Protective immunity elicited by ultraviolet-irradiated third-stage infective hookworm (Necator americanus and Ancylostoma caninum) larvae in mice and hamsters.

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.

Ancylostoma duodenale infection: a study of serum immunoglobulin G4 response to the excretory secretory antigen of adult worm

The serum anti-Ancylostoma duodenale immunoglobulin [Is] G4 antibody response to fraction III of the partially purified excretory secretory antigen of adult worm [Ad III ESA] was studied. This work included 60 patients with A duodenale infection [GI], 40 patients with other parasitic infections [GII] and 30 apparently healthy parasite-free controls [GIII]. Level of serum specific IgG4 was measured by indirect enzyme linked immunosorbent assay and compared with serum specific IgG, IgG 1, 2 and 3 subclass antibodies. Patients of GI had gastrointestinal manifestations and symptoms suggestive of anaemia and by investigations they had anaemia in 31.7% and eosinophilia in 100%. Measuring the intensity of A. duodenale infection, quantified as fecal egg counts, in patients of GI revealed that 60%, 30% and 10% had light, moderate and heavy infections, respectively. The serum anti-Ad III ESA IgG and IgG 1-4 subclass antibodies were significantly elevated in patients of GI compared with GIII. Serum specific IgG4 was expressed in 100% of patients of GI at a significantly highly elevated level than IgG1, IgG2 and IgG3. Specific IgG1 was expressed in 88.3% of patients of GI at a significantly elevated level than IgG2 and IgG3 which were expressed in 31.7% and 38.3%, respectively, and elevated to a moderate extent. Serum specific IgG4 showed a 1.0, 1.1, 3.1 and 2.6-fold increase in detection rate of positive cases than IgG, IgG1, IgG2 and IgG3, respectively. The highest ability to differentiate between infected and healthy subjects was by serum specific IgG4 recording a discrimination coefficient of 9.4, while IgG, IgG1, IgG2 and IgG3 recorded 5.2, 6.3, 3.2 and 3.4,respectively. Serum specific IgG4 showed a significant positive correlation with the intensity of A. duodenale infection demonstrated by IgG and IgG3, respectively. Detection of serum anti-Ad III ESA IgG4 antibody recorded a 100% sensitivity that was significantly higher than IgG1, IgG2 and IgG3, but insignificantly different from IgG. Finally, serum specific IgG4 recorded a 100% specificity that was significantly higher than IgG, IgG2, IgG3 and IgG1. They showed cross-reactions with ascariasis, lymphatic filariasis and strongyloidiasis. The results were discussed

Correlation between degree of protection and humoral antibody response in hamsters immunized with somatic and excretory secretory antigens of Ancylostoma ceylanicum.

Correlation between the degree of protection and induced serum antibody response in hamsters immunized with somatic and excretory-secretory (ES) antigens of adult. A. ceylanicum was investigated. Hamsters were immunized with non purified and Sephadex G-200 fractions (F1, F2 and F3) of somatic and ES antigens. The degree of protection was assessed in terms of percent worm reduction compared to controls against challenge infection. Induced humoral antibody response was determined by ELISA. Both somatic and ES antigens had shown moderate to significant protection but the latter was found more immunogenic as highest level of protection (67.02%) was achieved by these antigens. Humoral antibody was found highly elevated in animals immunized with protective doses of somatic and ES antigens. The maximum serum antibody titer i.e. 1:3200 was noticed in animals immunized with high protective dose (64.59% protection) of fraction F1 of ES antigens. Antibody titer correspond to the degree of protection and a positive correlation between induced humoral antibodies and protection level was established.