Immunizing pigs with Ascaris suum haemoglobin increases the inflammatory response in the liver but fails to induce a protective immunity

Abstract

To determine whether purified Ascaris suum haemoglobin (AsHb) is a suitable vaccine candidate for the control of Ascaris infections, pigs were vaccinated with AsHb in combination with QuilA adjuvant and challenged with A. suum eggs. The number of liver lesions and worms in the intestine was assessed on day 14, 28 and 56 post-infection (p.i.). No significant differences were found in the number of worms recovered between vaccinated and control pigs on any of these days. However, significantly more white spots were counted on the livers of vaccinated pigs on day 14 (+86%) and day 28 (+118%) p.i. compared with nonvaccinated controls. To investigate whether the increased immunoreactivity against the liver stage L3s in vaccinated pigs was triggered by and directed against AsHb, the transcription and expression of AsHb in this larval life stage was analysed by RT-PCR and immunoblotting. The results showed that neither the AsHb transcript nor protein was detectable in freshly hatched L3. However, the immunoblot analysis showed that vaccination with AsHb resulted in the production of antibodies binding to several other antigens of the L3, suggesting that these might be involved in the increased white spot development.

A Cross-Reactive Monoclonal Antibody to Nematode Haemoglobin Enhances Protective Immune Responses to Nippostrongylus brasiliensis

“…Vaccinated pigs showed no difference in faecal egg outputs or worm burdens, but had an increase in white spots on the liver, previously associated with growing resistance to parasite infection [38], [39]. This study also found that haemoglobin was not detectable at the protein level and barely detectable at the transcriptional level in freshly hatched L3 larvae, which may explain why the haemoglobin vaccination was not protective in Ascaris infection.…”

“…Recently, Ascaris haemoglobin was purified by chromatography from pseudocoleomic fluid of Ascaris suum and used to vaccinate pigs, after which they were challenged with Ascaris suum eggs [38]. Vaccinated pigs showed no difference in faecal egg outputs or worm burdens, but had an increase in white spots on the liver, previously associated with growing resistance to parasite infection [38], [39].…”

A comprehensive evaluation of an ELISA for the diagnosis of the two most common ascarids in chickens using plasma or egg yolks

“…Although the pig industry is facing a similar infection threat from roundworms, particularly Ascaris suum , a successful assay has been recently developed to identify infected animals [40, 41]. The data reported in the experimental part of this study were derived from animals with a long-history (≥ 28 weeks) of infection.…”

Diagnosis and Control of Ascariasis in Pigs

“…34e37 This would suggest that white spot formation is the result of secondary immunological reactions to antigenic material released by migratory or dying larvae, which seems to be in accordance with previous studies showing a significant relationship between the number of white spots and antibodies against Ascaris antigens. 12,36,38,39 Although the number of liver lesions indicates the recent passing of migrating A. suum larvae, there exists no relationship whatsoever between the number of lesions and the number of adult parasites that eventually end up in the small intestine. 40 Presence of hepatic lesions predict the presence of intestinal stages with low (29%) positive and high (94%) negative predictive values.…”

“…However, it is possible that this increased immunological response against migrating larvae invoked by the vaccination would manifest itself as increased numbers of lesions in the pig's liver. In a study by Vlaminck et al, 36 significantly more white spots were counted on the livers of vaccinated pigs on day 14 (þ86%) and day 28 (þ118%) after infection compared with non-vaccinated controls. Furthermore, a vaccine against Ascaris will need to be highly protective.…”