Vaccine adjuvant activity of a TLR4-activating synthetic glycolipid by promoting autophagy

Sci Rep. 2020 May 21;10(1):8422. doi: 10.1038/s41598-020-65422-1.

Abstract

Toll-like receptors (TLRs) play crucial roles in host immune defenses. Recently, TLR-mediated autophagy is reported to promote immune responses via increasing antigen processing and presentation in antigen presenting cells. The present study examined whether the synthetic TLR4 activator (CCL-34) could induce autophagy to promote innate and adaptive immunity. In addition, the potential of CCL-34 as an immune adjuvant in vivo was also investigated. Our data using RAW264.7 cells and bone marrow-derived macrophages showed that CCL-34 induced autophagy through a TLR4-NF-κB pathway. The autophagy-related molecules (Nrf2, p62 and Beclin 1) were activated in RAW264.7 cells and bone marrow-derived macrophages under CCL-34 treatment. CCL-34-stimulated macrophages exhibited significant antigen-processing activity and induced the proliferation of antigen-specific CD4+T cells as well as the production of activated T cell-related cytokines, IL-2 and IFN-γ. Furthermore, CCL-34 immunization in mice induced infiltration of monocytes in the peritoneal cavity and elevation of antigen-specific IgG in the serum. CCL-34 treatment in vivo did not cause toxicity based on serum biochemical profiles. Notably, the antigen-specific responses induced by CCL-34 were attenuated by the autophagy inhibitor, 3-methyladenine. In summary, we demonstrated CCL-34 can induce autophagy to promote antigen-specific immune responses and act as an efficient adjuvant.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives
  • Adenine / pharmacology
  • Adjuvants, Immunologic / pharmacology*
  • Animals
  • Autophagy / immunology*
  • Beclin-1 / metabolism
  • CD4-Positive T-Lymphocytes / immunology
  • Cell Line
  • Cell Proliferation / drug effects
  • Enzyme Activation / drug effects
  • Glycolipids / pharmacology*
  • Immunogenicity, Vaccine / immunology*
  • Immunoglobulin G / blood
  • Interferon-gamma / metabolism
  • Interleukin-2 / metabolism
  • Macrophages / immunology
  • Mice
  • Mice, Inbred C3H
  • Mice, Inbred C57BL
  • Monocytes / immunology
  • NF-E2-Related Factor 2 / metabolism
  • RAW 264.7 Cells
  • Serine / analogs & derivatives*
  • Serine / pharmacology
  • Toll-Like Receptor 4 / metabolism*
  • Vaccines / immunology

Substances

  • Adjuvants, Immunologic
  • Beclin-1
  • Becn1 protein, mouse
  • CCL 34
  • Glycolipids
  • IFNG protein, mouse
  • Immunoglobulin G
  • Interleukin-2
  • NF-E2-Related Factor 2
  • Nfe2l2 protein, mouse
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • Vaccines
  • Serine
  • 3-methyladenine
  • Interferon-gamma
  • Adenine