Preclinical and clinical trials of oncolytic vaccinia virus in cancer immunotherapy:a comprehensive review

Oncolytic virotherapy has emerged as a promising treatment for human cancers owing to an ability to elicit curative effects via systemic administration.Tumor cells often create an unfavorable immunosuppressive microenvironment that degrade viral structures and impede viral replication;however,recent studies have established that viruses altered via genetic modifications can serve as effective oncolytic agents to combat hostile tumor environments.Specifically,oncolytic vaccinia virus(OVV)has gained popularity owing to its safety,potential for systemic delivery,and large gene insertion capacity.This review highlights current research on the use of engineered mutated viruses and gene-armed OVVs to reverse the tumor microenvironment and enhance antitumor activity in vitro and in vivo,and provides an overview of ongoing clinical trials and combination therapies.In addition,we discuss the potential benefits and drawbacks of OVV as a cancer therapy,and explore different perspectives in this field.

Extracts from rabbit skin inflamed by the vaccinia virus attenuate bupivacaine-induced spinal neurotoxicity in pregnant rats

Extracts from rabbit skin inflamed by the vaccinia virus can relieve pain and promote repair of nerve injury. The present study intraperitoneally injected extracts from rabbit skin inflamed by the vaccinia virus for 3 and 4 days prior to and following intrathecal injection of bupivacaine into pregnant rats. The pain threshold test after bupivacaine injection showed that the maximum possible effect of tail-flick latency peaked 1 day after intrathecal injection of bupivacaine in the extract-pretreatment group, and gradually decreased, while the maximum possible effect in the bupivacaine group continued to increase after intrathecal injection of bupivacaine. Histological observation showed that after 4 days of intrathecal injection of bupivacaine, the number of shrunken, vacuolated, apoptotic and caspase-9-positive cells in the dorsal root ganglion in the extract-pretreatment group was significantly reduced compared with the bupivacaine group. These findings indicate that extracts from rabbit skin inflamed by the vaccinia virus can attenuate neurotoxicity induced by intrathecal injection of bupivacaine in pregnant rats, possibly by inhibiting caspase-9 protein expression and suppressing nerve cell apoptosis.

Lethality in mice infected with recombinant vaccinia virus expressing hepatitis C virus core protein

OBJECTIVE: To establish a mouse model of HCV core expression and investigate the toxicity of HCV core protein or the possible pathogenic effects. METHODS: A series of vaccinia viral expression vectors were engineered to express 5' portion of HCV genes including 5' non-translated region (NTR), core protein, and portion of the E1 gene. These HCV sequences were fused to a luciferase reporter gene and inserted into a vaccinia virus expression vector (pSC11) adjacent to the vaccinia virus promoter, p7.5. The recombinant DNA constructs were packed into infectious recombinant chimeric viruses. The expression of HCV core protein was examined in cultured cells after infection with these viruses. Death of the infected mice was investigated by specific correlation to the expression of HCV core protein and its expression levels. RESULTS: The recombinant virus (VNCE-LUA) expressed HCV core protein and an envelope-luciferase fusion protein in cultured cells. When Balb/c mice were inoculated intraperitoneally with more than 10~7 pfu per mouse of VNCE-LUA, death occurred immediately. The mortality was dependent on the amount of VNCE-LUA virus inoculated. All mice inoculated with 3×10~8 pfu of VNCE-LUA died within 4 days of infection and 50% of mice inoculated with 3×10~7 pfu of VNCE-LUA died within 7 days of infection. No death occurred in mice inoculated with 3×10~8 pfu of a control recombinant vaccinia virus, which expressed luciferase but not the HCV core and envelope proteins. Deletion of core sequences from VNCE-LUA rapidly reduced the mortality of infected mice whereas deletion of envelope sequence did not. SCID mice infected with VNCE-LUA died 2-3 days after infection, suggesting that the HCV-core induced mortality is not dependent on host T-or B-cell responses to core protein. CONCLUSIONS: HCV core protein can be lethal to mice when expressed in vivo and this specific lethality is independent of T-cells or B-cells. The findings and model itself provide a useful tool for further investigation on potential pathological effects as well as the potential toxicity of the HCV core protein.

ANTI-METASTATIC EFFECT OF ONCOLYSATES FROM MURINE MELANOMA CELLS TRANSFECTED WITH RECOMBINANT VACCINIA VIRUS ENCODING HUMAN IL-2

Oncolysates, debris of tumor cells, have been proven to be effective in active immunotherapy of cancer. In this experiment, the oncolysates from murine melanoma cells B16F10 transfected by recombinant vaccinia viruses encoding human IL2(IL2VBO) were used as vaccine. After treatment of tumor bearing mice with pulmonary metastases by intravenous injection of IL2VBO or rVVIL2, higher level IL2 activity was detected in the serum of IL2VBO or rVVIL2 treated mice at 8h. Further experiment results demonstrated that IL2VBO significantly reduced the number of pulmonary metastases and prolonged the survival time of tumorbearing mice when compared with other preparations. Fresh peripheral blood lymphocytes from IL2VBO treated mice showed potent cytotoxicity to B16F10 cells and YAC1 cells. But only cytotoxicity to B16F10 cells is more marked than that in rVVIL2 group, indicating that the IL2VBO could induce specific and non specific antitumor immunity. Because IL2 expression was at the same level in the serum of IL2VBO or rVVIL2 treated mice, the results suggested that the specific antitumor immunity induced by IL2VBO might contribute to the enhanced therapeutic effect of IL2VBO.

STRUCTURE AND EXPRESSION OF EPSTEIN-BARR VIRUS MEMBRANE ANTIGEN IN RECOMBINANT VACCINIA VIRUS

The Epstein-Barr virus membrane antigen was constructed and inserted into vaccinia virus, Tian-tan strain in order to study the effect of this virus on EB infection and tumorogenesis. The EBV-derived membrane antigen was expressed under the control of a 7.5 K promoter of vaccinia virus. The antibody against the membrane antigen of EB virus was produced on rabbits vaccinated with recombinant vaccinia virus.

EFFECTS OF GRANULOCYTE-MACROPHAGE COLONY STIMULATING FACTOR GENE ENCODED VACCINIA VIRUS VECTOR ON MURINE PULMONARY METASTATIC MELANOMA

A recombinant vaccinia virus expressing murine granulocyte-macrophage colony-stimulating factor (VVGM-CSF) was tested for its antitumor activity.Murine pulmonary metastasis was established by injecting 20×10~5 B16F10 melanoma cells into the tail vein of C57BL/6 mice. Three days after B16F10 inoculation,WGM-CSF or VVTK, a thymidine kinase gene deficient control vaccinia virus, were injected intraperitoneally twice weekly for 2 weeks. Two weeks later, the mice were sacrificed and pulmonary metastasis fool counted.The results demonstrated that VVGM-CSF treatment significantly decreased the number of pulmonary metastasis and prolonged the survival time of tumorbearing mice. Cytotoxic and phagocytic activities of the peritoncal macrophages were found to be markedly elevated in mice treated with WGM-CSF. Nitric oxide released from the macrophages was also found to be increased. These data, together with our other results,strongly demonstrated that continuous secretion of GMCSF and activation of macrophages might pal-tially explain the therapeutic effects of VVGM-CSF on murine pulmonary metastasis.

The Expression of Sperm Membrane Peptide-Hepatitis B SurfaceAntigen Fusion Protein with Recombinant Vaccinia Virus

A synthetic oligonucleotide, HSD-2a, encoding a peptide segment of the extracel-lular domain of a human sperm membrane protein, YWK-II, was fused with hepatitisB surface antigen gene (HBs gene ). The fused gene was then cloned to pUC18plasmid. The fused gene was prepared from the recombinant pUC18 plasmid byBamH I and Eco R I digestion, and then cloned into the transfer vector pGJP- 5 underthe control of P;., promoter, designated as pGJP-HSD/HBs. CV-1 cells were co-transfected with vaccinia virus (Tian Tan strain) and pGJP-HSD/IIBs and homolo-gous re combination occurred between the vaccinia virus TK gene of the plasmid flank-ing the foreign gene and the same sequences within the virus genome. TK phen0tyPerecombinant virus, vv-HSD/HBs, were selected from trandected HuTK' cells byplaque purthcation technique. The eopressi0n of HSD-b in spent medium and cellu-lar protein of HuTK cells infected with vv-HSD/HBs was determined by ELISAand Western-blot analysis using anti-rwK-II antiserum. The present study indicatesthat the vv-HSD/HBs seems promising as an antdertility vaccine.

Vaccinia virus viability under different environmental conditions and different disinfectants treatment

Monkeypox(mpox)outbreak in 2022 has caused more than 91,000 cases,has spread to 115 countries,regions,and territories,and has thus attracted much attention.The stability of poxvirus particles in the environment is recognized as an important factor in determining their transmission.However,few studies have investigated the persistence of poxviruses on material surfaces under various environmental conditions,and their sensitivity to biocides.Here,we systematically measured the stability of vaccinia virus(VACV)under different environmental conditions and sensitivity to inactivation methods via plaque assay,quantitative real‐time polymerase chain reaction(qPCR),and Gaussia luciferase(G‐luciferase)reporter system.The results show that VACV is stable on the surface of stainless steel,glass,clothing,plastic,towel,A4 paper,and tissue and persists much longer at 4℃ and?20℃,but is effectively inactivated by ultraviolet(UV)irradiation,heat treatment,and chemical reagents.Our study raises the awareness of long persistence of poxviruses in the environment and provides a simple solution to inactivate poxviruses using common disinfectants,which is expected to help the control and prevention of mpox virus and future poxvirus outbreaks.

Interleukin-2 expression and glioma cell proliferation following Vaccinia vector gene transfection in vivo

BACKGROUND： The effectiveness of gene therapy is closely related to the efficiency of vector transfection and expression. OBJECTIVE： This study was designed to transfect a human brain glioma cell line with recombinant Vaccinia virus expressing the interleukin-2 （rVV-IL-2） gene, and to observe IL-2 expression and glioma cell proliferation potential after transfection. DESIGN： Experimental observation. SETTING： Department of Neurosurgery, Shenyang Military Area Command of Chinese PLA. MATERIALS： The rVV-IL-2 vectors were obtained through homologous recombination and screening in the Second Military Medical University of Chinese PLA. The human brain glioma cell line and IL-2-dependent cells were produced by the Second Military Medical University of Chinese PLA. Human IL-2 was produced by Genzyme Corporation. METHODS： At passage day l, Veto cells were amplified l ; 1 for virus and cells. A human brain glioma cell line was transfected using amplified Vaccinia viral vectors at varying multiplicities of infection （MOI）. At 2, 4, 6, 8, 12, and 24 hours post-transfection, superuatant was collected to determine by MTT assay IL-2 expression levels in IL-2 dependent cells. The transfected and non-transfected cells were divided into 4 groups, namely MOI1 ： 1, MOI 5 ： 1, MOI 10 ： 1, and control groups. MAIN OUTCOME MEASURES： IL-2 expression at different time points after transfection of human brain glioma cells with varying MOI of Vaccinia viral vectors; in vitro proliferation capacity of human brain glioma cells among the 4 groups. RESULTS： IL-2 expression was detectable 4 hours after Vaccinia viral vector transfection and reached 300 kU/L by 8 hours. There was no significant difference in the proliferating rate of human brain glioma cells among the 4 groups （P 〉 0.05）. CONCLUSION： Vaccinia viral vectors can transfect human brain glioma cells in vitro and express high levels of IL-2. Vaccinia virus and high IL-2 expression do not influence the proliferation rate of human brain glioma cells in vitro.

ANTITUMOR EFFECT OF GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR(GM-CSF)-GENE ENCODED VACCINIA MELANOMA ONCOLYSATE AND ITS IMMUNOLOGICAL MECHANISMS

Vaccinia melanoma oncolysate (VMO) prepared by infecting B16F10 melanoma cells with recombinant vaccinia virus encoding murine GMCSF gene was tested for its therapeutic effect on the preestablished melanoma. C57BL/6 mice were inoculated s.c. with 1×105 B16F10 melanoma cells and received s.c. administration with VMO prepared with GMCSF gene encoded vaccinia virus(GMCSFVMO), VMO prepared with thymidine kinase genedeficient vaccinia virus(TKVMO), B16F10 melanoma oncolysate(BMO), or PBS 3 days after tumor inoculation. The same treatment was bolstered one week later. The results demonstrated that GMCSFVMO treatment significantly inhibited the growth of subcutaneous tumor and prolonged the survival period of tumorbearing mice. Further study elucidated that cytotoxicity of PBL and splenocytes towards B16F10 increased obviously after treatment with GMCSFVMO, but NK activity remained unchanged. These results suggest that the tumor oncolysate vaccine prepared with GMCSF geneencoded vaccinia virus might exert potent therapeutic effect on the preestablished tumor through the efficient induction of specific antitumor immune response of the host.

Improving Cross-Protection against Influenza Virus Using Recombinant Vaccinia Vaccine Expressing NP and M2 Ectodomain Tandem Repeats

Conventional influenza vaccines need to be designed and manufactured yearly.However,they occasionally provide poor protection owing to antigenic mismatch.Hence,there is an urgent need to develop universal vaccines against influenza virus.Using nucleoprotein(NP)and extracellular domain of matrix protein 2(M2e)genes from the influenza A virus A/Beijing/30/95(H3N2),we constructed four recombinant vaccinia virus-based influenza vaccines carrying NP fused with one or four copies of M2e genes in different orders.The recombinant vaccinia viruses were used to immunize BALB/C mice.Humoral and cellular responses were measured,and then the immunized mice were challenged with the influenza A virus A/Puerto Rico/8/34(PR8).NP-specific humoral response was elicited in mice immunized with recombinant vaccinia viruses carrying full-length NP,while robust M2e-specific humoral response was elicited only in the mice immunized with recombinant vaccinia viruses carrying multiple copies of M2e.All recombinant viruses elicited NP-and M2e-specific cellular immune responses in mice.Only immunization with RVJ-4M2eNP induced remarkably higher levels of IL-2 and IL-10 cytokines specific to M2e.Furthermore,RVJ-4M2eNP immunization provided the highest cross-protection in mice challenged with 20 MLD5〇of PR8.Therefore,the cross-protection potentially correlates with both NP and M2e-specific humoral and cellular immune responses induced by RVJ-4M2eNP,which expresses a fusion antigen of full-length NP preceded by four M2e repeats.These results suggest that the rational fusion of NP and multiple M2e antigens is critical toward inducing protective immune responses,and the 4M2eNP fusion antigen may be employed to develop a universal influenza vaccine.

CD4^＋ T-cell dependence of primary CD8^＋ T-cell response against vaccinia virus depends upon route of infection and viral dose

CD4^＋ T-cell help （CD4 help） plays a pivotal role in CD8^＋ T-cell responses against viral infections. However, the role in primary CD8^＋ T-cell responses remains controversial. We evaluated the effects of infection route and viral dose on primary CD8^＋ T-cell responses to vaccinia virus （VACV） in MHC class II^-/- mice. CD4 help deficiency diminished the generation of VACV-specific CD8^＋ T cells after intraperitoneal （i.p.） but not after intranasal （i.n.） infection. A large viral dose could not restore normal expansion of VACV-specific CD8^＋ T cells in i.p. infected MHC II-/- mice. In contrast, dependence on CD4 help was observed in i.n. infected MHC II-/- mice when a small viral dose was used. These data suggested that primary CD8~ T-cell responses are less dependent on CD4 help in i.n. infection compared to i.p. infection. Activated CD8~ T cells produced more I FN-y, TNF-a and granzyme B in i.n. infected mice than those in i.p. infected mice, regardless of CD4 help. IL-2 signaling via CD25 was not necessary to drive expansion of VACV-specific CD8~ T cells in i.n. infection, but it was crucial in i.p. infection. VACV-specific CD8^＋ T cells underwent increased apoptosis in the absence of CD4 help, but proliferated normally and had cytotoxic potential, regardless of infection route. Our results indicate that route of infection and viral dose are two determinants for CD4 help dependence, and intranasal infection induces more potent effector CD8^＋ T cells than i.D. infection.

Influence of glycosylation and oligomerization of vaccinia virus complement control protein on level and pattern of functional activity and immunogenicity

Vaccinia virus complement control protein(VCP)is one of the proteins encoded by vaccinia virus to modulate the host inflammatory response.VCP modulates the inflammatory response and protects viral habitat by inhibiting the classical and the alternative pathways of complement activation.The extended structure of VCP,mobility between its sequential domains,charge distribution and type of residues at the binding regions are factors that have been identified to influence its ability to bind to complement proteins.We report that a Lister strain of vaccinia virus encodes a VCP homolog(Lis VCP)that is functional,glycosylated,has two amino acids less than the well-characterized VCP from vaccinia virus WR strain(WR VCP),and the human smallpox inhibitor of complement enzymes(SPICE)from variola virus.The glycosylated VCP of Lister is immunogenic in contrast to the weak immunogenicity of the nonglycosylated VCP.Lis VCP is the only orthopoxviral VCP homolog found to be glycosylated,and we speculate that glycosylation influences its pattern of complement inhibition.We also correlate dimerization of VCP observed only in mammalian and baculovirus expression systems to higher levels of activity than monomers,observed in the yeast expression system.

Topography guiding the accelerated and persistently directional cell migration induced by vaccinia virus

The rapid transmission of vaccinia virus(VACV)in vivo is thought to be closely related to the cell migration induced by it.Cell migration involved in dynamic changes of cell-substrate adhesion and actin cytoskeleton organization,which can influence by the micro/nano-scale topographic structures that cells are naturally exposed to via contact guidance.However,migration behaviors of VACV-infected cells exposed to topographic cues are still unknown.Herein,we designed an open chip with microgrooved poly(dimethyl siloxane)(PDMS)substrate to explore the topography roles in VACV-induced cell migration.Differed from the random cell migration observed in traditional scratch assay on planar substrate,VACV-infected cells had a tendency to persistently migrate along the axis parallel to microgroove with increased velocity.Moreover,infected cells exhibited a dominant elongated protrusion aligned to the micro-grating axis compare to the shorter lamella extended in any direction on smooth substrate.Interestingly,the Golgi complex preferred to relocate behind the nucleus confined within the micro-grating axis in majority of infected migratory cells.The directional polarization of cells embodied in protrusion formation and Golgi reorientation was responsible for the directionally persistent migration behaviors induced by VACV on microgrooved substrate.Infected cells response to substrate topography,causing the actin-filled stretched protrusion containing numerous virions and accelerated movement is likely to facilitate direct and rapid spread of VACV.This work opens a window for us to understand the migration behaviors of infected cells in vivo,and also provides a cue for revealing the relationship between virus-induced cell migration and virus rapid spread.

Combined effects of oncolytic vaccinia virus and dendritic cells on the progression of melanoma B16-F10 in mice

Aim:We aimed to test the hypothesis that loading of dendritic cells(DCs)with both viral and tumor-specific antigens would enhance the efficacy antitumor DC-based therapy applied simultaneously with oncolytic virus.Methods:Vaccinia virus LIVP/GFP and melanoma B16-F10 were used in this study.DCs were pulsed with various combinations of viral and tumor-associated antigens.The maturation status of DCs was verified by expression of the markers CD80,CD86,and CCR7 and assessment of IL-6,TNF-α,and IL-12 secretion.The most efficient combination of antigens for DC loading was selected based on the analysis of the cytotoxic activity of T lymphocytes.Combination therapy using vaccinia virus LIVP/GFP and DCs pulsed with viral and tumor-specific antigens was administered to the B16-F10 melanoma/mouse C57Bl tumor model.Results:We found that loading of DCs with viral antigens,or with a combination of viral and tumor antigens,resulted in similar levels of expression of DC maturation markers.The maximal in vitro cytotoxicity against virus-infected and non-infected B16 melanoma cells exhibited T lymphocytes activated by DCs loaded with the heat inactivated lysate of vaccinia virus LIVP/GFP infected tumor cell.The results show that the combination of vaccinia virus LIVP/GFP and DCs loaded with both tumor and viral antigens inhibit tumor growth of B16-F10 murine melanoma by more than two-fold.Conclusions:Combination therapy with oncolytic vaccinia virus LIVP/GFP and tumor/virus antigen-loaded DCs limited the growth of established melanoma B16-F10,but no synergistic antitumor effects were observed.We propose that optimization of the therapy regimen could enhance the efficiency of combination therapy.