Live Attenuated Influenza Vaccines May Protect Against Emerging Strains

Live attenuated influenza vaccines (LAIV) stimulates multifaceted immune response for genetically diverse strands of Influenza A in children and may be a step towards universal vaccine for influenza, according to the results of a new study.

The study included 14 trivalent LAIV vaccinated children, from whom researchers collected blood samples before vaccination and up to 1 year after vaccination. Long-term cross-reactive T-cell response was assessed using fluorescent immunospot assay with heterologous H1N1 and H3N2 influenza A viruses and CD8 peptides from internal proteins M1, NP, and PB1. Hemagglutination inhibition was used to determine serum antibody responses.
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Before LAIV, pre-existing cross-reactive T-cells to genetically diverse influenza A strains were found in most of the children, and were further boosted after LAIV in 50% of the children.

Additional analyses showed significant increases in CD8+ T-cells that were mainly dominated by NP-specific responses.

Overall, the youngest children had the highest increases in T-cell responses after LAIV.

“Our unique trial is the first to show long-term cross-reactive T-cells elicited by LAIV in children,” the researchers concluded. “Although limited by small numbers, the findings support our hypothesis that the LAIV vaccine has the potential to provide cross-protective immunity to drifted and potentially hetero-variant strains. Hence the LAIV vaccine could possibly be a step towards the desired universal influenza vaccine.”

—Melissa Weiss

Reference:

Mohn KGI, Zhou F, Brokstad KA, Sridhar S, and Cox RJ. Live attenuated influenxa vaccination boosts durable cross-reactive and protection-associated T-cells in children [published online March 27, 2017]. J Infect Dis. https://doi.org/10.1093/infdis/jix165.