Intranasal Vaccination with Outer-Membrane Protein of Orientia tsutsugamushi induces Protective Immunity Against Scrub Typhus

Scrub typhus develops after the individual is bitten by a trombiculid mite infected with . Since it has been reported that pneumonia is frequently observed in patients with scrub typhus, we investigated whether intranasal (i.n.) vaccination with the outer membrane protein of (OMPOT) would induce a protective immunity against infection. It was particular interest that when mice were infected with , the bacteria disseminated into the lungs, causing pneumonia. The i.n. vaccination with OMPOT induced IgG responses in serum and bronchoalveolar lavage (BAL) fluid. The anti- IgA Abs in BAL fluid after the vaccination showed a high correlation of the protection against . The vaccination induced strong Ag-specific Th1 and Th17 responses in the both spleen and lungs. In conclusion, the current study demonstrated that i.n. vaccination with OMPOT elicited protective immunity against scrub typhus in mouse with infection causing subsequent pneumonia.