WASHINGTON (AP) — Scientists are developing a way to inject designer immune cells into transplant patients to help fight off severe viral infections.

Bone marrow transplants save thousands of lives but patients are vulnerable to infection for months, until their new immune system kicks in. Anti-viral medications don't work very well.

Scientists have long wanted to treat those patients with virus-fighting T cells from healthy donors, but it requires a custom-made dose that is too complicated and costly to be practical. Now, researchers at Baylor College of Medicine report a faster and easier way.

They brewed T cells in a laboratory that could fight five different viruses at once, and took just 10 days to create. The next step is trying to create a bank of these cells that could provide off-the-shelf treatment.