RESISTANCE AND IMMUNE-RESPONSE IN SCABIES-INFESTED HOSTS IMMUNIZED WITH DERMATOPHAGOIDES MITES

Seventy-one percent of rabbits immunized with a mixed (50:50) Dermatop hagoides farinae and D. pteronyssinus house dust mite extract were res istant to infestation by Sarcoptes scabiei var. canis. The resistance was evidenced by a marked reduction in parasite load. All immunized ho sts developed similar immunogen-specific antibody titers that were ind ependent of the levels of scabies infestation that developed when the hosts were infested with scabies. Resistant hosts exhibited significan tly lower scabies-specific immunoglobulin titers and produced antibody to fewer scabies antigens than did nonresistant hosts. All infested h osts (resistant and nonresistant) showed a cellular infiltrate in the scabietic lesions that was composed of neutrophils, plasma cells, macr ophages, and mononuclear cell. Resistant hosts were characterized by f ewer plasma cells in the infiltrate than were observed for non-resista nt hosts. Resistant hosts exhibited a gradual increase in the number o f infiltrating neutrophils, followed by a decrease that correlated wit h a decrease in the mite burden. Nonresistant hosts exhibited an early rapid increase, a decrease, and then a gradual increase in the concen tration of neutrophils as the mite load increased. These results clear ly showed that D. farinae/D. pteronyssinus antigens/epitopes can sensi tize the hosts to scabies mites and induce protective immunity. The lo wer circulating antibody levels and generally stronger inflammatory ce ll-mediated response of resistant hosts compared with nonresistant hos ts suggested that the mechanism by which immunization with Dermatophag oides mites induces immunity to scabies mites involved a down-regulate d T helper cell type 2 (Th2) response with reduced antibody production but an up-regulated and stronger Th1 (inflammatory cell-mediated) res ponse to scabies.