Effect of ultrasound treatment of the skin on activation of Langerhans cells and antibody production in rodents

In this study, we investigated whether stimulating the skin with ultrasound (US) could activate Langerhans cells (LCs) – antigen-presenting cells in the epidermis and stimulate antibody production following the subcutaneous and intradermal injection of ovalbumin (OVA) in hairless rats and BALB/c mice. Three different US frequencies (20 kHz, 1, and 3 MHz) were used and the expression of langerin was monitored as a marker for the activation of LCs in the epidermal sheet. In hairless rats, the langerin signal peaked at 12 h post-US treatment and returned to control levels at 24 h. Its expression increased with increasing irradiation time, up to 20 min, and 20 kHz US induced the highest langerin expression among the three frequencies tested. These results were reproduced in BALB/c mice. When the skin was pretreated with 20 kHz US at 0.41 W/cm(2) for 10 min, the production of OVA-specific immunoglobulin G1 in mice increased by 2.8- and 3.4-fold 28 days after subcutaneous or intradermal OVA injections, respectively. These findings indicate that stimulating the skin with US can trigger skin immune responses, leading to effective antigen-specific antibody production. US-assisted transdermal vaccine delivery delivers antigens to the skin and evokes an immune response, providing an effective noninvasive immunization strategy.