Finkeled giant virus discovered in Klosterneuburg

In concrete terms, this concerns the protozoan Naegleria fowleri, which dissects the brains of those affected after infection. Fortunately, the disease is rare; the protozoa are rarely found in our latitudes.

Single-celled organisms multiply in warm water
Naegleria are single-celled organisms found in water bodies worldwide and feed on other microorganisms. The species Naegleria fowleri, the causative agent of a serious brain disease and meningitis called “primary amoebic meningoencephalitis” (PAM), reproduces mainly in warm water above 30 degrees Celsius, according to the study published in the journal “Nature Communications”. The disease – the protozoa are absorbed through the nose while swimming – is extremely rare, but almost always fatal.

Opponent from the group “toilet nose viruses”
The team led by Patrick Arthofer and Matthias Horn from the Center for Microbiology and Environmental Systems Sciences at the University of Vienna has now been able to isolate giant viruses that infect several Naegleria species for the first time. They come from the group ‘Klosneuviruses’, the name of which refers to a spectacular discovery at the Klosterneuburg sewage treatment plant a few years ago: Viennese microbiologists, including Horn, came across several giant viruses during genome analysis. The Klosneuviruses represent a group of viruses that are still relatively unknown to science.

Virus species have a particularly large number of genes
“They are particularly interesting within the giant viruses: they have a particularly large number of genes that are otherwise only known from cellular organisms such as animals, plants, fungi or bacteria, and which would never have been associated with viruses before the discovery of the disease . Klosneuviruses,” Horn told the APA. It has also been shown that “Klosneuviruses are widespread worldwide and highly diverse.”

In the current study, the researchers looked for viruses that infect amoebae of the genus Naegleria – and found the Klosneuviruses: The giant virus now discovered with the common name Naegleriavirus was isolated from the sewage treatment plant in Klosterneuburg. “We used samples from the sewage treatment plant because we knew from previous studies that the diversity of giant viruses, for which there are no cultured representatives in the laboratory, is particularly high there,” Horn explains.

First ‘virus factory’, then cell death
For their research, the environmental samples were brought together with the protozoa grown in the laboratory – in this case it was Naegleria clarki as a harmless species. The result: the virus was accidentally ingested as food, destroying it within hours. The virus infects its host cell, after which a ‘virus factory’ forms within the amoeba cell, which multiplies the viral genetic material outside the cell nucleus and collects hundreds of new virus particles.

To keep the host cell alive during this time, the researchers suspect that the Naegleria virus uses special proteins that suppress the amoeba cell’s natural immune response and thus prevent premature cell death. Only after the viruses have successfully multiplied are the host cells destroyed and the viruses released.

Giant virus with health potential
“Both the structure of Naegleria virus and the course of infection are largely similar to known giant viruses characterized in the laboratory,” Horn said. A number of genes “that originally come from the chromosomes of the Naegleria but are incorporated into the viral genome” are probably important for the adaptation to the amoeba, such as those genes that can prevent the premature cell death of the Naegleria.

The giant viruses could perhaps also be used prophylactically to combat Naegleria fowleri in the treatment of polluted water, “but that would require further research first,” says Horn.