Publisher Correction: Science diplomacy for plant health.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A TLR9 agonist enhances therapeutic effects of telomerase genetic vaccine.

The telomerase reverse transcriptase (TERT) is an attractive target for cancer vaccination because its expression is reactivated in most tumors. In this study, we have evaluated the ability of a genetic vaccine targeting murine TERT (mTERT) based on DNA electroporation (DNA-EP) and adenovirus serotype 6 (Ad6) to exert therapeutic effects in combination with a novel TLR9 agonist, referred to as immune modulatory oligonucleotide (IMO), as an adjuvant. IMO was administered to mice at the same time as vaccine. IMO induced dose-dependent cytokine secretion and activation of NK cells. Most importantly, vaccination of mice with IMO in combination with mTERT vaccine conferred therapeutic benefit in tumor bearing animals and this effect was associated with increased NK, DC and T cell tumor infiltration. These data show that appropriate combination of a DNA-EP/Ad6-based cancer vaccine against TERT with IMO induces multiple effects on innate and adaptive immune responses resulting in a significant antitumor efficacy.

Engineered adenovirus serotypes for overcoming anti-vector immunity.

Adenovirus (Ad)-based gene transfer has been successfully utilised in gene therapy and vaccine applications. To date, an increasing number of human clinical trials utilise recombinant Ad-based vectors as a gene transfer platform. In particular, progress has been made recently in utilising Ad-based vectors as a vaccine platform in HIV, cancer immunotherapy approaches and in vaccination for other infections. Despite these successes, the scientific and bio-industrial communities have recently recognised that innate and pre-existing immunity against Ad vectors can constitute a serious obstacle to the development and application of this technology. It is essential to overcome vector-mediated immune responses, such as production of inflammatory cytokines and pre-existing immunity to Ad, because the induction of these responses not only shortens the period of gene expression but also leads to serious side effects. This review focuses on the biology of Ad infection and the approaches that are being adopted to overcome immunity against the Ad-based vectors.

Coadministration of telomerase genetic vaccine and a novel TLR9 agonist in nonhuman primates.

The human telomerase reverse transcriptase (hTERT) is an attractive target for human cancer vaccination because its expression is reactivated in most human tumors. We have evaluated the ability of DNA electroporation (DNA-EP) and adenovirus serotype 6 (Ad6) to induce immune responses against hTERT in nonhuman primates (NHPs) (Macaca mulatta). Vaccination was effective in all treated animals, and the adaptive immune response remained detectable and long lasting without side effects. To further enhance the efficacy of the hTERT vaccine, we evaluated the combination of hTERT vaccine and a novel TLR9 agonist, referred to as immunomodulatory oligonucleotide (IMO). Monkeys were dosed weekly with IMO concurrently with the vaccine regimen and showed increases in cytokine secretion and activation of natural killer (NK) cells compared with the group that received vaccine alone. Using a peptide array, a specific profile of B-cell reactive epitopes was identified when hTERT vaccine was combined with IMO. The combination of IMO with hTERT genetic vaccine did not impact vaccine-induced TERT-specific cell-mediated immunity. Our results show that appropriate combination of a DNA-EP/Ad6-based cancer vaccine against hTERT with IMO induces multiple effects on innate and adaptive immune responses in NHPs.

Treatment of mammary carcinomas in HER-2 transgenic mice through combination of genetic vaccine and an agonist of Toll-like receptor 9.

PURPOSE: Oligodeoxynucleotides containing unmethylated CpG dinucleotides induce innate and adaptive immunity through Toll-like receptor 9 (TLR9). In the present study, we have examined the ability of a novel agonist of TLR9, called immunomodulatory oligonucleotide (IMO), to enhance effects of a HER-2/neu plasmid DNA electroporation/adenovirus (DNA-EP/Ad) vaccine. EXPERIMENTAL DESIGN: BALB/NeuT mice were treated with DNA-EP vaccine alone, IMO alone, or the combination of two agents starting at week 13, when all mice showed mammary neoplasia. Tumor growth and survival were documented. Antibody and CD8+ T-cell responses were determined. Peptide microarray analysis of sera was carried out to identify immunoreactive epitopes. Additionally, microCT and microPET imaging was carried out in an advanced-stage tumor model starting treatment at week 17 in BALB/NeuT mice. RESULTS: The combination of DNA-EP and IMO resulted in significant tumor regression or delay to tumor progression. 2-Deoxy-2-[18F]fluoro-D-glucose microPET and microCT imaging of mice showed reduced tumor size in the DNA-EP/IMO combination treatment group. Mice treated with the combination produced greater antibody titers with IgG2a isotype switch and antibody-dependent cellular cytotoxicity activity than did mice treated with DNA-EP vaccine. An immunogenic B-cell linear epitope, r70, within the HER-2 dimerization domain was identified through microarray analysis. Heterologous DNA-EP/Ad vaccination combined with IMO increased mice survival. CONCLUSION: The combination of HER-2/neu genetic vaccine and novel agonist of TLR9 had potent antitumor activity associated with antibody isotype switch and antibody-dependent cellular cytotoxicity activities. These results support possible clinical trials of the combination of DNA-EP/Ad-based cancer vaccines and IMO.

Antiapoptotic small interfering RNA as potent adjuvant of DNA vaccination in a mouse mammary tumor model.

In vivo electroporation of plasmid DNA (DNA-EP) is an efficient and safe method for vaccines. It results in increased DNA uptake, enhances protein expression, and augments immune responses to the target antigen in a variety of species. To further improve the efficacy of DNA-EP, we evaluated small interfering RNA (siRNA) sequences targeting apoptotic genes as an adjuvant to cancer vaccine. Bak1 or Casp8 siRNA was coadministered with plasmid DNA encoding the extracellular and transmembrane domains of rat HER2 ECD.TM to BALB-neuT mice, which spontaneously develop HER2/neu-positive mammary tumors. The combination regimen significantly reduced spontaneous tumor progression in BALB-neuT mice, in an advanced disease setting, when compared with DNA-EP alone. The antitumor effect was associated with a noteworthy antibody isotype switch from IgG1 to IgG2a, when siRNA was coadministered with DNA-EP. CD8+ T cell responses increased significantly, as did the number of responders to vaccination. Coimmunization of siRNA and DNA-EP at the same physical location was essential for the enhanced therapeutic effect. Silencing of the targeted genes was confirmed by in vitro Western blots. siRNA sequences targeting apoptotic genes Bax and Fas did not improve tumor protection in this mouse model when compared with DNA-EP alone. These data demonstrate that some siRNA sequences can act in concert with DNA-EP to control HER2/neu-positive mammary carcinoma. These observations emphasize the potential of siRNA as adjuvant for therapeutic DNA vaccines.

A novel chimpanzee serotype-based adenoviral vector as delivery tool for cancer vaccines.

The use of adenovirus (Ad) as vaccine vectors is hindered by pre-existing immunity to human Ads in most of the human population. In order to overcome this limitation, uncommon alternative Ad serotypes need to be utilized. In this study, an E1-E3 deleted recombinant Ad based on the chimpanzee serotype 3 (ChAd3) was engineered to express human carcinoembryonic antigen (CEA) protein or rat neu extracellular/transmembrane domains (ECD.TM). ChAd3 vectors were tested in CEA transgenic (CEA.Tg) and BALB/NeuT mice, which show immunologic tolerance to these antigens. ChAd3 is capable of inducing an immune response comparable to that of hAd5 serotype-based vectors, thus breaking tolerance to tumor associated antigens (TAAs) and achieving anti-tumor effects. Of importance is that ChAd3 can overcome hAd5 pre-existing immunity and work in conjunction with DNA electroporation (DNA-EP) and other Ad vaccines based on common human serotypes.

Adenovirus vaccination against neu oncogene exerts long-term protection from tumorigenesis in BALB/neuT transgenic mice.

The transforming rat HER2/neu oncogene (neu), when embedded in the genome of transgenic BALB/c (neuT) mice, provokes the development of an invasive carcinoma in each of their 10 mammary glands. We used the neuT mice model system to evaluate the immunization efficiency and the protective effect of intramuscular injection of adenovirus (Ad) and/or of DNA with electrostimulation (DNA+ES), both expressing the rat p185(neu) protein. A neu cDNA sequence, which exclusively contains codons preferred by highly expressed mammalian genes, was used in this study. This "optimized" cDNA displayed higher expression in cultured cells and greater cell-mediated response than the original gene when injected as DNA+ES. Ad expressing the optimized sequence (Ad5-neu.opt) induced a higher immune response, as measured by the frequency of IFN-gamma-secreting spleen cells and antibody titers. Different Ad/DNA combinations and immunization schedules confirmed the superiority of Ad5-neu.opt in inducing a strong Th1-skewed humoral and CD8(+) cell-mediated response. Two Ad5-neu.opt injections of 10(9) viral particles at week 10 and 12 were sufficient to induce the highest response, which persisted at detectable levels up to 33 weeks of age. Anti-Ad5 antibodies elicited by previous injections neutralized the effect of an additional Ad5-neu.opt immunization at week 19. A group, which received 3 injections of DNA+ES at week 23, 27 and 31, in addition to the 3 Ad injections at week 10, 12 and 19 showed an increased frequency of IFN-gamma(+), CD8(+) PBMC at week 25, which persisted at detectable levels till week 38. Ad5-neu.opt administration at 10 and 12 weeks of age had a significant impact on tumor progression. At 44 weeks, 40% of the mice were completely protected from tumors with a mean tumor of 3.8. In contrast, control mice developed 10 tumors and died by week 27. Vaccination blocked the tumor development at the atypical hyperplasia stage present at the time of treatment. Tumors developing at later times express reduced levels of rat p185(neu) protein.

Xenogeneic immunization in mice using HER2 DNA delivered by an adenoviral vector.

The protective efficacy of xenogeneic vaccination with DNA encoding the HER2 oncogene was evaluated in BALB/c mice transgenic for the transforming form of the neu oncogene, which spontaneously develops carcinomas in all mammary glands. Intramuscular injection of either plasmid DNA followed by electrical stimulation (pVIJ-HER2 with ES) or an adenoviral vector (Ad5-HER2), both expressing the HER2 oncogene, was tested. Immunization using pVIJ-HER2 with ES elicited a cell-mediated response that was much lower than that elicited by the immunization with Ad5-HER2, as measured by the frequency of IFN-gamma-secreting spleen cells. The dominant T-cell epitope of the HER2 protein product (p185) in the BALB/c (H-2(d)) genetic background was identified. While the T-cell response elicited was only partially crossreactive with the corresponding rat epitopes because of sequence variations (89% similarity), a cytotoxic T-lymphocyte activity against the rat immunodominant epitope was also evident. The Ad5-HER2 vaccination induced also antibodies against p185, which crossreacted with the rat protein homolog. Both T- and B-cell responses slowly declined with time. Vaccination with Ad5-HER2 at 6 and 9 weeks of age delayed incidence and reduced multiplicity of tumors in neu transgenic mice.

Metabolic engineering of xanthophyll content in tomato fruits.

Ripe tomato fruits accumulate significant amounts of the linear carotene lycopene, but only trace amounts of xanthophylls (oxygenated carotenoids). We overexpressed the lycopene beta-cyclase (b-Lcy) and beta-carotene hydroxylase (b-Chy) genes under the control of the fruit-specific Pds promoter. Transgene and protein expression was followed through semi-quantitative reverse transcription-PCR, Western blotting, and enzyme assays. Fruits of the transformants showed a significant increase of beta-carotene, beta-cryptoxanthin and zeaxanthin. The carotenoid composition of leaves remained unaltered. The transgenes and the phenotype are inherited in a dominant Mendelian fashion. This is the first example of successful metabolic engineering of xanthophyll content in tomato fruits.