Efficient Priming of CD4+ and CD8+ T Cells by DNA Vaccination Depends on Appropriate Targeting of Sufficient Levels of Immunologically Relevant Antigen to Appropriate Processing Pathways

Abstract

The initial cellular events and interactions that occur following DNA immunization are likely to be key to determining the character and magnitude of the resulting immune response, and as such, a better understanding of these events could ultimately lead to the design of more effective pathogen-appropriate DNA vaccines. Therefore, we have used a variety of sensitive cell-based techniques to study the induction of adaptive immunity in vivo. We examined the efficacy of induction of Ag-specific CD4+ and CD8+ T cell responses in vivo by the adoptive transfer of fluorescently labeled Ag-specific TCR transgenic T cells and have demonstrated how such approaches can be used to study the effect of simple DNA construct manipulations on immunological priming. OVA-specific CD8+ and CD4+ T cells were activated and divided in vivo following immunization with DNA constructs that targeted OVA expression to different subcellular locations; however, the kinetics and degree of cell proliferation were dependent on the cellular location of the expressed protein. DNA vectors encoding cell-associated OVA resulted in greater CD8+ T cell division compared with other forms of OVA. In contrast, soluble secreted OVA targeted to the classical secretory pathway enhanced division of CD4+ T cells. Furthermore, the inclusion of mammalian introns to enhance protein expression increased the ability of poorly immunogenic forms of Ag to activate naive T cells, indicating that not only the location, but also the amount of Ag expression, is important for efficient T cell priming following DNA injection.

Secretory IgA Mediates Bacterial Translocation to Dendritic Cells in Mouse Peyer’s Patches with Restriction to Mucosal Compartment

“…Limited responsiveness of DCs to the SIgA-Ag immune complexes can possibly be due to the high degree of glycosylation of SIgA that would result in poor processing by DCs (42). Along the same line, SIgA can "sequester" the associated Ag, which leads to insufficient levels of immunostimulatory Ag to efficiently prime naive T cells (43). Differential uptake, routing, and processing of the Ag (44 -46) by myeloid CD11c ϩ CD11b ϩ DCs that are potent inducers of IL-10-secreting T cells (47) and IgA production from naive B cells (48) might as well contribute to modulate local responses.…”

Multimeric Soluble CD40 Ligand and GITR Ligand as Adjuvants for Human Immunodeficiency Virus DNA Vaccines

“…In contrast, the present report and two previous reports failed to find any adjuvant effects with pMemCD40L-like plasmids when secreted antigens were studied (e.g., TSSA from Treponema cruzi [61] or gp120 [88]). Antigen localization has been previously identified as an important variable for DNA vaccination (12,62,69,75,89) and has implications for the selection of adjuvanting molecules. When a DNA vaccine encodes nonsecreted, cell-associated antigen (either cytoplasmic or transmembrane), it may be crucial for dendritic cells to migrate to the vaccination site in order to take up antigen and transport it to the draining lymph node for presentation to T cells.…”

Reduction in RNA Levels Rather than Retardation of Translation Is Responsible for the Inhibition of Major Histocompatibility Complex Class I Antigen Presentation by the Glutamic Acid-Rich Repeat of Herpesvirus Saimiri Open Reading Frame 73

“…pOVA-GFP was generated by amplification of the OVA open reading frame from pcDNA-OVA (34), with the primers 5Ј-GGGCTCGAGATGGGCTCCA TCGGCGCAGC-3Ј (Xho1 site underlined) and 5Ј-GGGGGATCCCGAGGG GAAACACATCTGCC-3Ј (BamH1 site underlined) and insertion into pEGFP-N1. The EG-EA repeat, here termed 73R, was inserted into the Pst1 site of OVA-GFP as follows: the EG-EA repeat spanning amino acids 55 to 247 was amplified with the primers 5Ј-GGGCTGCAGAAGCAGCACTAACAGAAGA ACAACG-3Ј and 5Ј-GGGCTGCAGCACGTGGAGTACTTGGTCC-3Ј (Pst1 sites underlined) and cloned into pOVA-GFP, generating pOVA-P73R.…”