Population-level antibody estimates to novel influenza A/H7N9

Abstract

There are no contemporary data available describing human immunity to novel influenza A/H7N9. Using 1723 prospectively collected serum samples in southern Vietnam, we tested for antibodies to 5 avian influenza virus antigens, using a protein microarray. General-population antibody titers against subtype H7 virus are higher than antibody titers against subtype H5 and lower than titers against H9. The highest titers were observed for human influenza virus subtypes. Titers to avian influenza virus antigens increased with age and with geometric mean antibody titer to human influenza virus antigens. There were no titer differences between the urban and the rural location in our study.

Keywords: H7N9; influenza; microarray; pandemic; serology.

Figure 1.

Quantile-quantile plots showing comparisons of titer distributions among 5 antigens (n = 1723; upper left). Titer values and specific antigens are labeled on both axes. The 10 subplots in the lower-right part of the graph show quantile-quantile plots of the top quartile of individuals (n = 431) with the highest geometric mean antibody titers across the 5 avian influenza virus antigens. All pair-wise distribution comparisons show that the distributions are statistically significantly different (all P values are < 10⁻⁵, by the Kolmogorov-Smirnov and Wilcoxon rank-sum tests), except for the 2 panels marked “NS” (ie, not significant). Antigen abbreviations are A/Vietnam/1194/2004 (H5/04), A/Cambodia/R0405050/2007 (H5/07), A/Hubei/1/2010 (H5/10), A/Chicken/Netherlands/1/2003 (H7), and A/Guinea Fowl/Hong Kong/WF10/1999 (H9).

Figure 2.

Scatter plots of antibody titers by antigen and age group. Red lines show 70th, 80th, and 90th quantiles of the data points. A single red line at 10 indicates that the 70th, 80th, and 90th quantiles of that data set are all equal to 10.