Table 3.
Mean HI antibody titers against H3N2 influenza strains used for immunization and antigenically distinct strains in pigs of different vaccine groups.
| Geometric Mean HI Antibody Titers Per Group at: (Number of Pigs with Titer ≥40) |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 9 | Week 13 | ||||||||||
| Virus Strains | Inf.: 1°: 2°: |
NC95 PBS PBS |
NC95 G08 G08 |
NC95 PA10 PA10 |
NC95 G08 PA10 |
NC95 PA10 G08 |
NC95 PBS PBS |
NC95 G08 G08 |
NC95 PA10 PA10 |
NC95 G08 PA10 |
NC95 PA10 G08 |
| EU swine | |||||||||||
| G84 | 5 (0) | 160 (5) | 53 (3) | 184 (5) | 46 (4) | 5 (0) | 1470 (5) | 160 (4) | 279 (5) | 368 (5) | |
| ENG87 | 5 (0) | 15 (0) | 10 (0) | 17 (1) | 9 (0) | 5 (0) | 160 (5) | 30 (3) | 46 (5) | 23 (2) | |
| G08 | 5 (0) | 243 (5) | 139 (5) | 279 (5) | 80 (5) | 5 (0) | 2941 (5) | 485 (5) | 970 (5) | 1114 (5) | |
| N.A swine | |||||||||||
| TX98 | 13 (0) | 844 (5) | 640 (5) | 422 (5) | 1689 (5) | 17 (1) | 368 (5) | 1470 (5) | 243 (5) | 1940 (5) | |
| MN99 | 10 (0) | 485 (5) | 485 (5) | 368 (5) | 844 (5) | 10 (0) | 211 (5) | 735 (5) | 121 (5) | 1280 (5) | |
| ONT05 | 6 (0) | 106 (5) | 243 (5) | 80 (5) | 485 (5) | 5 (0) | 40 (3) | 845 (5) | 46 (3) | 485 (5) | |
| PA10 | 5 (0) | 121 (5) | 485 (5) | 70 (5) | 1114 (5) | 5 (0) | 80 (4) | 4457 (5) | 320 (5) | 1470 (5) | |
| IN11 | 5 (0) | 80 (4) | 184 (5) | 61 (4) | 279 (5) | 5 (0) | 121 (5) | 3880 (5) | 243 (4) | 1940 (5) | |
| IA11 | 5 (0) | 368 (5) | 640 (5) | 368 (5) | 1470 (5) | 6 (0) | 243 (5) | 3378 (5) | 422 (5) | 1689 (5) | |
| MO12 | 5 (0) | 121 (5) | 160 (5) | 160 (5) | 368 (5) | 5 (0) | 121 (5) | 211 (5) | 160 (5) | 279 (5) | |
| MO15 | 5 (0) | 160 (5) | 320 (5) | 243 (5) | 485 (5) | 5 (0) | 106 (5) | 640 (5) | 139 (5) | 422 (5) | |
| Human | |||||||||||
| VIC75 | 5 (0) | 23 (2) | 13 (1) | 20 (1) | 20 (1) | 5 (0) | 121 (5) | 35 (4) | 48 (3) | 70 (3) | |
| ENG88 | 5 (0) | 243 (5) | 139 (5) | 160 (5) | 320 (5) | 5 (0) | 106 (5) | 184 (5) | 160 (5) | 160 (5) | |
| NC95 | 80 (5) | 1689 (5) | 2560 (5) | 2229 (5) | 4457 (5) | 70 (5) | 1114 (5) | 5120 (5) | 2560 (5) | 5881 (5) | |
| WI05 | 6 (0) | 9 (0) | 6 (0) | 6 (0) | 7 (0) | 5 (0) | 5 (0) | 10 (1) | 5 (0) | 9 (0) | |
| PER09 | 6 (0) | 8 (0) | 11 (1) | 8 (0) | 10 (1) | 5 (0) | 7 (0) | 23 (2) | 7 (0) | 10 (1) | |
| VIC11 | 5 (0) | 5 (0) | 5 (0) | 5 (0) | 5 (0) | 5 (0) | 6 (0) | 7 (0) | 6 (0) | 12 (1) | |
| HK14 | 5 (0) | 6 (0) | 7 (0) | 5 (0) | 6 (0) | 5 (0) | 5 (0) | 35 (3) | 5 (0) | 7 (0) | |
| No. of strains (n/18) against which a titer ≥40 was achieved per group | 1 | 12 | 12 | 12 | 12 | 1 | 14 | 12 | 14 | 13 | |
Inf., 1°, 2°: virus strains used for infection, first, and second vaccination. N.A: North American. HI antibody titers were determined 2 weeks after the first (week 9) and second (week 13) vaccinations. The starting dilution in the HI test was 1:10. HI antibody titers below 10 were assigned a titer of 5. Five pigs were examined per group. HI titers ≥40 are considered sero-protective. Grey indicates geometric mean HI antibody titers (GMT) titers ≥40. The color coding of the test viruses is based on antigenic clusters of the HA. Viruses of different clusters differ by at least four antigenic units. The seven human seasonal H3N2 viruses belong to six different clusters [42,43,44]. The EU and N.A swine H3N2 viruses are given the same color as their human precursors, or a different shade if they represent antigenic drift variants of swine H3N2 viruses [6,45]. Full virus names: G84; A/swine/Gent/1/1984, ENG87; A/swine/England/163266/1987, G08; A/swine/Gent/172/2008, TX98; A/swine/Texas/4199-2/1998, MN99; A/swine/Minnesota/593/1999, ONT05; A/swine/Ontario/33853/2005, PA10; A/swine/Pennsylvania/A01076777/2010, IN11; A/Indiana/08/2011, IA11; A/swine/Iowa/A01049750/2011, MO12; A/swine/Missouri/A01476459/2012, MO15; A/swine/Missouri/A01840724/2015, VIC75; A/Victoria/3/1975, ENG88; A/England/427/1988, NC95; A/Nanchang/933/1995, WI05; A/Wisconsin/67/2005, PER09; A/Perth/16/2009, VIC11; A/Victoria/361/2011, HK14; A/Hong Kong/4801/2014.