Editing DNA vaccine (section)

== Delivery ==

[[Image:Gene therapy.jpg|thumb|right|DNA vaccine and Gene therapy techniques are similar.]]
DNA vaccines have been introduced into animal tissues by multiple methods. In 1999, the two most popular approaches were injection of DNA in [[Saline (medicine)|saline]]: by using a standard hypodermic needle, or by using a [[gene gun]] delivery.<ref name="Weiner1999">{{cite journal | vauthors = Weiner DB, Kennedy RC | title = Genetic vaccines | journal = Scientific American | volume = 281 | issue = 1 | pages = 50–57 | date = July 1999 | pmid = 10396782 | doi = 10.1038/scientificamerican0799-50 | url = http://www.sciamdigital.com/gsp_qpdf.cfm?ISSUEID_CHAR=8FF32714-CA1C-4025-BE8D-0FE4B5C348B&ARTICLEID_CHAR=14F98F90-1708-4B77-A8D4-44F867A153F | access-date = 2007-11-21 | url-status = dead | bibcode = 1999SciAm.281a..50W | archive-url = https://web.archive.org/web/20090325025916/http://www.sciam.com/media/inline/000052A5-43F6-1CBC-B4A8809EC588EEDF_arch2.gif | archive-date = 2009-03-25 }}</ref> Several other techniques have been documented in the intervening years.

=== Saline injection ===

Injection in saline is normally conducted intramuscularly (IM) in [[skeletal muscle]], or [[dermis|intradermally]] (ID), delivering DNA to extracellular spaces. This can be assisted either 1) by [[electroporation]];<ref name="Widera2000">{{cite journal | vauthors = Widera G, Austin M, Rabussay D, Goldbeck C, Barnett SW, Chen M, Leung L, Otten GR, Thudium K, Selby MJ, Ulmer JB | display-authors = 6 | title = Increased DNA vaccine delivery and immunogenicity by electroporation in vivo | journal = Journal of Immunology | volume = 164 | issue = 9 | pages = 4635–4640 | date = May 2000 | pmid = 10779767 | doi = 10.4049/jimmunol.164.9.4635 | doi-access = free }}</ref> 2) by temporarily damaging muscle fibres with [[myotoxins]] such as [[bupivacaine]]; or 3) by using [[hypertonic]] solutions of saline or [[sucrose]].<ref name="Alarcon1999" /> Immune responses to this method can be affected by factors including needle type,<ref name="Sedegah1994" /> needle alignment, speed of injection, volume of injection, muscle type, and age, sex and physiological condition of the recipient.<ref name="Alarcon1999" />

=== Gene gun ===

[[Gene gun]] delivery ballistically accelerates plasmid DNA (pDNA) that has been absorbed onto [[gold]] or [[tungsten]] microparticles into the target cells, using compressed [[helium]] as an accelerant.<ref name="Alarcon1999" /><ref name="Lewis1999" />

=== Mucosal surface delivery ===
Alternatives included [[aerosol]] instillation of naked DNA on [[mucosal]] surfaces, such as the [[human nose|nasal]] and [[human lung|lung]] [[mucosa]],<ref name="Lewis1999" /> and topical administration of pDNA to the eye<ref name="Daheshia1997">{{cite journal | vauthors = Daheshia M, Kuklin N, Kanangat S, Manickan E, Rouse BT | title = Suppression of ongoing ocular inflammatory disease by topical administration of plasmid DNA encoding IL-10 | journal = Journal of Immunology | volume = 159 | issue = 4 | pages = 1945–1952 | date = August 1997 | doi = 10.4049/jimmunol.159.4.1945 | pmid = 9257860 | s2cid = 43203331 | url = http://www.jimmunol.org/cgi/content/abstract/159/4/1945 | doi-access = free }}</ref> and vaginal mucosa.<ref name="Lewis1999" /> Mucosal surface delivery has also been achieved using cationic [[liposome]]-DNA preparations,<ref name="Robinson2000" /> [[biodegradable]] microspheres,<ref name="Chen1998">{{cite journal | vauthors = Chen Y, Webster RG, Woodland DL | title = Induction of CD8+ T cell responses to dominant and subdominant epitopes and protective immunity to Sendai virus infection by DNA vaccination | journal = Journal of Immunology | volume = 160 | issue = 5 | pages = 2425–2432 | date = March 1998 | doi = 10.4049/jimmunol.160.5.2425 | pmid = 9498786 | s2cid = 2250871 | url = http://www.jimmunol.org/cgi/content/abstract/160/5/2425 | doi-access = free }}</ref><ref name="Lewis1999" /> attenuated ''[[Salmonella|Salmonalla]]'',<ref>{{cite journal | vauthors = Lode HN, Huebener N, Zeng Y, Fest S, Weixler S, Gaedicke G | title = DNA minigene vaccination for adjuvant neuroblastoma therapy | journal = Annals of the New York Academy of Sciences | volume = 1028 | issue = 1 | pages = 113–121 | date = December 2004 | pmid = 15650237 | doi = 10.1196/annals.1322.012 | s2cid = 27240738 | bibcode = 2004NYASA1028..113L }}</ref> ''[[Shigella]]'' or ''[[Listeria]]'' vectors for oral administration to the intestinal mucosa<ref name="Sizemore1995">{{cite journal | vauthors = Sizemore DR, Branstrom AA, Sadoff JC | title = Attenuated Shigella as a DNA delivery vehicle for DNA-mediated immunization | journal = Science | volume = 270 | issue = 5234 | pages = 299–302 | date = October 1995 | pmid = 7569980 | doi = 10.1126/science.270.5234.299 | s2cid = 12532901 | bibcode = 1995Sci...270..299S | url = https://zenodo.org/record/1231043 }}</ref> and recombinant adenovirus vectors.<ref name="Lewis1999" />

=== Polymer vehicle ===

A hybrid vehicle composed of bacteria cell and synthetic [[polymers]] has been employed for DNA vaccine delivery. An ''[[E. coli]]'' inner core and poly(beta-amino ester) outer coat function synergistically to increase efficiency by addressing barriers associated with [[antigen-presenting cell]] gene delivery which include cellular uptake and internalization, [[phagocytosis|phagosomal]] escape and intracellular cargo concentration.{{Technical inline | date = October 2021}} Tested in mice, the hybrid vector was found to induce immune response.<ref>{{cite web|url= http://www.buffalo.edu/news/releases/2014/11/035.html |title=A hybrid vehicle that delivers DNA|author=Nealon, Cory|publisher=The State University of New York at Buffalo|date=25 November 2014|access-date=16 December 2014}}</ref><ref>{{cite journal | vauthors = Jones CH, Ravikrishnan A, Chen M, Reddinger R, Kamal Ahmadi M, Rane S, Hakansson AP, Pfeifer BA | display-authors = 6 | title = Hybrid biosynthetic gene therapy vector development and dual engineering capacity | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 111 | issue = 34 | pages = 12360–12365 | date = August 2014 | pmid = 25114239 | pmc = 4151754 | doi = 10.1073/pnas.1411355111 | doi-access = free | bibcode = 2014PNAS..11112360J }}</ref>

=== ELI immunization ===

Another approach to DNA vaccination is [[expression library]] immunization (ELI). Using this technique, potentially all the genes from a pathogen can be delivered at one time, which may be useful for pathogens that are difficult to attenuate or culture.<ref name="Alarcon1999" /> ELI can be used to identify which genes induce a protective response. This has been tested with ''[[Mycoplasma]] pulmonis'', a [[murine]] lung pathogen with a relatively small [[genome]]. Even partial expression libraries can induce protection from subsequent challenge.<ref name="Barry1995">{{cite journal | vauthors = Barry MA, Lai WC, Johnston SA | title = Protection against mycoplasma infection using expression-library immunization | journal = Nature | volume = 377 | issue = 6550 | pages = 632–635 | date = October 1995 | pmid = 7566175 | doi = 10.1038/377632a0 | s2cid = 4306972 | bibcode = 1995Natur.377..632B | doi-access = free }}</ref>

=== Helpful tabular comparison ===

{{Unreferenced section | date = October 2021}}
{| class="wikitable"
|+ Table 2. Summary of plasmid DNA delivery methods
! colspan=2| Method of delivery !! Formulation of DNA !! Target tissue !! Amount of DNA
|-
! rowspan=3 |Parenteral
| Injection (hypodermic needle)
| Aqueous solution in saline
| [[Intramuscular injection|IM]] (skeletal); [[Intradermal injection|ID]]; ([[Intravenous therapy|IV]], [[Intravenous therapy|subcutaneous]] and [[Intraperitoneal injection|intraperitoneal]] with variable success)
| Large amounts (approximately 100-200&nbsp;μg)
|-
| Gene gun
| DNA-coated gold beads
| {{abbr |ED|Epidermal}} (abdominal skin); vaginal mucosa; surgically exposed muscle and other organs
| Small amounts (as little as 16&nbsp;ng)
|-
| Pneumatic (jet) injection
| Aqueous solution
| {{abbr |ED|Epidermal}}
| Very high (as much as 300&nbsp;μg)
|-
| colspan=2| Topical application
| Aqueous solution
| Ocular; intravaginal
| Small amounts (up to 100&nbsp;μg)
|-
| colspan=2| Cytofectin-mediated{{technical inline| date = October 2021}}
| [[Liposomes]] (cationic); microspheres; recombinant adenovirus vectors; attenuated [[Shigella]] vector; aerosolised cationic [[lipid]] formulations
| IM; IV (to transfect tissues systemically); intraperitoneal; oral immunization to the intestinal mucosa; nasal/lung mucosal membranes
| variable
|}

{| class="wikitable"
|+ Table 3. Advantages and disadvantages of commonly used DNA vaccine delivery methods
! width="20%"| Method of delivery
! width="40%"| Advantage
! width="40%"| Disadvantage
|-
| Intramuscular or Intradermal injection
|
* No special delivery mechanism
* Permanent or semi-permanent expression
* pDNA spreads rapidly throughout the body
|
* Inefficient site for uptake due to morphology of muscle tissue
* Relatively large amounts of DNA used
* Th1 response may not be the response required
|-
| Gene gun
|
* DNA bombarded directly into cells
* Small amounts DNA
|
* Th2 response may not be the response required
* Requires inert particles as carrier
|-
| Jet injection
|
* No particles required
* DNA can be delivered to cells mm to cm below skin surface
|
* Significant shearing of DNA after high-pressure expulsion
* 10-fold lower expression, and lower immune response
* Requires large amounts of DNA (up to 300&nbsp;μg)
|-
| Liposome-mediated delivery
|
* High levels of immune response can be generated
* Can increase transfection of intravenously delivered pDNA
* Intravenously delivered liposome-DNA complexes can potentially transfect all tissues
* Intranasally delivered liposome-DNA complexes can result in expression in distal mucosa as well as nasal muscosa and the generation of IgA antibodies
|
* Toxicity
* Ineffectiveness in serum
* Risk of disease or {{Clarify | text = immune reactions | date = October 2021 | reason = What kind of immune reactions would be disadvantageous? }}
|}