Abstract
Background:
Newcastle disease virus (NDV) is a virus that causes a significant economic impact on the poultry industry and is primarily controlled through vaccination. Most of the vaccinations with the LaSota strain are either live attenuated or inactivated vaccines, both of which are from the Lentogenic pathotype.

Aim:
This study aimed to investigate the influence of vaccine type and genetic variations on Chicken Interleukin-4 (ChIL4) activation.

Methods:
Three groups were examined: Group K received killed vaccine, Group L received live vaccine, and Group C served as the control. Blood samples were collected on days 15, 25, and 35 post-vaccinations to assess ChIL4 levels using Enzyme-Linked Immunosorbent Assay (ELISA) and for molecular analysis using PCR.

Results:
Group K showed a gradual increase in ChIL4 levels from 11.19±0.17 to 13.70±0.38, while Group L exhibited an initial increase on day 15 followed by stabilization on days 25 and 35. In contrast, ChIL4 levels in Group C declined over time from 4.84±0.39 to 4.32±0.25. Molecular analysis revealed four genetic variations of the Single Nucleotide Polymorphism (SNPs) type at locations (3044, 3132, 3261, 3499) bp, with the third SNP at location (3261bp) resulting in an amino acid change from valine to isoleucine. Analysis indicated that variants for most of these SNPs occur more likely in Group K compared to the other two groups.

Conclusion:
These findings suggest that genetic variations, particularly SNPs, may play a significant role in ChIL4 activation, potentially impacting vaccine efficacy and immune response.

Key words: Single nucleotide polymorphism, Cytokine, PCR technique