Scientific Publications by FDA Staff

J Virol 2011 Feb;85(3):1246-56

Bacterial HA1 vaccine against pandemic H5N1 influenza: evidence of oligomerization, hemagglutination, and cross- protective immunity in ferrets.

Khurana S, Verma S, Verma N, Crevar CJ, Carter DM, Manischewitz J, King LR, Ross TM, Golding H

Impending influenza pandemic requires global vaccination to prevent large scale mortality and morbidity, but traditional influenza vaccine production is too slow for rapid responses. We have developed bacterial systems for expression and purification of properly folded functional hemagglutinin as a rapid response to emerging pandemic strains. A recombinant H5N1 (A/Vietnam/1203/2004) hemagglutinin globular domain (HA1), was produced in E coli under controlled redox refolding conditions. Importantly, the properly folded HA1 (1-320) contained ¿ 75% functional oligomers without addition of foreign oligomerization sequence. Site directed mutagenesis mapped the oligomerization signal to the HA1 N-terminal Ile-Cys-Ile residues at positions 3-5. The purified HA1 oligomers (but not monomers) bound fetuin and agglutinated red blood cells. Upon immunization of rabbits, the oligomeric HA1 (1-320) elicited potent neutralizing antibodies against homologous and heterologous H5N1 viruses more rapidly than HA1 (28-320) containing only monomers. Ferrets vaccinated with oligomeric HA1 (but not N-terminus-deleted, monomeric HA1) at 15 and 3 ¿g/dose were fully protected from lethality and weight loss following challenge with homologous (H5N1 A/Vietnam/1203/2004, clade 1) as well as heterologous clade 2.2 H5N1 (A/WooperSwan/Mongolia/244/2005) virus. Protection was associated with a significant reduction in viral loads in the nasal washes of homologous and heterologous virus challenged ferrets. This is the first study that describes the presence of an N-terminal oligomerization sequence in the globular domain of influenza hemagglutinin. Our findings suggest that functional oligomeric rHA1-based vaccines can be produced efficiently in bacterial systems and can be easily upscaled in response to a pandemic influenza threat.