Host responses in the bursa of Fabricius of chickens infected with virulent Marek's disease virus

The bursa of Fabricius serves as an important tissue in the process of Marek's disease virus (MDV) pathogenesis, since B cells of the bursa harbor the cytolytic phase of MDV replication cycle. In the present study, host responses associated with MDV infection in the bursa of Fabricius of chickens were investigated. The expression of MDV phosphoprotein (pp)38 antigen, MDV glycoprotein (gB) and MDV viral interleukin (vIL)-8 transcripts was at the highest at 4 days post-infection (d.p.i.) and then showed a declining trend. On the contrary, the expression of meq (MDV EcoRI Q) gene as well as the viral genome load increased gradually until day 14 post-infection. The changes in viral parameters were associated with significantly higher infiltration of macrophages and T cell subsets, particularly CD4+ T cells into the bursa of Fabricius. Of the genes examined, the expression of interferon (IFN)-alpha, IFN-gamma genes and inducible nitric oxide synthase (iNOS) was significantly up-regulated in response to MDV infection in the bursa of Fabricius. The results suggest a role for these cells and cytokines in MDV-induced responses in the bursa of Fabricius.

Gene expression profiling of chicken lymphoid cells after treatment with Lactobacillus acidophilus cellular components

Lactobacillus acidophilus has been shown to exert immunostimulating activities in a number of species, including the chicken. To examine the molecular mechanisms of this phenomenon, we investigated spatial and temporal expression of immune system genes in chicken cecal tonsil and spleen mononuclear cells in response to structural constituents of L. acidophilus. Using a low-density chicken immune system microarray, we found that cecal tonsil cells responded more rapidly than spleen cells to the bacterial stimuli, with the most potent stimulus for cecal tonsil cells being DNA and for splenocytes being the bacterial cell wall components. We also discovered that in both splenocytes and cecal tonsil cells, STAT2 and STAT4 genes were highly induced. Given the close interactions between cecal tonsil cells and commensal bacteria, we further examined the involvement of STAT2 and STAT4 signaling pathways in cellular responses to bacterial DNA. Our results revealed that the expression of STAT2, STAT4, IL-18, MyD88, IFN-alpha, and IFN-gamma genes were up-regulated in cecal tonsil cells after treatment with L. acidophilus DNA.

Assessment in mice of vapA–DNA vaccination against Rhodococcus equi infection

There is a need to produce a vaccine against Rhodococcus equi pneumonia in foals in which immunity against infection is largely based on a type 1, cell-mediated, immune response. The VapA protein of the virulence plasmid of R. equi is highly immunogenic. To assess the potential of vapA-DNA to produce immunity, C57BL/6 and BALB/c mice were immunized with a DNA vaccine constructed from vapA incorporated into pcDNA3.1. The plasmid construct expressed VapA in a COS-7 cell line. Intramuscular immunization of mice resulted in enhanced clearance of R. equi from the liver of intravenously challenged mice compared to non-immunized controls. This effect was more marked when pORF-IL-12, a plasmid expressing murine IL12, was included with the vaccine. Antibody developed to VapA, with an IgG2a response being more marked in mice immunized with pcDNA-vapA than in non-immunized or in mice immunized with the mixed vapA and IL-12 plasmid constructs. In conclusion, this study has shown for the first time that DNA immunization with vapA enhances the immune responses of mice against R. equi infection, that the IgG subisotype response is consistent with a type 1-based immune response, and that this can be enhanced by injection of the IL-12 gene.