Antibodies to surface epitopes of the carbohydrate larval antigen CarLA are associated with passive protection in strongylid nematode challenge infections

Abstract

Sheep were immunized by multiple truncated infections with the gastrointestinal nematodes Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia circumcincta. Three infections with T. colubriformis of 14 days plus five booster doses of L3 stimulated highly effective protection against challenge (99%). Three infections of 14 days plus three booster doses with H. contortus also resulted in significant protection against challenge infection (87%), but the same procedure was not effective for T. circumcincta. Antibodies derived from gastrointestinal mucus of these immunized sheep were tested for their ability to reduce worm burden following injection of antibody-coated exsheathed larvae into the abomasum (H. contortus and T. circumcincta) or duodenum (T. colubriformis) of nematode-naïve sheep in a passive immunity test. The IgG fraction from the mucus of immunized sheep reduced worm burdens by 62%, 76% and 91% in three tests with T. colubriformis but was not effective for either of the abomasal dwelling nematodes H. contortus and T. circumcincta. Antibodies in immune mucus predominantly recognized two larval surface antigens on immunoblots of L3 extract, a high MW surface glycoprotein and the carbohydrate larval antigen (CarLA). Antibodies raised against purified T. colubriformis glycoprotein Tc-120 and CarLA were tested in the passive immunity model and it was found that only the antibody against CarLA resulted in a significant reduction of infection (87%). The protective anti-CarLA antibodies strongly recognized the surface of living T. colubriformis L3. Antibodies from abomasal mucus of sheep immunized by H. contortus and T. circumcincta infections reacted weakly with CarLA and the larval surface and did not reduce worm counts in a passive immunity test. The results provide further evidence that the larval surface carbohydrate antigen CarLA has potential as a mucosal immunogen for a strongylid nematode vaccine.

Immune and haematological parameters of Blackbelly ewes infected with gastrointestinal nematodes

“…The supernatant, containing CWA, was collected and stored at -20 °C. In addition, hot water extraction of L3 (HWEL) was performed for surface antigens from exsheathed larvae of H. contortus and T. colubriformis (Harrison et al, 2008). Protein concentration of both antigenic preparations was determined with the method by Bradford (1976) and confi rmed by SDS-PAGE.…”

Current Status for Gastrointestinal Nematode Diagnosis in Small Ruminants: Where Are We and Where Are We Going?

“…However, false positive readouts due to nonspecific antigen-protein binding terminated development of an assay [68]. The revelation that protective antibodies against larvae potentially derived from the gut associated lymphoid tissue in the intestinal mucosa could be easily detected in the saliva has resulted in the commercialisation of a diagnostic test, the CarLA Saliva Test, for selection of GIN parasite resistant animals [58, 66, 69]. Detection of salivary antibodies is advantageous in comparison to WEC due to earlier detection (at the L3 stage rather than the adult) and saliva from sheep is more appealing for producers to collect than faeces.…”

Vaccinomics for the Major Blood Feeding Helminths of Humans

“…For example, the H-gal-GP and H11 antigen complexes from H. contortus are heavily glycosylated, a feature that permitted their initial purification and identification of native protein via lectin affinity chromatographies (Knox and Smith, 2001). Where they have been characterized at the molecular level, helminth glycans offer great promise as vaccine candidates (Cummings and Nyame, 1999;Harrison et al, 2008;Maass et al, 2009). …”