Abstract
Cellular immune responses play critical roles in the control of viral infection. However, the immune protection against avian viral diseases (AVDs), a major challenge to poultry industry, is yet mainly evaluated by measuring humoral immune response though antibody-independent immune protection was increasingly evident in the development of vaccines against some of these diseases. The evaluation of cellular immune response to avian viral infection has long been neglected due to limited reagents and methods. Recently, with the availability of more immunological reagents and validated approaches, the evaluation of cellular immunity has become feasible and necessary for AVD. Herein, we reviewed the methods used for evaluating T cell immunity in chickens following infection or vaccination, which are involved in the definition of different cellular subset, the analysis of T cell activation, proliferation and cytokine secretion, and in vitro culture of antigen-presenting cells (APC) and T cells. The pros and cons of each method were discussed, and potential future directions to enhance the studies of avian cellular immunity were suggested. The methodological improvement and standardization in analyzing cellular immune response in birds after viral infection or vaccination would facilitate the dissection of mechanism of immune protection and the development of novel vaccines and therapeutics against AVD.
Highlights
Immune protection against avian viruses is mainly mediated by adaptive humoral and cellular immunity (Koutsakos et al, 2019b)
For avian viral diseases (AVDs), the evaluation of cellular immune response, especially T cell-mediated immunity has become more and more important as antibody-independent immune protection was constantly observed in the development of vaccines against some of these diseases
With the availability of an array of immunological techniques, which can be used to define different immune cell subsets, examine the activation, cytokine secretion, and proliferation of T cells as well as to culture antigenpresenting cells (APC) and T cells in vitro, the evaluation of T cell immunity to viral infection in poultry has become feasible and realistic, which would help to dissect the mechanism of cell-mediated immune protection against AVDs and discover novel T cell subsets in birds
Summary
Immune protection against avian viruses is mainly mediated by adaptive humoral and cellular immunity (Koutsakos et al, 2019b). The level of neutralizing antibody is routinely detected for evaluating immune protection in birds after infection or vaccination. Antibody-independent immune protection was increasingly evident in the development of vaccines against some of these diseases. Some virus-vectored H7N9 subunit vaccines provided complete protection but did not induce high levels of neutralizing antibodies (Blanchfield et al, 2014; Hu et al, 2017; Stadlbauer et al, 2017; Shi et al, 2019). Inactivated H9N2 vaccines induced high antibody titers but were unable to completely block the transmission of H9N2 avian influenza virus (AIV) among the immunized flocks (Xu et al, 2018; Bi et al, 2020; Dai et al, 2021).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
