WH1fungin a surfactin cyclic lipopeptide is a novel oral immunoadjuvant

WH1fungin, a surfactin lipopeptide from Bacillus amyloliquefaciens WH1, can be used as an adjuvant for eliciting strong immune response by parenteral immunization. In this study, WH1fungin was firstly reported as an oral immunoadjuvant. In mice, WH1fungin markedly enhanced the immune response to co-administered protein antigens (OVA or GST), similar to levels elicited by CTB, but no immune response was elicited to itself. Both IgG1 and IgG2a antibodies elicited from the immunizations indicating a mixed Th1/Th2 response. Splenocytes from mice immunized with OVA plus WH1fungin responded to OVA CTL peptide stimulation resulting in an increase in CD8⁺TNF-α⁺ and CD8⁺IFN-γ⁺ T cell populations. These results further suggested that WH1fungin helps to elicit both humoral and cellular responses to OVA. More studies revealed that the potential mechanism as oral immunoadjuvant was that WH1fungin could form co-precipitates with antigens in a pH value similar to gastric juice. The precipitation protected the antigens from degradation by pepsin providing an explanation for the antigens to withstand the acidic and proteolytic environments of the gastrointestinal tract when co-administered with WH1fungin. Moreover, WH1fungin promoted the uptake of OVA by the intestine and by cultured DC2.4 cells, and increased the expression of cell surface markers and cytokines in DC2.4 cells. Taken together, WH1fungin is a potent oral immunoadjuvant with the ability of protecting protein antigens from acidic and proteolytic degradation, suggesting its potential usage in oral vaccine development.