Table 2. Antibody responses to 1 or 2 107.0-TCID50 doses of H9N2 reassortant influenza vaccine (A chicken/Hong Kong/G9/97 × A/Ann Arbor/6/60 ca).
Category | Participants, no. |
Participants with any antibody response, % |
H9 HI antibody titer |
Neutralizing-antibody titera |
Titer of serum IgG antibody to rH9 |
Titer of NW IgA antibody to rH9 |
||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Mean (SD) |
Participants with ≥4-fold increase, % |
Mean (SD) |
Participants with ≥4-fold increase, % |
Mean (SD) |
Participants with ≥4-fold increase, % |
Mean (SD) |
Participants with ≥4-fold increase, % |
|||||||
Before | After | Before | After | Before | After | Before | After | |||||||
H9N2 seropositive | ||||||||||||||
Dose 1 | 9 | 33 | 4.6(0.7) | 4.8 (0.8) | 0 | 6.2(1.8) | 6.9 (1.3) | 11 | 6.2(1.1) | 6.3(1.0) | 0 | 6.3(2.8) | 6.7(1.7) | 11 |
Dose 2 | 3 | 33 | 5.3(0.6) | 5.3(1.2) | 0 | 7.0(1.5) | 8.0(1.5) | 0 | 6.3(1.2) | 6.9(1.2) | 33 | 7.3(0.8) | 7.8(0.8) | 0 |
Both doses | 3 | 100 | 4.3(0.6) | 5.3(1.2) | 33 | 6.3(2.0) | 8.0(1.5) | 67 | 6.3(1.2) | 6.9 (1.2) | 67 | 5.3(2.9) | 7.8 (0.8) | 67 |
H9N2 seronegative | ||||||||||||||
Dose 1 | 41 | 29 | 1.9 (0.8) | 2.9 (1.4) | 29 | 3.1(1.1) | 3.8 (1.5) | 24 | 5.5 (0.9) | 5.9 (1.0) | 12 | 5.5 (1.4) | 6.1 (1.3) | 2 |
Dose 2 | 24 | 58 | 2.6(1.3) | 4.5(1.2) | 58 | 3.7(1.1) | 5.3(1.4) | 50 | 6.1(1.0) | 6.4(1.1) | 13 | 5.8(1.5) | 6.7(1.7) | 13 |
Both doses | 24 | 100 | 1.8(0.8) | 4.5(1.2) | 92 | 3.2(0.7) | 5.3(1.4) | 79 | 5.6(1.0) | 6.4(1.1) | 50 | 6.2(1.5) | 6.7(1.7) | 21 |
NOTE. All antibody titers are expressed as reciprocal log2 values. Specimens for measurement of serum and nasal-wash antibody were obtained as indicated in the “Participants, materials, and methods” section of the text; data shown are from before and 4–6 weeks after each vaccination. For measurement of serum IgG antibody and nasal-wash IgA antibody by ELISA, recombinant H9 of the G1 subtype was used. Immulon 2 plates were coated (30 ng/well) with recombinant baculovirus-expressed H9 G1 HA (influenza A/HK/1073/99 H9N2; Protein Sciences). The column entitled “Participants with response to both doses” displays the mean reciprocal log2 value for this subset of individuals before the first vaccination and after the second vaccination. “Percent of individuals with a response to both doses” also includes some individuals with a 2-fold response to each dose, so the percentage of participants with a response to both doses may be greater than the sum of the percentages responding to each dose. HI, hemagglutination inhibition; NW, nasal wash; rH9, recombinant H9.
The microneutralization assay used in the present study differed from that published elsewhere, in the following respects: (1) the source of Madin-Darby canine kidney cells was the Laboratory of Infectious Diseases of the National Institute for Allergy and Infectious Diseases of the National Institutes of Health; (2) the test virus was H9N2 G9/AA ca; (3) because the test virus was ts, incubation was at 32°C rather than 39°C; (4) the no. of cells/well was 2 × 104, rather than 1.5 × 104; and (5) the amount of virus per well was 80 TCID50 rather than 100 TCID50.