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Evaluation of the safety and efficacy of vaccination of nursing pigs with living tachyzoites of two strains of Toxoplasma gondii
Ist Teil von
The Journal of parasitology, 1994-06, Vol.80 (3), p.438-448
Ort / Verlag
Lawrence, KS: American Society of Parasitologists
Erscheinungsjahr
1994
Link zum Volltext
Quelle
MEDLINE
Beschreibungen/Notizen
The safety of vaccination and persistence and distribution of Toxoplasma gondii stages within tissues following vaccination were examined in 3-day-old nursing pigs vaccinated with living tachyzoites by intravenous and subcutaneous routes of either the TS-4 mutant strain or its parent RH strain of T. gondii. The efficacy of vaccination of nursing pigs with the TS-4 mutant was also examined in pigs challenged orally with oocysts following vaccination. Pigs were vaccinated with 3 × 105living tachyzoites when 3 days old and boosted with 3 × 105living tachyzoites when 17 days old. Group 1 had 2 pigs vaccinated intravenously (i.v.) with Hanks' balanced salt solution (HBSS) and served as a vaccination control. Group 2 had 5 pigs vaccinated i.v. with tachyzoites of the TS-4 mutant; 3 pigs were used to examine the safety, persistence, and distribution of the TS-4 mutant and 2 were used for oocyst challenge. Group 3 had 5 pigs vaccinated i.v. with tachyzoites of the RH strain and all were used to examine the safety, persistence, and distribution of the RH strain within their tissues. Group 4 had 3 pigs vaccinated subcutaneously (s.c.) with tachyzoites of the TS-4 mutant; 1 was used to determine the persistence and distribution of the TS-4 mutant within its tissues and the other 2 pigs were used for GT-1 oocyst challenge studies. Group 5 had 3 pigs vaccinated s.c. with tachyzoites of the RH strain and all were used to examine the safety, persistence, and distribution of the RH strain within their tissues. None of the control pigs or pigs vaccinated with the TS-4 mutant developed clinical signs of disease or died prior to oocyst challenge. The TS-4 mutant was not reisolated from the tissues of vaccinated pigs nor were microscopic lesions present in the tissues of pigs that had been killed and examined at necropsy. Severe disease with clinical signs consisting of dyspnea, inactivity, diarrhea, and ocular lesions was observed in the group 3 pigs vaccinated i.v. with the RH strain. One pig died 7 days after initial vaccination. Microscopic lesions were observed in numerous tissues of all group 3 pigs. Swelling, erythema, and ulcers were observed at the site of inoculation in the group 5 pigs that were vaccinated s.c. with the RH strain. Minimal to no microscopic lesions were observed in these group 5 pigs. The RH strain was reisolated from pigs in both groups vaccinated with this strain. Control pigs and pigs vaccinated with the TS-4 mutant were challenged orally with 8 × 104oocysts of the GT-1 strain at 33 days of age. Vaccination with the TS-4 mutant by intravenous or subcutaneous routes did not prevent tissue cyst formation in pigs following oocyst challenge. However, results of bioassays in mice indicated that pigs given the TS-4 mutant s.c. had fewer tissue cysts in their tissues after oocyst challenge.