Marek's disease vaccine activates chicken macrophages

Abstract

To provide insights into the role of innate immune responses in vaccine-mediated protection, we investigated the effect of Marek's disease (MD) vaccine, CVI988/Rispens, on the expression patterns of selected genes associated with activation of macrophages in MD-resistant and MD-susceptible chicken lines. Upregulation of interferon γ, interleukin (IL)-1β, IL-8, and IL-12 at different days post-inoculation (dpi) revealed activation of macrophages in both chicken lines. A strong immune response was induced in cecal tonsils of the susceptible line at 5 dpi. The highest transcriptional activities were observed in spleen tissues of the resistant line at 3 dpi. No increase in the population of CD3⁺ T cells was observed in duodenum of vaccinated birds at 5 dpi indicating a lack of involvement of the adaptive immune system in the transcriptional profiling of the tested genes. There was, however, an increase in the number of macrophages in the duodenum of vaccinated birds. The CVI988/Rispens antigen was detected in the duodenum and cecal tonsils of the susceptible line at 5 dpi but not in the resistant line. This study sheds light on the role of macrophages in vaccine-mediated protection against MD and on the possible development of new recombinant vaccines with enhanced innate immune system activation properties.

Keywords: CVI988/Rispens; Marek’s disease; cecal tonsils; duodenum; macrophages.

Fig. 1. Bar graphs showing gene expression patterns within the duodenum of both Marek's disease chicken lines at 5 and 10 days post-immunization (dpi). For a statistical analysis summary, please see Table 2. IFN, interferon; IL, interleukin.

Fig. 2. Bar graphs showing the expression patterns of the tested genes within the cecal tonsils of both Marek's disease lines at 3, 5, and 10 days post-immunization (dpi). For a statistical analysis summary, please see Table 3. IFN, interferon; IL, interleukin.

Fig. 3. Bar graphs showing the expression patterns of the tested genes in spleen macrophages of both Marek's disease lines at 3 and 5 days post-immunization (dpi). For a statistical analysis summary, please see Table 4. IFN, interferon; IL, interleukin.

Fig. 4. Images from the immunohistochemical analysis of CD3⁺ T cells and macrophage populations within the duodenum of control and vaccinated birds of the resistant and susceptible Marek's disease lines at 5 days post-immunization. The tissue samples were incubated with combination of mouse anti-chicken CD3⁺ T cells or macrophage monoclonal antibodies (primary) and biotinylated horse anti-mouse IgG (secondary) for detection of specific immune cells. Panels B and D show the CD3⁺ T cell populations within the duodenum of vaccinated birds of the resistant and susceptible lines, respectively, while panels A and C present the corresponding control tissues. Panels F and H show the macrophage populations within the duodenum of vaccinated birds of the resistant and susceptible lines, respectively, while panels E and G show the corresponding non-vaccinated control tissues. Scale bars = 200 µm (A–D), 20 µm (E–H).

Fig. 5. Images from the immunohistochemical analysis of CVI988/Rispens antigen gB within the duodenum and the cecal tonsil (CT) of the vaccinated birds of the resistant and susceptible lines at 5 days post-immunization. The tissue samples were incubated with combination of mouse anti-gB monoclonal antibody (primary) and biotinylated horse anti-mouse IgG for detection CVI988 virions. Panels B and D show the duodenum and CT tissues of birds of vaccinated resistant line 6₃, respectively, stained with the anti-gB of CVI988/Rispens, while panels A and C, respectively, are the corresponding non-vaccinated control tissues. The gB antigen of CVI988/Rispens is depicted within duodenum and the CT of the vaccinated birds of the susceptible line 7₂ in panels F and H, respectively, while the corresponding control tissues are represented in panels E and G, respectively. Scale bars = 200 µm (A–H).