Liposomal Fba and Met6 peptide vaccination protects mice from disseminated candidiasis

Epitopes from the Candida cell surface proteins Fba and Met6 are putative vaccine targets for invasive candidiasis. Here, we describe a Candida vaccine approach in which short peptides derived from Fba and Met6 are used in spontaneous nanoliposome antigen particle (SNAP) format. SNAP was enabled by the interaction of cobalt porphyrin phospholipid in liposomes with three histidine residues on the N-terminus of synthetic short peptide immunogens from Fba (F-SNAP), Met6 (M-SNAP), or bivalent Fba and Met6 (FM-SNAP). Liposomes were adjuvanted with synthetic monophosphoryl lipid and QS-21. In mice, immunization with F-SNAP, M-SNAP, or FM-SNAP induced antigen-specific IgG responses and mixed Th1/Th2 immunity. The duplex FM-SNAP vaccine elicited stronger antibody responses against each peptide, even at order-of-magnitude lower peptide dosing than a comparable adjuvanted, conjugate vaccine. Enzyme-linked immunosorbent spot analysis revealed the induction of antigen-specific, cytokine-producing T cells. Compared to F-SNAP or M-SNAP, higher production of TNFα, IL-2, and IFNγ was observed with re-stimulation of splenocytes from bivalent FM-SNAP-immunized mice. When vaccinated BALB/c mice were challenged with Candida auris, analysis of the fungal burden in the kidneys showed that SNAP vaccination protected from disseminated candidiasis. In a lethal fungal exposure model in A/J mice, F-SNAP, M-SNAP, and FM-SNAP vaccination protected mice from candidiasis challenge. Together, these results show that further investigation into the SNAP adjuvant platform is warranted using Fba and Met6 epitopes for a pan-Candida peptide vaccine that provides multifaceted protective immune responses.

This study introduces a promising vaccine strategy against invasive candidiasis, a severe fungal infection, by targeting specific peptides on the surface of Candida. Using a novel approach called spontaneous nanoliposome antigen particle (SNAP), we combined peptides from two key Candida proteins, Fba and Met6, into a vaccine. This vaccine induced robust immune responses in mice, including the production of protective antibodies and the activation of immune cells. Importantly, mice vaccinated with SNAP were shielded from disseminated candidiasis in experiments. These findings highlight a potential avenue for developing a broad-spectrum vaccine against Candida infections, which could significantly improve outcomes for patients at risk of these often deadly fungal diseases.