Mucosal antibody response in influenza infected children

Seasonal influenza virus infections in humans cause annual epidemics that result in millions of human infections worldwide and have significant health and economic burdens (Molinari, N.A. et al, 2007). The 2009 H1N1 pandemic caused 86,000,000 persons to be infected and 19,000 deaths. Pandemic influenza causes viruses to undergo antigenic shifts, therefore individuals can have numerous influenza infections during their lifetime. As a result of the H1N1 strains' antigenic shift, vaccines are reformulated annually. Low robust immunities make children and the elderly a primary target to influenza. The immunological response, especially at the site of infection, in a naturally-infected influenza patient has not been well characterized. The overall aim of the study was to examine the mucosal antibody response to influenza during the course of a natural infection. We used the nasal lavages of participants enrolled in a clinical study (FLU09) based at the Le Bonheur's Children Hospital in Memphis, TN. These patients were previously confirmed to be infected with the pandemic strain of H1N1. We determined the level of influenza-specific IgA and IgG against the major antigenic protein, hemagglutinin (HA) using enzyme-linked immunosorbent assay (ELISA). We found that influenza-specific IgA and IgG were detectable in the nasal compartment as early as upon enrollment and showed age-specific trends in the kinetics of antibody response. In summary, we have developed a method to detect influenza-specific antibody at the site of infection and showed age-specific antibody response.