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BackgroundImmune-related hepatitis (irHepatitis) is a relatively common immune-related adverse event (irAE) of checkpoint inhibitors. Often, it responds well to steroids; however, in refractory cases, further therapy is needed. Anti-tumor necrosis factor (TNF) antibodies are used for management of multiple irAEs, but there are little data in irHepatitis. Here, we report on safety and efficacy of infliximab in 10 cases of steroid-refractory irHepatitis.MethodsWe retrospectively reviewed patients treated with infliximab for steroid-refractory grade ≥3 irHepatitis at the Department of Dermatology, University Hospital Zurich. The positive response to infliximab was defined as no further increase in alanine aminotransferase (ALT)/aspartate aminotransferase (AST) above 50% than at the time of first infliximab infusion and control of irHepatitis without therapies other than steroids and infliximab.Results10 patients with steroid-resistant irHepatitis grade ≥3 were treated with infliximab 5 mg/kg, of whom 7 (70%) responded positively. In two cases, the liver values increased over 50% before the irHepatitis could be controlled. In another case, therapies other than infliximab and steroids were given. At the median follow-up of 487 days, 90% of the patients demonstrated resolved irHepatitis without AST/ALT elevation following infliximab infusions.ConclusionsTreatment of irHepatitis with infliximab did not result in hepatotoxicity and led to long-lasting positive response in 9 of 10 of the cases. Further research is needed to evaluate the role of anti-TNF antibodies in management of irHepatitis.

Background The opportunistic pathogen Naegleria fowleri establishes infection in the human brain, killing almost invariably within 2 weeks. The amoeba performs piece-meal ingestion, or trogocytosis, of brain material causing direct tissue damage and massive inflammation. The cellular basis distinguishing N. fowleri from other Naegleria species, which are all non-pathogenic, is not known. Yet, with the geographic range of N. fowleri advancing, potentially due to climate change, understanding how this pathogen invades and kills is both important and timely. Results Here, we report an -omics approach to understanding N. fowleri biology and infection at the system level. We sequenced two new strains of N. fowleri and performed a transcriptomic analysis of low- versus high-pathogenicity N. fowleri cultured in a mouse infection model. Comparative analysis provides an in-depth assessment of encoded protein complement between strains, finding high conservation. Molecular evolutionary analyses of multiple diverse cellular systems demonstrate that the N. fowleri genome encodes a similarly complete cellular repertoire to that found in free-living N. gruberi . From transcriptomics, neither stress responses nor traits conferred from lateral gene transfer are suggested as critical for pathogenicity. By contrast, cellular systems such as proteases, lysosomal machinery, and motility, together with metabolic reprogramming and novel N. fowleri proteins, are all implicated in facilitating pathogenicity within the host. Upregulation in mouse-passaged N. fowleri of genes associated with glutamate metabolism and ammonia transport suggests adaptation to available carbon sources in the central nervous system. Conclusions In-depth analysis of Naegleria genomes and transcriptomes provides a model of cellular systems involved in opportunistic pathogenicity, uncovering new angles to understanding the biology of a rare but highly fatal pathogen.

Of the 40 described Naegleria species, only N. fowleri can establish infection in humans, killing almost invariably within two weeks. In the brain, the amoeba performs piece-meal ingestion, or trogocytosis, of brain material causing massive inflammation. Conversely, its close relative Naegleria gruberi, which is used as a laboratory model organism, is non-pathogenic. The exact pathogenicity factors distinguishing N. fowleri from its harmless relatives are unclear. We have here taken an -omics approach to understanding N. fowleri biology and infection at the system level. We provide the first analysis of genomic diversity between strains, finding little conservation in synteny but high conservation in protein complement. We also demonstrate that the N. fowleri genome encodes a similarly complete cellular repertoire to that found in N. gruberi. Our comparative genomic analysis, together with a transcriptomic analysis of low versus high pathogenicity N. fowleri cultured in a mouse infection model, allowed us to construct a model of cellular systems involved in pathogenicity and furthermore provides ~500 novel candidate pathogenicity factors in this currently rare but highly fatal pathogen.