Flow cytometric assessment of chicken T cell-mediated immune responses after Newcastle disease virus vaccination and challenge

The objective of this study was to use flow cytometry to assess chicken T cell-mediated immune responses. In this study two inbred genetic chicken lines (L130 and L133) were subjected to two times vaccination against Newcastle disease (ND) and a subsequent challenge by ND virus (NDV) infection. Despite a delayed NDV-specific antibody response to vaccination, L133 appeared to be better protected than L130 in the subsequent infection challenge as determined by the presence of viral genomes. Peripheral blood was analyzed by flow cytometry and responses in vaccinated/challenged birds were studied by 5-color immunophenotyping as well as by measuring the proliferative capacity of NDV-specific T cells after recall stimulation. Immunophenotyping identified L133 as having a significantly lower CD4/CD8 ratio and a lower frequency of γδ T cells than L130 in the peripheral T cell compartment. Furthermore, peripheral lymphocytes from L133 exhibited a significantly higher expression of CD44 and CD45 throughout the experiment. Interestingly, also vaccine-induced differences were observed in L133 as immune chickens had a significantly higher CD45 expression on their lymphocytes than the naïve controls. Immune chickens from both lines had a significantly higher frequency of circulating γδ T cells than the naïve controls both after vaccination and challenge. Finally, the proliferative capacity of peripheral CD4+ and CD8+ cells specific for NDV was addressed 3 weeks after vaccination and 1 week after infection and found to be significantly higher in L133 than in L130 at both sampling times. In conclusion, we found the applied flow cytometric methods very useful for the study of chicken T cell biology.