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Seasonal flu vaccines may protect against additional avian strains
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Influenza vaccinations may provide cross-protection against additional strains of influenza not covered by the vaccine, according to researchers.
“[This finding is exciting] because it suggests that the seasonal flu vaccine boosts antibody responses and may provide some measure of protection against a new pandemic strain that could emerge from the avian population,” Paul G. Thomas, PhD, associate member at the department of immunology at St. Jude Children’s Research Hospital in Memphis, Tenn., said in a press release. “There might be a broader extent of reactions than we expected in the normal human population to some of these rare viral variants.”
Thomas and colleagues evaluated plasma samples from 95 participants attending the 2010 meeting of the American Ornithologist Union — a cohort with diverse exposure to North American migratory wild bird populations. The researchers exposed the samples to avian influenza virus subtypes H3, H4, H5, H6, H7, H8 and H12 proteins using ELISA and hemagglutination (HA) inhibition (HAI) assays.
The ELISA tests revealed the presence of antibodies against avian influenza proteins in 77% of the participants. Along with a strong antibody response to the seasonal H3N2 human virus-derived H3 subtype — a part of the 2009-2010 vaccine— in the majority of participants, many also demonstrated robust, detectable antibody responses to group 1 HA (avian H5, H6, H8, H12) and group 2 HA (avian H4, human H7) influenza subtypes. Some degree of detectable antibodies against four or more HA proteins was present in 66% of participants, and a few demonstrated responses to all subtypes tested. Most of these subtypes previously had not been observed in humans.
Further analyses revealed that significant antibody responses did not necessarily translate to significant T-cell responses to avian viruses. The researchers also found that participants who received seasonal influenza vaccination had significantly greater antibodies to the avian H4, H5, H6 and H8 subtypes. Those with exposure to poultry had significantly stronger antibody responses to the H7 subtype vs. those not exposed to poultry, but these participants did not have increased antibody responses to any other subtypes. Immunity did not appear to be affected by exposure to other types of birds.
“Together, our data indicate that the individual who mounts a robust antibody response does not necessarily mount an equally robust cellular response, and therefore vaccination strategies that elicit both cellular and humoral responses would be advantageous,” the researchers wrote. “New vaccination modalities, including adjuvants and attenuated viral vectors, may support this aim of eliciting broad population immunity by utilizing multiple immune effector mechanisms.”
Disclosure: The researchers report no relevant financial disclosures.
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