The recombinant viruses entered cells through HER2, independently of gD activation by its receptors, or despite deletion of key residues that are part of the receptors binding sites in gD. In essence, the scFv in gH substituted for gD-mediated activation and rendered a functional gD non-essential for entry via HER2. The retargeting through genetic modifications obtained in the above-mentioned studies has clear advantages over retargeting through coupling of appropriate moieties to virions, and even more so over non-replicating viruses (see, for example 39 ). Second, the tropism of HSV can be modified by engineering a heterologous ligand in gH. Its functions have been taken over by the scFv in gH. R-LM11 and R-LM11L infected derivatives of receptor-negative J or CHO cells that expressed HER2/neu as the sole receptor. The recombinant viruses entered cells through HER2, independently of gD activation by its receptors, or despite deletion of key residues that are part of the receptors’ binding sites in gD. So far, retargeting strategies entailed genetic modifications to gD, in particular the insertion of novel ligands, coupled with appropriate deletions for detargeting purposes 30,32 38. Previous attempts to develop systems for HSV-mediated cell fusion, or HSV infection independent of gD led to partial indications as follows.
The binding and penetration phases of HSV entry into cells can be experimentally dissociated. These observations suggest that cell-associated gD may sequester or down-regulate a cellular protein required for HSV entry and that ST and CHO-K1 cells fail to express such a mediator of HSV entry. This receptor mediated efficient entry of HSV-1 strains into CHO-K1 cells and ST cells and also enhanced the entry of an HSV-2 strain. Herpes simplex virus 1 (HSV-1) enters cells via initial binding of envelope glycoproteins (g) C and B to cell-surface glycosaminoglycans (GAGs) and subsequent membrane fusion involving envelope gD, gB, and gH/gL. Three different receptors for HSV-1 gD have been identified: (i) herpesvirus entry mediator A (HveA or HVEM), (ii) nectin-1 or herpesvirus entry mediator C (HveC; also known as poliovirus receptor-related protein 1), and (iii) heparan sulfate (HS) modified by the activity of 3-O-sulfotransferase-3 (3-OST-3). Thus, redefining the viral host range by genetic manipulation of gD remains a challenging strategy for HSV retargeting. These results are the first demonstration that the soluble adapter approach can be used to target HSV infection to a novel receptor. The safety and efficacy of viral therapies for solid tumors can be enhanced by redirecting the virus infection to tumor-specific cell-surface markers. Successful retargeting of herpes simplex virus type 1 (HSV-1) has been achieved using vectors that carry a modified envelope glycoprotein D (gD) engineered to interact directly with novel receptors. An alternate retargeting strategy that does not require target-specific engineering of viral gD involves the use of bispecific adapters to promote virus interaction with novel receptors.
Construction of a Fully Retargeted Herpes Simplex Virus 1 Recombinant Capable of Entering Cells Solely via Human Epidermal Growth Factor Receptor 2. Effective retargeting to tumor-specific receptors has been achieved by insertion in gD of heterologous ligands. An obstacle to the genetic engineering of HER2-retargeted viruses stems from the fact that it is an orphan receptor, i.e., no natural ligand is known. Herpes simplex virus-1 entry into cells mediated by a novel member of the TNF/NGF receptor family. Overview of Tropism Retargeting Based on Modification of gD An alternative strategy to more potent oncolytic HSVs, capable of replicating and killing cancer cells independently of intrinsic defects in the tumor and overcoming most of the limitations imposed by the tumor heterogeneity, is to render the virus highly cancer-specific by retargeting its tropism to cancer-specific receptors of choice and detargeting from natural receptors. Infection mediated by sHA102 was highly efficient, involved specific binding of sHA102 to viral gD, required heparin-sensitive virus attachment to the cells, and took place by a pH-independent endocytic mechanism as opposed to the pH-dependent mechanism mediating HSV infection of HVEM-expressing CHO cells 27. Soluble forms of HVEM and nectin-1 have been shown to inhibit HSV-1 entry through the cognate cellular receptors by competition for gD binding 28. This retargeting strategy can be combined to create specific recognition by genetic modifications of the virion envelope for incorporation of targeting moiety. Spear PG: Herpes simplex virus-1 entry into cells mediated by a novel member of the TNF/NGF receptor family.
Herpes Simplex Virus-1 Entry Into Cells Mediated By A Novel Member Of The Receptor Family
In one aspect, HSV vectors of the present invention can directly infect cells through interaction with cell proteins other than typical mediators of HSV infection. In recent years, the potential of viral vectors or genetically engineered viruses for the treatment of a variety of human diseases has been a topic of intense study worldwide. Based on this understanding of the HSV-1 cell attachment and entry process, gC and gD have been modified to eliminate recognition of their natural receptors ( detargeting ) and insert a targeting element to provide a novel interaction with specific receptors on the target cell ( retargeting ). The importance of cell-mediated immunity in controlling herpesvirus replication and in limiting reactivation of latent virus in vivo is apparent from the dramatic increase in severity and frequency of disease in immunodeficient persons. The virus establishes latent infections in B lymphocytes and can induce proliferation of B cells through expression of a limited number of viral genes. Then viral gD can bind to any one of several entry receptors, including HVEM (I), a member of the TNF-receptor family; Thus, it has been concluded that the initial interaction of HSV with cells is binding to cell surface heparan sulfate and that gB, gC, or both can mediate this binding. Calculations show that herpes simplex virus glycoprotein D has such avidity for its receptors that it can hold the virion against the plasma membrane of a neuron strongly enough for glycoprotein B (gB) to disrupt both leaflets of the bilayer. A novel herpes simplex virus glycoprotein, gL, forms a complex with. The most popular approach to generate oncolytic viruses has been by adapting their surface-exposed components. In order to achieve CAR-independent infection by adenoviruses, the viral tropism can be modified via genetic engineering of adenovirus capsid proteins. Virus attachment, entry, and subsequent cell-cell fusion are mediated via the two measles receptors: CD46 and the signaling lymphocyte activation molecule (SLAM). Campadelli-Fiume G, Cocchi F, Menotti L and Lopez M. The novel receptors that mediate. The initial step of cell attachment or binding during herpes simplex virus type-1 (HSV-1) entry is mediated by envelope glycoprotein B (gB) and C (gC). The rare modification of 3-O-sulfation on HS chain is governed by enzymes known as 3-O-sulfotransferase (3-OST). It has been suggested that HSV-1 glycoprotein C (gC) may further enhance viral binding through HS, but it is not essentially required for cell entry 26. It is interesting to mention that a recently discovered isoform, 3-OST-5, can generate both gD receptor and AT binding sites.
Construction Of A Fully Retargeted Herpes Simplex Virus 1 Recombinant Capable Of Entering Cells Solely Via Human Epidermal Growth Factor Receptor 2
Therefore, many other treatment methods that can kill tumor cells without these side-effects are being tried in research and clinical studies. To overcome this obstacle, several tumor-targeting approaches using MAbs to TAAs have been developed (Table I) (21). These tend to be larger viruses that are amenable to genetic engineering to produce or enhance their tumor selectivity. Herpes simplex virus (HSV)based vectors have favorable biologic features for gene therapy of leukemia and lymphoma. One type of HSV vector, the amplicon, is essentially a eukaryotic expression plasmid that contains the following genetic elements: (1) HSV-derived origin of DNA replication (ori) and packaging sequence ( a sequence); (2) transcriptional unit driven typically by the HSV-1 immediate early (IE) 4/5 promoter or an alternative promoter followed by an SV-40 polyadenylation site; and (3) bacterial origin of replication and antibiotic resistance gene for propagation inEscherichia coli. The mechanism by which HSV gains entry into the target cell has been studied in detail. Nature Genetics (2008). Nectin-1 serves as an entry and cell-cell spread mediator of herpes simplex virus type 1 (HSV-1) 3. Exons 2-14 of the CLPTM1 and exons 1-6 of the PVRL1 gene were analysed by a direct sequencing method using DNA extracted from whole blood 12. It has been shown mainly by use of cadherin-deficient L fibroblasts stably expressing each nectin that nectins first form homo-cis-dimers and then homo- or hetero-trans-dimers, causing cell-cell adhesion, and that the formation of the cis-dimers is necessary for the formation of the trans-dimers 22. Knocking down of gD receptors by siRNAs interference implicates nectin-1 and HVEM as the major mediators of entry. HCjE cells express all three major entry receptors, with nectin-1 and HVEM playing the predominant role in mediating entry. 1 2 HSV-1 infection of the eye results in various diseases such as stromal keratitis, epithelial keratitis, and conjunctivitis. It has been demonstrated recently that based on cell type, HSV-1 entry can be pH dependent or independent.
We recognized that EBV would likely encode one or more genes to mediate its plasmid replication and because no EBV gene function was then known, we set out to define the cis- and trans-acting elements of EBV’s plasmid replicon. We have recently focused on HSV-1 entry receptors and oncogenic signaling pathways within cancer cells as potential biomarkers of T-VEC response. In some cases studies with HCMV can highlight novel pathways or novel capabilities of known cellular pathways. Currently, more than a dozen viruses of various species have been tested in preclinical studies for their efficacy in treating tumors of different tissue origins, and several of them have entered clinical trials. (iii) Unlike many other viruses that only bind to a single receptor, HSV can enter cells by binding to one of the four cellular receptors that are widely expressed on most cell types. As such, the virus has a wide tropism, and oncolytic viruses derived from it can be applied therapeutically to many different types of tumors. Credited as the first oncolytic virus to be purposely generated by genetic engineering technology, G207 was constructed from HSV-1 by deleting both copies of the 34. In the context of natural HSV infection, the coupling of viral entry to the activation of DC signaling pathways is likely to be counterbalanced by viral disruption of DC maturation. In addition, HSV-1 can induce DC activation directly, via binding of glycoprotein D (gD) to the DC surface and activation of NF- B and p38 MAPK.