Table 1.
Long term trickle infection of pigs with A. suum results in reduced liver white spots and L4 recovered from the small intestine 14 days post challenge infection with 2,000 infective eggs.
Fig 1.
The detection of a 12kDa A. suum L3 antigen in the L3 PBS extract by intestinal antibodies.
IgG and IgA antibodies purified from the supernatant of purified mononuclear cells (MNC) from mesenteric lymph nodes or the intestinal mucus were used to screen the L3 PBS extract on Western blot. Antibodies from immune pigs (Group B) strongly react to an antigen migrating at 12 kDa. Pigs from the challenged control group (Group A) also had antibodies against the 12kDA antigen, but the reactivity on Western blot was lower than in immune pigs. Conjugate alone (cc) did not react with the antigen.
Fig 2.
The As12 antigen is produced and secreted by the early L3 stage of A. suum and is also present in A. lumbricoides L3.
(A) The detection of the As12 antigen by IgG antibodies purified from the intestinal mucus of A. suum immune pigs in PBS extracts of different A. suum life stages (Egg L3, L3 E/S, Lung L3, L4, L5, Adult male and female worms) and (B) in the PBS extract of A. suum and A. lumbricoides L3.
Fig 3.
Exploring the properties and composition of the As12 antigen.
(A) Coomassie staining, carbohydrate staining and Western blot developed with mucosal IgG antibodies from immune pigs (Group B) of the complete L3PBS extract (1), the pellet after Folch extraction (2), the upper ‘methanol phase’ (3) and the lower ‘chloroform phase’ (4). (B) Recognition of the As12 antigen by mucosal IgG antibodies from immune pigs after chemical or enzymatic treatments of the A. suum L3 PBS extract: untreated (1&17); overnight digestion at 37°C with pronase (2); lipase (3); trypsin (4); pepsin (5); overnight incubation at 37°C (6), 60°C (7) and 90°C (8); overnight incubation with 20mM periodic acid at 37°C (9) and 60°C (10), 1M NaOH at 37°C (11) and 60°C (12), 1M trifluoracetic acid at 37°C (13) and 60°C (14); 1M HCl at 37°C (15) or 60°C (16); 48 hrs incubation in 48% HF at 4°C (18); overnight incubation at 37°C without (19) or with PNGase-F (20) and 48 hrs. incubation at 37°C with (21) or without (22) Jack Bean ß-N-Acetylglucosaminidase. (C) Recognition of A. suum L3 PBS antigens by purified mucosal IgG antibodies from immune pigs (1) and specific anti-phosphorylcholine antibodies (TEPC-15) (2).
Fig 4.
Mucosal antibodies from immune pigs recognize antigens on the surface of A. suum L3 that likely contain phosphorylcholine groups and are actively secreted by living larvae.
(A) UV-microscopy images (400x) of A. suum L3 larvae stained by mucosal antibodies from naïve pigs, challenge control pigs (Group A) or immunized pigs (Group B) and incubated with FITC labeled anti-pig IgG. (B) UV-microscopy image (400x) of A. suum L3 larva partially stained by mucosal antibodies from immune pigs and incubated with FITC labeled anti-pig IgG. (C) A UV-microscopy image (400x) of an A. suum L3 larva stained by anti-PC antibodies and (D) a stained larva in the process of shedding these antigen-antibody complexes. (E) The percentage of A. suum L3 stained by mucosal antibodies from immune pigs decreased over time when L3 were kept alive in culture media (dotted line) but not when L3 were killed after staining (full line) (P < 0.01).
Fig 5.
Vaccinating pigs with a purified As12 fraction in combination with AlOH adjuvant does not induce protection against subsequent challenge infection despite increased serum antibody responses to the antigen.
(A) The number of white spots counted on the liver and the number L4 recovered from the small intestine at necropsy 14 days after a challenge infection with 1,000 infective A. suum eggs in 6 pigs vaccinated with As12 + AlOH (Group A) and 6 adjuvant control pigs (GroupB). (B) The total IgG response in the serum directed against the As12 antigen fraction was significantly elevated in the vaccinated group one week after the third immunization, at the time of infection (Day 35) and the day of necropsy (Day 49) in comparison to the adjuvant control group (P < 0.01).
Fig 6.
Pigs and humans infected with Ascaris develop antibodies to the As12 antigen.
(A) The total IgG response to the As12 purified fraction over time in pigs exposed to trickle infections (500 A. suum eggs/week) over a 30-week time period shows significantly higher IgG responses from 6 weeks after the first challenge infection onwards (P < 0.05). (B) The serological response to the As12 fraction of 91 experimentally infected pigs increased significantly after 7 and 14 weeks of infection (P < 0.001). The optimal cut-off was determined by ROC analysis and set at 0.50 (dotted line). (C) Relative ELISA recognition of As12 by either TEPC-15 monoclonal antibodies or purified mucosal IgG antibodies from trickle infected pigs from group B after pre-incubation with increasing concentrations of PC-Cl salt (0, 10 and 25 μg/ml). (D) Total IgG response against As12 was significantly higher in the 25 A. lumbricoides infected humans than in the 20 uninfected or 24 hookworm-infected individuals (P < 0.001). The cut-off was set at an OD of 0.26 by ROC analysis (dotted line).