ABSTRACT
Objective To obtain acquired immunity evidence in hamsters elicited by third stage hookworm larvae of Necator americanas(NaL3).morphology changes of NaL3 and inflammatory responses in the skin and undedying subcutaneous tissue and muscles of hamsters were observed.Methods Hamsters were immunized subcutaneously with one dose of 150 NaL3 at 2 weeks earlier,and then challenged pereutaneously with 900 NaL3.Skins were excised from post-challenge hamsters at 6,24,72 hours and 1,2 weeks,and then examined under light microscopy.Non-immunized hamsters served as negative controls.Results In non-immunized hamsters the number of NaL3 were 15,33,11.0 and 0 at 6,24,72 hours and 1,2 weeks post-infection.No damaged or dead NaL3 section was observed.All NaL3 exhibited no structural damage and infihrating inflammatory cells were absent from the sunDunding tissues.There were no cutaneous changes.In contrast.the total number of Nak sections in the skin of immunized hamsters were 25,53,15,5 and 4 at 6,24,72 hours and 1,2 weeks post-challenge.Among these NaL3 sections,damaged and dead section number were 0,24,6,0,0 and 0,0,7,5,4.At 24 hours post-challenge the Nak exhibited cutieular swelling and damage.By 72 hours post-challenge pyknosis of the somatic cells nuclei and sparseness or loss of definition in the internal structures of NaL3 were seen.One or two weeks after chanenge,the NaL3 showed severe damage or even dead with remnants.Inflammatory responses including macrophages,epithelioid cells and eosinophils infiltrating and granulomata forming were mainly seen around the NaL3 sections in the skin of immunized hamsters.Conclusions Hamsters initially immunized with NaL3 exhibited obvious acquired immunity protection against percutaneously challenged infection as evidenced by vigorous inflammatory responses in the skin and underlying subcutaneous tissue and muscle.
ABSTRACT
The protective immunity elicited by ultraviolet-irradiated third-stage infective larvae of Necator americanus (UV-NaL3) and Ancylostoma caninum (UV-AcL3) was evaluated in laboratory mice (a non-permissive model) and hamsters (a permissive model). After optimizing the time of exposure to UV-irradiation, both oral and subcutaneous vaccination routes with UV-AcL3 in mice were explored. Oral vaccination was more effective at reducing the number of challenge AcL3 entering the lungs, whereas subcutaneous vaccination was more effective at blocking muscle entry. When UV-irradiated NaL3 and non-irradiated AcL3 were used as vaccines in hamsters, both of them were effective at reducing adult hookworm burdens. However, the length of protection afforded by UV-irradiated L3 was substantially greater than that resulting from immunization with non-irradiated L3. A single dose was less effective than multiple doses. The protective immunity elicited by UV-irradiated NaL3 given once every other week for a total of three immunizations was similar to that elicited by non-irradiated AcL3 given during the same schedule. Protection was not significantly affected by administering the L3 on a weekly basis for a total of three immunizations, even though the antibody titers were reduced using this schedule. These studies will facilitate the elucidation of the mechanisms underlying larval protection.