Interestingly, the predicted T-cell epitopes are primarily located outside of the variable domains of TSA56 (Supplementary Figure S2).32 By contrast, antigenic determinants for antibody responses generally overlap with variable domains of TSA56,42, 43 and immunological pressure on the major outer membrane protein during vertebrate host infection might be a crucial driver of genetic diversification of O. tsutsugamushi. The gene discussed is PROS1; the disease is infection.