Viruses use “GPS” to move precisely within insects

Viruses are expert parasites that have evolved to infect a wide 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 through insect hosts can provide important insights into how to block their transmission.

Virus movement within insects

A recently published study in Journal of Virology provides insight into how viruses move strategically within their insect hosts and how this movement contributes to the spread of infection to other animals.

This knowledge is particularly important for combating viruses such as Zika, Dengue and West Nile viruses, which are transmitted from insects to humans and livestock.

Navigating on specific routes

“Viruses that use insects as hosts must navigate specific routes through different insect tissues to complete their life cycle. The routes can vary considerably depending on the virus's life cycle,” the study authors noted.

“Both entomopathogenic viruses and insect-borne viruses must navigate through the polarized cells of the midgut epithelium to cause systemic infection. In addition, insect-borne viruses must also navigate through the polarized epithelium of the salivary glands for transmission.”

Tracing the pathways of proteins

To study virus movement, researchers used fruit flies as a model to trace the pathways of proteins from two different viruses. One virus was insect-specific, while the other could infect both insects and animals, including humans.

By studying these viral proteins, the team gained a better understanding of how they navigate insect hosts to facilitate transmission.

“We used Drosophila as a model to study tissue-specific polarized transport of these viral envelope proteins and identified one of the virus-encoded signals and several host proteins associated with the regulation of polarized transport in the midgut epithelium,” the researchers explained.

Precise movement of viruses

Gary Blissard is a professor at the Boyce Thompson Institute and co-lead author of the study.

“Even when expressed individually, without the rest of the virus, these proteins migrated to exactly the right places in the insect cells,” said Professor Blissard.

In the insect's gut, the virus proteins migrated to the bottom of the cells and positioned themselves so that they could enter the insect's body cavity. This movement paved the way for further spread of the viruses.

Different behavior of virus proteins

In the salivary glands, however, the two virus proteins behaved differently. While the insect virus protein still moved to the cell floor, the animal virus protein often migrated to the cell surface.

This is an ideal place for the formation of new virus particles and their release into saliva, ready to infect another animal host.

Guided by “GPS” signals

This precise positioning is crucial to the viruses' life cycle and ability to spread. It's almost as if the virus proteins have an internal “GPS” that guides them to the right places in the insect host.

The study found that this “GPS” consists of amino acid sequence signals encoded in the viral proteins themselves.

These signals are recognized by the host insect's protein transport systems and help direct the virus proteins to their target locations. The researchers also identified parts of the insect's cellular machinery that hijack the virus proteins to reach their final destinations.

Interruption of virus movement

This discovery opens the door to potential new strategies to combat virus transmission.

If scientists can disrupt the GPS of the virus proteins or the cellular mechanism they rely on, they may be able to prevent the viruses from reaching or leaving the insect's salivary glands.

This could effectively prevent the virus from using the insect as a vector and stop its spread to new hosts.

Further implications of the study

“Our research highlights the incredible adaptations that viruses have evolved to navigate complex biological systems such as insects,” said Nicolas Buchon, associate professor in the Department of Entomology at Cornell University and co-lead author of the study.

“It is a reminder of the ongoing evolutionary arms race between viruses and their hosts and of the importance of basic research in understanding these complex biological processes.”

By uncovering the molecular mechanisms behind virus movement within insects, this research paves the way for new approaches to combat insect-borne diseases.

This knowledge could also be applied to the control of pests in agriculture, leading to better public health measures and improved plant protection in the future.

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