Recombinant Influenza Hemagglutinin (HA) Trimer

Background

Hemagglutinin (HA) is the major surface glycoprotein of influenza viruses, mediating receptor binding and membrane fusion. Influenza HA is synthesised as an immature precursor (HA0) that must be proteolytically cleaved into HA1 and HA2 polypeptides for the activation of membrane fusion. Mature HA protein exists on the virus surface in a non-covalent homotrimeric form, with each monomer consisting of two structural-functional domains: the head and the stem. HA1 is the major component of the spherical head and is located at the membrane-distal end, comprising the receptor binding domain (RBD), which is crucial in viral attachment, while HA2 is the major component of the stem and is located at the membrane-proximal end that is responsible for viral and cell membrane fusion in the endosome.

Fig. 1 Influenza virus A hemagglutinin (HA) protein structure

Challenges in Producing Recombinant Influenza HA Trimers

Recombinant production of influenza HA trimers faces several well-documented challenges. First, maintaining the native prefusion trimeric conformation of HA is inherently difficult. Without stabilizing elements such as foldon tags or engineered mutations, HA frequently misfolds or exists as monomers and incomplete oligomers.

Second, the formation of correct disulfide bonds between HA1 and HA2 and within each monomer is often inefficient; the level of host cell chaperones such as PDI or ERp57 strongly influences the proportion of correctly folded trimers.

Third, HA is heavily glycosylated, and host-dependent glycan heterogeneity can affect both stability and antigenicity, resulting in diffuse or heterogeneous electrophoretic profiles.

Finally, yields and solubility are frequently limited, particularly for stem-only or truncated constructs, and expression often requires careful optimization of host cell conditions or refolding procedures to obtain sufficient amounts of functional protein.

Recombinant Influenza HA Trimer Proteins at Creative Diagnostics

Creative Diagnostics has successfully developed several trimeric influenza HA proteins for better support of influenza vaccine and drug development. These HA trimer proteins are produced in HEK293 mammalian cells, ensuring proper folding, trimerization, and mammalian-like glycosylation. High-purity preparations are confirmed by SDS-PAGE, demonstrating the correct size and integrity of the expressed trimer.

SDS-PAGE

Custom constructs, tags or mutations can be requested to fit your specific research needs. Don't hesitate to get in touch with us for more information.