Antigen clade matching enhances protective efficacy of H5N1 DNA vaccines delivered by electroporation or lipid nanoparticles 2267127
Highly pathogenic avian influenza viruses (HPAIs) continue to threaten both agriculture and human health. Recent H5N1 clades have caused zoonotic infections in humans with mortality rates approaching 50%. However, currently licensed H5 vaccines are based on ancestral strains and may provide suboptimal protection against circulating variants. Rapidly adaptable DNA vaccine platforms offer a promising approach for clade-specific protection. Codon-optimized plasmid DNA vaccines expressing hemagglutinin (HA) from two recently circulating H5N1 clades (2.3.2.1c and 2.3.4.4b) were generated and delivered by either intramuscular electroporation (EP) or a lipid nanoparticle (LNP) formulation. Cellular and humoral responses were evaluated by multiparameter flow cytometry and ELISpot and by ELISA and pseudovirus neutralization, respectively. Protective efficacy was evaluated in lethal H5N1 murine challenge models. EP delivery of clade 2.3.2.1c HA (pCamb) elicited strong humoral and cellular responses and achieved complete protection against homologous viral challenge, but only partial protection against heterologous 2.3.4.4b challenge. In contrast, vaccination with clade 2.3.4.4b HA (pMich) DNA supported robust immune responses and full protection against contemporary clade challenge. Co-immunization with both plasmids via EP induced broad binding and neutralizing antibodies and conferred complete protection from clade 2.3.4.4b challenge. Moreover, formulation of the pMich plasmid optimized LNPs generated durable, protective immunity following a single dose, effective at both acute and memory timepoints. These studies demonstrate that antigenic clade-matching is likely critical for protection against H5N1 and suggest that currently stockpiled H5N1 vaccines may not protect against contemporary viruses. Further this data suggests that DNA vaccine platforms including EP or LNP formulations can provide a flexible approach for rapid adaptation to evolving influenza strains. NIH NIAID CIVICs Vaccines and Immunotherapy (VAC)