Antibody contributes to heterosubtypic protection against influenza A-induced tachypnea in cotton rats

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 by ^a
	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.

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