Ebola relies on a molecular “inside man” to sneak into cells.

Mice lacking the virus’s accomplice, a protein called NPC1, are completely protected from Ebola infection, scientists report May 26 in mBio. Designing drugs that target NPC1 could potentially stop Ebola from breaking and entering into humans cells, suggests study coauthor Kartik Chandran and colleagues.

In 2011, Chandran, a virologist at Albert Einstein College of Medicine in New York City, and other scientists fingered NPC1 as Ebola’s potential partner in crime (SN Online: 8/24/11). The protein rests in cell membranes and helps the virus slip past a cell’s defenses. Once inside a host cell, Ebola can settle in and hijack the molecular tools it needs to multiply.

But scientists didn’t know just how crucial NPC1 was for Ebola’s dirty work. So Chandran and colleagues injected mice missing NPC1 with a mouse version of the virus. NPC1-free mice fended off the virus completely — they showed no signs of the disease. Mice with the protein weren’t so lucky: They died within nine days of the injection.

NPC1 typically transports cholesterol through a cell; without the protein, people can develop dementia. But the study’s authors think patients could tolerate an NPC1-blocking drug because treatments would be short.