Transcriptional Profiles Associated with Marek’s Disease Virus in Bursa and Spleen Lymphocytes Reveal Contrasting Immune Responses during Early Cytolytic Infection

Abstract

Marek’s disease virus (MDV), an alpha herpes virus, causes a lymphoproliferative state in chickens known as Marek’s disease (MD), resulting in severe monetary losses to the poultry industry. Because lymphocytes of bursa of Fabricius and spleen are prime targets of MDV replication during the early cytolytic phase of infection, the immune response in bursa and spleen should be the foundation of late immunity induced by MDV. However, the mechanism of the MDV-mediated host immune response in lymphocytes in the early stage is poorly understood. The present study is primarily aimed at identifying the crucial genes and significant pathways involved in the immune response of chickens infected with MDV CVI988 and the very virulent RB1B (vvRB1B) strains. Using the RNA sequencing approach, we analyzed the generated transcriptomes from lymphocytes isolated from chicken bursa and spleen. Our findings validated the expression of previously characterized genes; however, they also revealed the expression of novel genes during the MDV-mediated immune response. The results showed that after challenge with CVI988 or vvRB1B strains, 634 and 313 differentially expressed genes (DEGs) were identified in splenic lymphocytes, respectively. However, 58 and 47 DEGs were observed in bursal lymphocytes infected with CVI988 and vvRB1B strains, respectively. Following MDV CVI988 or vvRB1B challenge, the bursal lymphocytes displayed changes in IL-6 and IL-4 gene expression. Surprisingly, splenic lymphocytes exhibited an overwhelming alteration in the expression of cytokines and cytokine receptors involved in immune response signaling. On the other hand, there was no distinct trend between infection with CVI988 and vvRB1B and the expression of cytokines and chemokines, such as IL-10, IFN-γ, STAT1, IRF1, CCL19, and CCL26. However, the expression profiles of IL-1β, IL-6, IL8L1, CCL4 (GGCL1), and CCL5 were significantly upregulated in splenic lymphocytes from chickens infected with CVI988 compared with those of chickens infected with vvRB1B. Because these cytokines and chemokines are considered to be associated with B cell activation and antigenic signal transduction to T cells, they may indicate differences of immune responses initiated by vaccinal and virulent strains during the early phase of infection. Collectively, our study provides valuable data on the transcriptional landscape using high-throughput sequencing to understand the different mechanism between vaccine-mediated protection and pathogenesis of virulent MDV in vivo.

Fully Attenuated meq and pp38 Double Gene Deletion Mutant Virus Confers Superior Immunological Protection against Highly Virulent Marek’s Disease Virus Infection

“…Transcriptome profiling has been used to evaluate the host immune response to MDV infection during the early cytolytic phase by analysis of splenic lymphocytes ( 37 ) and was employed in the current study to elucidate why Md5BAC Δ meq Δ pp38 gave superior protection to CVI988/Rispens. Transcriptome profiling was performed during Md5BAC Δ meq Δ pp38 and CVI988/Rispens lytic replication at 5 dpi, using uninfected spleen samples as negative control.…”

“…The protective mechanism of an MDV vaccine remains to be elucidated, but previous studies have demonstrated that both pathogenic and nonpathogenic strains stimulate differential gene expression in vitro and in vivo ( 37 , 45 ). CVI988/Rispens inoculation caused altered transcriptome profiles in splenic lymphocytes compared with pathogenic virus in the early cytolytic infection phase ( 37 ). Interestingly, Md5BAC Δ meq Δ pp38 was found to confer superior protection to CVI988/Rispens ( Fig.…”

Transcription analysis of chicken embryo fibroblast cells infected with the recombinant avian leukosis virus isolate GX14FF03

“…CXCL8, a proin ammatory factor, is associated to the incidence and progression of a variety of in ammatory diseases, including proliferation, angiogenic responses, tumour metastasis, and encouraging infected tissue healing [21]. Previous studies showed that IL8L1 has a causal role in establishing acute in ammation; play important role in PPI network; probably associates with vIL8, which recruits T cells to B cells infected with MDV and leads to transduction of viral signal from B to T cells [22]. IL8L1 was enriched in 15.87% (40/252) GO terms, and the rate was high as 86.67% (26/30) in the top 30 GO terms.…”

Differential Replication and Cytokine Response between Vaccine and Very Virulent Marek’s Disease Viruses in Spleens and Bursas during Latency and Reactivation

“…MDV infections result in alterations in the infiltration and proliferation of B cells and CD4+ T cells. As main lymphoid organs in chickens, both the spleen and bursa not only support MDV replication, but also play an important role in immune response [ 15 , 22 , 23 ]. Moreover, the spleen mainly contains B and T lymphocytes, which are dominant target cells of MDV.…”

“…Our previous study reported that MDV/CVI988 and MDV/RB1B (a vvMDV strain) elicited different host immune responses in early cytolytic infection phase (5 dpi) in vivo experiments. In particular, the transcription level of some cytokines in the splenic lymphocytes, including IL-1β, IL-6, IL-8L1, and CCL4, which are related to B cell activation and antigenic signal transduction to T cells, were significantly upregulated by MDV/CVI988 infection compared with MDV/RB1B infection [ 15 ]. Considering the different pathological responses of the host after infection with the MDV vaccine strain and virulent strain, we speculate that the replication and immune activation status of MDV with different virulence levels also differ during the latent infection and reactivation phases.…”