In Pichia pastoris, secretion of the A33 single-chain antibody fragment (A33scFv) was shown to reach levels of approximately 4 g l(-1) in fermentor cultures. In this study, we investigated whether manipulating chaperone and foldase levels in P. pastoris could further increase secretion of A33scFv. Cells were engineered to cooverexpress immunoglobulin binding protein (BiP) and/or protein disulfide isomerase (PDI) with A33scFv during growth in methanol as the sole carbon and energy source. Cooverexpression of BiP resulted in increased secretion levels of A33scFv by approximately threefold. In contrast, cooverexpression of PDI had no apparent effect on secretion of A33scFv. In cells cooverexpressing BiP and PDI, A33scFv secretion did not increase and protein levels remained the same as the control strain. We believe that secretion of A33scFv is increased by cooverexpression of BiP as a result of an increase in folding capacity inside the endoplasmic reticulum (ER). In addition, lack of increased single-chain secretion when PDI is coexpressed was unexpected due to the presence of disulfide bonds in A33scFv. We also show that during PDI cooverexpression with the single-chain there is a sixfold increase in BiP levels, indicating that the former is possibly inducing an unfolded protein response due to excess chaperone and recombinant protein in the ER.

A neutrophil-predominant inflammatory infiltrate in a cutaneous biopsy can be associated with a broad spectrum of diseases. Here we describe three cases showing a neutrophil-predominant dermal infiltrate admixed with abundant acellular bodies surrounded by capsule-like vacuolated spaces, which strikingly mimicked Cryptococcus. Two cases occurred within the settings of underlying hematologic malignancies; the third case was associated with immune dysregulation. Two patients were acutely ill in the medical intensive care unit. Fungal work-up, including cultures and multiple stains were negative. Because of clinical deterioration in these patients, transmission electron microscopy was pursued to definitively rule out fungal infection. In both cases, characteristics most compatible with autolysing human cells, not Cryptococcus, were identified. Chemotherapy and high-dose steroids were given, but both patients eventually succumbed to their diseases. To the best of our knowledge, these represent the first reported cases of autolysing human cells mimicking Cryptococcus organisms within neutrophilic infiltrates. They highlight the therapeutic dilemmas arising with histopathologic mimics, as well as the importance of thorough investigation to distinguish mimickers from true infectious organisms. We believe recognition of this microscopic pitfall will be useful to dermatopathologists faced with similar findings in the future, and may prevent unnecessary delay of appropriate therapy in acutely ill patients.

The secreted proteome of Pichia pastoris X-33 was investigated in methanol-induced cultures with a goal to enhance the secretion and purification of recombinant proteins. In a fed-batch fermentation at 30 °C, more host proteins were found in greater concentrations compared to cultures grown at 25 °C. Protein samples collected directly from the culture media at 25 °C, as well as separated by two-dimensional (2D) gel, were subjected to ESI-MS/MS analysis. A total of 75 proteins were identified in the media from different conditions including pre- and post-methanol induction and in a strain overexpressing a recombinant schistosomiasis vaccine, Sm14-C62V. The identified proteins include native secreted proteins and some intracellular proteins, most of which have low isoelectric points (pI < 6). 2D gel analyses further revealed important characteristics, such as abundance, degradation, and glycosylation of these identified proteins in this proteome. Cell wall-associated proteins involved in cell wall biogenesis, structure, and modification comprised the majority of the secreted proteins which have been identified. Intracellular proteins such as alcohol oxidase and superoxide dismutase were also found in the proteome, suggesting some degree of cell lysis. However, both protocols show that their concentrations are significantly lower than the native secreted proteins. This study identifies proteins secreted or released into the culture media in the methanol-induced fermentation cultures of P. pastoris X-33 and suggests potential biotechnology applications based on the discovery of this proteome.

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