Adjuvants for inactivated vaccine against Avibacterium paragallinarum

Abstract

Avibacterium paragallinarum causes a severe respiratory disease characterized by catarrhal inflammation of the mucous membranes of the nasal cavity, infraorbital sinuses, and conjunctivitis. The study aims to determine the reactogenicity and protective properties of inactivated vaccines against Av. paragallinarum is made using mineral‐salt adjuvant aluminum hydroxide (AH) and high molecular weight acrylic acid‐carbomer polymer. Vaccine samples were made of inactivated Av. paragallinarum cultures of strains B‐7770 (serotype “A”), “1130917 / AmsB” (serotype “B”), and 150215 / TulaC2 (serotype “C”). A milliliter of each vaccine contained 1.0 billion microbial cells of each Av. paragallinarum serotype. The first sample contained AH adjuvant, and 2nd sample had a carbomer in it. Vaccines were tested on 60 days old layer hens. Ten birds were immunized with each vaccine sample to determine reactogenicity. The vaccine was injected intramuscularly between the radius and ulna in a volume of 2.0 cm3. Ten days after immunization, the birds were euthanized and autopsied to measure the local tissue response at the region of vaccine administration. Three groups of chickens (n=10) were formed to measure the immunogenic activity. Birds of the first and second groups were intramuscularly inoculated with one vaccine sample in a volume of 1.0 cm3. The chickens of the 3rd group were not vaccinated. After 28 days of research, all chickens were infected with a mixture of Av. paragallinarum “A,” “B,” and “C” serotypes. The culture mixture was applied intraocularly at 10 50% infectious doses for each serotype. All birds vaccinated with the AH and carbomer vaccines had swelling of soft tissues and petechial hemorrhagic lesions of the muscles near the inoculation area. Fibrin plates (0.2x1.5 cm) were found in the muscles of the inoculation area in 5 AH cases. No clinical manifestation of the disease was found in both vaccinated groups, which indicates good protective properties of the tested vaccine samples. All 10 chickens of the 3rd group showed symptoms of a respiratory disease after infection with Av. paragallinarum, which reveals a high susceptibility of unvaccinated hens to the bacteria. Inactivated vaccine against Av. paragallinarum with carbomer as an adjuvant is less reactogenic than a similar vaccine made using AH. At the same time, both vaccine samples have good protective properties.