Table 1.

Subtype-specific antibody responses are evident in sera from A/PR/8/34(H1N1) and A/Wuhan/95(H3N2)-infected animals.

	Antibody titer as measured bya
	HAI		NI		Neutralization		Neut + C1q
Serum source	H1N1	H3N2	H1N1	H3N2	H1N1	H3N2	H1N1	H3N2
Naïve serum	<10	<10	0	0	<100	<100	<100	<100
H1N1-immune	640	<10	80	0	1600	<100	3200	<100
H3N2-immune	<10	160	0	320	<100	200	<100	800

^aStandard hemagglutination inhibition (HAI), neuraminidase inhibition (NI) and neutralization (neut) assays in the absence as well as presence of complement factor C1q were performed as described in Materials and Methods. Viruses used for these assays were A/PR/8/34 (H1N1) and A/Wuhan/359/95 (H3N2) that had been used to infect the cotton rats that were the source of this serum pool. Animals were boosted several times by rechallenging them with the same virus before serum was collected. The lowest dilution of serum used in the HAI assay was 1/10 and therefore no inhibition of agglutination is recorded as a titer of < 10. The lowest dilution of serum used in the neutralization assay was 1/100 and therefore no neutralization is recorded as a titer of < 100.