Multi-epitope HA Vaccine Confers Cross-protective Immunity to H۵N۸ and H۹N۲

Introduction: Avian influenza viruses, notably H۵N۸ (HPAI) and H۹N۲ (LPAI), threaten public health due to their zoonotic potential and genetic adaptability. These viruses circulate in poultry and can sometimes directly infect humans after contact with infected birds. Some existing vaccines have proven useful in controlling these infections. Traditional vaccines targeting the variable hemagglutinin (HA) head domains necessitate frequent updates. This study designs a chimeric HA (cHA H۹/H۵) vaccine targeting conserved epitopes from H۵N۸ and H۹N۲ HA proteins to elicit broad immunity.Materials & Methods: A multi-epitope construct, integrating B-cell and cytotoxic T lymphocyte (CTL) epitopes linked via stabilizing sequences (KK, AAY, GPGPG), was codon-optimized, expressed in Escherichia coli BL۲۱(DE۳), and purified (>۹۵% purity, ۲۲ mg/L yield). Specific pathogen-free chickens (n=۲۰/group) received two doses of cHA H۹/H۵ formulated with Alum or Freund’s adjuvants, compared to commercial H۵N۸/H۹N۲ vaccines. Humoral responses were assessed via hemagglutination inhibition (HI) assays. Results: The cHA H۹/H۵ vaccine induced robust HI titers against homologous H۹N۲ (log₂ GMT ۱۰–۱۲) and hetero-subtypic H۵N۸ (log₂ GMT ۶–۸), surpassing commercial vaccines. While H۹N۲ vaccines lacked cross-reactive H۵N۸ antibodies, cHA H۹/H۵ elicited neutralizing titers (۲۰–۸۰) against H۵N۸. Freund’s adjuvant significantly enhanced immunogenicity, with sustained post-boost antibody levels. Conclusion: These results highlight the cHA H۹/H۵ vaccine’s ability to overcome strain-specific limitations by targeting conserved epitopes, inducing cross-reactive immunity that is critical for pandemic preparedness. Adjuvant selection proved pivotal in optimizing responses, aligning with prior chimeric HA vaccine research. This study advances the development of universal influenza vaccines, offering a promising strategy to mitigate risks posed by evolving avian influenza variants.

کلیدواژه ها:

Avian Influenza ، Chimeric vaccine ، H۵N۸ ، H۹N۲