Recombinant Trimeric HA Protein Immunogenicity of H5N1 Avian Influenza Viruses and Their Combined Use with Inactivated or Adenovirus Vaccines

Abstract

BackgroundThe highly pathogenic avian influenza (HPAI) H5N1 virus continues to cause disease in poultry and humans. The hemagglutinin (HA) envelope protein is the primary target for subunit vaccine development.Methodology/Principal FindingsWe used baculovirus-insect cell expression to obtain trimeric recombinant HA (rHA) proteins from two HPAI H5N1 viruses. We investigated trimeric rHA protein immunogenicity in mice via immunizations, and found that the highest levels of neutralizing antibodies resulted from coupling with a PELC/CpG adjuvant. We also found that the combined use of trimeric rHA proteins with (a) an inactivated H5N1 vaccine virus, or (b) a recombinant adenovirus encoding full-length HA sequences for prime-boost immunization, further improved antibody responses against homologous and heterologous H5N1 virus strains. Data from cross-clade prime-boost immunization regimens indicate that sequential immunization with different clade HA antigens increased antibody responses in terms of total IgG level and neutralizing antibody titers.Conclusion/SignificanceOur findings suggest that the use of trimeric rHA in prime-boost vaccine regimens represents an alternative strategy for recombinant H5N1 vaccine development.

Oligomeric Recombinant H5 HA1 Vaccine Produced in Bacteria Protects Ferrets from Homologous and Heterologous Wild-Type H5N1 Influenza Challenge and Controls Viral Loads Better than Subunit H5N1 Vaccine by Eliciting High-Affinity Antibodies

“…Our finding is in agreement with previous studies demonstrating the importance of trimeric and oligomeric influenza vaccines, particularly for eliciting cross-protective immunity against heterologous challenge (4,25,51,52), but here we define for the first time the role of antibody avidity in reduction of viral loads in the upper respiratory tract, which will be very important not only for controlling virus replication and prevention of lung infection but also for limiting virus transmission. In previous studies with adjuvant-containing versus non-adjuvant-containing H5N1 vaccine, we demonstrated strong correlation between antibody affinity for functional rHA1 (in SPR) and cross-clade neutralization (15,19).…”

Cross-Reactive Neuraminidase-Inhibiting Antibodies Elicited by Immunization with Recombinant Neuraminidase Proteins of H5N1 and Pandemic H1N1 Influenza A Viruses

“…BALB/c mice (6 to 8 weeks old) purchased from the Taiwan National Laboratory Animal Center were immunized twice intramuscularly with a 3-week interval with 2 or 20 g of rNA proteins plus 10 g CpG and 10% poly(ethylene glycol)-block-poly(lactide-co-epsilon-caprolactone) (PEGb-PLACL), squalene, and Span85 (PELC) emulsion as described in a previous report (28). Serum samples were collected 2 weeks after the second inoculation; splenocytes were harvested and isolated 1 week later.…”

A plant-produced H1N1 trimeric hemagglutinin protects mice from a lethal influenza virus challenge

“…[24][25][26] Another approach to generate recombinant tHA is to enforce and stabilize the trimerization of recombinant HA using trimerization motifs. 22,[27][28][29] Trimerization of viral HA is due to specific interactions along heptad repeat (HR) regions of the HA2 domain. These HR regions undergo significant structural changes, which leads to viral infection of the host cell.…”

“…Other studies that explored trimerization of recombinant HA used the trimerization motif from the leucin zipper GCN4pII. 28,29 Lin et al demonstrated the immunogenicity of this trimeric HA produced in a baculovirus-insect cell expression system in mice and evaluated the potential of this trimeric HA as an influenza vaccine using a prime-boost strategy with recombinant adenovirus vector. However, a direct comparison of the immunogenicity of the monomeric vs. the trimeric HA was not present in their study.…”

“…However, a direct comparison of the immunogenicity of the monomeric vs. the trimeric HA was not present in their study. 28 On the other hand, Weldon et al developed trimeric HA using the motif from GCN4pII expressed in a baculovirus-insect cell system and demonstrated its enhanced immunogenicity compared with monomeric HA. 29 In our study described here, significant differences in the protective efficacy of the plant-produced tHA-BC antigen compared with monomeric HAC1 was not demonstrated.…”