We have developed a protocol for rapid production of recombinant hemagglutinin (rHA) of influenza viruses. This procedure does not require access to virus strains. Using only DNA sequence data from the CDC/WHO influenza virus database, we synthesized chemically HA genes de novo, using a procedure optimized for protein expression in E. coli. Our protocol reduces the time required to produce an influenza vaccine to about one month compared to the 6-8 months needed for the traditional egg-based preparation. In addition, we have developed a cloning protocol utilizing influenza virus RNAs as templates for reverse transcription-polymerase chain reaction (rPCR) gene amplification. Using these procedures, bacterial seed clones/cultures have been constructed and used to produce pilot plant quantities of rHA. We have now developed standardized downstream processing protocols for protein extraction, purification, refolding, and vaccine formulation. A second protocol designed to broaden the immune response has been developed using the chemically synthesized polypeptides conjugated to genetically inactivated diphtheria toxin. Using our production protocols, time-consuming delays required by restrictive regulations related to select agents, USDA control measures for avian derived pathogens, and high-level biosafety containment are completely avoided. As shown below, we have successfully produced rHA immunogens representing five influenza A virus strains and a M2e-diphtheria toxoid conjugate vaccine: -------- H5N1 rHA Vietnam 1203/2004 Clade 1 60,000 MWt, 526 AA*, 6.9 pI, D17-Q531 HA residues, AY818135 accession number# H5N1 rHA Indonesia 5/2005 Clade 2a 59,790 MWt, 526 AA, 6.7 pI, D17-Q531 HA residues, ABP51969 accession number H1N1 rHA California 05/2009 pandemic 57,499 MWt, 512 AA, 6.9 pI, D18-Q528 HA residues, FJ966952 accession number H3N2 rHA California 7/2004 seasonal 58,561 MWt, 523 AA, 8.2 pI, Q17-K538 HA residues, 119760 accession number H5N1 rHA BHG Qinghai 1/2004 Clade 2b 60,104 MWt, 526 AA, 6.8 pI, D17-Q537 HA residues, DQ659327 accession number all A virus strains M2e peptide 2658 MWt, 22 AA, 3.9 pI, S2-D23 HA residues, various accession numbers * Amino acid residues. Numbers correspond to the full-length influenza HA0 protein before cleavage of the signal peptide and at the HA1/HA2 polybasic amino acid proteinase cleavage site. # Primary structure, i.e. amino acid residues representing the first amino acid of the mature influenza HA protein to the truncated -COOH end. Numbering is based on full length HA0 protein as recorded for the amino acid sequence assignment from the appropriate Gene Bank accession number. -------- The recombinant protein constructs were designed to represent the mature configuration of HA with the transmembrane domain, which spans the viral capsid, deleted from the carboxyl terminal. This domain was replaced with a Gly3X-His6X tag to facilitate purification of the expressed protein using Ni-ion chelating chromatography. Using five representative virus strains, rHA was produced in E. coli. The expressed protein was purified from inclusion bodies by urea solubilization and Ni-ion column chromatography. The solubilized rHA was further processed by rapid dilution into refolding buffer, extensive dialysis, and spin-filter concentration. Vaccine candidates were formulated by adsorbing the rHA onto alum, treating it with formalin, or by both. The purified rHA derived from the A/Vietnam/1203/2004 (H5N1), A/Indonesia/5/2005 (H5N1), and A/swine pandemic/2009 (H1N1) influenza viruses were used in investigational vaccine formulation and immunization studies. Injected into young outbred mice three times 2 weeks apart (2.5-5 mcg/mouse), rHA induced antibodies with hemagglutination inhibition titers of 40 or higher, suggesting that rHA could induce protective immune responses against influenza virus infection (FDA guidelines require a minimal titer of 40). Our preliminary data suggest that the alum-absorbed rHA vaccine, produced in just four weeks, can fulfill the FDA requirements. Antibody neutralization experiments based on plaque reduction analysis and inhibition of viral replication within a unique tissue culture cell line are planned. Synthetic M2e peptides were linked covalently to a genetically detoxified diphtheria toxin (DT-H21G) via thioether linkages. MALDI-MS analyses showed an average of 7 chains M2e per DT molecule with a mass ratio of DT: M2e = 1:0.3. This conjugate, soluble or alum adsorbed, induced high anti-M2e IgG antibodies in young outbred mice after the 2nd and 3rd injections (0.4 to 1.4 p<0.0005). An antibody response was also observed against the DT carrier protein. Our preliminary results suggest that this candidate vaccine may induce immunity against heterologous strains of influenza A virus. We used the HA fusion peptide of H5N1 virus for preparing investigational vaccines: two sequences containing 9 amino acids of the fusion peptide plus a linker and a longer 18 amino acids sequence plus linker were synthesized and conjugated to BSA. Injected sc into young general purpose mice, at a fraction of a human dose, these conjugates were immunogenic and induced booster responses. The induced antibodies bound to rHA and the influenza virus as well as to the peptides. This methodology of linking the highly conserved fusion peptide to carrier protein can broaden a protective immune response against influenza A virus strains and some influenza B strains. This would eliminate the need for annual vaccination.

Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Zip Code