Immunocytochemistry of Psoroptes cuniculi stained by sera from naive and infested rabbits: preliminary results.

Immunocytochemistry was used to identify possible target antigens in the digestive system of Psoroptes cuniculi. Sera from three recently acutely infested rabbits, from rabbits with a mild long lasting infestation, and from a rabbit with repeated mite infestations and no longer able to maintain a population of P. cuniculi were used to determine any antibody specificity to the mite digestive system. The reactivity of these sera was compared with sera from three un-infested animals. The different pool of sera targeted different mite antigens; in particular, sera from the resistant rabbit and the chronically infested rabbits reacted with gut cells, faecal material and cuticle, while sera from the recently infested rabbits reacted with gut contents, faecal material and cuticle of the parasites but not with gut cells. Finally, sera from un-infested rabbits did not demonstrate any specificity to P. cuniculi antigens reacting only with mite gut contents in a weak manner. These preliminary data suggest the presence of antibodies induced in the host blood by infection, which act against the parasite by binding to antigen at the surface of its gut.

Identification of an antigen from the sheep scab mite, Psoroptes ovis, homologous with house dust mite group I allergens.

Infestation of sheep with the ectoparasitic mite Psoroptes ovis, results in a severe allergic dermatitis. Currently, little is known about the allergens/antigens that stimulate the allergic response. We have isolated an 836-bp cDNA from a P. ovis cDNA library which displays strong homology to cysteine proteases and, in particular, to the group I house dust mite allergens Der p 1, Der f 1 and Eur m 1. The cDNA was expressed in Escherchia coli, fused to a hexahistidine tag and the recombinant protein (Pso o 1) purified using a nickel-affinity column. The recombinant Pso o 1 was tested for recognition by immunoglobulin (Ig)G and IgE in serum from P. ovis naïve and P. ovis infested sheep. Using Western blots, both classes of antibody to Pso o 1 were detected in postinfestation serum. In enzyme-linked immunosorbent assays, a pronounced IgG-antibody response to Pso o 1 was detected in five of five sheep 3 weeks postinfestation. The IgE-antibody response to whole mite extract was poor in four of five animals. However, a marked IgE response occurred in the fifth animal, and IgE anti Pso o 1 was detected in the serum.