The Evaluation of Cellular Immunity to Avian Viral Diseases: Methods, Applications, and Challenges

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.

Effect of CpG-Oligonucleotide in Enhancing Recombinant Herpes Virus of Turkey-Laryngotracheitis Vaccine-Induced Immune Responses in One-Day-Old Broiler Chickens

“…However, it remains to be investigated if these two phenotypically distinct populations of macrophages induced in response to CpG-ODN stimulation have any biologically distinct functions in chickens. In the context of present study observation of enhanced splenic γδT cell frequencies in the adjuvanted vaccine group, previous reports have also highlighted an important role for this cell-type in defense against viruses in chickens [ 45 , 46 ]. For example, we have previously shown that chickens infected with MDV had significantly higher number of splenic γδT cells and that these cells expressed elevated levels of IFNγ, suggesting their important role in antiviral defense [ 46 ].…”

The Immunological Basis for Vaccination

“…This is facilitated by the availability of well-established methods to detect antibodies using commercially available test systems and the increasing use of automated detection systems, which allow the fast processing of large numbers of barcoded samples. Parameters of the CMI are mostly investigated in research-associated questions; tests are less standardized, and due to the limited number of tools for chickens, not easily applicable under field conditions (82–84). Neither are local antibody responses, as they are determined in tears, tracheal washes, or gut lavage, which are more labor intensive to collect and may require sacrificing the birds.…”

How to Break through the Bottlenecks of in Ovo Vaccination in Poultry Farming

“…This method breaks through the limitations of traditional research methods, enabling the comprehensive exploration of the dynamic alterations in immune cell composition and interaction, thereby expanding our understanding of the intricate nature of immune responses upon vaccination. The application of this novel research paradigm to study in ovo immunization mechanism will bring us new opportunities to break through the bottlenecks restricting the development and technological advancement of in ovo vaccination [ 61 , 62 ].…”