About Influenza A Hemagglutinin (HA) (A/California/07/2009, H1N1) Recombinant Protein

Influenza A (H1N1) viruses are important human respiratory pathogens responsible for seasonal influenza outbreaks and the 2009 influenza pandemic (H1N1pdm09). The A/California/07/2009 (H1N1) strain became the prototype virus of the pandemic lineage and has served as a reference strain for influenza surveillance, vaccine development, and immunological research. Its hemagglutinin (HA) protein remains one of the best-characterized influenza antigens and has been widely used in studies of viral evolution, antibody responses, and antiviral therapeutics.

The viral hemagglutinin (HA) glycoprotein is the major surface antigen of influenza A virus and mediates attachment to α2,6-linked sialic acid receptors on host epithelial cells, followed by receptor-mediated endocytosis and membrane fusion. Because HA is the primary target of neutralizing antibodies and the principal antigen incorporated into seasonal influenza vaccines, recombinant HA proteins are indispensable tools for vaccine research, serological assays, and structural biology. eEnzyme's Influenza A Hemagglutinin (HA) (A/California/07/2009, H1N1) Recombinant Protein is expressed in HEK293 cells and comprises the full-length ectodomain (amino acids 18–529) with a C-terminal 6×His tag, providing native mammalian glycosylation and proper protein folding. The purified recombinant protein is suitable for ELISA, Western blotting, neutralizing antibody characterization, receptor-binding studies, vaccine development, and diagnostic assay development.

Applications

Biological Significance of Influenza A H1 Hemagglutinin

Hemagglutinin is the key viral glycoprotein responsible for initiating influenza virus infection by recognizing terminal sialic acid receptors on host cells. Following endocytosis, HA undergoes a low pH-induced conformational change that drives fusion of the viral and endosomal membranes, allowing viral ribonucleoproteins to enter the host cell cytoplasm. Because HA is the dominant antigen exposed on the viral surface, it is the principal target of protective immune responses elicited by natural infection and vaccination. Continuous antigenic drift within the HA protein leads to the emergence of new influenza variants, requiring regular updates of seasonal influenza vaccines. The A/California/07/2009 (H1N1) HA remains a benchmark antigen for evaluating vaccine potency, antibody responses, and influenza virus evolution.

The Influenza A Hemagglutinin (HA) (A/California/07/2009, H1N1) Recombinant Protein provides a high-quality research reagent for investigating influenza virus biology, evaluating vaccine-induced immunity, screening broadly neutralizing antibodies, and supporting the development of next-generation influenza vaccines, diagnostics, and antiviral therapeutics. Its mammalian expression system preserves native glycosylation and conformational epitopes, making it particularly valuable for immunological, structural, and translational influenza research.

Selected Citations:
1) Influenza Anti-Stalk Antibodies: Development of a New Method for the Evaluation of the Immune Responses to Universal Vaccine. Vaccines 8, 43 (2020). 
2) Single-Cell Analysis Suggests that Ongoing Affinity Maturation Drives the Emergence of Pemphigus Vulgaris Autoimmune Disease. Cell Rep. 28, 909-922.e6 (2019).