Specific antibody response of mice after immunization with COS-7 cell derived avian influenza virus (H5N1) recombinant proteins

To develop avian influenza H5N1 recombinant protein, the hemagglutinin (HA), neuraminidase (NA), matrix (M), and non-structural (NS1) of avian influenza H5N1 isolates from Thailand were engineered to be expressed in prokaryotic (E. coli) and mammalian cell (COS-7) system. The plasmid pBAD-His and pSec-His were used as vectors for these inserted genes. Mice immunized with purified recombinant proteins at concentration 50–250 μg intramuscularly with Alum adjuvant at week 0, week 2, and week 3 showed a good immunogenicity measured by ELISA and neutralization assay. The HA and NS recombinant proteins produced in COS-7 cells can induce specific antibody titer detected by neutralization assay significantly higher than corresponding recombinant proteins produced in E. coli system. The antibody produced in immunized mice could neutralize heterologous avian influenza virus determined by micro-neutralization assay. This study shows that avian influenza virus H5N1 recombinant proteins produced in mammalian cell system were able to induce neutralizing antibody response.