Plasma cell and serum antibody responses to influenza vaccine in preterm and full-term infants

Background: Preterm (PT) infants are at greater risk for severe influenza infection and experience decrements in long-term antibody responses to vaccines. This may related to defects in antibody secreting cell (ASC) generation. Objective: To investigate the relationships among the frequencies of influenza-specific antibody secreting cells, ASC numbers and subsets, and antibody responses to influenza vaccines (IV) among PT and full term (FT) infants. Design/methods: We enrolled 11 former PT (<32 weeks' gestation, <1500 g' birth weight) and 11 FT infants, 6-17 months of age, receiving their first influenza immunizations. Infants received two doses of inactivated trivalent (T)IV or quadrivalent (Q)IV during the 2012-2013 and 2013-2014 influenza seasons, respectively, at 0 and 28 days, and blood was drawn at 0, 10, 35, and 56 days and 9 months. Vaccine-specific antibody was measured by hemagglutination inhibition (HAI) at 0 and 56 days and 9 months, vaccine-specific ASC numbers by enzyme linked immunospot (ELISPOT) at 10 and 35 days, and ASC subsets by flow cytometry at 0, 10 and 35 days. Results: PT infants had post-vaccine HAI titers to all 4 vaccine strains at least equal to Fr infants at 56 days and 9 months after beginning immunization. Influenza-specific ASC ELISPOT responses at 35 days were higher among PT than FT infants (median 100 v. 30 per 106 PBMC, p = 0.04). ASC numbers at 35 days were positively correlated with serum HAI titers at 56 days (p = 0.50-0.80). There were no statistical differences between PT and Fr infants in the frequency of five ASC subsets and no specific ASC subset correlated with durability of serum antibody titers. Conclusions: Influenza-specific ASC numbers in both FT and PT infants correlated with peak antibody titers, but ASC subsets did not correlate with durability of antibody response. (C) 2017 Elsevier Ltd. All rights reserved.