Vaccination of pigs with Toxoplasma gondii antigens incorporated in immunostimulating complexes (iscoms)

Abstract

Immunity to Toxoplasma gondii was studied in pigs, after vaccination with T. gondii antigens incorporated into immunostimulating complexes. Nine pigs (group 1 - G1) were inoculated subcutaneously with T. gondii iscoms (LIV-5 sample) and three doses were given at 21 and 13 day-intervals. The results were compared in other three groups of nine pigs each: animals in group 2 (G2) were immunized with the LIV-5 antigens without Quil A, animals in group 3 (G3) were inoculated with tachyzoites of RH T. gondii isolate, and animals in group 4 (G4) received no vaccination. Four animals were neither vaccinated nor challenged with T. gondii (group 5 - G5). Thirty days after vaccination, pigs were challenged orally with 5´10(4) oocysts at AS-28 T. gondii isolate. Euthanasia was carried out 47 days after challenge and specimens of the heart, muscle, brain, liver, tongue and retina were inoculated into mice. Three out of nine pigs from G2 and one out of nine pigs from G4 showed hypertermia after the challenge. Antibody response was analysed by indirect fluorescent antibody test. The first iscom immunization (G1) induced low antibody levels, the second and third produced high antibody levels, similarly to the RH isolate infection (G3). Western blotting analysis indicated that the antibody response in animals in G1, after challenge, was more intense than in animals in the non-vaccinated group. T. gondii was not isolated by bioassays from tissues of iscom vaccinated pigs, while recovery was obtained from four animals in G4, one in G2 and one in G3.

Vaccination of pigs with the S48 strain of Toxoplasma gondii – safer meat for human consumption

“…It has previously been reported that as little as one tissue cyst (containing possibly thousands of infective bradyzoites) is enough to cause infection [ 39 ]. Other research, which has studied the vaccination of pigs to reduce tissue cyst burden, has mainly focused on microscopic identification of tissue cysts and/or detection of parasite DNA from mice used in the bioassay [ 21 , 23 - 25 , 35 , 40 , 41 ]. In these studies there is no detailed information about mouse survival and clinical signs of T. gondii during the bioassay itself.…”

QuilA-Adjuvanted T. gondii Lysate Antigens Trigger Robust Antibody and IFNγ+ T Cell Responses in Pigs Leading to Reduction in Parasite DNA in Tissues Upon Challenge Infection

“…In addition, there is a knowledge gap whether this vaccine offers protection against T. gondii infection in other livestock species. Vaccination of pigs with T. gondii antigens incorporated in ISCOMs (immunostimulating complexes) elicited humoral immune responses, however it was not assessed if this vaccine affects the number of tissue cysts after challenge with T. gondii (15). Recently, it has been demonstrated that vaccination of pigs with T. gondii S48 strain might reduce the parasite load in skeletal muscles (16).…”

Protection against Toxoplasma gondii cysts in pigs immunized with rROP2 plus Iscomatrix

“…Kringel et al (2004) used tachyzoites from the RH strain plus CpG-oligodeoxynucleotides to infect pigs and observed 10 times more anti-T. gondii IgG from the immunized pigs. Freire et al (2003) showed that an Iscom + T. gondii surface antigens (SAgs) vaccine for pigs was capable of stimulating a humoral immune response. Jongert et al (2008) immunized pigs with a DNA vaccine expressing T. gondii GRA1 and GRA7, and they produced high levels of IgG antibodies.…”

“…Previous studies have used live vaccines and killed vaccines to protect pigs against T. gondii cyst formation (Dubey et al, 1991(Dubey et al, , 1994Pinckney et al, 1994;Freire et al, 2003;Kringel et al, 2004;Garcia et al, 2005;Cunha et al, 2012;Burrells et al, 2015). However, live vaccines (RH and S48) carry the risk of reverting to virulence and becoming infective for humans; therefore, it is essential to produce a killed vaccine against T. gondii (Burrells et al, 2015).…”