Since 2003, the H5N1 influenza virus, more commonly known as the bird flu, has been responsible for the deaths of millions of chickens and ducks and has infected more than 650 people, leading to a 60 percent mortality rate for the latter. Luckily, this virus has yet to achieve human-to-human transmission, but a small number of mutations could change that, resulting in a pandemic. Now a team of investigators from St. Jude Children’s Research Hospital, Stanford University Medical Center, and MacroGenics has developed an antibody that has proven 100 percent protective against the virus in two species of animal models [ferrets (image) and mice]. The research was published online on February 11, 2015 in the Journal of Virology, a publication of the American Society for Microbiology (ASM). Antivirals have been potential sources of protection, but they are hampered by the propensity of viruses to rapidly mutate, which often results in resistance. “We have seen this in H5N1 viruses,” said corresponding author Richard Webby, Ph.D., a Member in the Infectious Diseases Department at St. Jude Children’s Research Hospital, Memphis, TN, and Director of the World Health Organization (WHO) Collaborating Center for Studies on the Ecology of Influenza Viruses in Lower Animals and Birds. Vaccines, Dr. Webby said, must be developed to match each flu virus, something which would likely take at least six months following the emergence of a pandemic. Additionally, vaccines are somewhat ineffective in the elderly and in immunocompromised individuals. The investigators turned to antibodies, which target antigens on viruses as specifically as keys to locks, thus disabling them. Regardless, mutations can also render antibodies ineffective.