Banana lectin, also known as BanLec, was identified as a potent inhibitor of the replication of the HIV virus in 2010. The discovery of antiviral activity, while encouraging, was dampened by knowledge of another property of BanLec, namely its ability to induce cell division.
This trait, known scientifically as mitogenicity, is a major obstacle to the use of BanLec as a topical antiviral. While the protein may neutralise viruses, it could also make it easier for them to enter the bloodstream if the cell division it triggers disrupts the natural barrier of the skin.
Faced with this shortcoming, a team led by researchers at the University of Michigan has looked for ways to improve the side effect profile of BanLec without affecting its potency as an antiviral. The work led to the substitution of a single amino acid and the publication of the paper “Engineering a Therapeutic Lectin: Uncoupling Mitogenicity from Antiviral Activity” in the journal Cell.
Researchers with no involvement in the project have hailed it as a notable paper. “Using some nifty bio-engineering the researchers were able to silence the unwanted side effects, but maintain the virus killing ability. It was able to potently inhibit viruses like influenza, hepatitis C and HIV grown in culture,” Jonathan Ball, professor of molecular virology, University of Nottingham, said.
The broad-spectrum antiviral activity of BanLec derives from its ability to bind to the sugars that coat the surfaces of many viruses. Once the lectin has bound to these sugars, the virus is rendered harmless. This led to the idea that BanLec could be used as an anti-HIV coating on condoms, in which context it would act as a biological barrier.
Outstanding questions
The publication of preclinical data showing the protein can be modified to reduce its mitogenicity without compromising potency has reignited interest in the potential of BanLec. However, as with any preclinical-stage program, significant questions about whether BanLec can succeed in humans remain.
For some, side effects are still a worry. “I would be somewhat concerned that although the inflammatory properties of BanLec have been abolished, it would still bind to normal cellular proteins in the body with unforeseen consequences,” Professor Jonathan Stoye, group leader and virologist at The Francis Crick Institute, said.