Publication Q&A: Blunting Specific T-dependent Antibody Responses with Engineered ‘Decoy’ B Cells

Dec. 11, 2024 – Ragan Pitner, PhD, an immunology researcher in the lab of David Rawlings, MD, in Seattle Children’s Research Institute’s Center for Immunity and Immunotherapies, together with his colleagues, identified a way to engineer immune cells that normally make antibodies (B cells) into “decoy” immune cells that prevent other immune cells from making unwanted antibodies, thus preventing drug rejection. Dr. Pitner is an affiliate member of the Invent at Seattle Children’s Postdoctoral Scholars Program.

The researchers demonstrated the therapeutic potential of this approach using a small-animal model of hemophilia A, a genetic disorder where the blood doesn't clot properly due to lack of a specific protein called factor VIII (FVIII). Traditionally, patients with hemophilia are treated with replacement therapy, where the missing clotting factor is infused into the bloodstream. However, 30% of hemophilia A patients develop inhibitor antibodies against factor VIII following protein replacement therapy. In this study, the decoy B cells blocked the anti-FVIII immune response at the cellular level.

Children’s contributing authors: Ragan Pitner, PhD (first author), Noelle Dahl, Meng-Ni Fan, PhD, Xiaohe Cai, Kelsey Roe, PhD, Carol Miao, PhD, Richard James, PhD, and David Rawlings, MD (corresponding author)

Read this article in the journal Molecular Therapy (published Oct. 2, 2024).

Is this research a first in any way?

Dr. Ragan Pitner (left) and Dr. David Rawlings

To make these decoy B cells, we used a gene-editing technique called CRISPR to delete (or “knock out”) a specific master gene called Blimp1. This was the first demonstration that B cells that were Blimp1-knockout could be used to alter immune responses.

Here’s an analogy: Imagine B cells are soldiers that need specific one-on-one training. It’s a highly difficult job, so each of these soldiers requires at least a little solo face time with a specific general — a T cell in this scenario. Usually, there are enough generals to train the soldiers one-on-one. Now, imagine an enemy snuck 10 “decoy” soldiers for every real one into the boot camp. All of the decoy soldiers are extremely good at getting to the front of the line and look exactly to the generals like any other soldier they need to train. However, after the decoy soldier leaves training, they don’t go fight. They effectively wasted the generals’ time and energy training someone who won’t fight, thereby preventing most of the real soldiers from receiving the training they need to fight. This is the first study to demonstrate that such an approach could work. It's unprecedented to use a decoy approach like this for immune regulation.

What’s the potential impact?

This research could lead to improved strategies for preventing the immune systems of children and adults with certain gene deficiencies from rejecting life-saving drugs or gene therapies.

What are the next steps and long-term goals for this research?

In our initial research, we showed the decoy B cell approach could work to prevent the generation of drug-inhibiting antibodies. Immediate next steps are related to improving that process with an eye toward more complex applications.

We are currently working to improve the decoy approach by engineering the B cells to carry immune-suppressing cargo meant only for specific T cells. Back to the earlier analogy: Imagine that we not only want to waste the generals’ time, but we now want to give our decoy soldiers bribes to pass on to the generals to get them on our side. When the engineered B cells talk to disease-associated T cells, they shut down disease-associated immune responses. We're focused on seeing what sort of cargo we can give the B cells to make them more effective.

Long term, we hope to develop this technology into one that can be used to treat autoimmune diseases like multiple sclerosis, lupus or rheumatoid arthritis.

With whom did you collaborate to make this work possible? Who supported the research?

We worked with Jaime Chao, PhD, and Michael Gerner, PhD, in the University of Washington Department of Immunology to generate important microscopy data. We received critical reagents from Nathan Avery and P. Clint Spiegel, PhD, in the Chemistry Department at Western Washington University. Meng-Ni Fan, PhD, and Xiaohe Cai in the research institute’s Miao Lab contributed to our hemophilia A experiments.

This work was supported in part by the Children’s Guild Association Endowed Chair in Pediatric Immunology, the Hansen Investigator in Pediatric Innovation Endowment, the National Center for Advancing Translational Sciences of the National Institutes of Health, as well as a second award from the National Institutes of Health.

Further reading

• Engineering B Cells for Future Therapies
• New Cell-Based Therapy Drives Progress Toward Diabetes Treatment, Prevention
• Seattle Children’s Researchers Highlight Achievements in Novel Therapies at Gene and Cell Therapy Meeting