated in phages and their satellites. Satellite viruses have the potential to revolutionize our understanding of antiviral strategies. By studying the complex relationship between viruses and their satellites, researchers may uncover new avenues for antiviral therapy.
In recent work, a satellite phage called MiniFlayer was discovered. MiniFlayer, unlike other satellite viruses, has evolved a unique lifestyle. It has lost the ability to lie dormant and has instead developed a short appendage that allows it to latch onto its helper virus like a vampire. The helper and its passenger then travel together to find a host, where the viral drama unfolds once again.
Further research is needed to understand how MiniFlayer subdues its helper and whether the helper has evolved countermeasures. The study of viral satellites, such as MiniFlayer, has the potential to expand our arsenal of antiviral therapeutics.