Bacterial ghosts (BGs) are empty cell envelopes derived from Gram-negative bacteria. They not only represent a potential platform for development of novel vaccines but also provide a tool for efficient adjuvant and antigen delivery system. In the present study, we investigated the interaction between BGs of Escherichia coli (E. coli) and bovine monocyte-derived dendritic cells (MoDCs). MoDCs are highly potent antigen-presenting cells and have the potential to act as a powerful tool for manipulating the immune system. We generated bovine MoDCs in vitro from blood monocytes using E. coli expressed bovine GM-CSF and IL-4 cytokines. These MoDCs displayed typical morphology and functions similar to DCs. We further investigated the E. coli BGs to induce maturation of bovine MoDCs in comparison to E. coli lipopolysaccharide (LPS). We observed the maturation marker molecules such as MHC-II, CD80 and CD86 were induced early and at higher levels in BG stimulated MoDCs as compared to the LPS stimulated MoDCs. BG mediated stimulation induced significantly higher levels of cytokine expression in bovine MoDCs than LPS. Both pro-inflammatory (IL-12 and TNF-α) and anti-inflammatory (IL-10) cytokines were induced in MoDCs after BGs stimulation. We further analysed the effects of BGs on the bovine MoDCs in an allogenic mixed lymphocyte reaction (MLR). We found the BG-treated bovine MoDCs had significantly (p<0.05) higher capacity to stimulate allogenic T cell proliferation in MLR as compared to the LPS. Taken together, these findings demonstrate the E. coli BGs induce a strong activation and maturation of bovine MoDCs.

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SUMMARYAn investigation, using Rhode Island Red, New Hampshire, Columbian and Australorp, was conducted to study the correlation between chorioallantoic membrane (CAM)-infection phenotype to challenge with Bryan strain of Rous sarcoma virus (BS-RSV) of subgroup A and subsequent mortality, following hatching. A total of 806 CAMs and 438 chicks over nine hatch-replicates in three experiments provided evidence that infection via an inoculation of the CAM induced rapid and high mortality, about 72%, averaged over the four breeds, from a fibrosarcomatous liver tumour (LT) in CAM-susceptible chicks. In contrast, only 14% of chicks inoculated via the yolk sac died from liver tumours.

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