Blessing instead of curse: giant virus discovered in sewage treatment plant near Vienna

A blessing instead of a curse
A giant virus was discovered in a sewage treatment plant near Vienna

April 25, 2024, 11:41 am

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At first glance, giant viruses seem like the new super-epidemic, especially if they've just been discovered in a sewage treatment plant near Vienna. But appearances can be deceiving: viral giants can also be real lifesavers. Researchers have discovered that they kill amoebas that are dangerous to humans.

It looks ominous at first: researchers have discovered a new giant virus in a sewage treatment plant near Vienna. Indeed, giant viruses turn out to be unexpected helpers against deadly diseases. Because they attack amoeba found in water, like the research team led by Patrick Orthoff from the University of Vienna. In the journal “Nature Communications”. writes

These single-celled organisms are called Nagleria fowleri and can cause severe encephalitis in people. Nagleria thrives primarily in warm water above 30 degrees. Amoeba can be ingested through the nose while swimming. According to experts, this happens very rarely, but it always ends in death. The newly discovered giant virus is the first to infect this dangerous protozoa. Hence the common name: Nagleria virus.

How it attacks its victims is interesting: the giant virus is mistaken for food by amoebas and destroys them within hours. Before doing so, the Naegleria virus introduces its genes into the host cell, setting up a kind of factory in it to produce new viruses. “To keep the host cell alive during this time, the amoeba uses special proteins that suppress the cell's natural immune response and prevent premature cell death. Co-author Florian Panholzl of the University of Vienna explains.. “It is only after the viruses have successfully replicated that the host cell is destroyed and the viruses are released.”

Unusually many genes for a virus

Naegleria viruses come from the group “Klosneuviruses”, whose name refers to an amazing discovery a few years ago at the Klosterneuburg sewage treatment plant: Viennese microbiologists found various giant viruses during genetic analyses. Klosneuviruses refer to a group of viruses still unknown to science.

“They are particularly interesting among the giant viruses: they contain a large number of genes known only from cellular organisms such as animals, plants, fungi or bacteria, and which would never have been associated with viruses before the discovery of clozeneuviruses,” microbiologist Matthias Horn from the University of Vienna told the Austrian news agency ABA. It has also been shown that “Closneuviruses are widespread and highly diverse throughout the world.”

Closer analyzes of Naegleria virus revealed that this giant virus has an unusually double-stranded DNA of 1.16 million base pairs. It contains genetic instructions for at least 59 viral proteins and at least 31 genes that actually belong to the translational machinery of cellular organisms. Based on similarities to the genomes of some single-celled organisms, Orthofer and his colleagues suspect that the giant virus adopted these genes from earlier hosts.

Antiviral drug

With their discovery, the researchers believe that Naegleria viruses could be used against deadly amoebas in the future. “These viruses may represent the first step toward an antiviral drug against Naegleria fowleri,” the study says.

Because Naegleria occurs primarily in warm, human-impacted waters and swimming pools, giant viruses can even be used there as a preventative measure. “This discovery fundamentally opens up the possibility of preventive treatment of perishable water, for example as part of water treatment in swimming pools,” says microbiologist Horn. However, this will first require further investigations. “However, the virus now discovered will help us better understand the biology of Nagleria and their interactions with viruses.”