A replicating RNA vaccine protects cynomolgus macaques against lethal clade 2.3.4.4b influenza A H5N1 virus challenge.

Summary

In a lethal nonhuman primate challenge model, both a contemporary clade 2.3.4.4b HA repRNA vaccine and a historical H5 HA repRNA vaccine protected cynomolgus macaques from H5N1, lowering viral loads and respiratory illness. Findings support the repRNA platform and suggest historical H5 antigens may still provide cross-protection against drifted 2.3.4.4b strains.

Key Findings

• Both contemporary 2.3.4.4b HA and historical H5 (A/Vietnam/1203/2004) repRNA vaccines protected cynomolgus macaques from lethal 2.3.4.4b H5N1 challenge.
• Vaccination reduced viral loads and signs of respiratory illness in the NHP model.
• Historical H5 HA elicited cross-protective immunity against contemporary drifted 2.3.4.4b H5N1.
• Demonstrates the repRNA platform can elicit protective immunity in a lethal NHP influenza model.

Clinical Implications

Supports pandemic preparedness by validating a flexible RNA platform and suggesting some stockpiled historical H5 antigens may still mitigate severe disease; informs decisions on updating stockpiles and prioritizing platforms for rapid scale-up.

Limitations

• Preclinical animal study; human immunogenicity, safety, and efficacy remain to be established.
• Sample size and durability of protection are not specified in the abstract; correlates of protection need definition.

Future Directions

Advance to phase 1/2 clinical trials to assess safety and immunogenicity; map correlates of protection and durability; evaluate heterologous boosting and dose-sparing; inform stockpile update strategies.