Synthetically Functionalized Retroviruses Produced from the Bioorthogonally Engineered Cell Surface

Cancer Cell-Derived, Drug-Loaded Nanovesicles Induced by Sulfhydryl-Blocking for Effective and Safe Cancer Therapy

Extracellular vesicles (EVs) pose great promise as therapeutic carriers due to their ideal size range and intrinsic biocompatibility. Limited scalability, poor quality control during production, and cumbersome isolation and purification processes have caused major setbacks in the progression of EV therapeutics to the clinic. Here, we overcome these setbacks by preparing cell-derived nanovesicles induced by sulfhydryl-blocking (NIbS), in the desirable size range for therapeutic delivery, that can be further loaded with the chemotherapeutic drug, doxorubicin (DOX), resulting in NIbS/DOX. Applicable to most cell types, this chemical blebbing approach enables efficient, quick, and simple harvest and purification as well as easily scalable production. Cellular uptake and intracellular release of DOX was improved using NIbS/DOX compared to a liposomal formulation. We also confirmed that in tumor-challenged C57BL/6 mice NIbS/DOX significantly slowed tumor growth and led to improved survival compared to treatment with free drug or liposomal drug. NIbS are a promising therapeutic carrier for improving cancer treatment outcomes since they are easy to prepare at a large scale, good candidates for drug loading, and capable of efficient administration of therapeutic agents with avoided nonspecific major distribution in vital organs. In addition, the utility of NIbS can be easily expanded to immunotherapy, gene therapy, and cell therapy when they are derived from applicable cell types.

Stimulus-responsive viral vectors for controlled delivery of therapeutics

Virus-based therapies have gained momentum as the next generation of treatments for a variety of serious diseases. In order to make these therapies more controllable, stimulus-responsive viral vectors capable of sensing and responding to specific environmental inputs are currently being developed. A number of viruses naturally respond to endogenous stimuli, such as pH, redox, and proteases, which are present at different concentrations in diseases and at different organ and organelle sites. Additionally, rather than relying on natural viral properties, efforts are underway to engineer viruses to respond to endogenous stimuli in new ways as well as to exogenous stimuli, such as temperature, magnetic field, and optical light. Viruses with stimulus-responsive capabilities, either nature-evolved or human-engineered, will be reviewed to capture the current state of the field. Stimulus-responsive viral vector design considerations as well as gaps in current research efforts will be identified.

Fluorescence molecular painting of enveloped viruses

In this study, we describe a versatile, flexible, and quick method to label different families of enveloped viruses with glycosylphosphatidylinositol-modified green fluorescent protein, termed fluorescence molecular painting (FMP). As an example for a potential application, we investigated virus attachment by means of flow cytometry to determine if viral binding behavior may be analyzed after FMP of enveloped viruses. Virus attachment was inhibited by using either dextran sulfate or by blocking attachment sites with virus pre-treatment. Results from the FMP-flow cytometry approach were verified by immunoblotting and enzyme-linked immunosorbent assay. Since the modification strategy is applicable to a broad range of proteins and viruses, variations of this method may be useful in a range of research and applied applications from bio-distribution studies to vaccine development and targeted infection for gene delivery.

Postexit surface engineering of retroviral/lentiviral vectors

Gene delivery vectors based on retroviral or lentiviral particles are considered powerful tools for biomedicine and biotechnology applications. Such vectors require modification at the genomic level in the form of rearrangements to allow introduction of desired genes and regulatory elements (genotypic modification) as well as engineering of the physical virus particle (phenotypic modification) in order to mediate efficient and safe delivery of the genetic information to the target cell nucleus. Phenotypic modifications are typically introduced at the genomic level through genetic manipulation of the virus producing cells. However, this paper focuses on methods which allow modification of viral particle surfaces after they have exited the cell, that is, directly on the viral particles in suspension. These methods fall into three categories: (i) direct covalent chemical modification, (ii) membrane-topic reagents, and (iii) adaptor systems. Current applications of such techniques will be introduced and their advantages and disadvantages will be discussed.