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

item VLAMINCK, JOHNNY - Ghent University
item MARTINEZ-VALLADARES, MARIA - University Of Leon
item DEWILDE, SYLVIA - University Of Antwerpen
item MOENS, LUC - University Of Antwerpen
item TILLEMAN, KELLY - Ghent University
item DEFORCE, DIETER - Ghent University
item Urban, Joseph
item CLAEREBOUT, EDWIN - Ghent University
item VERCRUYSSE, JOSEF - Ghent University
item GELDHOF, PETER - Ghent University

Submitted to: Parasite Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2011
Publication Date: 4/1/2011
Citation: Vlaminck, J., Martinez-Valladares, M., Tilleman, K., Deforce, D., Dewilde, S., Moens, L., Urban Jr, J.F., Claerebout, E., Vercruysse, J., Geldhof, P. 2011. Immunizing pigs with Ascaris suum hemoglobin increases the inflammatory response in the liver but fails to induce a protective immunity. Parasite Immunology. 33:250-254.

Interpretive Summary: The large round worm parasite of pigs, Ascaris suum, continues to be an economic problem in swine production facilities worldwide, and the problem has re-emerged as an added health concern where pig management provides access to soil and restricts the use of anthelmintic drugs. A strategy to overcome these limitations is to develop vaccines to protect pigs against infection and reduce the intensity of the worm numbers and tissue reactions in the liver and lung that result from the migration of the larval stage of the infection through the body. The worms produce a hemoglobin protein that appears to be essential for survival in the host and is excreted by different stages of the worm in the host. This protein was used as a potential vaccine candidate to induce immunity to infection. It was found that immunization resulted in no significant reduction in the numbers of adult worms found in vaccinated pigs after exposure to an infection with Ascaris eggs. There was, however, more white spots seen in the livers of vaccinated pigs indicating that the immune response contributed to a stronger reaction to the migrating larvae. These results did not succeed in supporting the use of this Ascaris hemoglobin for vaccination, but indicated that it contributes to greater liver reactivity that can result in economic loss. This information will be of interest to the swine health industry and scientists that develop strategies to control parasitic infection in livestock through vaccination.

Technical Abstract: To determine whether purified Ascaris suum hemoglobin (AsHb) is a suitable vaccine candidate for the control of Ascaris infections, pigs were 30 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, 35 significantly more white spots were counted on the livers of vaccinated pigs on day 14 (+86%) and day 28 (+118%) p.i. compared with non-vaccinated controls. To investigate whether the increased immune reactivity 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 analyzed by RT-PCR and 40 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.