No abstract

Gestational choriocarcinomas are derived from placental trophoblast cells, with HLA-C being the only class I polymorphic molecule expressed. However, choriocarcinomas have not been profiled for endoplasmic reticulum aminopeptidase 2 (ERAP2) expression. ERAP2 trims peptides presented by human leukocyte antigens (HLA) that have shown to modulate immune response. Over 50% of choriocarcinomas we screened lack ERAP2 expression, which suggests that the absence of ERAP2 expression allows immune evasion of choriocarcinoma cells. We demonstrate that the ability of choriocarcinoma cells to activate lymphocytes was lowest with cells lacking ERAP2 (JEG-3) or HLA-C (JAr). This observation suggests that activation is dependent on expression of both ERAP2 and HLA-C molecules. In addition, an ERAP2 variant in which lysine is changed to asparagine (K392N) results in increased trimming activity (165-fold) for hydrophobic peptides and biologically never been detected. We hypothesize that homozygosity for the N392 ERAP2 variant is prohibited because it modulates the immune recognition of placental trophoblasts. We demonstrate that NK-cell activation and killing were significantly dependent on forced expression of the N392 ERAP2 isoform in JEG-3 cells. Cytotoxicity was confirmed by 7AAD killing assays showing that N392 ERAP2-isoform expressing JEG-3 cells had the highest percentage of apoptotic cells independent of the expression level of CD11a on lymphocytes. This is the first report showing that N392 ERAP2 promotes an immune clearance pathway for choriocarcinoma cells, and provides an explanation for why embryonic homozygosity for the N392 ERAP2 variant is not detected in any population.

No abstract

There is a dire need for effective treatments against microbial pathogens. Yet, the continuing emergence of drug resistance necessitates a deeper knowledge of how pathogens respond to treatments.

Mounting evidence demonstrates that nutritional environment can alter pathogen drug sensitivity. While the nutrient-rich media used for standard in vitro culture contains supra-physiological nutrient concentrations, pathogens encounter a relatively restrictive environment in vivo. We assessed the effect of nutrient limitation on the protozoan parasite that causes malaria and demonstrated that short-term growth under physiologically-relevant mild nutrient stress (or metabolic priming) triggers increased tolerance of the potent antimalarial drug dihydroartemisinin (DHA). We observed beneficial effects using both short-term survival assays and longer-term proliferation studies, where metabolic priming increases parasite survival to a level previously defined as DHA resistant (>1% survival). We performed these assessments by either decreasing single nutrients that have distinct roles in parasite metabolism or using a media formulation with reductions in many nutrients that simulates the human plasma environment. We determined that priming-induced DHA tolerance was restricted to parasites that had newly invaded the host red blood cell but the effect was not dependent on genetic background. The molecular mechanisms of this intrinsic effect mimic aspects of genetic artemisinin tolerance, including translational repression, autophagy, and protein export. This finding suggests regardless of the impact on survival rates, environmental stress could stimulate changes that ultimately directly contribute to drug tolerance. Because metabolic stress is likely to occur more frequently in vivo compared to the stable in vitro environment, priming-induced drug tolerance has ramifications for how in vitro results translate to in vivo studies. Improving our understanding of how pathogens adjust their metabolism to impact survival of current and future drugs is an important avenue of research to prevent and slow the spread of resistance.