DNA Vaccine Expressing Conserved Influenza Virus Proteins Protective Against H5N1 Challenge Infection in Mice
Suzanne L. Epstein* , Terrence M. Tumpey†, Julia A. Misplon*, Chia-Yun Lo*, Lynn A. Cooper‡, Kanta Subbarao‡, Mary Renshaw‡, Suryaprakash Sambhara‡, and Jacqueline M. Katz‡
Author affiliations: *Food and Drug Administration Rockville, Maryland, USA; †United States Department of Agriculture, Athens, Georgia, USA; ‡Centers for Disease Control and Prevention, Atlanta, Georgia, USA;
Figure 1. DNA vaccination induces T cell responses. a) Enzyme-linked immuno spot (ELISPOT) assay for interferon-γ (IFN-γ) secreting cells. Mice were immunized three times with A/NP+A/M or influenza B nucleoprotein DNA (B/NP DNA) intramuscularly. Spleen cells were analyzed by ELISPOT, using peptides at 1 μg/ml or A/PR/8 live virus. Results are the mean of three experiments. No response to A/PR/8 virus occurred in one experiment. Concanavalin A (Con A) responses: A/NP+A/M groups, >274 for all experiments; B/NP groups, >329 for all experiments. b) Cytotoxic T cell assay. Mice were vaccinated as above or with live A/PR/8 virus given on the day of the second DNA injection. Spleens were harvested 2½ weeks after the third DNA injection. Spleen cells were restimulated in vitro with live A/PR/8 or B/AA. After 7 days of culture, restimulated effector cells at various ratios were mixed with P815 target cells infected with A/PR/8 or B/AA, and lactate dehydrogenase (LDH) release measured.
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