Mubareka for assistance in preparing the IRB protocol, and J. to Cal/09 Vaccination The observation that individuals infected with p2009 IAV  or immunized with the NJ/76 vaccine had elevated titers of anti-HA stalk antibodies led us to investigate whether vaccination with Cal/09 would also Docosahexaenoic Acid methyl ester boost anti-HA stalk antibody titers. Therefore, both control subjects and NJ/76 vaccinees were administered the monovalent Cal/09 vaccine between October 2009 and January 2010. Subjects returned to have blood drawn 6C8 months later. Endpoint IgG titers against NC/99 HA and cH6/1 HA were determined for pooled postvaccination serum from Docosahexaenoic Acid methyl ester both groups by ELISA. These were compared to the prevaccination values determined Rabbit Polyclonal to DNAJC5 in Figure?1and 1in order to calculate the fold-change in IgG titers against each HA protein post-Cal/09 vaccination (Table?3). Endpoint IgG titers of control subjects rose greater than 2-fold against cH6/1, whereas IgG endpoint titers of Docosahexaenoic Acid methyl ester NJ/76 vaccinees did not increase. No boost was observed against NC/99 HA in either group, as would be expected. In fact, a decrease in NC/99 reactivity was observed in the serum samples of NJ/76 vaccinees post-Cal/09 vaccination. Although we do not fully understand the reason for this decrease, it may be due to displacement of NC/99 antibody-producing cells with those reactive against Cal/09. These data indicate that Cal/09 vaccination is also capable of boosting titers of anti-HA stalk antibodies but only in individuals who had not been previously exposed to NJ/76. Table?3. Post-Cal/09 Vaccination Docosahexaenoic Acid methyl ester IgG Endpoint Titer Changes Against NC/99 HA and cH6/1 HA
cH6/1ND200>28008001NC/9916001600116008000.5 Open in a separate window Abbreviations: HA, hemagglutinin; IgG, immunoglobulin G; ND, not detected. Vaccination With NJ/76 or Cal/09 Boosted Neutralizing Antibodies Against Virus Containing Homologous HA Stalk and a Heterologous HA Head It was important to determine whether the boost in anti-HA stalk antibodies experienced after NJ/76 or Cal/09 vaccination corresponded to enhanced neutralization titers against virus containing a heterosubtypic HA head domain. To test this, we performed a microneutralization assay against a cH5/1 N3 virus using our pooled serum samples. The cH5/1 N3 virus was used to detect the presence of HA stalk neutralizing antibodies, as it contains an H5 HA head domain, a PR8 HA stalk, and an N3 from Miss/06. A cH6/1N3 virus would also have been interchangeable for the purposes of this assay but was not available. In agreement with the IgG endpoint titer data against cH6/1, Docosahexaenoic Acid methyl ester serum samples from NJ/76 vaccinees exhibited markedly more potent neutralization titers against cH5/1 N3 than did control subjects prior to vaccination with Cal/09 (2430 vs 90). However, only control subjects experienced a boost in neutralizing antibodies subsequent to vaccination (810, up from 90; Figure?3A). As expected, NJ/76 vaccinees had neutralization titers against Cal/09 that were 3-fold more potent than control subjects prior to Cal/09 vaccination (90 vs 30). Both groups experienced a boost in neutralizing antibody titers against Cal/09 subsequent to Cal/09 vaccination (Figure?3B). Taken together, these data demonstrate that the anti-HA stalk antibodies boosted by vaccination with 1976 and 2009 H1N1 viruses correspond to an enhanced capacity to neutralize virus harboring a homologous HA stalk and a heterosubtypic HA head domain. Open in a separate window Figure?3. NJ/76 and Cal/09 vaccines boosted broadly neutralizing antibodies. Microneutralization assays were performed on MDCK against (A) cH5/1 N3 and (B) Cal/09 virus using TPCK-trypsin-treated, pooled serum samples collected.