Lentiviral Vector Purification Using Nanofiber Ion-Exchange Chromatography.

Lentiviral vectors (LVs) are used in cell and gene therapies due to their ability to transduce both dividing and non-dividing cells while carrying a relatively large genetic payload and providing long-term gene expression via gene integration. Current cultivation methods produce titers of 105-107 transduction unit (TU)/mL; thus, it is necessary to concentrate LVs as well as remove process- and product-related impurities. In this work, we used a packaging cell line WinPac-RD-HV for LV production to simplify upstream processing. A direct capture method based on ion-exchange chromatography and cellulose nanofibers for LV concentration and purification was developed. This novel scalable stationary phase provides a high surface area that is accessible to LV and, therefore, has potential for high-capacity operation compared to traditional bead-based supports. We were able to concentrate LVs 100-fold while achieving a two-log removal of host cell protein and maintaining up to a 90% yield of functional vector.

Differential Effects of Integrin αv Knockdown and Cilengitide on Sensitization of Triple-Negative Breast Cancer and Melanoma Cells to Microtubule Poisons.

Low survival rates of patients with metastatic triple-negative breast cancer (TNBC) and melanoma, in which current therapies are ineffective, emphasize the need for new therapeutic approaches. Integrin ß1 appears to be a promising target when combined with chemotherapy, but recent data have shown that its inactivation increases metastatic potential owing to the compensatory upregulation of other integrin subunits. Consequently, we analyzed the potential of integrin subunits αv, α3, or α4 as targets for improved therapy in seven TNBC and melanoma cell lines. Experiments performed in an integrin αvß1-negative melanoma cell line, MDA-MB-435S, showed that knockdown of integrin subunit αv increased sensitivity to microtubule poisons vincristine or paclitaxel and decreased migration and invasion. In the MDA-MB-435S cell line, we also identified a phenomenon in which change in the expression of one integrin subunit changes the expression of other integrins, leading to an unpredictable influence on sensitivity to anticancer drugs and cell migration, referred to as the integrin switching effect. In a panel of six TNBCs and melanoma cell lines, the contribution of integrins αv versus integrins αvß3/ß5 was assessed by the combined action of αv-specific small interfering RNA or αvß3/ß5 inhibitor cilengitide with paclitaxel. Our results suggest that, for TNBC, knockdown of integrin αv in combination with paclitaxel presents a better therapeutic option than a combination of cilengitide with paclitaxel; however, in melanoma, neither of these combinations is advisable because a decreased sensitivity to paclitaxel was observed.

Manipulating adenoviral vector ion-exchange chromatography: Hexon versus fiber.

The serotype specificity of adenovirus ion-exchange chromatography has previously been studied using standard particle-based columns, and the hexon protein has been reported to determine retention time. In this study, we have submitted Adenovirus type 5 recombinants to anion-exchange chromatography using methacrylate monolithic supports. Our experiments with hexon-modified adenoviral vectors show more precisely that the retention time is affected by the substitution of amino acids in hypervariable region 5, which lies within the hexon DE1 loop. By exploring the recombinants modified in the fiber protein, we have proven the previously predicted chromatographic potential of this surface constituent. Modifications that preserve the net charge of the hexon protein, or those that cause only a small charge difference in the fiber protein, in addition to shortening the fiber shaft, did not change the chromatographic behavior of the adenovirus particles. However, modifications that include the deletion of just two negatively charged amino acids in the hexon protein, or the introduction of a heterologous fiber protein, derived from another serotype, revealed recognizable changes in anion-exchange chromatography. This could be useful in facilitating chromatography-approach purification by creating targeted capsid modifications, thereby shifting adenovirus particles away from particular interfering substances present in the crude lysate.

A novel application of methacrylate based short monolithic columns: concentrating Potato spindle tuber viroid from water samples.

Potato spindle tuber viroid (PSTVd) is the causal agent of a number of agriculturally important diseases. It is a single-stranded, circular and unencapsidated RNA molecule with only 356-360 nucleotides and no coding capacity. Because of its peculiar structural features, it is very stable ex vivo and it is easily transmitted mechanically by contaminated hands, tools, machinery, etc. In this work, we describe the development and optimization of a method for concentrating PSTVd using Convective Interaction Media (CIM) monolithic columns. The ion-exchange chromatography on diethylamine (DEAE) monolithic analytical column (CIMac DEAE-0.1 mL) resulted in up to 30% PSTVd recovery whilst the hydrophobic interaction chromatography on C4 monolithic analytical column (CIMac C4-0.1 mL) improved it up to 60%. This was due to the fact that the binding of the viroid to the C4 matrix was less strong than to the highly charged anion-exchange matrix and could be easier and more completely eluted under the applied chromatographic conditions. Based on these preliminary results, a C4 HLD-1 (High Ligand Density) 1 mL monolithic tube column was selected for further experiments. One-litre-water samples were mixed with different viroid quantities and loaded onto the column. By using reverse transcription quantitative polymerase chain reaction (RT-qPCR), the viroid RNA was quantified in the elution fraction (≈5 mL) indicating that 70% of the viroid was recovered and concentrated by at least two orders of magnitude. This approach will be helpful in screening irrigation waters and/or hydroponic systems' nutrient solutions for the presence of even extremely low concentrations of PSTVd.

Stem pitting and seedling yellows symptoms of Citrus tristeza virus infection may be determined by minor sequence variants.

The isolates of Citrus tristeza virus (CTV), the most destructive viral pathogen of citrus, display a high level of variability. As a result of genetic bottleneck induced by the bud-inoculation of CTV-infected material, inoculated seedlings of Citrus wilsonii Tanaka displayed different symptoms. All successfully grafted plants showed severe symptoms of stem pitting and seedling yellows, while plants in which inoculated buds died displayed mild symptoms. Since complex CTV population structure was detected in the parental host, the aim of this work was to investigate how it changed after the virus transmission, and to correlate it with observed symptoms. The coat protein gene sequence of the predominant genotype was identical in parental and grafted plants and clustered to the phylogenetic group 5 encompassing severe reference isolates. In seedlings displaying severe symptoms, the low-frequency variants clustering to other phylogenetic groups were detected, as well. Indicator plants were inoculated with buds taken from unsuccessfully grafted C. wilsonii seedlings. Surprisingly, they displayed no severe symptoms despite the presence of phylogenetic group 5 genomic variants. The results suggest that the appearance of severe symptoms in this case is probably induced by a complex CTV population structure found in seedlings displaying severe symptoms, and not directly by the predominant genomic variant.