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LAIV may provide immunity to diverse influenza strains without prior exposure
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Live-attenuated influenza vaccines increase durable, cross-reactive T-cell responses among children, with potential to provide cross-protective immunity among drifted and hereto-variant influenza strains, according to data published in The Journal of Infectious Diseases.
“Vaccination is the most cost-effective strategy to combat the public health burden of influenza. However, current influenza vaccines require annual updating to cover new emerging strains, which constantly evolve to circumvent antibodies,” Kristin G-I Mohn, MD, PhD, and colleagues wrote. “Thus the challenge is to develop broadly cross-reactive vaccines that are protective in the face of constant viral evolution.”
To analyze the vaccine’s efficacy against emerging strains of influenza, researchers assessed the long-term cross-reactive T-cell response in 14 children who had received trivalent LAIV vaccines. A fluorescent immunospot assay with heterologous H1N1 and H3N2 influenza A viruses and CD8 peptides from the internal proteins was used. Blood samples that were used in this study were collected from the participating children before vaccination and up to 1 year after vaccination.
Cross-reactive T-cells to genetically diverse influenza A were found in the majority of children before vaccination; however, 50% of the children demonstrated an additional boost after receiving LAIV. When T-cells were examined more closely, researchers found notable increases in CD8+ T-cells.
Younger children who received LAIV demonstrated the most significant increase in T-cell responses.
“Cross-reactive T-cells are considered important in limiting disease severity and death in the absence of strain-specific antibodies, such as during a pandemic. It is noteworthy, that the overall levels of pre-existing hetero-variant influenza specific [interferon-gamma] T-cells were high, with most children having levels of more than 100 SFU/million PBMCs pre-vaccination, which were boosted after receiving LAIV,” Mohn and colleagues wrote. “These findings indicate a considerable number of pre-existing influenza-specific T-cells with cross-reactive potential in our pediatric population, confirming findings at a population level. These pre-existing T-cells may explain the diversity of clinical symptoms after infection, from asymptomatic to fulminant pneumonia.” – by Katherine Bortz
Disclosure: The researchers report no relevant financial disclosures.
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