This single-center, double-blind, placebo-controlled study will recruit in total 39 participants with either Mild Cognitive Impairment due to Alzheimer's disease (MCI) or Mild Alzheimer's disease dementia (mild AD). There will be 3 Dose levels. An initial cohort of 13 subjects will be randomized to a Dose level 1 (0.1 mg/kg vs. placebo) lasting 8 weeks. An additional 13 subjects will be recruited and randomized into Dose level 2 (0.25 mg/kg vs. placebo) for 8 weeks and 13 subjects for the last Dose level 3 (0.5 mg/kg vs. placebo) for 8 weeks. The primary objective will be to assess safety and tolerability of CpG 1018.

Inclusion Criteria:

1. 65-85 years of age
2. MCI due to AD or mild AD dementia per NIA-AA specified criteria published in 2018
3. Montreal Cognitive Assessment (MoCA) score ≥17 AND;
4. Positive Florbetaben PET amyloid scan, or other positive PET amyloid scan performed within one year of study enrollment
5. Must be able to provide consent or assent (If applicable).
6. Must be willing and able to participate in all study related procedures.
7. Must have a reliable study partner to provide information on the subject's cognitive and functional status. Study partner must have sufficient contact with the subject, as determined by the PI, and be available to accompany the subject to clinic visits or by phone.

Exclusion Criteria:

1. History of psychiatric illness (e.g. hallucinations, major depression, suicidal ideation or delusions) that could interfere with completion of study related procedures as determined by PI
2. History of autoimmune disorders or antibody-mediated disease, severe asthma, or other serious infection or systemic illness, as determined by PI
3. Use of corticosteroids or immunosuppressive drugs within 30 days of study entry
4. History of splenectomy
5. Renal impairment
6. Use of chloroquine within 8 weeks of study entry
7. Inability to undergo MRI imaging
8. History of TIA, stroke or seizures within 12 months of screening
9. Any neurological condition other than AD that could contribute to cognitive impairment (including related to possible "long COVID") as determined by PI
10. Participation in any other current AD investigational interventional trial
11. Current use of an anti-coagulant
12. Current use of drugs that are major substrates of cytochrome P450 (CYP) enzyme 1A2
13. Recent exposure to COVID-19 infection within 14 days or recent onset of symptoms within 14 days that may be related to COVID-19 infection

The de-identified participant data from the final research dataset used in the published manuscript will be shared upon reasonable request beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research provided the investigator who proposes to use the data executes a data use agreement with NYU Langone Health. Requests may be directed to: Alok.Vedvyas@nyulangone.org. The protocol and statistical analysis plan will be made available on Clinicaltrials.gov only as required by federal regulation or as a condition of awards and agreements supporting the research.

Beginning 9 months and ending 36 months following article publication or as required by a condition of awards and agreements supporting the research.

The investigator who proposed to use the data will have access to the data upon reasonable request. Requests should be directed to Alok.Vedvyas@nyulangone.org. To gain access, data requestors will need to sign a data access agreement.