Editing DNA vaccine (section)

==== Other types of T-cell help ====
The type of T-cell help raised is influenced by the delivery method and the type of immunogen expressed, as well as the targeting of different lymphoid compartments.<ref name=Alarcon1999 /><ref name=References1996>{{cite journal | vauthors = Boyle CM, Morin M, Webster RG, Robinson HL | title = Role of different lymphoid tissues in the initiation and maintenance of DNA-raised antibody responses to the influenza virus H1 glycoprotein | journal = Journal of Virology | volume = 70 | issue = 12 | pages = 9074–9078 | date = December 1996 | pmid = 8971047 | pmc = 191015 | doi = 10.1128/JVI.70.12.9074-9078.1996 }}</ref> Generally, saline needle injections (either IM or ID) tend to induce TH1 responses, while gene gun delivery raises TH2 responses.<ref name=Feltquate1997 /><ref name=References1996 /> This is true for intracellular and plasma membrane-bound antigens, but not for secreted antigens, which seem to generate TH2 responses, regardless of the method of delivery.<ref name="Sällberg1997">{{cite journal | vauthors = Sällberg M, Townsend K, Chen M, O'Dea J, Banks T, Jolly DJ, Chang SM, Lee WT, Milich DR | display-authors = 6 | title = Characterization of humoral and CD4+ cellular responses after genetic immunization with retroviral vectors expressing different forms of the hepatitis B virus core and e antigens | journal = Journal of Virology | volume = 71 | issue = 7 | pages = 5295–5303 | date = July 1997 | pmid = 9188598 | pmc = 191766 | doi = 10.1128/JVI.71.7.5295-5303.1997 }}</ref>

Generally the type of T-cell help raised is stable over time, and does not change when challenged or after subsequent immunizations that would normally have raised the opposite type of response in a naïve specimen.<ref name=Feltquate1997 /><ref name=References1996 /> However, Mor ''et al.''. (1995)<ref name=Mor1995 /> immunized and boosted mice with pDNA encoding the circumsporozoite protein of the mouse [[malaria]]l parasite ''[[Plasmodium yoelii]]'' (PyCSP) and found that the initial TH2 response changed, after boosting, to a TH1 response.