Immunization with Bacillus Calmette-Guérin (BCG) alleviates neuroinflammation and cognitive deficits in APP/PS1 mice via the recruitment of inflammation-resolving monocytes to the brain

Neurobiol Dis. 2017 May;101:27-39. doi: 10.1016/j.nbd.2017.02.001. Epub 2017 Feb 9.

Abstract

The immune system plays a crucial role in the progression of Alzheimer's disease (AD). Recently, immune-dependent cascade induced by systemic immune activation has been verified to play a beneficial role in AD mouse models. Here, we tested whether Bacillus Calmette-Guérin (BCG) immunization alters AD pathology and cognitive dysfunction in APP/PS1 AD mouse model, and with 4Aβ1-15 vaccination as positive control. It was found that BCG treatment reversed the cognitive decline to the extent observed in 4Aβ1-15 group, but did not reduce the β-amyloid (Aβ) burden in the brain. Then, we demonstrated the enhanced recruitment of inflammation-resolving monocytes across the choroid plexus and perivascular spaces to cerebral sites of plaque pathology in APP/PS1 mice immunized with BCG. Furthermore, elevated splenocyte Foxp3+ regulatory T cell levels in the control APP/PS1 mice were down-regulated back to the wild-type (WT) levels by BCG treatment but not 4Aβ1-15 vaccination. In addition, BCG treatment induced the production of more circulating interferon (IFN)-γ than the controls and 4Aβ1-15 vaccination. Though the similar reductions in brain levels of pro-inflammatory cytokines were observed in the BCG and 4Aβ1-15 groups compared to the controls, only BCG had the great effect in upregulating cerebral anti-inflammatory cytokine levels as well as elevating the expression of neurotrophic factors in the brain of APP/PS1 mice. Thus, it is suggested that BCG exerts a beneficial immunomodulatory effect in APP/PS1 mice through mitigation of systemic immune suppression, induction of IFN-γ response and alleviation of the neuroinflammatory response.

Keywords: AD; Anti-inflammation; BCG; IFN-γ; Monocytes; Vaccination.

MeSH terms

  • Alzheimer Disease / drug therapy*
  • Alzheimer Disease / immunology*
  • Alzheimer Disease / pathology
  • Alzheimer Disease / psychology
  • Amyloid beta-Peptides / immunology
  • Animals
  • BCG Vaccine / therapeutic use*
  • Brain / drug effects
  • Brain / immunology*
  • Brain / pathology
  • Disease Models, Animal
  • Female
  • Forkhead Transcription Factors / metabolism
  • Gliosis / drug therapy
  • Gliosis / immunology
  • Gliosis / pathology
  • Humans
  • Interleukin-10 / metabolism
  • Male
  • Maze Learning / drug effects
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Monocytes / drug effects
  • Monocytes / immunology*
  • Monocytes / pathology
  • Peptide Fragments / immunology
  • Spleen / cytology
  • T-Lymphocytes, Regulatory / drug effects
  • T-Lymphocytes, Regulatory / immunology

Substances

  • Amyloid beta-Peptides
  • BCG Vaccine
  • Forkhead Transcription Factors
  • Foxp3 protein, mouse
  • IL10 protein, mouse
  • Peptide Fragments
  • amyloid beta-protein (1-15)
  • Interleukin-10