HUMAN NATURAL YEAST KILLER TOXIN-LIKE CANDIDACIDAL ANTIBODIES

A murine mAb (mAbKT4, IgG1) that neutralizes in vitro the anti-Candida activity of a killer toxin (KT) from the yeast Pichia anomala acted a s an idiotypic (Id) vaccine in eliciting anti-id Abs with toxin-like a ctivity (KT-IdAb) in a rat vaginitis model, In this study, we demonstr ate that intravaginal or intragastric inoculations of Candida albicans bearing a receptor for the toxin was able to recall KT-IdAb productio n in the vagina of the animals primarily immunized with mAbKT4 and als o to elicit by themselves an Ab that functionally mimicked the KT (KTA b), Anti-id-like, KT-like Abs were also consistently found in the vagi nal fluid of human vaginitis patients who were infected by Candida but who had never been exposed to the Id vaccine. These Abs were as candi dacidal in vitro as those raised in rat vagina by the Id vaccination, and, likewise, their cytocidal effect was totally neutralized by previ ous reaction with mAbKT4, Importantly, they were also able to confer a significant anticandidal protection in the rat vaginitis model, compa rable to that achievable by KT-IdAb passively transferred to naive rat s from Id-vaccinated animals, Thus, candidacidal Abs representing the internal image of a yeast KT are part of the Ab repertoire that follow s infection or immunization with Candida, It is speculated that the ho st's immune response may exploit the KT receptor of microbial pathogen s to produce microbicidal Abs, possibly mirroring competition events a mong microorganisms in natural habitats.