Antibody therapy explored by Pitt, other researchers to combat bird flu

Roberta Burkhart, Pittsburgh Post-Gazette on May 4, 2025

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While the risk of contracting and dying from the H5N1 avian flu remains low for humans, researchers continue to hunt for vaccines and treatments in case the virus mutates to spread more easily between animals and humans — or among humans themselves.

A team that includes researchers from the University of Pittsburgh and the National Institutes of Health Vaccine Research Center say they have found that an antibody therapy lessened the severity and prevented death in monkeys that contacted the bird flu.

The journal Science in late January published the team's findings, which explore the preventive effects of administering a neutralizing antibody before infection to minimize severe disease caused by H5N1 avian flu.

Douglas Reed, associate professor of immunology at Pitt's School of Medicine and a faculty member of its Center for Vaccine Research, said this type of therapy differs from a traditional vaccine but the basic principle of using antibody therapy to prevent and treat disease has been around for more than 100 years.

"Vaccines help the body make its own antibodies. In contrast, inoculation with a broadly neutralizing antibody offers more direct protection by binding to and neutralizing H5N1 virus particles," said Mr. Reed, who is the study's co-corresponding author.

The NIH's National Cancer Institute describes a neutralizing antibody as one that "binds to a virus and interferes with its ability to infect a cell."

In the study, monkeys were inoculated with a neutralizing antibody called MEDI8852, which was developed by biopharmaceutical company AstraZeneca, before being infected with bird flu three days later.

"We chose this specific antibody because it targets a part of the influenza virus called the stalk region of the hemagglutinin protein, which stays the same across different flu strains. Focusing on this stable part of the virus makes it harder for the virus to mutate and avoid the antibody," Mr. Reed said.

Stalk-targeting antibodies, like the one used in the study, have been found to protect against a wider variety of flu viruses than those that target less conserved parts, Mr. Reed explained.

"That said, antibody inoculation is not intended to protect against an infection, but can make the disease symptoms less severe and protect against death."

Whether the virus will mutate beyond animal to human transmission is difficult to know, and experts continue to warn that a mutation like that could lead to a pandemic on the scale of COVID-19 — or larger.

"H5N1 is showing all signs that it could be as severe if not more severe than [COVID-19] when it entered the population. It's hard to predict. We already know that hundreds have died [from avian flu infection] over the past 20 years," Andrew Pekosz told the Post-Gazette in January. He is professor and vice chair of the molecular microbiology and immunology department at the Johns Hopkins Bloomberg School of Public Health in Baltimore.

"There is a big potential for this virus to cause a lot of suffering in the human population should it acquire the ability to transmit from person to person," he said.

For the monkeys in the study, "the antibody protected against disease and death," Mr. Reed said, though researchers "did see disease breakthrough at lower doses." That information was used to establish a "threshold protection."

Researchers also noted that the protective serum levels "remained stable for eight to 12 weeks, which suggests to us that this prophylactic treatment could be useful for protecting first responders during the early stages of a H5N1 outbreak," he said.

More studies are needed to be able to use the treatment in humans, he said, but "this antibody already has been in clinical trials for seasonal influenza and was shown to be safe."

Because the neutralizing antibody "targets a region that is relatively conserved in all influenza viruses, it could provide universal protection against different types of influenza, including seasonal flu, but more testing is still needed. We see this immunization approach as one of many in the arsenal of infection prevention tools for controlling infection outbreaks."

Since 2024, the Centers for Disease Control and Prevention has confirmed one U.S. death and 70 human infections from the bird flu; since January 2022, also per the CDC, nearly 170 million wild and domestic birds have been affected by the highly pathogenic avian influenza. The sick birds have been reported in all U.S. states.

As of Friday, more than 1,000 cattle herds across 17 states had been infected with H5N1 since March 2024, according to data from the U.S. Department of Agriculture. No infections have been reported in Pennsylvania.