Therapeutic effects of bovine enterovirus infection on rabbits with experimentally induced adult T cell leukaemia

Enterovirus E infects bovine peripheral blood mononuclear cells. Implications for pathogenesis?

Introduction

Enterovirus E (EV-E) is a common viral pathogen endemic in cattle worldwide. Little is known, however, about its potential interactions with bovine immune cells.

Material and Methods

The EV-E-permissiveness of bovine peripheral blood mononuclear cells (PBMCs) was evaluated. The infectious titres of extracellular virus were measured and the intracellular viral RNA levels were determined by reverse transcription quantitative PCR after cell inoculation. The effects of EV-E on cell viability and proliferative response were investigated with a methyl thiazolyl tetrazolium bromide reduction assay, the percentages of main lymphocyte subsets and oxidative burst activity of blood phagocytes were determined with flow cytometry, and pro-inflammatory cytokine secretion was measured with an ELISA.

Results

Enterovirus E productively infected bovine PBMCs. The highest infectious dose of EV-E decreased cell viability and T-cell proliferation. All of the tested doses of virus inhibited the proliferation of high responding to lipopolysaccharide B cells and stimulated the secretion of interleukin 1β, interleukin 6 and tumour necrosis factor α pro-inflammatory cytokines.

Conclusion

Interactions of EV-E with bovine immune cells may indicate potential evasion mechanisms of the virus. There is also a risk that an infection with this virus can predispose the organism to secondary infections, especially bacterial ones.

Developing Picornaviruses for Cancer Therapy

Oncolytic viruses (OVs) form a group of novel anticancer therapeutic agents which selectively infect and lyse cancer cells. Members of several viral families, including Picornaviridae, have been shown to have anticancer activity. Picornaviruses are small icosahedral non-enveloped, positive-sense, single-stranded RNA viruses infecting a wide range of hosts. They possess several advantages for development for cancer therapy: Their genomes do not integrate into host chromosomes, do not encode oncogenes, and are easily manipulated as cDNA. This review focuses on the picornaviruses investigated for anticancer potential and the mechanisms that underpin this specificity.

Rescue and characterization of a recombinant HY12 bovine enterovirus carrying a foreign HA epitope in the 3A nonstructural protein

Full-length infectious cDNA clones for recombinant HY12 bovine enteroviruses designated as rHY12-3A-2-HA, rHY12-3A-3-HA, and rHY12-3A-9-HA were constructed by the insertion of an epitope from influenza virus hemagglutinin (HA) at the N-terminus of the HY12-encoded 3A protein at amino acid positions 2, 3, and 9. The recombinant HY12 viruses expressing the HA epitope were rescued and characterized using immunoperoxidase monolayer assay, western blotting, and electron microscopy. The three rescued recombinant marker viruses showed similar characteristics, such as TCID₅₀ titer, plaque size, and growth properties, to those of parental rHY12 virus. Comparative analysis of the nucleotide sequences demonstrated the three recombinant marker viruses remained stable for 15 passages with no genetic changes. The recombinant viruses remained viable in various permissive cell lines, including BHK-21, Vero, and PK15 cells, suggesting that the insertion of the HA epitope tag had no effect on virus infectivity. Mice infected with the recombinant marker viruses and the parental virus produced anti-HY12-virus antibodies, while the recombinant marker viruses also produced anti-HA-epitope-tag antibodies. Taken together, these results demonstrate that HY12 viruses containing genetic markers may be useful tools for future investigations of the mechanisms of viral pathogenesis and virus replication, as well as for vaccine development.

Construction and evaluation of HA-epitope-tag introduction onto the VP1 structural protein of a novel HY12 enterovirus

In this study, we investigated the feasibility of using enterovirus HY12 as a vector to express an exogenous hemagglutinin (HA)-epitope tag onto the HY12-encoded VP1 protein via a reverse genetic system. Characteristics of recombinant (r) HY12-VP1-HA marker virus were determined by immunoperoxidase monolayer assay, western blot, electron microscopy, and serum-neutralisation assay. Sequence analysis demonstrated that the marker virus stably maintained the HA-epitope-tag in MDBK cells, with no changes in viral morphological features observed relative to those of the parental rHY12 virus. Furthermore, detection by immunofluorescence assay revealed the expression of HA-epitope tag and VP2 protein, which distinguish the marker virus from parental rHY12 virus. In addition, neonatal mice infected with the recombinant marker virus showed various microscopic pathological lesions and generated anti-HY12 virus and -HA-epitope-tag antibodies. These results indicated that the recombinant marker virus represented a valuable platform to promote the development of novel genetic vaccines.

Isolation of two Chinese bovine enteroviruses and sequence analysis of their complete genomes

In this study, RNA corresponding to bovine enterovirus (BEV) was detected in 24.6 % of faecal samples (17/69) from diarrheic and healthy cattle in six different areas in China by an RT-PCR screening method. Furthermore, two cytopathic agents, designated as BHM26 and BJ50, were isolated from the bovine diarrheic fecal samples. During passage in MA104 cells, ultrathin sections of virus-infected monolayers were examined using a transmission electron microscope, and a large number of symmetrical virus crystals were seen in the cytoplasm, with monomorphic small viral particles of 27-30 nm in diameter. The full-length RNA genomes were 7433 and 7416 nucleotides long, respectively, with a genome organization analogous to that of picornaviruses. Phylogenetic analysis of the VP1 and VP3 capsid protein coding sequences suggested that the viruses BHM26 and BJ50 belong to genotype 2 of the BEV cluster B (BEV-B). In addition, sequence comparisons of the 5′ and 3′ UTRs and P1, P2 and P3 subgenomic regions of the two isolates suggested that there were intergenotypic recombination events occurring during evolution of the BHM26 and BJ50 isolates.

Bovine enterovirus 2: complete genomic sequence and molecular modelling of a reference strain and a wild-type isolate from endemically infected US cattle

Bovine enteroviruses are members of the family Picornaviridae, genus Enterovirus. Whilst little is known about their pathogenic potential, they are apparently endemic in some cattle and cattle environments. Only one of the two current serotypes has been sequenced completely. In this report, the entire genome sequences of bovine enterovirus 2 (BEV-2) strain PS87 and a recent isolate from an endemically infected herd in Maryland, USA (Wye3A) are presented. The recent isolate clearly segregated phylogenetically with sequences representing the BEV-2 serotype, as did other isolates from the endemic herd. The Wye3A isolate shared 82 % nucleotide sequence identity with the PS87 strain and 68 % identity with a BEV-1 strain (VG5-27). Comparison of BEV-2 and BEV-1 deduced protein sequences revealed 72-73 % identity and showed that most differences were single amino acid changes or single deletions, with the exception of the VP1 protein, where both BEV-2 sequences were 7 aa shorter than that of BEV-1. Homology modelling of the capsid proteins of BEV-2 against protein database entries for picornaviruses indicated six significant differences among bovine enteroviruses and other members of the family Picornaviridae. Five of these were on the 'rim' of the proposed enterovirus receptor-binding site or 'canyon' (VP1) and one was near the base of the canyon (VP3). Two of these regions varied enough to distinguish BEV-2 from BEV-1 strains. This is the first report and analysis of full-length sequences for BEV-2. Continued analysis of these wild-type strains should yield useful information for genotyping enteroviruses and modelling enterovirus capsid structure.

The significance of cytomegalovirus infection over the clinical course of adult T-cell leukemia/lymphoma

The significance of cytomegalovirus (CMV) infections developed over the clinical course of adult T-cell leukemia/lymphoma (ATLL) were evaluated in relation to the patient survival rate, ATL activity and immunocompetent cells. ATLL patients with CMV infections on admission exhibited a poor survival rate, while patients with CMV infections at any time after admission survived longer than those not infected with this virus. ATLL patients who exhibited a numbers of CMV infection on admission showed higher ATL activity and had lower numbers of CD8-positive and CD56-positive cells than those who developed CMV infections at any time after admission. Therefore, it appears likely that patients with CMV infections on admission were in an immunosuppressive state due to aggressive ATL activity.

Prevention of adult T-cell leukemia-like lymphoproliferative disease in rats by adoptively transferred T cells from a donor immunized with human T-cell leukemia virus type 1 Tax-coding DNA vaccine

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL) in infected individuals after a long incubation period. To dissect the mechanisms of the development of the disease, we have previously established a rat model of ATL-like disease which allows examination of the growth and spread of HTLV-1 infected tumor cells, as well assessment of the effects of immune T cells on the development of the disease. In the present study, we induced HTLV-1 Tax-specific cytotoxic T lymphocyte (CTL) immunity by vaccination with Tax-coding DNA and examined the effects of the DNA vaccine in our rat ATL-like disease model. Our results demonstrated that DNA vaccine with Tax effectively induced Tax-specific CTL activity in F344/N Jcl-rnu/+ (nu/+) rats and that these CTLs were able to lyse HTLV-1 infected syngeneic T cells in vitro. Adoptive transfer of these immune T cells effectively inhibited the in vivo growth of HTLV-1-transformed tumor in F344/N Jcl-rnu/rnu (nu/nu) rats inoculated with a rat HTLV-1 infected T cell line. Vaccination with mutant Tax DNA lacking transforming ability also induced efficient anti-tumor immunity in this model. Our results indicated a promising effect for DNA vaccine with HTLV-1 Tax against HTLV-1 tumor development in vivo.

Human tumor growth is inhibited by a vaccinia virus carrying the E2 gene of bovine papillomavirus

BACKGROUND

Papillomavirus is the etiologic agent associated with cervical carcinoma. The papilloma E2 protein is able to regulate negatively the expression of E6 and E7 papilloma oncoproteins. Therefore, a new, highly attenuated vaccinia virus known as modified vaccinia virus Ankara (MVA), which carries the papillomavirus E2 gene, was used for the treatment of tumors associated with human papillomavirus.

METHODS

Analysis of expression of the E2 gene from the recombinant vaccinia virus was performed by reverse transcription-polymerase chain reaction of RNA isolated from infected cells. Detection of the E2 protein was done by immunoprecipitation from proteins labeled with [(35)S]-methionine, isolated from infected cells. The therapeutic effect of the MVA E2 recombinant virus over human tumors was tested in nude mice bearing tumors generated by inoculation of HeLa cells. Series of 10 nude mice with tumors of different sizes were injected with MVA, MVA E2, or phosphate-buffered saline. Tumor size was monitored every week to assess growth.

RESULTS

The MVA E2 recombinant virus efficiently expressed the E2 protein in BS-C-1 cells. This protein was able to repress, in vivo, the papillomavirus P105 promoter, which controls the expression of the E6 and E7 oncoproteins. In nude mice the MVA E2 virus reduced tumor growth very efficiently. In contrast, tumors continued to grow in mice treated with MVA or PBS. The life expectancy of MVA E2-treated mice was also increased three- to fourfold compared with that of animals that received MVA or PBS.

CONCLUSIONS

The growth of human tumors was efficiently inhibited by the MVA E2 recombinant vaccinia virus. The absence of side effects in treated animals suggested that the MVA E2 virus is a safe biologic agent that could in the future be used in humans for the treatment of cervical carcinoma.