Cytokine Immune Response Following Vaccination against Fowl Pox Disease in Specific Pathogen Free Chickens

Fowlpox is an infectious disease with a relatively slow spread in all ages of poultry. It is characterized by skin lesions in dry form or diphtheria-like lesions in the mouth in wet form. The disease has been observed to result in diminished growth rates and a reduction in egg production. This disease is among the most ancient diseases known to affect poultry. The virulence of the bacterium was initially demonstrated in 1902 by Marks & Sticher. The disease is widespread on a global scale, affecting birds of all ages, races, and genders. The virus is highly infectious and causes significant mortality in birds. The present study was conducted to investigate the presence of Th1 and Th2 cells, as well as the cytokines IFN-γ and IL-4, in the culture medium of peripheral blood mononuclear cells (PBMCs) stimulated with the mitogen concanavalin A (ConA) in vaccinated and control chickens. The present study comprised three groups of 40 21-day-old specific pathogen-free chicks. One group was inoculated with phosphate-buffered saline (PBS) and served as a negative control, while the other two groups were vaccinated with the Razi Institute fowlpox vaccine and a commercial fowlpox vaccine, respectively. The injection of the vaccine was administered in the wing. The chicks were maintained for a period of five weeks following the inoculation procedure. Blood samples were collected from each group on a weekly basis, continuing until the fifth week following the vaccination. Peripheral blood mononuclear cells (PBMCs) were isolated from each blood sample using a centrifuge Ficoll-Hypaque protocol. The concentration of inflammatory cytokines (IFN-γ) and anti-inflammatory (IL-4) in peripheral blood mononuclear cells was measured using the enzyme-linked immunosorbent assay (ELISA) method. A statistical analysis and a quantitative evaluation (P<0.05) were employed to ascertain the significant differences between the groups. The results of this study demonstrated that 7 days after vaccination, 90 to 100% of the vaccinated birds exhibited swelling at the injection site. The ratio of the concentration of IFN-γ to IL-4 in the culture medium of vaccinated chicks was higher than that of the control group. The study posits that the induction of enhanced immune responses subsequent to vaccination against fowlpox is predominantly attributable to the Th1 lymphocytes response.