Cell engineering for muscle gene therapy: Extemporaneous production of retroviral vector packaging macrophages using defective herpes simplex virus type 1 vectors harbouring gag, pol, env genes

HSV-1 Amplicon Vectors as Genetic Vaccines

HSV-1 amplicon vectors have been used as platforms for the generation of genetic vaccines against both DNA and RNA viruses. Mice vaccinated with such vectors encoding structural proteins from both foot-and-mouth disease virus and rotavirus were partially protected from challenge with wild-type virus (D'Antuono et al., Vaccine 28:7363-7372, 2010; Laimbacher et al., Mol Ther 20:1810-1820, 2012; Meier et al., Int J Mol Sci 18:431, 2017), indicating that HSV-1 amplicon vectors are attractive tools for the development of complex and safe genetic vaccines.This chapter describes the preparation and testing of HSV-1 amplicon vectors that encode individual or multiple viral structural proteins from a polycistronic transgene cassette. We further put particular emphasis on generating virus-like particles (VLPs) in vector-infected cells. Expression of viral genes is confirmed by Western blot and immune fluorescence analysis and generation of VLPs in vector-infected cells is demonstrated by electron microscopy. Furthermore, examples on how to analyze the immune response in a mouse model and possible challenge experiments are described.

HSV-1 amplicon vectors as genetic vaccines

HSV-1 amplicon vectors have been used as platforms for the generation of genetic vaccines against both DNA and RNA viruses. Mice vaccinated with such vectors encoding structural proteins from both foot-and-mouth disease virus and rotavirus were partially protected from challenge with wild-type virus (D'Antuono et al. Vaccine 28: 7363-7372, 2010; Laimbacher et al. Mol Ther 20: 1810-1820, 2012), indicating that HSV-1 amplicon vectors are attractive tools for the development of complex and safe genetic vaccines. This chapter describes the use of HSV-1 amplicon vectors that encode individual or multiple viral structural proteins from a polycistronic transgene cassette in mammalian cells. More precisely, amplicon vectors that encode multiple structural viral proteins support the in situ production of viruslike particles (VLPs) in vector-infected cells. The expression of the viral genes is confirmed by Western blot and immune fluorescence analysis, and the generation of VLPs in vector-infected cells is demonstrated by electron microscopy.

HSV-1 amplicon vectors launch the production of heterologous rotavirus-like particles and induce rotavirus-specific immune responses in mice

Virus-like particles (VLPs) are promising vaccine candidates because they represent viral antigens in the authentic conformation of the virion and are therefore readily recognized by the immune system. As VLPs do not contain genetic material they are safer than attenuated virus vaccines. In this study, herpes simplex virus type 1 (HSV-1) amplicon vectors were constructed to coexpress the rotavirus (RV) structural genes VP2, VP6, and VP7 and were used as platforms to launch the production of RV-like particles (RVLPs) in vector-infected mammalian cells. Despite the observed splicing of VP6 RNA, full-length VP6 protein and RVLPs were efficiently produced. Intramuscular injection of mice with the amplicon vectors as a two-dose regimen without adjuvants resulted in RV-specific humoral immune responses and, most importantly, immunized mice were partially protected at the mucosal level from challenge with live wild-type (wt) RV. This work provides proof of principle for the application of HSV-1 amplicon vectors that mediate the efficient production of heterologous VLPs as genetic vaccines.

HSV-1-derived amplicon vectors: recent technological improvements and remaining difficulties--a review

Amplicons are defective and non-integrative vectors derived from herpes simplex virus type 1. As the vector genome carries no virus genes, amplicons are both non-toxic for the infected cells and non-pathogenic for the inoculated organisms. In addition, the large transgenic capacity of amplicons, which allow delivery of up to 150 Kbp of foreign DNA, makes these vectors one of the most powerful, interesting and versatile gene delivery platforms. We present here recent technological developments that have significantly improved and extended the use of amplicons, both in cultured cells and in living organisms. In addition, this review also discusses the many difficulties still pending to be solved, in order to achieve stable and physiologically regulated transgene expression.

HSV-1 amplicon vectors: a promising and versatile tool for gene delivery

Amplicons are defective and non-integrative vectors derived from herpes simplex virus type 1. They carry no virus genes in the vector genome and are, therefore, not toxic to the infected cells or pathogenic for the transduced organisms, making these vectors safe. In addition, the large transgenic capacity of amplicons, which allow delivery of < or = 150 Kbp of foreign DNA, make these vectors one of the most powerful, interesting and versatile gene delivery platforms. Here, the authors present recent technological developments that have significantly improved and extended the use of amplicons, both in cultured cells and in living organisms. In addition, this review illustrates the many possible applications that are presently being developed with amplicons and discuss the many difficulties still pending to be solved in order to achieve stable and physiologically regulated transgenic expression.

HSV-1-based amplicon vectors: design and applications

Amplicons are defective, helper-dependent herpes simplex virus type 1 (HSV-1)-based vectors able to convey more than 100 kbp of foreign DNA to the nucleus of mammalian cells. This unique feature make amplicons very appealing for preventive or therapeutic gene transfer requiring the transduction of very large pieces of DNA, as well as for upstream fundamental studies, such as functional genomics. Several recent achievements in amplicon technology have allowed to produce relatively large amounts of essentially helper-free amplicons, as well as to expand the host range of these vectors. In this review, we will update the current know-how concerning design, construction, and recent applications, as well as the potential and current limitations, of this interesting and promising class of vectors.

Retroviral vectors for human gene delivery

The potential for gene therapy to cure a wide range of diseases has lead to high expectations and a great increase in research efforts in this area. At present, viral vectors are the most efficient means of delivering a corrective gene into human cells. While a number of different viral vectors are under development, retroviral vectors are currently the most common type used in clinical trials today. However, the production of retroviral vectors for gene therapy applications faces a number of challenges. Of primary concern is the low titre of vector stocks produced by packaging cells in culture and the inherent instability of retroviral vector activity. The problems facing large-scale retroviral vector production are outlined in this review and the research efforts by a number of groups who have attempted to optimise production methods are presented.