Continuing evolution of H6N2 influenza a virus in South African chickens and the implications for diagnosis and control

Table 3 Detection of H6N2 antibodies in three field scenarios using hemagglutination inhibition (HI) assays and ELISAs

	A Vaccinated chicken, no field challenge*					B Vaccinated chicken with field challenge**					C Non-vaccinated chicken with field challenge***
Serum titration	ELISA		HI log₂ titre			ELISA		HI log₂ titre			ELISA		HI log₂ titre
Serum titration	BioChek titre¹	IDEXX S/N²	2002 H6N2_Ag	1998 H6N8_Ag	2016H6N2_Ag	BioChek titre¹	IDEXX S/N²	2002 H6N2_Ag	1998 H6N8_Ag	2016 H6N2_Ag	BioChek titre¹	IDEXX S/N²	2002 H6N2_Ag	1998 H6N8_Ag	2016 H6N2_Ag
0	667 (1)	0.88	8	4	9	10,755(7)	0.15	12	8	12	5753 (4)	0.23	8	5	12
1:1	336 (0)	0.56	7	2	7	7383 (5)	0.13	10	7	11	3910 (3)	0.12	5	2	10
1:2	124 (0)	0.72	6	2	6	4850 (4)	0.49	9	7	10	2296 (2)	0.20	4	2	9
1:4	50 (0)	0.71	5	1	5	3802 (3)	0.44	8	6	10	1494 (2)	0.13	3	2	8
1:8	1 (0)	0.74	4	0	4	2155 (2)	0.17	7	5	8	869 (1)	0.23	2	0	7
1:16	1 (0)	0.79	3	0	3	1107 (1)	0.21	6	4	6	556 (0)	0.34	2	0	6
1:32	1 (0)	0.83	3	0	3	556 (0)	0.27	5	2	4	331 (0)	0.28	1	0	5
1:64	1 (0)	0.73	2	0	2	253 (0)	0.48	4	2	3	131 (0)	0.40	0	0	4
1:128	1 (0)	1.1	1	0	1	96 (0)	0.66	3	1	3	82 (0)	0.56	0	0	3
1:256	1 (0)	1.07	0	0	1	12 (0)	0.87	2	0	3	1 (0)	0.65	0	0	3

* Prime-boost vaccinated with commercial inactivated whole virus H6N2 vaccine (strain W-04/2002)
** Vaccinated once with commercial H6N2 inactivated vaccine (strain W-04/2002), challenged with H6N2 strain H44954/2016
*** Challenged with H6N2 strain H44954/2016
¹Titer group in brackets
²Sample to negative ratio
Ag-Antigen
Positive serological test results are highlighted in boldface

ISSN: 1746-6148