The Role of Fatty Acids in Vaccine Efficacy

Rabies is an acute zoonotic infectious disease caused by central nervous system invasion by rabies virus. At present, there is still a lack of effective treatment, and once clinical symptoms appear, it is almost 100% fatal. Rabies vaccination within 24 hours of exposure may reduce the incidence of rabies. Pre-exposure prophylaxis is also effective, and the current recommended pre-exposure vaccination program in China is 0 days, 7th day, 21st days.

The health of the human body is inseparable from various nutrients. There are studies suggesting that arachidonic acid(ARA) has an immunomodulatory effect, but there is limited evidence for its effect on vaccines. Therefore, this study will explore the effects of nutritional supplements on the effectiveness of rabies vaccination.

• Arachidonic acid (Dietary supplement): D3 ARA group will receive ARA capsules from the third day of the study. D6 ARA group will receive ARA capsules from the sixth day of the study
• Sunflower oil (Dietary supplement): The placebo group and D6 ARA group will receive sunflower oil capsules from the third day of the study. D6 ARA group will stop receiving sunflower oil capsules from the fifth day of the study.
• Rabies Vaccine (Vero Cell) for Human Use (Biological): Every participant will receive three doses of rabies vaccination.

Primary outcomes

• Changes of rabies virus antibody titers [Day 6, 13, 16, 19, 26 of the study]: specific antibody titers
• Changes of neutralizing antibody titers [Day 6, 13, 16, 19, 26 of the study]: To test the ability of binding to rabies virus

Secondary outcomes

• serum blood fatty acid profiles [Day 6, 13, 16，19 of the study]: to test the change of fatty acid profiles after intervention
• C-reactive protein [Day 6, 13, 16 and 19 of the study]: to test the potential C-reactive protein changes triggered by ARA supplementation
• Routine analysis of intestinal flora: alpha diversity [Day 3 and day 19 of the study]: The alpha diversity of microbiota in feces samples will be examined to explore the potential gut-immune response caused by intervention.
• Routine analysis of intestinal flora: beta diversity [Day 3 and day 19 of the study]: The beta diversity of microbiota in feces samples will be examined to explore the potential gut-immune response caused by the intervention.
• Routine analysis of intestinal flora: species abundance histogram [Day 3 and day 19 of the study]: The species abundance histogram of microbiota in feces samples will be examined to explore the potential gut-immune response caused by the intervention.
• Routine analysis of intestinal flora: Lefse [Day 3 and day 19 of the study]: The Lefse of microbiota in feces samples will be conducted to explore the potential gut-immune response caused by the intervention.
• Routine analysis of intestinal flora: PLS-DA [Day 3 and day 19 of the study]: The PLS-DA of microbiota in feces samples will be conducted to explore the potential gut-immune response caused by the intervention.
• Routine analysis of intestinal flora: KEGG pathway [Day 3 and day 19 of the study]: The KEGG pathway microbiota in feces samples will be analyzed to explore the potential gut-immune response caused by the intervention.
• Routine analysis of intestinal flora: differential KO expression [Day 3 and day 19 of the study]: The differential KO expression microbiota in feces samples will be analyzed to explore the potential gut-immune response caused by the intervention.
• Macrogenomic sequencing difference of intestinal flora [Day 3 and day 19 of the study]: The macrogenomic sequencing analysis of microbiota in feces samples will be conducted to explore the potential gut-immune response caused by the intervention.
• Fecal fatty acid content [Day 3 and day 19 of the study]: The fatty acid content in feces samples will be examined to explore the change of fatty acid intake caused by the intervention.

Other outcomes

• Adverse events by ARA [Day 3 to day 30 of the trial.]: To examine the safety of using ARA, including allergy, gastrointestinal discomfort and others.
• Serum triglyceride levels [Days 3 and day 19 of the study.]: To examine the changes of blood lipids in blood after intervention and evaluate the intervention safety. The spacific measurements include: Triglycerides (TG), high-density lipoprotein cholesterol (HDL-CHO), low-density lipoprotein cholesterol (LDL-C), and total cholesterol (TC).
• Blood count: red blood cells [tested on day 3 and day 19 of the trial.]: To evaluate the intervention safety.
• Blood count: white blood cells [tested on day 3 and day 19 of the trial.]: To evaluate the intervention safety.
• Blood count: hemoglobin [tested on day 3 and day 19 of the trial.]: To evaluate the intervention safety.
• Blood count: hematocrit [tested on day 3 and day 19 of the trial.]: To evaluate the intervention safety.
• Blood count: platelets [tested on day 3 and day 19 of the trial.]: To evaluate the intervention safety.
• Anxiety [tested on day 13 of the trial.]: Evaluated with General Anxiety Disorder-7 items. The scores are between 0 to 21, higher scores mean a worse outcome.
• Depression [tested on day 13 of the trial.]: Evaluated with Patient Health Questionaire-9 items. The scores are between 0 to 27, higher scores mean a worse outcome.

Sex: All, ages: 18 Years to 45 Years, accepts healthy volunteers

Inclusion Criteria:

* 1）18-45 years old;
* 2）BMI 18.5-24.9 kg/m2;
* 3）Have not received rabies vaccination.

Exclusion Criteria:

* 1\) Those who have severe disorders of abnormal lipid metabolism;
* 2\) Those who have used lipid-lowering drugs, weight loss drugs, and insulin drugs in the past three months;
* 3\) Those who have received other vaccines in the past three months;
* 4\) Those who have used probiotics or prebiotics in the past three months;
* 5\) Those who have used steroids and immunosuppressants, other hormonal drugs in the past year;
* 6\) Those with immunodeficiency diseases;
* 7\) Those with a history of severe vaccine allergies;
* 8\) Those who have disorders of liver and kidney metabolism;
* 9\) Those who have had fever, cold, severe diarrhea and other diseases in the past month.
* 10\) Smokers in the last year.

• Shen T, Welburn SC, Sun L, Yang GJ. Progress towards dog-mediated rabies elimination in PR China: a scoping review. Infect Dis Poverty. 2023 Apr 6;12(1):30. doi: 10.1186/s40249-023-01082-3. PMID 37024944

• Study Protocol (PDF, 2023-05-20)
• Informed Consent Form (PDF, 2023-05-20)

• Ai Zhao, Doctor, Study chair, Tsinghua University