DNA Vaccines: MHC II-Targeted Vaccine Protein Produced by Transfected Muscle Fibres Induces a Local Inflammatory Cell Infiltrate in Mice

Abstract

Vaccination with naked DNA holds great promise but immunogenicity needs to be improved. DNA constructs encoding bivalent proteins that bind antigen-presenting cells (APC) for delivery of antigen have been shown to enhance T and B cell responses and protection in tumour challenge experiments. However, the mechanism for the increased potency remains to be determined. Here we have constructed DNA vaccines that express the fluorescent protein mCherry, a strategy which allowed tracking of vaccine proteins. Transfected muscle fibres in mice were visualized, and their relationship to infiltrating mononuclear cells could be determined. Interestingly, muscle fibers that produced MHC class II-specific dimeric vaccine proteins with mCherry were for weeks surrounded by a localized intense cellular infiltrate composed of CD45+, MHC class II+ and CD11b+ cells. Increasing numbers of eosinophils were observed among the infiltrating cells from day 7 after immunization. The local infiltrate surrounding mCherry+ muscle fibers was dependent on the MHC II-specificity of the vaccine proteins since the control, a non-targeted vaccine protein, failed to induce similar infiltrates. Chemokines measured on day 3 in immunized muscle indicate both a DNA effect and an electroporation effect. No influence of targeting was observed. These results contribute to our understanding for why targeted DNA vaccines have an improved immunogenicity.

The Magnitude and IgG Subclass of Antibodies Elicited by Targeted DNA Vaccines Are Influenced by Specificity for APC Surface Molecules

“…Further complicating the issues discussed above, the DNA vaccines of the current experiments were delivered i.m., and the types of targetable APC in skeletal muscle may be restricted compared with the body as a whole (41). Moreover, electroporation could influence APC composition due to its inflammatory effect (42,43). Finally, vaccine proteins could drain as soluble molecules to lymph nodes, and target residential APC.…”

Antigen Targeting to Human HLA Class II Molecules Increases Efficacy of DNA Vaccination

“…Electroporation increases the number of transfected cells and hence the levels of secreted APC-targeted vaccine proteins. Additionally, local inflammation induced by electroporation may contribute to enhanced immune responses (44,45). In this study, we have compared DNA delivery by i.d.…”

Efeitos da eletroporação <i>in vivo</i> na resposta imunológica induzida por uma vacina de DNA contra tumores induzidos por HPV-16.

“…mostraram que esse influxo de células está particularmente relacionado à administração de pulsos elétricos e não ao DNA plamidial, visto que animais que receberam apenas a EP apresentaram resultados semelhantes aos que receberam a EP associada à inoculação com DNA. Outros estudos demonstraram que a EP, além de aumentar a eficiência de transfecção, também é capaz de promover uma inflamação local, induzindo a produção de citocinas inflamatórias e o recrutamento de células do sistema imune como monócitos, macrófagos (LEBLANC et al, 2008;LUXEMBOURG et al, 2006;), células dendríticas, células natural killer, (AIHARA et al, 1998;BEST et al, 2009;LØVÅS et al, 2014;MIR et al, 1999), células B e T infiltradas (LIU et al, 2008), tornando o ambiente mais propício para a apresentação de antígenos e o desencadeamento da uma resposta imune efetiva.…”