Murine Immune Responses and Immunization Against Polyplax serrata (Anoplura: Polyplacidae)

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Abstract
Mice with restricted grooming capabilities were infested with the solenophagous louse, Polyplax serrata (Burmeister). Louse burdens on Cox/Swiss and C3H/HeSN mice increased for approximately 1 mo, reaching burden/host weight ratios of 1.14 and 1.26 mg/g, respectively, followed by a steady decline. Fifty days after initial ectoparasite contact, both strains were resistant to lice. Resistance was anamnestic, lasting several months with second infestation weights reduced by 98 and 78% on Cox/Swiss and C3H/HeSN, respectively. Furthermore, mice were systemically resistant because infestations on naive body sites of resistant hosts were reduced by 59%. Host resistance was associated with the development of antilouse immune responses. After the first week of a primary infestation, the draining lymph nodes contained cells that proliferated in vitro to louse antigens. Skin responses to louse antigens were also detected: (1) delayed, (2) immediate and delayed, and (3) no significant reactivity on days 19, 34, and 54, respectively. The presence of systemic antilouse responses provided an immunologic basis for immunization against lice. Intradermal injections of soluble louse components reduced primary infestation weights by 62%. Immunized mice had immediate and delayed skin responses containing an inflammatory infiltrate 1 wk following immunization. This study, using the natural host of P. serrata, demonstrates an inducible, anamnestic immune component in louse resistance.