The human genome contains genetic remnants of ancient viruses, and recent research suggests that these may play a role in the progression of neurodegenerative diseases. This study, published in Nature Communications, has been conducted by scientists at DZNE.
Historically, it's been proposed that viral infections might be linked to the onset of certain neurodegenerative diseases. However, the study points to a mechanism that doesn't involve external pathogens. Instead, the focus is on "endogenous retroviruses" present in our DNA “During evolution, genes from numerous viruses have accumulated in our DNA. Most of these gene sequences are mutated and normally muted,” notes Ina Vorberg, who heads a research group at DZNE and also holds a professorship at the University of Bonn. “However, there is evidence that endogenous retroviruses are activated under certain conditions and contribute to cancer and neurodegenerative diseases. Indeed, proteins or other gene products derived from such retroviruses are found in the blood or tissue of patients.”
A Closer Look at Tau Aggregates
Vorberg and her team turned their attention to specific proteins from the envelope of endogenous retroviruses, specifically HERV-W and HERV-K. While typically inactive, some studies suggest that HERV-W might play a role in multiple sclerosis, while HERV-K has been associated with the neurologic disorder amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The team discovered that these viral proteins might aid in the transfer of tau aggregates between cells. These protein clumps are often found in the brains of those with diseases like Alzheimer's and FTD.
“Certainly, conditions in the brain are much more complex than our cellular model system can replicate them. Nevertheless, our experiments show that endogenous retroviruses can influence the spread of tau aggregates between cells,” explains Vorberg. “Endogenous retroviruses would thus not be triggers of neurodegeneration, but could fuel the disease process once it is already underway.”
How Viral Proteins Might Facilitate Disease Progression
Vorberg's research indicates that viral proteins might act as transport facilitators for tau aggregates. These proteins can become part of the cell membrane and the membrane of extracellular vesicles, tiny fat bubbles secreted by cells.
“For the transport of tau aggregates from cell to cell, we see two pathways in particular. Transfer between cells that are in direct contact, and transport within vesicles that act as cargo capsules, so to speak, and pass from one cell to another to eventually merge with it,” elaborates Vorberg. “In both scenarios, membranes have to fuse. Proteins from the envelope of viruses can promote this process. That’s because many viruses are adapted to fuse with host cells. This happens by means of special proteins that viruses carry on their surfaces. If precisely these proteins are incorporated into the cell membrane and the membrane of extracellular vesicles, it is understandable that the tau aggregates then spread more easily.
Potential Therapeutic Approaches
As people age, changes in gene regulation might reactivate once dormant endogenous retroviruses. Since most neurodegenerative diseases appear later in life, this offers potential treatment paths. Vorberg suggests two possible therapeutic strategies: suppressing gene expression to inactivate endogenous retroviruses or neutralizing the viral proteins, possibly using antibodies.
The team believes it's plausible that dementia patients with tau aggregates have higher levels of certain antibodies. If they could isolate and biotechnologically reproduce these, a passive vaccine might be developed. As part of their future research agenda, Vorberg's team is collaborating with DZNE colleagues in Berlin and Bonn to search for these antibodies. Additionally, they're exploring antiviral drugs, as preliminary findings in cell cultures show these can halt the spread of protein aggregates. “This is another approach we intend to pursue,” concludes Vorberg.
Historically, it's been proposed that viral infections might be linked to the onset of certain neurodegenerative diseases. However, the study points to a mechanism that doesn't involve external pathogens. Instead, the focus is on "endogenous retroviruses" present in our DNA “During evolution, genes from numerous viruses have accumulated in our DNA. Most of these gene sequences are mutated and normally muted,” notes Ina Vorberg, who heads a research group at DZNE and also holds a professorship at the University of Bonn. “However, there is evidence that endogenous retroviruses are activated under certain conditions and contribute to cancer and neurodegenerative diseases. Indeed, proteins or other gene products derived from such retroviruses are found in the blood or tissue of patients.”
A Closer Look at Tau Aggregates
Vorberg and her team turned their attention to specific proteins from the envelope of endogenous retroviruses, specifically HERV-W and HERV-K. While typically inactive, some studies suggest that HERV-W might play a role in multiple sclerosis, while HERV-K has been associated with the neurologic disorder amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The team discovered that these viral proteins might aid in the transfer of tau aggregates between cells. These protein clumps are often found in the brains of those with diseases like Alzheimer's and FTD.
“Certainly, conditions in the brain are much more complex than our cellular model system can replicate them. Nevertheless, our experiments show that endogenous retroviruses can influence the spread of tau aggregates between cells,” explains Vorberg. “Endogenous retroviruses would thus not be triggers of neurodegeneration, but could fuel the disease process once it is already underway.”
How Viral Proteins Might Facilitate Disease Progression
Vorberg's research indicates that viral proteins might act as transport facilitators for tau aggregates. These proteins can become part of the cell membrane and the membrane of extracellular vesicles, tiny fat bubbles secreted by cells.
“For the transport of tau aggregates from cell to cell, we see two pathways in particular. Transfer between cells that are in direct contact, and transport within vesicles that act as cargo capsules, so to speak, and pass from one cell to another to eventually merge with it,” elaborates Vorberg. “In both scenarios, membranes have to fuse. Proteins from the envelope of viruses can promote this process. That’s because many viruses are adapted to fuse with host cells. This happens by means of special proteins that viruses carry on their surfaces. If precisely these proteins are incorporated into the cell membrane and the membrane of extracellular vesicles, it is understandable that the tau aggregates then spread more easily.
Potential Therapeutic Approaches
As people age, changes in gene regulation might reactivate once dormant endogenous retroviruses. Since most neurodegenerative diseases appear later in life, this offers potential treatment paths. Vorberg suggests two possible therapeutic strategies: suppressing gene expression to inactivate endogenous retroviruses or neutralizing the viral proteins, possibly using antibodies.
The team believes it's plausible that dementia patients with tau aggregates have higher levels of certain antibodies. If they could isolate and biotechnologically reproduce these, a passive vaccine might be developed. As part of their future research agenda, Vorberg's team is collaborating with DZNE colleagues in Berlin and Bonn to search for these antibodies. Additionally, they're exploring antiviral drugs, as preliminary findings in cell cultures show these can halt the spread of protein aggregates. “This is another approach we intend to pursue,” concludes Vorberg.