Flu Vaccine Plus GLA-SE Figure 3. GLA-SE enhances serum HI titers to the A/H1N1 and A/H3N2 components in Fluzone. NHPs (N = 3/group) were injected with saline (-), or were immunized with Fluzone (2007–2008) alone (+), or Fluzone formulated with emulsion (SE), or GLA-SE (1, 5, 25 or 50 mg). Serum samples were collected 4 weeks after the prime and boost immunizations, at day 30 or day 58, respectively. Shown are the HI titers from individual animals (diamonds) and GMT (indicated by the horizontal bars 6 the 95% CI) against the three components of the Fluzone vaccine. doi:10.1371/journal.pone.0013677.g003 titers induced against drifted A/H1N1 and A/H3N2 influenza variants following experimental vaccination. NHP that were primed and boosted with escalating doses of Fluzone+GLA-SE exhibited higher HI titers not only against the vaccine strain but also to the most recent drifted influenza variant (A/H1N1/Brisbane), a component of the subsequent years vaccine formulation (Figure 4). HI responses against H1N1 strains included in vaccine formulations from 1998 to 2006 were also examined. Vaccination with Fluzone alone did not elicit responses against these strains. However, when Fluzone was administered with 5–50 mg GLA-SE, robust HI titers were achieved (Figure 4) following a boost immunization (cross-reactive titers reached levels PLoS ONE | www.plosone.org 5 October 2010 | Volume 5 | Issue 10 | e13677