Mehdi Benkahla, Ph.D.

What if viral infections could trigger type 1 diabetes?

FUNDED BY: The generosity of the donors to the Sierra Shapery Memorial SPARK Award.

What was the goal of your SPARK project?

The incidence of type 1 diabetes (T1D) has been increasing over the years, and this can only be explained by changes in the environment. Decades of research have provided epidemiological evidence for an association between T1D and viruses, particularly coxsackieviruses of the Enterovirus genus. We just don’t know how these viruses are implicated in the crime.

I set out to shed light on this mystery by using a newly developed model of human pancreatic slices (HPS), which can be kept alive in vitro. The goal was to infect the HPS using a coxsackievirus B3 genetically engineered to express an enhanced green fluorescent.

I wanted to know: Which cell types in the pancreas are susceptible to infection? What is the impact of viral infection on beta cell function? Which inflammatory responses are induced and do they correlate with beta cell function? What is the effect of viral infection on islet-resident macrophages and other immune interactions? What is the effect of viral infection on HLA class I expression and autophagy in islet pancreatic cells?

Did you face any challenges?

Yes, the challenge I faced was the scarcity of human pancreatic slices. Our supplier had very low inventory; we would get one donor every six months or so, which is not enough for our experiments. Now, we get samples of human pancreas from a different supplier, Prodo Labs, and slice it ourselves with the help of our colleagues at Moores Cancer Center at UC San Diego Health.

SPARK project results:

We followed the fluorescent protein markers to see how infection spread in the HPS. After 3 days of infection, the green fluorescent protein (GFP) was detected by high resolution confocal microscopy in the insulin-producing beta cells. These infected beta cells were also expressing HLA-I, which is a molecule by which cells present antigen to the immune system to trigger an immune response. HLA-I is also a hallmark of T1D.

We also observed that tissue-resident macrophages (an immune cell type that eliminates infected cells) were also infected by CVB3. Our 3D analysis shows that HLA-I is hyperexpressed in the CVB3-infected slices compared to the controls.

Since the HPS have tissue-resident immune cells, we wanted to study the impact of the infection on CD68+ macrophages. Do they become attracted
to islets during CVB3 infection? We quantified the number of macrophages in CVB3-infected and non-infected islets, and we observed that in our model at day 3 post-infection, macrophages were not more attracted to the islets during CVB3 infection.

What’s next for this project?

More effort is needed to generate a better understanding of the consequences of viral infections in the pancreas and its role in the onset of type 1 diabetes. We plan to evaluate the impact of CVB3-GFP infection on beta cells and tissue-resident macrophages and if the infection could lead to an immune destruction of beta cells when cocultured with PBMCs. Tissue-resident macrophages will be characterized by single-cell RNA-seq and their interaction with PBMCs will be assessed. Using the preliminary data generated during my SPARK project, we’ve applied for follow-on funding from NIH in the form of an R21. We’ve also secured other sources of human pancreatic tissues from City of Hope and Prodolabs, as well as initiated a collaboration with Moores Cancer Center for slicing pancreas tissue samples.

What’s next for Mehdi?

I will continue to further this research as I complete the last year of my post doc at LJI. For the next steps in my career, I hope to move to industry and obtain a position at a biotech that studies type 1 diabetes. I’m also open to moving into new research areas where I can continue to learn new skills.