Viruses are complex parasites that have evolved to infect a variety of host species. Some viruses, known as arboviruses, use insects to spread their infections to other hosts, such as humans and animals. Understanding how these viruses move between insect hosts could provide important insights into how to prevent their transmission.
Virus movement inside insects
A recently published study Journal of VirologyIt sheds light on how viruses move strategically within their insect hosts and how this movement facilitates the spread of infection to other animals. This knowledge is especially important in the fight against viruses that spread from insects to humans and animals, such as Zika, dengue fever and West Nile virus.
Navigation along specific routes
“Viruses that use insects as hosts must follow specific routes through different insect tissues to complete their life cycle. The pathways can differ significantly depending on the life cycle of the virus, the authors of the study noted.
“Both pathogenic insect viruses and insect-borne viruses must pass through the polarized cells of the midgut epithelium to establish a systemic infection. Insect-borne viruses also need to pass through the polarized salivary gland epithelium for transmission.”
Tracing protein pathways
To investigate the movement of the viruses, the researchers used fruit flies as models to follow the pathways of proteins from two different viruses: one specific to insects, while the other can infect both insects and animals, including humans.
By studying these viral proteins, the team gained a better understanding of how these proteins move between insect hosts to facilitate transmission.
“Using Drosophila as a model to study the tissue-specific polarized trafficking of these viral envelope proteins, we identified one of the virus-encoded signals and several host proteins associated with the regulation of polarized trafficking in the midgut epithelium,” the researchers explained.
Correct movement of viruses
Gary Blissard is a professor at the Boyce Thompson Institute and co-author of the study.
“Even when expressed alone, without the rest of the virus, these proteins were transported to specific locations in insect cells,” said Professor Blissard.
In the insect’s gut, viral proteins migrate to the bottom of the cells and position themselves to move into the insect’s body cavity. This movement creates conditions for further spread of the viruses.
Different behaviors of viral proteins
But the two viral proteins behaved differently in the salivary glands. Only the protein from the insect virus still moved toward the bottom of the cell, while the protein from the virus that can infect animals mostly moved toward the top of the cell—the perfect place to pick up new virus particles and release them into the saliva, ready to infect another host animal.
Guided by “GPS” signals
Such precise positioning is critical to viral life cycles and their ability to spread, as if viral proteins have a built-in “GPS” that guides them to the right places inside the host insect.
The study showed that this “GPS” consists of amino acid sequence signals encoded in the viral proteins themselves.
These signals are recognized by the host insect’s own protein transport systems, which help guide the viral proteins to their target destinations. The researchers also identified parts of the insect’s cellular machinery that capture the viral proteins to reach their final destinations.
Violation of the movement of viruses
The discovery opens the door to potential new strategies to combat the virus’ transmission. If scientists can find a way to disrupt the viral proteins’ GPS, or the cellular machinery they rely on, they could prevent the virus from reaching or exiting the insects’ salivary glands. This could effectively prevent the virus from using an insect as a vector and stop it from spreading to new hosts.
Wider implications of the study
“Our work highlights the incredible adaptations that viruses have evolved to navigate complex biological systems like insects,” said Nicolas Bouchon, associate professor of entomology at Cornell University and one of the study’s lead authors.
“This is a reminder of the ongoing evolutionary arms race between viruses and their hosts and the importance of basic research in understanding these complex biological processes.”
By revealing the molecular mechanisms of virus movement in insects, this research paves the way for new approaches to combating insect-borne diseases. This knowledge may also have applications in agricultural pest management, ultimately leading to better public health measures and improved crop protection in the future.
Source: Port Altele
