Intimin-Specific Immune Responses Prevent Bacterial Colonization by the Attaching-Effacing PathogenCitrobacter rodentium

ABSTRACTThe formation of attaching and effacing (A/E) lesions on gut enterocytes is central to the pathogenesis of enterohemorrhagic (EHEC)Escherichia coli,enteropathogenicE. coli(EPEC), and the rodent pathogenCitrobacter rodentium.Genes encoding A/E lesion formation map to a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). Here we show that the LEE-encoded proteins EspA, EspB, Tir, and intimin are the targets of long-lived humoral immune responses inC. rodentium-infected mice. Mice infected withC. rodentiumdeveloped robust acquired immunity and were resistant to reinfection with wild-typeC. rodentiumor aC. rodentiumderivative, DBS255(pCVD438), which expressed intimin derived from EPEC strain E2348/69. The receptor-binding domain of intimin polypeptides is located within the carboxy-terminal 280 amino acids (Int280). Mucosal and systemic vaccination regimens using enterotoxin-based adjuvants were employed to elicit immune responses to recombinant Int280α from EPEC strain E2348/69. Mice vaccinated subcutaneously with Int280α, in the absence of adjuvant, were significantly more resistant to oral challenge with DBS255(pCVD438) but not with wild-typeC. rodentium. This type-specific immunity could not be overcome by employing an exposed, highly conserved domain of intimin (Int388–667) as a vaccine. These results show that anti-intimin immune responses can modulate the outcome of aC. rodentiuminfection and support the use of intimin as a component of a type-specific EPEC or EHEC vaccine.