Fig 1.
Comparison of NA activity between cell lysates and supernatants.
(A) NA activity in cell lysates and supernatants at different time points following infection. Cells were infected with NIBRG-14 (H5N1) virus at a multiplicity of infection of 0.001. Each data point represents the mean of three separate experiments. (B) NA activity in cell lysates and supernatants with different viral inocula. MDCK cells were infected with different dilutions of NIBRG-14, with NA activity measured in either the cell culture supernatant or cell lysates 20 h after inoculation. The total NA activity in the supernatants was calculated and compared with the activity in the cell lysates. (C) The neutralizing antibody titers of serum samples measured by the NA-MNT. The neutralizing antibody titer of NIBSC reference sheep antisera (shRef H5N1), high (huHiPos) and moderate (HuMoPos) seropositive samples, and negative (huNeg) human sera were determined by NA-MNT using either cell supernatants or lysates. Each test was repeated five times, with the CVs calculated accordingly. Note: HuHiPos, HuMoPos, and huNeg samples were obtained from a clinical study of the H5N1 candidate vaccine.
Table 1.
NA-MNT and ELISA-MNT intra-assay variation (n = 8).
Table 2.
NA-MNT and ELISA-MNT inter-assay variation (n = 9).
Fig 2.
Correlations between the HI assay, ELISA-MNT, and NA-MNT for the measurements of anti-H5N1 antibodies.
Antibodies were measured in 40 serum samples from healthy volunteers immunized with two doses of inactivated H5N1 influenza vaccine and compared between the (A) HI assay and ELISA-MNT (B) NA-MNT and HI assay, and (C) NA-MNT and ELISA-MNT. Linear regression equations and correlation coefficients were calculated by linear regression analysis of the log transformed data.
Table 3.
Serology results from 40 healthy volunteers received two doses of inactivated H5N1 influenza vaccine.
Fig 3.
H7N9 antibody responses and correlations among the HI assay, ELISA-MNT, and NA-MNT.
92 serum samples from human subjects immunized with either (A) one dose or (B) two doses of candidate H7N9 influenza vaccine were analyzed using either HI assay, NA-MNT, or ELISA-MNT. The correlations among the titers in the 92 serum samples after immunization with one dose of candidate H7N9 influenza vaccines were measured by (C) HI assay versus NA-MNT or (D) ELISA-MNT versus NA-MNT. The correlations among the titers in the 92 serum samples after immunization with two doses of candidate H7N9 influenza vaccines were measured by (E) HI assay versus NA-MNT or (F) ELISA-MNT versus NA-MNT. Linear regression equations and correlation coefficients were calculated by linear regression analysis of the log transformed data.