Extravasation of staphylococcal α-toxin in normal and injured CNS regions lacking blood-brain barrier function: observations after ventral root replantation

Staphylococcus aureus plays an important role as a bacterial pathogen after traumatic injury. The majority of isolated strains produces α-toxin, a 33-kDa protein, with membrane-damaging and lethal effects. The central nervous system (CNS) has been considered as the possible target for the lethal action of this toxin. A transfer of α-toxin across an intact blood-brain barrier (BBB) is however unlikely. The aim of the present study was to determine if α-toxin is accumulated in CNS regions which lack the BBB function. The distribution of α-toxin after intravascular injections, in normal mice and rats as well as in rats subjected to ventral root replantation, was assessed using immunogold technique. The results show that, although α-toxin does not cross the BBB, α-toxin-like immunoreactivity could be detected in the area postrema and at the optic nerve-retinal junction. Extravasation of α-toxin was also shown to occur in the spinal cord even 22 months after ventral root replantation. This finding suggests that axon regeneration after ventral root replantation takes place in macromolecular environment which is totally different from the normal CNS. The implications of vascular spread of α-toxin to regions devoid of BBB function are discussed in relation to the bacterial infections which might complicate severe spinal injuries.