• Influenza virus;
  • mucosal and systemic immunity;
  • secretory nasal IgA;
  • serum IgG

Please cite this paper as: Fujimoto et al. (2012) Induction and maintenance of anti-influenza antigen-specific nasal secretory IgA levels and serum IgG levels after influenza infection in adults. Influenza and Other Respiratory Viruses 6(6), 396–403.

Objectives  To determine the induction and changes in anti-influenza virus secretory IgA (s-IgA) levels in nasal washes and serum IgG levels in patients with influenza.

Methods  The study recruited 16 patients with influenza aged 35·6 ± 9·6 years in 2007/2008 and 2008/2009 seasons. Nasal washes and serum were obtained throughout the first year. Anti-viral s-IgA levels and neutralization activities in nasal washes, and serum anti-viral IgG levels and hemagglutination inhibition (HI) titers were measured.

Results  Anti-viral(H1N1) s-IgA to total IgA ratio and neutralizing antibody titer were low in nasal washes of all patients, whereas serum levels of anti-viral IgG and HI titers varied widely at day 1·4 ± 1·0 postinfection. Both nasal s-IgA and serum IgG levels later increased significantly, reaching peak levels at day 9·6 ± 3·3 postinfection. The induced nasal s-IgA then returned toward the initial levels within 300 days, although the levels at day 143 ± 70 were 3·03-fold of the initial. Individual serum IgG levels also returned toward the initial levels within 300 days, although the mean levels remained high probably because of re-infection in a subgroup of patients. Although influenza A (H3N2) was a minor epidemic subtype in both flu seasons, a significant rise in nasal anti-viral (H3N2) s-IgA levels and a slightly increase in serum IgG levels were noted.

Conclusion  Low levels of nasal anti-viral s-IgA and neutralizing antibody were noted compared with a wide range of serum anti-viral IgG and HI titers at the onset of infection. Elevated s-IgA and IgG returned toward the initial levels within 300 days of infection with minor exceptions.