Tumor resistance to anti-mesothelin CAR-T cells caused by binding to shed mesothelin is overcome by targeting a juxtamembrane epitope

Despite many clinical trials, CAR-T cells are not yet approved for human solid tumor therapy. One popular target is mesothelin (MSLN) which is highly expressed on the surface of about 30% of cancers including mesothelioma and cancers of the ovary, pancreas, and lung. MSLN is shed by proteases that cleave near the C terminus, leaving a short peptide attached to the cell. Most anti-MSLN antibodies bind to shed MSLN, which can prevent their binding to target cells. To overcome this limitation, we developed an antibody (15B6) that binds next to the membrane at the protease-sensitive region, does not bind to shed MSLN, and makes CAR-T cells that have much higher anti-tumor activity than a CAR-T that binds to shed MSLN. We have now humanized the Fv (h15B6), so the CAR-T can be used to treat patients and show that h15B6 CAR-T produces complete regressions in a hard-to-treat pancreatic cancer patient derived xenograft model, whereas CAR-T targeting a shed epitope (SS1) have no anti-tumor activity. In these pancreatic cancers, the h15B6 CAR-T replicates and replaces the cancer cells, whereas there are no CAR-T cells in the tumors receiving SS1 CAR-T. To determine the mechanism accounting for high activity, we used an OVCAR-8 intraperitoneal model to show that poorly active SS1-CAR-T cells are bound to shed MSLN, whereas highly active h15B6 CAR-T do not contain bound MSLN enabling them to bind to and kill cancer cells.

[Significance of the sampling points and the aerobic microbiological culture for the diagnosis of respiratory infections in reptiles]

Respiratory diseases play an important role in reptiles kept in captivity. Microbiological examinations are described as an essential part of the diagnostic possibilities. Therefore the aim of this study was to collect data on the usefulness of results obtained after aerobic culture (sheepblood, brilliantgreen, sabouraud's agar) of swabs and tracheal lavages following standardized sampling. Respiratory symptoms were found in 24.3% of the snakes, 16.5% of the tortoises/turtles and 1.6% of the lizards presented in the clinic for birds and reptiles at the university Leipzig. Altogether, 52% of the examined samples were found to be bacteriologically and 31% mycologically of pathologic significance. The tracheal lavage proved to be more sensitive in comparison to swabs taken from the pharynx. The bacteria most often found in the samples were Pseudomonas aeruginosa, Klebsiella pneumoniae and Stenotrophomonas maltophila. Mycologic culture revealed Aspergillus sp. and yeast most often. In boids and pythons, the highest number of bacteriologic results assessed to be of pathological significance were found (75%). Mycologically, samples from tortoises were found most often to have a result of pathological significance (48%). To summarize the aerobic cultivation on standard media (in this study: Columbia-Agar with sheep blood, brilliant-green-, Sabouraud-Agar) can be recommended as an initial diagnostic measure in reptiles presented with respiratory symptoms; further pathogens (eg, viral examination, Mycoplasma) should be checked additionally.