title: Humoral and cell-mediated immunity to pandemic H1N1 influenza in a Canadian cohort one year post-pandemic: implications for vaccination.
abstract: We evaluated a cohort of Canadian donors for T cell and antibody responses against influenza A/California/7/2009 (pH1N1) at 8-10 months after the 2nd pandemic wave by flow cytometry and microneutralization assays. Memory CD8 T cell responses to pH1N1 were detectable in 58% (61/105) of donors. These responses were largely due to cross-reactive CD8 T cell epitopes as, for those donors tested, similar recall responses were obtained to A/California 2009 and A/PR8 1934 H1N1 Hviruses. Longitudinal analysis of a single infected individual showed only a small and transient increase in neutralizing antibody levels, but a robust CD8 T cell response that rose rapidly post symptom onset, peaking at 3 weeks, followed by a gradual decline to the baseline levels seen in a seroprevalence cohort post-pandemic. The magnitude of the influenza-specific CD8 T cell memory response at one year post-pandemic was similar in cases and controls as well as in vaccinated and unvaccinated donors, suggesting that any T cell boosting from infection was transient. Pandemic H1-specific antibodies were only detectable in approximately half of vaccinated donors. However, those who were vaccinated within a few months following infection had the highest persisting antibody titers, suggesting that vaccination shortly after influenza infection can boost or sustain antibody levels. For the most part the circulating influenza-specific T cell and serum antibody levels in the population at one year post-pandemic were not different between cases and controls, suggesting that natural infection does not lead to higher long term T cell and antibody responses in donors with pre-existing immunity to influenza. However, based on the responses of one longitudinal donor, it is possible for a small population of pre-existing cross-reactive memory CD8 T cells to expand rapidly following infection and this response may aid in viral clearance and contribute to a lessening of disease severity.
authors: Department of Immunology, University of Toronto, Toronto, Ontario, Canada.
authors: Lisa E
authors: LE
authors: Wagar
authors: Laura
authors: L
authors: Rosella
authors: Natasha
authors: N
authors: Crowcroft
authors: Beth
authors: B
authors: Lowcock
authors: Paulina C
authors: PC
authors: Drohomyrecky
authors: Julie
authors: J
authors: Foisy
authors: Jonathan
authors: J
authors: Gubbay
authors: Anu
authors: A
authors: Rebbapragada
authors: Anne-Luise
authors: AL
authors: Winter
authors: Camille
authors: C
authors: Achonu
authors: Brian J
authors: BJ
authors: Ward
authors: Tania H
authors: TH
authors: Watts
mesh_terms: D000328:Adult; D000368:Aged; D000914:Antibodies, Viral / Q000276:immunology; D000917:Antibody Formation / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D015331:Cohort Studies; D003429:Cross Reactions / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D007111:Immunity, Cellular / Q000276:immunology*; D056724:Immunity, Humoral / Q000276:immunology*; D007156:Immunologic Memory / Q000276:immunology; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000276:immunology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D058873:Pandemics / Q000517:prevention & control*; D016133:Polymerase Chain Reaction; D057566:Self Report; D014019:Tissue Donors; D014611:Vaccination; D055815:Young Adult
chemical_list: D000914:Antibodies, Viral