Finally, while sleep deprivation has been identified as an important risk factor for development of PTSD, repeated immunization of male C57BL/6N mice with M. vaccae NCTC 11659 (s.c., 0.1 mg in 0.1 mL sterile BBS on day –18, –11, and –4 days before the onset of sleep deprivation) has been shown to prevent a stress-induced sleep and behavioral phenotype that shares features with human PTSD [23]. Here, BBS2 is linked to post-traumatic stress disorder.