Intranasal vaccination with an inactivated whole influenza virus vaccine induces strong antibody responses in serum and nasal mucus of healthy adults

Abstract

Haemagglutination inhibition (HI) and neutralization (NT) titers as well as haemagglutinin (HA) specific antibody responses were examined in 50 healthy adults aged between 22 and 69 y old after two intranasal administrations of an inactivated whole virus vaccine derived from A/Victoria/210/2009 virus (45 μg HA per dose) at 3 week intervals. Serum HI titers after two-doses of the nasal vaccine showed>2.5-fold rise in the ratio of geometric mean titer upon vaccination,>40% of subjects with a ≥ 4-fold increase in titer and>70% of subjects with a titer of ≥ 1:40, all parameters associated with an effective outcome of vaccination in the criteria defined by the European Medicines Agency. Serum neutralizing antibody responses correlated with HI antibody responses, although NT titers were about 2-fold higher than HI titers. These high levels of serum responses were accompanied by high levels of HI and neutralizing antibody responses in nasal mucus as measured in concentrated nasal wash samples that were about 10 times diluted compared with natural nasal mucus. Serum and nasal HI and neutralizing antibody responses consisted of HA-specific IgG and IgA antibody responses, with IgG and IgA antibodies being dominant in serum and nasal responses, respectively.

Keywords: haemagglutination-inhibiting antibody; healthy adult volunteer; influenza virus; intranasal vaccination; neutralizing antibody.

Figure 1. HI antibody responses in serum. (A) HI antibody responses before and after primary and secondary vaccination are shown for serum. A paired t test was performed to compare data from week 0 (pre) and 6 (post). Correlation coefficient (r) and p value were calculated. *; p < 0.05. (B) The relationship of serum HI antibody responses before and after secondary vaccination. The abscissa and ordinate show the pre- and post-vaccination HI titers, respectively. Further, it is shown how these relate to conversion rate and protection rate, which are on the border or within the area marked by the bold line and by the light gray background, respectively. Each circle represents an individual and shows the relation between the pre- and post-vaccination titers. Gray circles indicate subjects between 60 and 69 y-of-age.

Figure 2. Neutralizing antibody responses and correlation between HI and NT titers in serum. (A) Neutralizing antibody responses before and after primary and secondary vaccination are shown. A paired t test was performed to compare data from week 0 (pre) and 6 (post). The correlation coefficient (r) and p value were calculated. **; p < 0.01. (B) Correlation between HI and NT titers in serum 3 weeks after the secondary nasal vaccination. The abscissa and ordinate show HI and NT titers, respectively. Pearson r value and p value were calculated. Each individual is represented by a circle showing corresponding HI and NT titers. Gray circles indicate subjects between 60 and 69 y-of-age.

Figure 3. HI and neutralizing antibody responses in nasal mucus. HI (A) and NT (B) titers before and after primary and secondary vaccination. A paired t test was performed to compare data from week 0 (pre) and 6 (post). The correlation coefficient (r) and p value were calculated. *; p < 0.05, ***; p < 0.001. (C) Correlation between HI and NT titers in nasal wash 3 weeks after the secondary nasal vaccination. The abscissa and ordinate show HI and NT titers, respectively. Pearson r value and p value were calculated. Each circle represents an individual showing corresponding HI and NT titers. Gray circles indicate subjects between 60 and 69 y-of-age.