Viral voyager

How do you describe something the naked eye can’t see and requires its own vocabulary to describe?

That’s a challenge Dr. Kristen Conn regularly faces. As an assistant professor in the Western College of Veterinary Medicine’s (WCVM) Department of Veterinary Microbiology, Conn hopes to advance the understanding of herpesviruses. While Conn started out studying herpes simplex virus (HSV) in humans, herpesviruses present many opportunities for translational research in cattle and horses.

Conn’s work targets the functions of a protein called ICP4, which has a similar protein in equine herpesvirus (EHV) called IE1. ICP4 and IE1 are “essential transcription activators,” which means they are required for virus replication.

The DNA genomes of HSV and EHV are assembled into chromatin, a complex of DNA and histone proteins, like the DNA within host cells. Histones are basic proteins that help condense DNA into chromatin — the structure that controls DNA replication and gene expression.

To allow expression of the virus genes and virus replication, the virus chromatin is disrupted. The proteins ICP4 and IE1 are required to activate expression of some viral genes; how they do this isn’t yet fully understood and how they disrupt the viral chromatin isn’t known. If researchers could learn how to prevent ICP4 or IE1 from activating viral gene expression, they could prevent replication of the virus.

“There’s a lot of opportunity to begin to investigate how the animal alphaherpesviruses are regulated by chromatin, and use human herpes simplex virus as a model to develop questions to ask and investigate with the animal alphaherpesviruses,” says Conn.

EHV infection is present in most horses and often causes no side effects. However some strains of the virus, such as EHV-1, can cause serious effects such as respiratory infection, abortion and neurologic disease.

Better understanding of how the virus is regulated could lead to better treatment for the disease.

“There’s still plenty of room for improved treatments in infected animals,” says Conn. “If you can find additional … therapies that you can give in addition to vaccines or anti-viral treatments that help keep the virus silent [latent], you can hopefully prevent or limit any associated disease or spread.”

Over the next two years, the Townsend Equine Health Research Fund (TEHRF) is supporting Conn’s investigation of how EHV-1 protein expression is regulated, which will allow further research into the development of new therapies to prevent diseases associated with EHV-1.

Focus on inside world of cells

This work on animal herpesviruses is new for Conn, who completed an undergraduate degree at the University of Saskatchewan (USask) and a PhD degree in biochemistry at the University of Alberta (U of A), before moving on to postdoctoral training at the MRC-University of Glasgow Centre for Virus Research.

While Conn originally wanted to become a veterinarian after a family trip to WCVM’s Vetavision open house as a child, her introductory biochemistry classes turned her focus to the microscopic world.

“When I took the introductory biochemistry classes, I found a new love for what happens inside of cells,” she says.

At the U of A, her research focused on how HSV alters histone dynamics — the binding and unbinding of histones to DNA in chromatin. In Glasgow, her work focused on aspects of the anti-viral response within cells.

When Conn returned to Saskatoon to join the WCVM in July 2018, her focus shifted toward how herpesvirus affects animals. “It’s the perfect location to move into animal herpesviruses,” says Conn, who is setting up her lab and recruiting graduate students. The next step: growing stocks of HSV and EHV for future experiments.

The search for a ‘light switch’

Conn is looking for the light switch — something that can turn on and off the replication and spread of the virus, and promote latency. Latency is when the virus lies dormant within the cell, which decreases the chance of an infected animal (or human) shedding and spreading the virus.

She’s passionate as she explains her work, her eyes lighting up with the description of the complex processes that regulate viral expression. “Finding all these little pieces can help you develop a bigger picture of how the cellular mechanisms are working,” she says.

“It’s a little bit of luck, too. By understanding how the virus chromatin is regulated, you might be able to identify a factor that is absolutely critical for that chromatin to become transcriptionally active. If you can find a molecule or a mechanism to target that factor, then you can hopefully keep the virus transcriptionally silenced.”

Understanding what’s going on within the tissue culture dish requires advanced imaging, molecular biology and biochemistry techniques. The virus itself is too small to see even under a typical confocal microscope, and requires the use of click chemistry, which “marks” the virus DNA using a chemical reaction.

Conn shows pictures of what HSV looks like using this technique. It’s a black thumbprint, with a constellation of white dots. Enlarged, it’s possible to see the interaction with proteins in the cell — if you know how to look.

Within that infinitesimally small world, Conn hopes to find answers that could improve the health of multiple species — including horses.


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