Transduction of Vero cells and bovine monocytes with a herpes simplex virus-1 based amplicon carrying the gene for the bovine herpesvirus-1 Circ protein

Improvement of HSV-1 based amplicon vectors for a safe and long-lasting gene therapy in non-replicating cells

A key factor for developing gene therapy strategies for neurological disorders is the availability of suitable vectors. Currently, the most advanced are adeno-associated vectors that, while being safe and ensuring long-lasting transgene expression, have a very limited cargo capacity. In contrast, herpes simplex virus-based amplicon vectors can host huge amounts of foreign DNA, but concerns exist about their safety and ability to express transgenes long-term. We aimed at modulating and prolonging amplicon-induced transgene expression kinetics in vivo using different promoters and preventing transgene silencing. To pursue the latter, we deleted bacterial DNA sequences derived from vector construction and shielded the transgene cassette using AT-rich and insulator-like sequences (SAm technology). We employed luciferase and GFP as reporter genes. To determine transgene expression kinetics, we injected vectors in the hippocampus of mice that were longitudinally scanned for bioluminescence for 6 months. To evaluate safety, we analyzed multiple markers of damage and performed patch clamp electrophysiology experiments. All vectors proved safe, and we managed to modulate the duration of transgene expression, up to obtaining a stable, long-lasting expression using the SAm technology. Therefore, these amplicon vectors represent a flexible, efficient, and safe tool for gene delivery in the brain.

A novel alphaherpesvirus associated with fatal diseases in banded Penguins

A novel avian alphaherpesvirus, preliminarily designated sphenicid alphaherpesvirus 1 (SpAHV-1), has been independently isolated from juvenile Humboldt and African penguins (Spheniscus humboldti and Spheniscus demersus) kept in German zoos suffering from diphtheroid oropharyngitis/laryngotracheitis and necrotizing enteritis (collectively designated as penguin-diphtheria-like disease). High-throughput sequencing was used to determine the complete genome sequences of the first two SpAHV-1 isolates. SpAHV-1 comprises a class D genome with a length of about 164 kbp, a G+C content of 45.6 mol% and encodes 86 predicted ORFs. Taxonomic association of SpAHV-1 to the genus Mardivirus was supported by gene content clustering and phylogenetic analysis of herpesvirus core genes. The presented results imply that SpAHV-1 could be the primary causative agent of penguin-diphtheria-like fatal diseases in banded penguins. These results may serve as a basis for the development of diagnostic tools in order to investigate similar cases of penguin diphtheria in wild and captive penguins.

The early UL3 gene of equine herpesvirus-1 encodes a tegument protein not essential for replication or virulence in the mouse

The UL3 gene of equine herpesvirus-1 (EHV-1) is retained in the genome of defective interfering particles and encodes a ~33kDa myristylated protein. Further characterization showed that the UL3 gene is trans-activated only by the sole immediate early (IE) protein and encodes an early protein that is dispensable for EHV-1 replication and localizes in the tegument of purified virions. UL3-deleted EHV-1 (vL11ΔUL3) exhibits properties of host cell tropism, plaque size, and growth kinetics similar to those of the parental virus. Expression levels of EHV-1 proteins representative of all three gene classes in vL11ΔUL3-infected cells were identical to those in cells infected with parental virus. Mice intranasally infected with vL11ΔUL3 and parental virus showed no significant difference in mortality or virus lung titers. These findings suggest that the UL3 protein does not play a major role in the biology of EHV-1 in cell culture or virulence in the mouse.

Adaptive and innate transforming growth factor beta signaling impact herpes simplex virus 1 latency and reactivation

Innate and adaptive immunity play important protective roles by combating herpes simplex virus 1 (HSV-1) infection. Transforming growth factor β (TGF-β) is a key negative cytokine regulator of both innate and adaptive immune responses. Yet, it is unknown whether TGF-β signaling in either immune compartment impacts HSV-1 replication and latency. We undertook genetic approaches to address these issues by infecting two different dominant negative TGF-β receptor type II transgenic mouse lines. These mice have specific TGF-β signaling blockades in either T cells or innate cells. Mice were ocularly infected with HSV-1 to evaluate the effects of restricted innate or adaptive TGF-β signaling during acute and latent infections. Limiting innate cell but not T cell TGF-β signaling reduced virus replication in the eyes of infected mice. On the other hand, blocking TGF-β signaling in either innate cells or T cells resulted in decreased latency in the trigeminal ganglia of infected mice. Furthermore, inhibiting TGF-β signaling in T cells reduced cell lysis and leukocyte infiltration in corneas and trigeminal ganglia during primary HSV-1 infection of mice. These findings strongly suggest that TGF-β signaling, which generally functions to dampen immune responses, results in increased HSV-1 latency.

Genotypic characterization of two bacterial artificial chromosome clones derived from a single DNA source of the very virulent gallid herpesvirus-2 strain C12/130

The identification of specific genetic changes associated with differences in the pathogenicity of Marek's disease virus strains (GaHV-2) has been a formidable task due to the large number of mutations in mixed-genotype populations within DNA preparations. Very virulent UK isolate C12/130 induces extensive lymphoid atrophy, neurological manifestations and early mortality in young birds. We have recently reported the construction of several independent full-length bacterial artificial chromosome (BAC) clones of C12/130 capable of generating fully infectious viruses with significant differences in their pathogenicity profiles. Two of these clones (vC12/130-10 and vC12/130-15), which showed differences in virulence relative to each other and to the parental strain, had similar replication kinetics both in vitro and in vivo in spite of the fact that vC12/130-15 was attenuated. To investigate the possible reasons for this, the nucleotide sequences of both clones were determined. Sequence analysis of the two genomes identified mutations within eight genes. A single 494 bp insertion was identified within the genome of the virulent vC12/130-10 clone. Seven non-synonymous substitutions distinguished virulent vC12/130-10 from that of attenuated vC12/130-15. By sequencing regions of parental DNA that differed between the two BAC clones, we confirmed that C12/130 does contain these mutations in varying proportions. Since the individual reconstituted BAC clones were functionally attenuated in vivo and derived from a single DNA source of phenotypically very virulent C12/130, this suggests that the C12/130 virus population exists as a collection of mixed genotypes.

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.

Host cell targets of immediate-early protein BICP22 of bovine herpesvirus 1

The immediate-early (IE) protein BICP22 of bovine herpesvirus 1 (BHV-1) acts as transrepressor protein on viral promoters of different kinetic classes. In the present work, we looked for host cell targets of BICP22 using a yeast two-hybrid system and identified seven candidates: (1) JIK, a serine/threonine kinase of the sterile 20 protein (STE20) family that inhibits stress-related pathways; (2) cAMP response element binding protein-like 2 (CREBL2), which in its bZip domain shares homology with CREB, modulating transcription of cAMP responsive genes; (3) DNA-dependent ATPase and helicase (ATRX), a protein of the SNF2 family altering nucleosome structure; (4) scaffold attachment factor B (SAF-B), which helps to organize chromatin into topologically separated loops; (5) peptidylglycine alpha-amidating monooxygenase COOH-terminal interactor protein 1 (PAMCIP1), involved in regulation of the secretory pathway in the perinuclear area; (6) zinc finger protein (ZNF38) found in proliferating cells and possibly associated with meiosis in male and female gametogenesis; (7) FLJ22709, hypothetical protein conserved among various species, containing an occludin/ELL domain. To confirm some of the interactions by confocal fluorescence microscopy, BICP22 was tagged with red fluorescent protein in an amplicon, and selected target sequences were tagged with green fluorescent protein in plasmid expression vectors. Upon amplicon transduction of Vero cells and plasmid transfection, CREBL2 and ZNF38 both colocalized with BICP22 in distinct nuclear domains.