Study of detergent-mediated liberation of hepatitis B virus-like particles from S. cerevisiae homogenate: identifying a framework for the design of future-generation lipoprotein vaccine processes

Virus-like particles (VLPs) are expressed intracellularly in Saccharomyces cerevisiae and the recovery process involves the use of a detergent, which facilitates the release of VLP from host cell components. The detergent-mediated liberation of VLPs is a critical step in primary recovery and is responsible for setting the backdrop for subsequent purification in terms of product yield and characteristics of the process stream. In this paper the use of Triton X-100 detergent for the recovery of lipid envelope VLPs, using the hepatitis B surface antigen (HBsAg) as the VLP model, was investigated. To develop a framework that can be adopted in process design for future generation VLP vaccine candidates, the impact of Triton X-100 was characterized via different response factors: (i) recovery and activity of the HBsAg; (ii) level of protein and lipid contamination from the host cell; and (iii) indirect impact on the performance of an ultrafiltration step following primary recovery. Our studies identified that an increase in detergent concentration favors recovery of HBsAg only to a specific threshold, 0.5% v/v Triton X-100. Further increase in detergent results in delipidation of HBsAg leading to loss in antigenic activity. The level of contamination due to host protein and lipid co-liberation is in proportion with the amount of detergent employed. Greater membrane resistance during ultrafiltration was observed for samples generated using higher concentrations of detergent due to the increase in membrane fouling by the contaminants. Based on this study, Triton X-100 concentrations in the range of 0.2-0.5% v/v appears to be most suitable for recovery of native HBsAg. Choosing between 0.2-0.5% v/v would involve identifying a suitable tradeoff between desired product yield and the level of contamination that can be tolerated by downstream operations.     

Linkage to CFA29 detected in a genome-wide linkage screen of a canine pedigree segregating Sry-negative XX sex reversal

Canine Sry-negative XX sex reversal is a disorder of gonadal development wherein individuals having a female karyotype develop testes or ovotestes. In this study, linkage mapping was undertaken in a pedigree derived from one proven carrier American cocker spaniel founder male and beagle females. All affected dogs in the analysis were XX true hermaphrodites and confirmed to be Sry negative by polymerase chain reaction. A genome-wide linkage screen conducted using 245 microsatellite markers revealed highest LOD score of 3.4 (marker CPH9) on CFA29. Fine mapping with additional microsatellites in the region containing CPH9 localized the Sry-negative XX sex reversal locus to a 5.4-Mb candidate region between markers CPH9 and FH3003 (LOD score 3.15). Insignificant LOD scores were found at genome-wide screen or fine mapping markers that were within 10 Mb of 45 potential candidate genes reported to have a role in mammalian sex determination or differentiation. Together, these results suggest that a novel locus on CFA29 may be responsible for sex reversal in this pedigree.     

Arbitrarily primed-PCR based diversity assessment reflects hierarchical groupings of Indian tetraploid wheat genotypes

Genetic diversity analysis using PCR with arbitrary decamer primers (RAPD — random amplified polymorphic DNA) was carried out in a set of 63 tetraploid wheat genotypes which comprised 24 durum landraces, 18 durum cultivars, nine dicoccum cultivars, ten less commonly cultivated species and two wild tetraploid species. The durum and dicoccum wheat genotypes are a part of the germplasm used in Indian tetraploid wheat breeding programs. A total of 206 amplification products were obtained with 21 informative primers, of which 162 were polymorphic. The highest degree of polymorphism was seen in the wild and less commonly cultivated species (68.9%). Durum released cultivars showed greater polymorphism (50.6%) than landraces (44.8%), while dicoccum cultivars showed a considerably low level of polymorphism (23.6%). Cluster analysis led to the separation of wild and cultivated genotypes, and among cultivated emmer wheat distinct groups were formed by the durum cultivars, durum landraces and dicoccum cultivars. The subgroupings of landraces had no relation to their geographical distribution. The durum cultivars formed subgroups based on common parentage in their pedigree. Among species, wild timopheevi wheat (T. araraticum) and its cultivated form (T. timopheevi) formed a distinct group distant from all other genotypes. The present study is a first attempt at determining the genetic variation in Indian tetraploid wheats at the molecular level. Received: 10 January 1999 / Accepted: 30 January 1999     

Metabolism of dimethylterephthalate byAspergillus niger

Aspergillus niger (AG-1) metabolized dimethylterephthalate through monomethylterephthalate, terephthalate and protocatechuate. Degradation of dimethylterephthalate was followed by extraction of residual dimethylterephthalate from the spent medium. The quantitative UV analysis showed that 58% of the dimethylterephthalate supplement was taken up in 144 h. The metabolites were isolated from resting cell cultures. Thin layer chromatography analysis of the extract revealed the presence of two intermediates, monomethylterephthalate and terephthalate. Use of an inhibitor in resting cell culture experiment demonstrated the accumulation of protocatechuate. The time course of protocatechuate accumulation was also studied. Metabolites were identified by employing various physicochemical methods. Enzyme studies using cell-free extracts exhibited dimethylterephthalate esterase and protocatechuate dioxygenase activities. Protocatechuate was oxidized by themeta cleavage pathway. A tentative pathway for the degradation of DMTP has been proposed inA. niger.Abbreviations A. niger Aspergillus niger (AG1) - DMSO dimethyl sulfoxide - DMTP dimethylterephthalate - MMTP monomethylterephthalate - MS mass spectra - NMR nuclear magnetic resonance spectra - PCA protocatechuate - TLC thin layer chromatography - TP terephthalate - UV ultra violet spectra     

Future of antibody purification

Antibody purification seems to be safely ensconced in a platform, now well-established by way of multiple commercialized antibody processes. However, natural evolution compels us to peer into the future. This is driven not only by a large, projected increase in the number of antibody therapies, but also by dramatic improvements in upstream productivity, and process economics. Although disruptive technologies have yet escaped downstream processes, evolution of the so-called platform is already evident in antibody processes in late-stage development. Here we perform a wide survey of technologies that are competing to be part of that platform, and provide our [inherently dangerous] assessment of those that have the most promise.     

Degradation of terephthalic acid by a Bacillus species

Abstract A Gram-positive bacterium with the ability to utilize terephthalic acid as sole carbon source was isolated from soil. The strain was identified as a Bacillus sp. Protocatechuate was shown to be a key intermediate in the degradation of terephthalate. Oxygen uptake studies were carried out with the probable intermediates. The presence of different enzymes was tested for. A mechanism is proposed for the degradation of terephthalate.     

Retention of plastic-tipped dart tags in African tigerfish Hydrocynus vittatus

Estimates of tag retention and tagging-related mortality are essential for mark-recapture experiments. Mortality and tag loss were estimated from 15 tigerfish Hydrocynus vittatus marked using Hallmark model PDL plastic-tipped dart tags released into a 1 730 m² pond at Kamutjonga Inland Fisheries Institute, Namibia, and inspected bi-monthly for the presence or absence of tags. No mortality was observed during the experiment. All marked fish had lost their tags after 10 months and 50% tag loss was estimated at 3.9 months. The high tag loss rate indicates that PDL plastic-tipped dart tags are not suitable for long-term studies on this species.