Potential therapy derived from banana protein is effective against SARS-CoV-2

Posted by Caroline on November 25th, 2022

On January 13, 2020, a paper was published online touting the creation of a possible therapy that could be used against all known strains of the flu. A week later, the first laboratory-confirmed case of SARS-CoV-2 sparked the two-and-a-half-year COVID-19 pandemic in the United States. Interestingly, before the virus temporarily halted their work, the international team of researchers for this flu paper also investigated treatments for the coronavirus.

"We thought MERS would be a big target at the time, because its 35 percent mortality rate was a concern for us," said David Markovitz, MD, a professor of internal medicine in the Division of Infectious Diseases at the University of Michigan School of Medicine.

A paper in Cell Reports Medicine details the efficacy of H84T-BanLec against all known human-infecting coronaviruses, including Middle East Respiratory Syndrome (MERS), the original SARS, and SARS-Cov2 (including omicron variants). Along with Markovitz were two senior authors, Dr. Peter Hinterdorfer of the Institute of Biophysics at Johannes Kepler University and Kwok-Yung Yuen, MD, MBBS, University of Hong Kong. The lead author of the paper is Jasper Fuk-Woo Chan, MD, of the University of Hong Kong.

Markovitz said: "When COVID-19 happened, we certainly wanted to study the potential of this therapy and find that it was effective against every type of coronavirus in vitro and in vivo. Whether it was systemic injection or intranasal injection in animal models, or early in the disease as prevention or treatment, it is effective.”

H84T-BanLec is a lectin (a carbohydrate-binding protein) isolated from banana fruit. It achieves its remarkable virus-blocking ability by binding to high-mannose glycans, which are present on the surface of viruses but rarely on normal healthy human cells. After binding, the virus cannot enter cells to infect them. Using atomic force microscopy and related methods, the team confirmed that H84T forms multiple strong bonds with the spike protein, which Markovitz said may explain why coronaviruses have difficulty resisting lectins.

Despite their antiviral potential, lectins have traditionally been avoided as possible treatments because they are proteins that can stimulate the immune system in harmful ways, Markovitz explained. However, H84T-BanLec was modified to eliminate this effect and did not show deleterious effects in animal models.

While several drugs are currently available to treat COVID-19, including Remdesivir, Palo Verde and Monoclonal Antibodies, they vary in effectiveness, side effects, and ease of use, and as SARS-CoV2 continues to evolve, many drugs have proven to be less effective.

According to the team, H84T-BanLec holds unique promise because it is effective against all coronavirus variants and influenza viruses. Markowitz and his team hope to see the therapy take a more difficult step from animal models to human trials. The team envisions a nasal spray or drops that could be used to prevent or treat coronavirus and flu infections in seasonal and pandemic situations. They also want to study the use of H84T-BanLec to fight cancer, because cancer cells, like viruses, have a lot of mannose glycans on their surfaces.