The Role of Dendritic Cells in the Host Response to Marek's Disease Virus (MDV) as Shown by Transcriptomic Analysis of Susceptible and Resistant Birds.

Despite the successful control of highly contagious tumorigenic Marek's disease (MD) by vaccination, a continuous increase in MD virus (MDV) virulence over recent decades has put emphasis on the development of more MD-resistant chickens. The cell types and genes involved in resistance therefore need to be recognized. The virus is primarily lymphotropic, but research should also focus on innate immunity, as innate immune cells are among the first to encounter MDV. Our previous study on MDV-macrophage interaction revealed significant differences between MHC-congenic lines 61 (MD-resistant) and 72 (MD-susceptible). To investigate the role of dendritic cells (DCs) in MD resistance, bone-marrow-derived DCs from these lines were infected with MDV in vitro. They were then characterized by cell sorting, and the respective transcriptomes analysed by RNA-seq. The differential expression (DE) of genes revealed a strong immune activation in DCs of the susceptible line, although an inherent immune supremacy was shown by the resistant line, including a significant expression of tumour-suppressor miRNA, gga-mir-124a, in line 61 control birds. Enrichment analysis of DE genes revealed high expression of an oncogenic transcription factor, AP-1, in the susceptible line following MDV challenge. This research highlights genes and pathways that may play a role in DCs in determining resistance or susceptibility to MDV infection.

Erratum: Chakraborty, P. et al. Macrophages from Susceptible and Resistant Chicken Lines have Different Transcriptomes following Marek's Disease Virus Infection. Genes 2019, 10, 74.

The authors wish to make the following correction to their paper published in Genes [...].

Isolation of multidrug-resistant Escherichia coli, Staphylococcus spp., and Streptococcus spp. from dogs in Chattogram Metropolitan Area, Bangladesh.

OBJECTIVES: Antibacterial resistance is a great concern in human and food animal medicine, and it poses a significant concern in pet animals like dogs. This cross-sectional study was conducted to evaluate the antimicrobial resistance pattern of Escherichia coli, Staphylococcus spp., and Streptococcus spp. along with the carryover of some resistance genes in E. coli from dogs in the Chattogram metropolitan area, Bangladesh. MATERIALS AND METHODS: Rectal swab (n = 50), nasal swab (n = 50), and skin swab (n = 50) samples were collected from dogs having respiratory infections, skin infections, and/or enteritis, respectively. Three types of bacteria were identified and isolated by conventional bacteriological techniques and biochemical tests. Antimicrobial susceptibility testing was carried out against 12 antimicrobials by disk diffusion methods. Six resistance genes, namely bla TEM, bla CTX-M, tetA, tetB, Sul-I, and Sul-II, were screened for phenotypically resistant E. coli isolates by the polymerase chain reaction. RESULTS: A total of 39 (78%) E. coli, 25 (50%) Staphylococcus spp., and 24 (48%) Streptococcus spp. isolates were isolated from the rectal swab, nasal swab, and skin swab samples, respectively. In the cultural sensitivity test, the E. coli isolates showed resistance to ceftriaxone (79%) and sulfamethoxazole/trimethoprim (64%). Doxycycline (80%) demonstrated the highest resistance among Staphylococcus isolates, followed by sulfamethoxazole/trimethoprim (60%). Streptococcus isolates showed the highest resistance to penicillin (63%), followed by ceftriaxone (54%), while no isolate showed resistance to gentamycin. The prevalence of bla TEM, bla CTX-M, tetA, tetB, Sul-I, and Sul-II genes in phenotypically resistant E. coli isolates were 100%, 61.29%, 100%, 8.33%, 56%, and 72%, respectively. CONCLUSIONS: Spillover of such multidrug-resistant bacteria and resistance genes from pet dogs pose a serious public health risk.

Macrophages from Susceptible and Resistant Chicken Lines have Different Transcriptomes following Marek's Disease Virus Infection.

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.

Marek's disease virus infection of phagocytes: a de novo in vitro infection model.

Marek's disease virus (MDV) is an alphaherpesvirus that induces T-cell lymphomas in chickens. Natural infections in vivo are caused by the inhalation of infected poultry house dust and it is presumed that MDV infection is initiated in the macrophages from where the infection is passed to B cells and activated T cells. Virus can be detected in B and T cells and macrophages in vivo, and both B and T cells can be infected in vitro. However, attempts to infect macrophages in vitro have not been successful. The aim of this study was to develop a model for infecting phagocytes [macrophages and dendritic cells (DCs)] with MDV in vitro and to characterize the infected cells. Chicken bone marrow cells were cultured with chicken CSF-1 or chicken IL-4 and chicken CSF-2 for 4 days to produce macrophages and DCs, respectively, and then co-cultured with FACS-sorted chicken embryo fibroblasts (CEFs) infected with recombinant MDV expressing EGFP. Infected phagocytes were identified and sorted by FACS using EGFP expression and phagocyte-specific mAbs. Detection of MDV-specific transcripts of ICP4 (immediate early), pp38 (early), gB (late) and Meq by RT-PCR provided evidence for MDV replication in the infected phagocytes. Time-lapse confocal microscopy was also used to demonstrate MDV spread in these cells. Subsequent co-culture of infected macrophages with CEFs suggests that productive virus infection may occur in these cell types. This is the first report of in vitro infection of phagocytic cells by MDV.