Plasmid DNAs expressing influenza virus hemagglutinin glycoproteins have been tested for their ability to raise protective immunity against lethal influenza challenges of the same subtype. In trials using two inoculations of from 50 to 300 micrograms of purified DNA in saline, 67-95% of test mice and 25-63% of test chickens have been protected against a lethal influenza challenge. Parenteral routes of inoculation that achieved good protection included intramuscular and intravenous injections. Successful mucosal routes of vaccination included DNA drops administered to the nares or trachea. By far the most efficient DNA immunizations were achieved by using a gene gun to deliver DNA-coated gold beads to the epidermis. In mice, 95% protection was achieved by two immunizations with beads loaded with as little as 0.4 micrograms of DNA. The breadth of routes supporting successful DNA immunizations, coupled with the very small amounts of DNA required for gene-gun immunizations, highlight the potential of this remarkably simple technique for the development of subunit vaccines.

https://www.pnas.org/content/pnas/90/24/11478.full.pdf

DNA vaccines: protective immunizations by parenteral, mucosal, and gene-gun inoculations

The development and widespread use of vaccines against infectious agents have been a great triumph of medical science. One reason for the success of currently available vaccines is that they are capable of inducing long-lived antibody responses, which are the principal agents of immune protection against most viruses and bacteria. Despite these successes, vaccination against intracellular organisms that require cell-mediated immunity, such as the agents of tuberculosis, malaria, leishmaniasis, and human immunodeficiency virus infection, are either not available or not uniformly effective. Owing to the substantial morbidity and mortality associated with these diseases worldwide, an understanding of the mechanisms involved in generating long-lived cellular immune responses has tremendous practical importance. For these reasons, a new form of vaccination, using DNA that contains the gene for the antigen of interest, is under intensive investigation, because it can engender both humoral and cellular immune re...

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DNA vaccines: immunology, application, and optimization*.

A method for delivering an isolated polynucleotide such as DNA or RNA, to the interior of a cell in a mammal comprising the injection of an isolated polynucleotide into a muscle of the mammal where the polynucleotide is taken up by the cells of the muscle and exerts a therapeutic effect on the mammal. The method can be used to deliver a therapeutic polypeptide to the cells of the mammal, to provide an immune response upon in vivo translation of the polynucleotide, to deliver antisense polynucleotides, to deliver receptors to the cells of the mammal or to provide transitory gene therapy.

Induction of a protective immune response in a mammal by injecting a DNA sequence

Vaccination with naked DNA elicits cellular and humoral immune responses that have a T helper cell type 1 bias. However, plasmid vectors expressing large amounts of gene product do not necessarily induce immune responses to the encoded antigens. Instead, the immunogenicity of plasmid DNA (pDNA) requires short immunostimulatory DNA sequences (ISS) that contain a CpG dinucleotide in a particular base context. Human monocytes transfected with pDNA or double-stranded oligonucleotides containing the ISS, but not those transfected with ISS-deficient pDNA or oligonucleotides, transcribed large amounts of interferon-α, interferon-β, and interleukin-12. Although ISS are necessary for gene vaccination, they down-regulate gene expression and thus may interfere with gene replacement therapy by inducing proinflammatory cytokines.

http://science.sciencemag.org/content/sci/273/5273/352.full.pdf

Immunostimulatory DNA Sequences Necessary for Effective Intradermal Gene Immunization

Since the discovery, over a decade and a half ago, that genetically engineered DNA can be delivered in vaccine form and elicit an immune response, there has been much progress in understanding the basic biology of this platform. A large amount of data has been generated in preclinical model systems, and more sustained cellular responses and more consistent antibody responses are being observed in the clinic. Four DNA vaccine products have recently been approved, all in the area of veterinary medicine. These results suggest a productive future for this technology as more optimized constructs, better trial designs and improved platforms are being brought into the clinic.

/pdf/dna-vaccines-ready-for-prime-time-38tzkhpl9b.pdf

DNA vaccines: ready for prime time?

Cytotoxic T lymphocytes (CTLs) specific for conserved viral antigens can respond to different strains of virus, in contrast to antibodies, which are generally strain-specific. The generation of such CTLs in vivo usually requires endogenous expression of the antigen, as occurs in the case of virus infection. To generate a viral antigen for presentation to the immune system without the limitations of direct peptide delivery or viral vectors, plasmid DNA encoding influenza A nucleoprotein was injected into the quadriceps of BALB/c mice. This resulted in the generation of nucleoprotein-specific CTLs and protection from a subsequent challenge with a heterologous strain of influenza A virus, as measured by decreased viral lung titers, inhibition of mass loss, and increased survival.

https://science.sciencemag.org/content/sci/259/5102/1745.full.pdf

Heterologous protection against influenza by injection of DNA encoding a viral protein

The fate of plasmid DNA complexed with cationic lipids delivered intravenously in mice was evaluated at selected timepoints up to 6 months postinjection. Blood half-life and tissue distribution of plasmid DNA and potential expression in tissues were examined. Southern blot analyses of blood indicated that intact plasmid DNA was rapidly degraded, with a half-life of less than 5 min for intact plasmid, and was no longer detectable at 1 hr postinjection. Southern analyses of tissue demonstrated that intact DNA was differentially retained in the lung, spleen, liver, heart, kidney, marrow, and muscle up to 24 hr postinjection. After 7 days, no intact plasmid DNA was detectable by Southern blot analysis; however, the plasmid was detectable by the polymerase chain reaction (PCR) in all tissues examined at 7 and 28 days postinjection. At 6 months postinjection, femtogram levels of plasmid were detected only in muscle. Immunohistochemical analyses did not detect encoded protein in the tissues harboring residual plasmid at 1 or 7 days postinjection.

Cancer gene therapy using plasmid DNA: pharmacokinetic study of DNA following injection in mice.

Cytolytic T-lymphocyte-mediated killing is thought to be an important effector mechanism in controlling viral infections. Recently, we reported that intramuscular injection of plasmid DNA containing the nucleoprotein (NP) gene of the influenza virus resulted in generating nucleoprotein-specific cytolytic T cells and antibodies. Gene-injected mice were subsequently protected from a lethal challenge with live influenza virus. Here we show that a single intramuscular injection of a small dose of nucleoprotein plasmid DNA generates nucleoprotein-specific cellular and humoral immune responses that last 1 year. The cellular response is associated with the CD8* subpopulation of T cells. Thus, plasmid DNA injections can be used to induce longlasting immune responses against the viral gene product without an exposure to live virus itself.

Long-Term Anti-Nucleoprotein Cellular and Humoral Immunity Is Induced by Intramuscular Injection of Plasmid DNA Containing NP Gene

To evaluate the safety of a plasmid DNA-lipid complex, a series of good laboratory practice (GLP) safety studies were conducted with VCL-1005, a plasmid DNA expression vector containing both the human class I MHC HLA-B7 heavy-chain and the beta 2-microglobulin (beta 2m) light-chain genes formulated with the cationic lipid, DMRIE/DOPE. In mice, the repeated intravenous injection of VCL-1005 at plasmid DNA doses of 0.1, 1.0, or 10 micrograms for 14 days had only incidental effects on clinical chemistry and hematology, and did not result in any organ pathology. Repeated intrahepatic injections of VCL-1005 in mice did not result in significant liver histopathology or significant alterations in liver enzymes. In cynomolgus monkeys, the repeated intravenous administration of VCL-1005 at a cumulative dose of 720 micrograms of DNA had no effects on clinical chemistry, hematology, or organ pathology. Thus, systemic administration of a plasmid DNA expression vector containing the coding sequence for a foreign MHC class I molecule did not result in significant toxicity or a pathological immune response in animals. These results suggest that the direct transfer of VCL-1005, a plasmid DNA-lipid complex, could be used for the safe in vivo delivery of recombinant DNA for a cancer gene therapy trial.

Stanislaw H. Gromkowski

Papers

Heterologous protection against influenza by injection of DNA encoding a viral protein

Cancer gene therapy using plasmid DNA: pharmacokinetic study of DNA following injection in mice.

Long-Term Anti-Nucleoprotein Cellular and Humoral Immunity Is Induced by Intramuscular Injection of Plasmid DNA Containing NP Gene

Cancer gene therapy using plasmid DNA: safety evaluation in rodents and non-human primates

Immunization with plasmid DNA using a pneumatic gun.