Comparison of complement dependent lytic, hemagglutination inhibition and microneutralization antibody responses in influenza vaccinated individuals

Abstract

Virus specific, non-neutralizing antibodies such as complement dependent lytic (CDL) antibodies may reduce morbidity following infection through the clearance of infectious virus particles and infected cells. We examined hemagglutination inhibition (HAI), microneutralization (MN) and CDL antibody titers to influenza A H1 and H3 virus strains in 23 healthy young adults who received the 2005-2006 trivalent inactivated influenza vaccine. Post vaccination, we detected statistically significant increases in MN and CDL antibodies but not in HAI antibodies. Statistically significantly higher fold increases in CDL antibodies post vaccination were seen compared with MN and HAI antibodies post vaccination. However, the overall fold increases were modest, likely related to the fact that most of the subjects had received influenza vaccination previously. This study showed that influenza vaccination is not only capable of increasing the level of antibodies that neutralize virus but also antibodies that can cause lysis of infected cells. The biological significance of these CDL antibodies merits further investigation in clinical studies.

Figure 1. Serum HAI, MN and CDL A/ New Caledonia antibody responses following receipt of influenza vaccine. The mean Log ₁₀ HAI, MN, and CDL titers for the 23 subjects in this study are shown before vaccination, at 2–3 weeks and at 9–10 weeks after vaccination. MN data presented here is a subset of data previously published. X axis represents the prevaccination and post vaccination timepoints tested and the Y axis represents the mean log₁₀ antibody titer. Statistically significant (p < 0.05) increases between prevaccination to either of the post vaccination timepoints are denoted by * and were calculated using paired t test.

Figure 2. H3N2 A/ Wisconsin serum HAI, MN and CDL antibody responses following receipt of influenza vaccine. The mean Log ₁₀ HAI, MN, and CDL HAI, MN, and CDL titers for the 23 subjects in this study are shown before vaccination, at 2–3 weeks and at 9–10 weeks after vaccination. MN data presented here is a subset of data previously published X axis represent the prevaccination and post vaccination timepoints tested and the Y axis represents the mean log₁₀ antibody titer. Statistically significant (p < 0.05) increases between prevaccination to either of the post vaccination timepoints are denoted by * and were calculated using paired t test.

Figure 3. Comparison of HAI, MN and CDL endpoint dilution fold increases post vaccination. Peak fold increases in log₁₀ HAI and MN titers and CDL endpoint dilution antibody titers were calculated from the prevaccination timepoint to the peak post vaccination timepoint for the H1N1 A/New Caledonia virus and the H3N2 A/Wisconsin virus. X axis represents the antibody assay tested and the Y axis represents the fold increase in the log₁₀ antibody response. Statistically significant (p < 0.05) differences in fold antibody titers post vaccination are denoted by * and were calculated using unpaired t test.