No abstract

SummaryRecombinant hepatitis B surface antigen (HBsAg) constitutes currently used vaccines against hepatitis B virus, and has been successfully employed as a carrier for foreign epitopes.With the aim of developing an inexpensive, easily administered vaccine source for global immunization, several groups have expressed HBsAg in plant systems. Transgenic plant-derived HBsAg assembles into virus-like particles (VLPs) and is immunogenic in both mice and humans. However, HBsAg expression is relatively low in transgenic plant systems.The time-consuming and labour-intensive process of generating transgenic plants also significantly limits high-throughput analyses of various HBsAg fusion antigens. In this paper, the high-yield rapid production of HBsAg in plant leaf using a novel viral transient expression system is described. Nicotiana benthamiana leaves infiltrated with the MagnICON viral vectors produced HBsAg at high levels, averaging 295 μ g/g leaf fresh weight at 10 days post-infection, as measured by a polyclonal enzyme-linked immunosorbent assay.Transiently expressed HBsAg accumulated as the full-length product, formed disulphidelinked dimers, displayed the conformational 'a' antigenic determinant and assembled into VLPs. Immunization of mice with partially purified HBsAg elicited HBsAg-specific antibodies.Furthermore, it was found that transient production of HBsAg using vacuum infiltration of whole plants, rather than syringe infiltration of leaves, was readily scalable, and greatly improved the accumulation of correctly folded HBsAg that displays the protective 'a' determinant.

No abstract

No abstract

Many, if not most, of the cancer cells arrested in the microvasculature during metastasis appear to be rapidly killed by mechanical trauma, associated with shape-transitions, which require increases in cell surface area. The hypothesis has been advanced that such increases in surface area occur in 2 phases: First, there is an apparent increase due to surface unfolding, which is reversible and non-lethal. Second, there is a true increase, during which cell surface membranes are stretched, with an increase in membrane tension. When tension exceeds a critical level, the surface membranes rupture and this irreversible change is lethal. In the present study, cell surface area has been incrementally increased by a hypotonic environment. Down to approximately 70 mM/kg, a reversible, non-lethal increase in cell volume was observed, associated with electron microscopic evidence of unfolding. At and below 70 mM/kg, irreversible, lethal changes occurred, associated with increased susceptibility to the mechanical trauma associated with membrane-filtration. These observations are consistent with the hypothesis in question.