The researchers analysed the virus's genetic information during the acute phase of infection.
Image Credit: © Daniel Todt
Scientific Frontline: Extended "At a Glance" Summary: Early Evolution of Hepatitis E Viruses
The Core Concept: Hepatitis E viruses undergo dynamic genetic mutations during the first few weeks of an acute infection, altering their population structure early in the disease progression.
Key Distinction/Mechanism: While the acute phase exhibits lower overall genetic diversity compared to the chronic phase, the virus utilizes transcomplementation. Through this mechanism, defective virus variants survive and replicate by exploiting the intact viral polymerases of co-existing, functional variants within the same host.
Major Frameworks/Components:
- Polymerase Gene Mutations: Frequent, recurrent mutations occur at specific sites on the viral polymerase, an enzyme essential for viral replication and a primary target for antiviral medications.
- Transcomplementation: A biological mechanism that allows structurally flawed or replication-deficient viral variants to persist and reproduce within mixed viral populations.
- Intra-Host Population Dynamics: The highly rapid shift in variant frequency, where individual viral mutations appear, multiply, or disappear within a matter of weeks.
Branch of Science: Virology, Molecular Biology, and Computational Infection Research.
Future Application: These findings lay the foundation for forecasting viral adaptability, improving antiviral drug designs targeting viral polymerase, and better managing treatment protocols for immunocompromised patients at risk of chronic infection.
Why It Matters: Charting the early genetic shifts of the hepatitis E virus is crucial for understanding how it navigates the human immune system, offering critical insights that could prevent acute infections from transitioning into severe, chronic illnesses.
Changes in the virus’s genetic material occur as early as the first few weeks of a hepatitis E virus infection. Researchers in Bochum have examined the dynamics and identified characteristic mutation patterns.
Knowing how viruses change in the initial weeks of an infection can provide important information about their adaptability. Researchers from the Ruhr University Bochum Departments of Molecular and Medical Virology and Translational and Computational Infection Research, Germany, have taken a closer look at the early phase of hepatitis E infections. To do this, they worked closely with the blood donation service of the Heart and Diabetes Center NRW in Bad Oeynhausen, a hospital of Ruhr University Clinics Bochum. The team analyzed samples from 80 blood donors who were determined to have an HEV infection during a routine screening.
Early Evolution Despite Low Variety
Otherwise healthy individuals usually do not notice an acute hepatitis E infection; the immune system generally eliminates the virus within a few weeks. However, the infection can become chronic in individuals with a compromised or medicinally suppressed immune system.
To better understand which changes occur during the initial weeks of the infection, the research team specifically focused on this early phase. “The virus develops during an acute infection,” explains Saskia Janshoff, doctoral student and lead author of the study. “We wanted to learn how diverse the virus populations are during this period and which changes occur frequently.” The analyses showed relatively low genetic virus diversity among the blood donors compared to the chronic phase of the infection. However, the researchers were able to identify certain changes that recurred in multiple donors.
Recurrent Mutations in the Polymerase Gene
For sequencing, the team focused on the viral polymerase in particular. This enzyme is important for the replication of the virus and is also a target for antiviral medications. The researchers discovered four sites in the genetic material where similar changes occurred especially frequently.
In lab experiments, the researchers examined the effects of these mutations. “We noticed that some variants of the virus were barely capable of replicating on their own,” says Dr. André Gömer. Nevertheless, they could apparently exist within mixed virus populations. This is possible through a mechanism known in the field as transcomplementation: defective virus variants benefit from the simultaneous presence of intact viral polymerases and can thus still be replicated.
Dynamic Changes Within a Few Weeks
Various samples from individual blood donors who were examined repeatedly throughout the course of infection provided further insight. The researchers observed changes in the makeup of the virus population in individual patients within a few weeks. “The early stages of an infection are highly dynamic,” says Gömer. “Individual variants occur, alter their frequency, or disappear. Such processes can only be made visible by repeatedly taking samples.”
Basis for Further Studies
It has not yet been fully explained why some mutations occur and exist temporarily despite their limited replicability. The researchers hypothesize that certain changes could influence the interaction with the immune system. However, further studies are required to show whether this actually benefits the virus. The study thus provides new insight into the early evolution of the hepatitis E virus and lays a foundation for future work on the significance of genetic changes for the course of the disease and the response to therapy.
Cooperation Partners: Researchers from Ruhr University Bochum, the Ruhr University Bochum University Hospital, Bielefeld University, the HepE-Hub, TWINCORE Hannover, the Hannover Medical School, and the German Center for Infection Research were involved in the work.
Funding: The work was funded by the Federal Ministry of Research, Technology, and Space (VirBio; 01KI2106; HepEDiaSeq 01EK2106A/B) and the German Center for Infection Research.
Published in journal: mBio
Title: Intra-host viral population dynamics during acute hepatitis E virus infection
Authors: Saskia Janshoff, Ricarda Plümers, Alina Kohl, Maximilian Klaus Nocke, Patrick Behrendt, Cornelius Knabbe, Rui Costa, Tanja Vollmer, Daniel Todt, Eike Steinmann, and Andre Gömer
Source/Credit: Ruhr-Universität Bochum | Meike Drießen
Edited by: Scientific Frontline
Reference Number: vi071326_01
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