RESUMO
Molecular farming of vaccines has been heralded as a cheap, safe and scalable production platform. In reality, however, differences in the plant biosynthetic machinery, compared to mammalian cells, can complicate the production of viral glycoproteins. Remodelling the secretory pathway presents an opportunity to support key post-translational modifications, and to tailor aspects of glycosylation and glycosylation-directed folding. In this study, we applied an integrated host and glyco-engineering approach, NXS/T Generation™, to produce a SARS-CoV-2 prefusion spike trimer in Nicotiana benthamiana as a model antigen from an emerging virus. The size exclusion-purified protein exhibited a characteristic prefusion structure when viewed by transmission electron microscopy, and this was indistinguishable from the equivalent mammalian cell-produced antigen. The plant-produced protein was decorated with under-processed oligomannose N-glycans and exhibited a site occupancy that was comparable to the equivalent protein produced in mammalian cell culture. Complex-type glycans were almost entirely absent from the plant-derived material, which contrasted against the predominantly mature, complex glycans that were observed on the mammalian cell culture-derived protein. The plant-derived antigen elicited neutralizing antibodies against both the matched Wuhan and heterologous Delta SARS-CoV-2 variants in immunized hamsters, although titres were lower than those induced by the comparator mammalian antigen. Animals vaccinated with the plant-derived antigen exhibited reduced viral loads following challenge, as well as significant protection from SARS-CoV-2 disease as evidenced by reduced lung pathology, lower viral loads and protection from weight loss. Nonetheless, animals immunized with the mammalian cell-culture-derived protein were better protected in this challenge model suggesting that more faithfully reproducing the native glycoprotein structure and associated glycosylation of the antigen may be desirable.
RESUMO
PURPOSE: Mesenteric embolization is an established treatment for lower gastrointestinal bleeding. The aim of this study was to determine the outcome of angiography and embolization and its influencing factors. METHODS: A prospective database of all mesenteric angiograms performed for lower gastrointestinal bleeding at a tertiary center between 1998 and 2008 was analyzed in combination with chart review. RESULTS: There were 107 angiograms performed during 83 episodes of lower gastrointestinal bleeding in 78 patients. Active bleeding was identified in 40 episodes (48%), and embolizations were performed in 37 (45%). One patient without active bleeding on angiogram also underwent embolization, making a total of 38 embolizations. Overall mortality was 7% with 4 deaths due to rebleeding and 2 deaths due to a medical comorbidity (respiratory failure, pneumonia). Short-term complications of angiography were false aneurysm (1 patient) and Enterobacter sepsis (1 patient). Long-term complications were groin lymphocele (1 patient) and late rebleed from collateralization (1 patient). In 43 episodes, angiography did not demonstrate active bleeding. Twelve (28%) of these patients continued to bleed, 9 of whom had successful surgery. Of the 38 patients who had embolizations, all had immediate cessation of bleeding. Nine patients (24%) later rebled; 5 of these patients required surgery and 3 had reembolizations. Of the 3 patients who underwent reembolization, 2 developed ischemic bowel and 1 stopped bleeding; surgery was required in 1 patient. CONCLUSIONS: Mesenteric angiography for lower gastrointestinal bleeding effectively identifies the site of bleeding in 48% of patients and allows embolization in 45%. Embolization achieves clinical success in 76% of patients but repeat embolization is associated with a high rate of complications.