BanLec: the banana-derived antiviral agent

A substance originally found in bananas and carefully edited by scientists could someday fight off a wide range of viruses, new research suggests.

And the process used to create the virus-fighting form may help scientists develop even more drugs, by harnessing the “sugar code” that our cells use to communicate.

The new research focuses on a protein called banana lectin, or BanLec, that reads the sugars on the outside of both viruses and cells. Five years ago, scientists showed it could keep the virus that causes AIDS from getting into cells – but it also caused side effects that limited its potential use.

Now, an international team of scientists have created a new form of BanLec that still fights viruses in mice, but does not have a property that causes irritation and unwanted inflammation.

They succeeded in peeling apart these two functions by pinpointing the part of the molecule that triggered side effects. Altering a gene, they engineered a new version of BanLec, called H84T.

The result: a form of BanLec that worked against the viruses that cause AIDS, hepatitis C and influenza in tests in tissue and blood samples – without causing inflammation. The researchers also showed that H84T BanLec protected mice from getting infected by flu virus.

“What we’ve done is exciting because there is potential for BanLec to develop into a broad spectrum antiviral agent, something that is not clinically available to physicians and patients right now,” says David Markovitz, M.D., professor of internal medicine at the University of Michigan Medical School. “But it’s also exciting to have created it by engineering a lectin molecule for the first time, by understanding and then targeting the structure.”

BanLec could become useful in a pandemic response

The new version of BanLec has one less “Greek key” site on its surface for sugars to attach. This makes it impossible for sugars on the surface of immune system cells called T cells to attach in multiple spots at once and trigger inflammation. But it still allows BanLec to grab on to sugars on the surface of viruses and keep them from getting into cells.

Several years of research still lie ahead before BanLec can be tested in humans. But Markovitz and his colleagues hope that their team’s work can help address the lack of antiviral drugs that work well against many viruses or against viruses that change rapidly, such as influenza.

“Better flu treatments are desperately needed,” says Markovitz. “Tamiflu is only modestly effective, especially in critically ill patients, and influenza can develop resistance to it. But we also hope that BanLec could become useful in situations such as emergency pandemic response, and military settings, where the precise cause of an infection is unknown but a viral cause is suspected.”

The team continues to test H84T BanLec against other viruses in mice and tissue samples.

Discovery opens doors to work on other lectins

The team’s achievement in engineering a lectin molecule opens doors to other work on other lectins. Lectin molecules read the sugar code of sugar molecules that cover the surface of many viruses and cells.

Scientists still don’t fully understand all the things that the sugar code controls – but suspect it may be almost as powerful for controlling how our cells work as the DNA code inside cells. Sugars, and the lectins that attach to them, seem to play a key role in how cells “talk” to one another, call for help, and perform other functions.

In fact, one of the mysteries remaining for BanLec work is just how the T cells of the immune system actually attach to it. Hans-Joachim Gabius, Ph.D., the leader of the German part of the team, is working to explore this further, and to use this newly-engineered tool to look at other aspects of the sugar code.