Future antibody therapies could target the H5N1 avian influenza virus (green).Credit: Steve Gschmeisner/Science Image Library
Researchers are increasingly working to develop antibody therapies to treat infectious diseases. Treatments are designed to reduce the severity of infections such as bird flu, and treat chronic conditions such as HIV. Synthetic antibodies could also make vaccines for diseases like Covid-19 more effective.
Antibodies are part of the immune system’s defense against infection. Scientists produce synthetic versions by combining B cells taken from mice and human cell lines. Most approved antibody drugs are intended to treat cancer and autoimmune diseases.
Monoclonal antibodies are also widely used in antiviral therapies to treat severe infections caused by Ebola, respiratory syncytial virus (RSV) and SARS-CoV-2, says Runhong Zhou, who studies immune responses at the University of Hong Kong. He adds that previous efforts to develop antivirals for bird flu have not been successful because the virus undergoes mutations that make treatment less effective. Antibody drugs for COVID-19 have also become less effective over time for the same reason.
Bird flu treatment
For H5N1 avian influenza, Zhu and his colleagues developed an antibody that has two targets: the stem region of proteins on the surface of the virus and receptors on a person’s cells. In cell-based experiments, they found that the antibody neutralized multiple live strains of avian influenza virus and was superior to the monoclonal antibody model — which targets only one specific antigen — in preventing viral particles from binding to or entering cells. Their results suggest that targeting the virus stem and host receptors at the same time “represents a good strategy to enhance the efficacy of antibodies,” says Zhou, who was among the teams to present their findings in this area at the International Symposium of the Alliance for Epidemic Research in Melbourne last week. But it is still unclear how long protection will last, or whether antibody treatment can create mutations in the virus that allow it to evade the immune system.
Hsiang Hong, a medical student at Columbia University in New York City, is also part of a team using antibodies to the H5N1 virus. He says he and his colleagues are developing a team of monoclonal antibodies that target multiple parts of the H5N1 virus to track how it evolves over time and identify potential treatments that could target several types of the virus.
Helping hand
Antibodies can also enhance the effectiveness of other treatments, such as vaccines, which need to be updated because most viruses mutate frequently as they evolve.
Antibodies that can bind to highly conserved parts of SARS-CoV-2 could help vaccines remain effective even as the virus mutates, says Ziwei Chen, an immunology researcher at the University of Hong Kong. Chen and his team identified several regions of the surface of the SARS-CoV-2 particle that do not change when the virus undergoes mutation. They also found that several antibodies targeting these highly conserved regions were effective in neutralizing various coronaviruses, including SARS-CoV-1, which causes severe acute respiratory syndrome, variants of SARS-CoV-2 and some coronaviruses found in pangolins and bats.