Dietary supplementation of arachidonic acid promotes humoral immunity.

Vaccination offers the most effective protection against contagious infectious diseases primarily by inducing humoral immunity. Vaccination efficacy is influenced by various factors. We report that dietary administration of arachidonic acid (ARA) significantly boosts rabies vaccine-induced production of neutralizing antibodies and protection against lethal rabies virus (RABV) infection in mice. In human volunteers, oral supplementation of ARA accelerates the expression of neutralizing antibodies to the levels sufficient for protection against RABV as early as one week after primary immunization. Mechanistically, ARA is enriched in lymph nodes and metabolized into immune modulators there. One of the ARA metabolites, prostaglandin I (PGI), via the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) axis, upregulates the expression of costimulatory molecule CD86, and activates activation-induced cytidine deaminase (AID) in B cells. These results suggest that ARA can be a potent dietary adjuvant to foster germinal center (GC) B cell response and humoral immunity.