TLR4 and infection: Moreover, the role of TLR4 in the host defense against A. baumannii can be affected by the virulence of bacterial strains, the structures and abundance of LPS, the routes (intranasal vs. intravenous or intraperitoneal) of infection, the strain and sex of the mice, and the infection model (lethal vs. sublethal) (Maclean et al., 2009; Lin et al., 2012; Vinogradov et al., 2014; Pires et al., 2020).