Etf-1 is highly produced and secreted by E. chaffeensis in human monocytes (Lin et al., 2011; Liu et al., 2012); neutralization of secreted Etf-1 by delivering anti-Etf-1 IgG into the cytoplasm of host cells inhibited cellular infection by E. chaffeensis (Liu et al., 2012), whereas ectopic Etf-1 expression enhanced E. chaffeensis infection (Lin et al., 2016). Here, ETF1 is linked to infection.