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Fig. 1 | Virology Journal

Fig. 1

From: A novel epitope-blocking ELISA for specific and sensitive detection of antibodies against H5-subtype influenza virus hemagglutinin

Fig. 1

Discrimination between the anti-H5 HA positive and negative sera in the H5 EB-ELISA. Serum samples of the nonimmunized chickens and chickens immunized with LPAIVs and recombinant HA protein from the H5N1 HPAIV (rH5-E. coli) to obtain the reference and experimental antisera, respectively, were analyzed in the EB-ELISA as described in the Methods section. Data on the analyzed samples are provided in Table 1 and Additional file 1: Tables S2–S4. Annotations for the horizontal axes refer to serum category and subcategory. The reference antisera were denoted according to the HA and NA subtypes of AIV used for chicken inoculation. Denotations of antisera against H5-subtype AIVs were completed with HI titers determined using the homologous virus strains and provided in the certificates. The * and ** symbols were applied to discriminate between different virus strains of the same HA and NA subtype, while the # symbol followed by the numbers (1, 2 or 3) discriminate among the antiserum batches. Experimental antisera were denoted according to the vaccine HA subtype and HI titers against heterologous H5N2 LPAIV adapted from our previous paper [10]. Annotations of the vertical axes refer to the test results, expressed as the inhibition percentages. The cutoff value of the test was calculated from the inhibition percentages set for anti-H5 HA negative sera of the nonimmunized chickens (arithmetic mean + 2xSD) and shown as the horizontal line. The results for individual serum subcategories are presented as the arithmetic means ± SD of the inhibition percentages calculated for the indicated number of independent sample assays (n) or samples tested (N). Triangle and circle symbols represent the results for the control and the remaining sera, respectively. Samples showing inhibition above the cutoff value of 38.5% were considered positive against HA of H5-subtype influenza viruses

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