Influenza hemagglutinin-viral protein complexes (HA-VP complexes)

The vaccine-internal heterologous complexes of influenza hemagglutinin and associated viral proteins within the Fluviral formulation represent the antigenic components of a specific split-virus influenza vaccine (Health Canada, 2001). These complexes are composed of the surface glycoproteins Hemagglutinin (HA) and Neuraminidase (NA), along with internal viral proteins such as Matrix protein 1 (M1) and Nucleoprotein (NP) (Skowronski et al., 2003). The primary biological role of HA within these complexes is to serve as the immunogen that triggers the production of neutralizing antibodies, which prevent the influenza virus from binding to sialic acid receptors on host respiratory cells (UniProt P03435). Historically, the Fluviral formulation gained significant attention due to its association with Oculorespiratory Syndrome (ORS), an adverse reaction characterized by bilateral conjunctivitis and respiratory symptoms (Spika et al., 2003). Research indicated that the manufacturing process of Fluviral at the time resulted in a higher concentration of large, unsplit viral aggregates and heterologous protein complexes compared to other vaccines, which likely contributed to increased reactogenicity (Babiuk et al., 2004). Consequently, these complexes are critical for both the efficacy of the vaccine in preventing influenza infection and the potential for specific vaccine-associated adverse events.

Other names

Fluviral aggregatesHeterologous influenza protein complexesHA-NA-M1-NP complexesSplit-virus vaccine aggregates

The complexes act as antigens that are processed by antigen-presenting cells to induce B-cell and T-cell responses, specifically leading to the production of neutralizing antibodies against the hemagglutinin protein to prevent viral entry into host cells (Skowronski et al., 2003).