Development, Immunogenicity and Protective Efficacy of an Associated Inactivated Vaccine Against Highly Pathogenic Avian Influenza and Newcastle Disease in Chickens.

Background

The simultaneous circulation of highly pathogenic avian influenza (HPAI) H5N8 (clade 2.3.4.4b) and virulent Newcastle disease virus (NDV) genotype VII creates a cumulative risk for the poultry industry, rendering monovalent vaccination insufficient. This study aimed to develop and evaluate a combined inactivated vaccine against AIV H5N8 and NDV genotype VII based on local endemic strains.

Methods

The vaccine was formulated as a water-in-oil emulsion (30:70) using Montanide™ ISA 78 VG. Evaluation included physicochemical characterization, safety assessment in chickens, immunogenicity evaluation via the hemagglutination inhibition (HI) test, and protective efficacy following challenge with virulent isolates.

Results

The formulation demonstrated high stability and complete safety without adverse reactions. By 28 days post-immunization, the vaccine induced a robust, balanced humoral response with antibody titers reaching 9.10 ± 0.23 log2 against NDV and 9.00 ± 0.26 log2 against AIV, indicating no antigenic interference. Upon challenge, the vaccinated group exhibited 100% clinical protection and survival, compared to 100% mortality in controls. Furthermore, vaccination significantly reduced viral shedding, limiting horizontal spread.

Conclusions

The developed combined inactivated vaccine demonstrates high safety, stability, and protective efficacy. It represents a promising candidate for comprehensive specific prophylaxis in endemic regions, effectively limiting horizontal pathogen transmission and mitigating economic losses in poultry production.