IL-12 DNA as molecular vaccine adjuvant increases the cytotoxic T cell responses and breadth of humoral immune responses in SIV DNA vaccinated macaques

Abstract

Intramuscular injection of macaques with an IL-12 expression plasmid (0.1 or 0.4 mg DNA/animal) optimized for high level of expression and delivered using in vivo electroporation, resulted in the detection of systemic IL-12 cytokine in the plasma. Peak levels obtained by day 4–5 post injection were paralleled by a rapid increase of IFN-γ, indicating bioactivity of the IL-12 cytokine. Both plasma IL-12 and IFN-γ levels were reduced to basal levels by day 14, indicating a short presence of elevated levels of the bioactive IL-12. The effect of IL-12 as adjuvant together with an SIVmac239 DNA vaccine was further examined comparing two groups of rhesus macaques vaccinated in the presence or absence of IL-12 DNA. The IL-12 DNA-adjuvanted group developed significantly higher SIV-specific cellular immune responses, including IFN-γ⁺ Granzyme B⁺ T cells, demonstrating increased levels of vaccine-induced T cells with cytotoxic potential, and this difference persisted for 6 mo after the last vaccination. Coinjection of IL-12 DNA led to increases in Gag-specific CD4⁺ and CD4⁺CD8⁺ double-positive memory T cell subsets, whereas the Env-specific increases were mainly mediated by the CD8⁺ and CD4⁺CD8⁺ double-positive memory T cell subsets. The IL-12 DNA-adjuvanted vaccine group developed higher binding antibody titers to Gag and mac251 Env, and showed higher and more durable neutralizing antibodies to heterologous SIVsmE660. Therefore, co-delivery of IL-12 DNA with the SIV DNA vaccine enhanced the magnitude and breadth of immune responses in immunized rhesus macaques, and supports the inclusion of IL-12 DNA as vaccine adjuvant.

Keywords: :

• in vivo electroporation
• HIV
• SIVsmE660
• SIVmac239
• antibody
• neutralizing antibody
• avidity
• central memory
• transitional memory
• effector memory

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We are grateful to D. Weiss, J. Treece, I. Kalisz, V. Kalyanaraman, P. Markham and staff at Advanced BioScience Laboratories, Inc., Rockville, for their expert help. We thank A. Valentin for discussions, J. Bear and B. Chowdhury for technical assistance, and T. Jones for editorial assistance. This work was supported by the Intramural Research Program of the National Cancer Institute, National Institutes of Health (NCI/NIH) and by NIH HHSN 27201100016C.

B.K.F., G.N.P.: designed, coordinated the study, analyzed the data, and wrote the paper

R.J., M.R., V.P., V.K., C.A., B.G., A.vG.: performed experiments and analyzed the data

C.L., D.C.M.: performed and analyzed NAb assays

W.H., Y.G.: performed binding Ab and avidity assays

K.E.B., N.Y.S.: contributed electroporation delivery methods and devices