A Phosphorylcholine-Containing Glycolipid-like Antigen Present on the Surface of Infective Stage Larvae of Ascaris spp. Is a Major Antibody Target in Infected Pigs and Humans

Abstract

BackgroundThe pig parasite Ascaris suum plays and important role in veterinary medicine and represents a suitable model for A. lumbricoides, which infects over 800 million people. In pigs, continued exposure to Ascaris induces immunity at the level of the gut, protecting the host against migrating larvae. The objective of this study was to identify and characterize parasite antigens targeted by this local immune response that may be crucial for parasite invasion and establishment and to evaluate their protective and diagnostic potential.Methodology/Principal FindingsPigs were immunized by trickle infection for 30 weeks, challenged with 2,000 eggs at week 32 and euthanized two weeks after challenge. At necropsy, there was a 100% reduction in worms recovered from the intestine and a 97.2% reduction in liver white spots in comparison with challenged non-immune control animals. Antibodies purified from the intestinal mucus or from the supernatant of cultured antibody secreting cells from mesenteric lymph nodes of immune pigs were used to probe L3 extracts to identify antibody targets. This resulted in the recognition of a 12kDa antigen (As12) that is actively shed from infective Ascaris L3. As12 was characterized as a phosphorylcholine-containing glycolipid-like antigen that is highly resistant to different enzymatic and chemical treatments. Vaccinating pigs with an As12 fraction did not induce protective immunity to challenge infection. However, serological analysis using sera or plasma from experimentally infected pigs or naturally infected humans demonstrated that the As12 ELISA was able to detect long-term exposure to Ascaris with a high diagnostic sensitivity (98.4% and 92%, respectively) and specificity (95.5% and 90.0%) in pigs and humans, respectively.Conclusions/SignificanceThese findings show the presence of a highly stage specific, glycolipid-like component (As12) that is actively secreted by infectious Ascaris larvae and which acts as a major antibody target in infected humans and pigs.

Pro-fibrinolytic potential of the third larval stage of Ascaris suum as a possible mechanism facilitating its migration through the host tissues

“…AsL3 were obtained following the protocol described by Vlaminck et al [16] with minor modifications. Adult female worms of A. suum were collected from the intestines of naturally infected pigs from a local abattoir and dissected in order to extract the uterus and obtain the eggs.…”

Diagnostic tools for soil-transmitted helminths control and elimination programs: A pathway for diagnostic product development

“…Recent technology development efforts have also focused on improved analytical sensitivity, such as molecular assays [ 6 , 14 – 17 ] and enhanced visualization of helminth eggs [ 7 , 18 ]. Another early area of investigation includes serological and urine-based measurements [ 19 , 20 ]. However, all these methods potentially incur additional costs-per-test and resource requirements for STH programs that need to be considered, relative to the benefits of enhanced efficiency and accuracy [ 21 ].…”

Detection of Ascaris lumbricoides infection by ABA-1 coproantigen ELISA

“…The pseudocoelomic fluid was then centrifuged for 15 min at 10,000 × g and 4°C and the supernatant filtered (0.22 μm) and stored at -80°C until use. Adult worm protein extracts were produced as described before [ 26 ]. Briefly, extracts were prepared by grinding the adult worms with a mortar and pestle that was placed in a bath of liquid nitrogen.…”