Treatment is commonly with amphotericin B or triazole drugs such as itraconazole or voriconazole

that regulate expression of genes involved in different biological processes such as cell proliferation, immune responses, inflammation and cell death. In resting conditions, these transcription factors remain in the cytosol sequestered by inhibitors, the IkB proteins. Following cellular receptor stimulation, the IKK kinase complex is activated through K63-linked polyubiquitination and phosphorylates NF-kB inhibitors. This results in their K48-linked ubiquitination by the SCFb-TrCP E3 ligase complex and consequently proteasomal degradation/processing. The NF-kB transcription factors are then released in the cytosol and translocated to the nucleus to regulate the expression of genes involved in pro-inflammatory signalling. Deubiquitinases can negatively regulate NF-kB signalling through cleavage of K63-linked chains, which form scaffolds for the activation of the IKK kinase complexes. The NF-kB pathway is classified as either classical or alternative on the basis of the IKK subunits that are activated by upstream kinases and which lead to the activation of different NF-kB transcription factors. Many bacterial pathogens, including Salmonella enterica, have acquired sophisticated mechanisms to interfere with the NF-kB signalling pathway. Salmonella has two type three secretion systems, encoded within the Salmonella pathogenicity islands 1 and 2 that deliver virulence effector proteins into the host cell. In the case of the SPI-1 T3SS, these mediate bacterial invasion into host cells, while the SPI-2 T3SS translocates effectors across the vacuolar membrane of intracellular bacteria to promote replication. SopE, SopE2 and SopB constitute a subset of SPI-1 effectors that are important for invasion and promote intestinal inflammation through the activation of the NFkB and MAPK pathways independently of immune receptors. AvrA has 11606371 been reported to inhibit NF-kB activity and proinflammatory cytokine secretion, but does not seem to interact with or affect the activity 19911773 of known proteins involved in the NF-kB pathway. The SPI-2 T3SS effector SspH1 binds to the kinase PKN1, which in turn regulates NF-kB and JNK signalling. Constitutively active PKN1 and SspH1 were shown to negatively regulate NF-kB signalling when expressed ectopically in epithelial cells. Our group GFT505 web showed that the Salmonella Typhimurium SPI-2 T3SS effector SseL is a DUB with a preference for K63-linked chains and that it contributes to macrophage cell death, but no difference in degradation of IkBa or production of the proinflammatory cytokine TNF-a was detected in macrophages infected with either wild-type or sseL mutant strain of S. Typhimurium. A subsequent study proposed that SseL deubiquitinates IkBa, thereby preventing its degradation and reducing NF-kB signalling. SseL was also suggested to reduce innate immune responses in vivo. Due to the discrepancies between this work and our previous results, we carried out further experiments on the potential influence of SseL on the NF-kB pathway. Our results fail to provide evidence that SseL targets the NF-kB pathway. Role of SseL on the NF-kB Pathway Results Microarray analysis of macrophage mRNAs To broaden the analysis of a possible role of SseL in immune modulation, we first analysed variations in mRNA levels from uninfected bone marrow-derived macrophages and BMM infected with either wt or DsseL strains at 10 h post-bacterial uptake using a genome-wide DNA microarray representing 28853 genes. BMM were chosen as they provide a mo