Intranasal Vaccination With Recombinant Antigen-FLIPr Fusion Protein Alone Induces Long-Lasting Systemic Antibody Responses and Broad T Cell Responses.

A simple formulation is urgently needed for mucosal vaccine development. We employed formyl peptide receptor-like 1 inhibitory protein (FLIPr), an FcγR antagonist secreted by Staphylococcus aureus, as a vector to target ovalbumin (OVA) to dendritic cells (DCs) via intranasal administration. Our results demonstrate that intranasal administration of recombinant OVA-FLIPr fusion protein (rOVA-FLIPr) alone efficiently delivers OVA to DCs in nasal lymphoid tissue. Subsequently, OVA-specific IgG and IgA antibodies in the circulatory system and IgA antibodies in mucosal tissue were detected. Importantly, activation of OVA-specific CD4+ and CD8+ T cells and induction of a broad-spectrum cytokine secretion profile were detected after intranasal administration of rOVA-FLIPr alone in immunocompetent C57BL/6 mice. Furthermore, we employed immunodeficient AG129 mice as a Zika virus infection model and demonstrated that intranasal administration of recombinant Zika virus envelope protein domain III-FLIPr fusion protein induced protective immune responses against the Zika virus. These results suggest that antigen-FLIPr fusion protein alone via intranasal administration can be applied to mucosal vaccine development.

Potassium Regulation in Medaka (Oryzias latipes) Larvae Acclimated to Fresh Water: Passive Uptake and Active Secretion by the Skin Cells.

Molecular mechanisms of Na+, Cl-, and Ca2+ regulation in ionocytes of fish have been well investigated. However, the regulatory mechanism of K+ in fishes has been largely unknown. In this study, we investigated the mechanism of K+ regulation in medaka larvae acclimated to fresh water. Using a scanning ion-selective electrode technique (SIET) to measure the K+ fluxes at skin cells, significant K+ effluxes were found at ionocytes; in contrast, significant K+ influxes were found at the boundaries between keratinocytes. High K+ water (HK) acclimation induced the K+ effluxes at ionocytes and suppressed the K+ influxes at keratinocytes. The K+ effluxes of ionocytes were suppressed by VU591, bumetanide and ouabain. The K+ influxes of keratinocytes were suppressed by TAP. In situ hybridization analysis showed that mRNA of ROMKa was expressed by ionocytes in the skin and gills of medaka larvae. Quantitative PCR showed that mRNA levels of ROMKa and NKCC1a in gills of adult medaka were upregulated after HK acclimation. This study suggests that medaka obtain K+ through a paracellular pathway between keratinocytes and extrude K+ through ionocytes; apical ROMKa and basolateral NKCC1a are involved in the K+ secretion by ionocytes.