Abstract
Despite successful control by vaccination, Marek’s disease (MD) has continued evolving to greater virulence over recent years. To control MD, selection and breeding of MD-resistant chickens might be a suitable option. MHC-congenic inbred chicken lines, 61 and 72, are highly resistant and susceptible to MD, respectively, but the cellular and genetic basis for these phenotypes is unknown. Marek’s disease virus (MDV) infects macrophages, B-cells, and activated T-cells in vivo. This study investigates the cellular basis of resistance to MD in vitro with the hypothesis that resistance is determined by cells active during the innate immune response. Chicken bone marrow-derived macrophages from lines 61 and 72 were infected with MDV in vitro. Flow cytometry showed that a higher percentage of macrophages were infected in line 72 than in line 61. A transcriptomic study followed by in silico functional analysis of differentially expressed genes was then carried out between the two lines pre- and post-infection. Analysis supports the hypothesis that macrophages from susceptible and resistant chicken lines display a marked difference in their transcriptome following MDV infection. Resistance to infection, differential activation of biological pathways, and suppression of oncogenic potential are among host defense strategies identified in macrophages from resistant chickens.
Highlights
Marek’s disease (MD) is an oncogenic viral disease of chickens caused by the Gallid alphaherpesvirus 2, which is traditionally known as Marek’s disease virus (MDV)
Flow cytometric characterization of bone marrow-derived macrophages (BMDMs) with KUL01 and CD45 staining at 1 dpi revealed that the proportion of infected macrophages was around three times higher in line 72 (34–38%), which is susceptible to MDV, than in line 61 (11–12%), which is resistant to MDV infection (Figure 1a)
On the day of infection, pre-sorted eGFP+ CD45- chick embryo fibroblasts (CEF)s were co-cultured with BMDMs at a ratio of 1:5 (CEF:BMDM)
Summary
Marek’s disease (MD) is an oncogenic viral disease of chickens caused by the Gallid alphaherpesvirus 2, which is traditionally known as Marek’s disease virus (MDV). Effective vaccination has led to successful control of this disease, but as none of these vaccines can induce sterile immunity against MD, the virulence of MDV has been increasing over the years amid the introduction of new generations of vaccines [1]. This emphasizes the necessity for implementation of alternative control methods for MD. The estimates of heritability of MD resistance are as high as 61% [2], suggesting good potential for genetic improvement for meat and egg production [3]
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