Antibody responses to influenza A(H1N1)pdm infection

Abstract

We investigated humoral immune response to influenza A(H1N1)pdm infection and found 32 (22%) of the infected individuals identified by PCR failed to produce a ≥ 4-fold hemagglutinin inhibition assay (HAI) response; a subset of 18 (56%) produced an alternate antibody response (against full-length HA, HA stalk, or neuraminidase). These individuals had lower pre-existing HAI antibody titers and showed a pattern of milder illness. An additional subset of 14 (44%) did not produce an alternate antibody response, had higher pre-existing antibody titers against full-length & stalk HA, and were less sick. These findings demonstrate that some individuals mount an alternate antibody response to influenza infection. In order to design more broadly protective influenza vaccines it may be useful to target these alternate sites. These findings support that there are influenza cases currently being missed by solely implementing HAI assays, resulting in an underestimation of the global burden of influenza infection.

Keywords: Antibodies; Hemagglutination inhibition; Influenza; Neuraminidase.

Figure 1.. Pee-exposure and post-exposure correlation plots among HAI responders & alternative responders

Correlation of antibody levels as measured by Pearson correlation coefficient, comparing pre (A,C) and post (B,D) exposure levels for both HAI responders and non-responders, Brighter colors indicate greater correlation, Red colors indicate positive correlation, purple colors indicate negative correlation, HA = hemagglutinin, NA = neuraminidase, HAI = hemagglutination inhibition assay.