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document
The role of nasal IgA in children vaccinated with live attenuated influenza vaccine . BACKGROUND Immunoglobulin A ( IgA ) is the predominant antibody produced in response to mucosal infections . The role of IgA in providing protection against influenza in children vaccinated with live attenuated influenza vaccine ( LAIV ) has not been well described . METHODS Nasal IgA responses were assessed using data from 3 prospective , 2-year , randomized studies comparing LAIV with placebo in children 6-36 months of age . In each study , samples were collected in a subset of patients ; a new cohort was enrolled each year . Ratios of strain-specific nasal IgA to total nasal IgA were calculated and prevaccination to postvaccination geometric mean fold-rises ( GMFRs ) were evaluated . Mean postvaccination IgA ratios were compared for subjects with and without confirmed influenza illness by study and in pooled analyses . RESULTS Across studies , a higher percentage of children receiving LAIV had a ≥ 2-fold increase in strain-specific IgA ratio compared with placebo recipients . GMFRs after LAIV in years 1 and 2 ranged from 1.2 to 6.2 , compared with 0.5-2.2 among placebo recipients . Similar responses were observed in subjects who were baseline seronegative and seropositive based on serum hemagglutination inhibition antibody titers . In years 1 and 2 , the mean postvaccination strain-specific to total IgA ratio was 3.1-fold ( P < 0.01 ) and 2.0-fold ( P < 0.03 ) higher among LAIV recipients with no evidence of culture-confirmed influenza illness compared with LAIV recipients who developed culture-confirmed influenza illness ; a similar and consistent trend was observed for each individual study and type/subtype . CONCLUSIONS The current analysis demonstrates that nasal IgA contributes to the efficacy of LAIV and can provide evidence of vaccine-induced immunity . However , the inherent heterogeneity in nasal antibody levels and variability in nasal specimen collection hinders the precise evaluation of mucosal antibody responses . Other studies have demonstrated that LAIV-induced immunity is also partially explained by T-cell immunity , serum antibody responses , and innate immunity , consistent with the multi-faceted nature of immunity induced by wild-type influenza infection and other live virus vaccines .
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Intervention_Pharmacological
nasal IgA
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Intervention_Pharmacological
Immunoglobulin A ( IgA
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Intervention_Pharmacological
IgA
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Intervention_Pharmacological
live attenuated influenza vaccine ( LAIV )
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Intervention_Control
placebo
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Intervention_Pharmacological
nasal IgA
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Intervention_Pharmacological
IgA
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Intervention_Pharmacological
LAIV
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Outcome_Physical
geometric mean fold-rises ( GMFRs )
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Outcome_Physical
Mean postvaccination IgA ratios