Seasonal influenza vaccination correlates to cross-reactive antibody responses in bird handlers

NIAID CEIRS | Research Publication Commentary

Oshansky CM et al. Seasonal influenza vaccination is the strongest correlate of cross-reactive antibody responses in migratory bird handlers. mBio. 2014 Dec 9.

Vaccines are a powerful and effective tool to combat influenza outbreaks and are routinely used to protect humans from seasonal influenza infections. Novel influenza strains of pandemic potential can arise from viruses circulating in wild aquatic birds, the natural reservoir for avian influenza. Protection from gradual changes in circulating human influenza virus requires periodic reformulation of the seasonal influenza vaccine, but protection from novel viruses that arise by genetic reassortment or mutation remains a challenge. Therefore, researchers continue to investigate how to enhance vaccine protection against new viruses by studying the complete human immune response to influenza.

In this paper, Oshansky et al. investigated whether individuals with occupational exposure to wild bird populations had an increased immune response to diverse avian influenza viruses. Indeed, they found that most individuals with exposure to wild birds had an immune response to one or more avian hemagglutinin (HA) subtypes. This response did not correlate to exposure to a particular avian species, except that those individuals with occupational or recreational exposure to poultry displayed a specific immune response to H7 HA. Interestingly, the strongest correlate for development of a detectable antibody response to a broad range of avian influenza viruses was prior seasonal influenza vaccination. This finding suggests that individuals who received the seasonal influenza vaccine may generate a better response to novel influenza strains. Many antibodies that bind to HA do not have protective activity; indeed, when sera were tested for ability to block virus attachment to cells there was no correlation between high binding antibodies and high neutralization. It would be interesting to see if high-binding antibodies confer protection by other mechanisms.

Although cell-mediated immune responses are important for resolving infections, the researchers found that individuals with a significant antibody response did not necessarily mount a robust cellular immune response. The authors conclude that influenza vaccines that result in a robust response of both the cellular and antibody arms of the immune system might increase protective immune responses against a broad range of influenza strains.