Table 3.

Mean percentage macroscopic pneumonia, composite microscopic pneumonia, and trachea microscopic scores ± standard error of the mean (SEM) from pigs with maternally-derived antibodies (MDA) from exposed sows vaccinated with H1N1pdm09 whole inactivated virus (WIV-MDA) vaccine or experimentally infected with H1N1pdm09 (EXP-MDA), or from a non-boosted naturally exposed sow (NAT-MDA), or without MDA (No MDA) at 5 days post infection (dpi) with homologous H1N1pdm09(2:6) or heterologous H1N2-δ1(1:7) in Study 2.

Challenge Groups	Macroscopic percentage (%)	Microscopic scores (0-22)	Trachea histopathology (0-8)
Homologous
No MDA/NC	0.4 ± 0.1a	1.3 ± 0.1a	0.1 ± 0.1a
No MDA/H1N1	24.6 ± 2.3b	15.2 ± 0.6b	17 ± 03b,c
WIV-MDA/H1N1	0.7 ± 0.4a,c	5.3 ± 0.1c	0.8 ± 0.6a,b
EXP-MDA/H1N1	8.2 ± 1.8c	10.4 ± 0.9d	2.4 ± 0.2c
Heterologous
No MDA/NC	0.4 ± 0.1a	1.3 ± 0.1a	0.1 ± 0.1a
No MDA/H1N2	15.2 ± 2.0b	13.4 ± 0.7b	3.1 ± 0.5b
WIV-MDA/H1N2	28.9 ± 8.1c	13.4 ± 1.0b	3.0 ± 0.6b
EXP-MDA/H1N2	17.6 ± 2.0b,c	12.0 ± 0.8b	2.3 ± 0.4b
NAT-MDA/H1N2	16.2 ± 2.9b	17.7 ± 1.1c	3.5 ± 0.6b

^a,b,cStatistically significant differences in the same column identified with different lowercase letters (P ≤ 0.05).