Veterinary vaccines against Toxoplasma gondii

Moredun Research Institute, Pentlands Science Park, Edinburgh.
Memórias do Instituto Oswaldo Cruz (Impact Factor: 1.59). 04/2009; 104(2):246-51. DOI: 10.1590/S0074-02762009000200018
Source: PubMed


Toxoplasma gondii has a very wide intermediate host range and is thought to be able to infect all warm blooded animals. The parasite causes a spectrum of different diseases and clinical symptoms within the intermediate hosts and following infection most animals develop adaptive humoral and cell-mediated immune responses. The development of protective immunity to T. gondii following natural infection in many host species has led researchers to look at vaccination as a strategy to control disease, parasite multiplication and establishment in animal hosts. A range of different veterinary vaccines are required to help control T. gondii infection which include vaccines to prevent congenital toxoplasmosis, reduce or eliminate tissue cysts in meat producing animals and to prevent oocyst shedding in cats. In this paper we will discuss some of the history, challenges and progress in the development of veterinary vaccines against T. gondii.

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    • "Although Toxovax (S48 strain), a live vaccine, has been effective in preventing toxoplasmosis in sheep, it is unfortunately not suitable for human use. Thus, the vaccine against human toxoplasmosis remains an unsolved problem [10] [11]. T. gondii expresses several antigens that have been identified as potential vaccine candidates. "
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    ABSTRACT: Toxoplasmosis, responsible for ocular impairment, is caused by Toxoplasma gondii. We investigated the effect of Toxoplasma excretory-secretory antigens (ESA) on parasite load and distribution in the eye tissue of a murine model. Case and control groups were immunized with ESA and PBS, respectively. Two weeks after the second immunization, the mice were challenged intraperitoneally with virulent RH strain of Toxoplasma; eye tissue samples of both groups were collected daily (days 1, 2, 3, and the last day before death). Parasite load was determined using real-time quantitative PCR targeted at the B1 gene. Compared to the control group, infected mice that received ESA vaccine presented a considerable decrease in parasite load in the eye tissue, demonstrating the effect of ESA on parasite load and distribution. Diminution of parasite load in mouse eye tissue indicated that ESA might help control disease-related complications and could be a valuable immunization candidate against ocular toxoplasmosis. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Comparative Immunology Microbiology and Infectious Diseases 10/2014; 37(5-6):369-374. DOI:10.1016/j.cimid.2014.10.003 · 2.02 Impact Factor
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    • "This vaccine is based on the " incomplete " S48 strain, which is not able to form tissue cysts or oocysts, the main infective parasite stages. After inoculation into the host, the tachyzoites of the S48 strain undergo limited intracellular multiplication that primes a protective immune response (Innes et al., 2009b). Tissues from S48 immunized lambs did not transmit the infection to susceptible mice or cats if ingested (Wilkins et al., 1988). "
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    ABSTRACT: This study evaluates the influence of immunizing lambs with the incomplete S48 strain of Toxoplasma gondii, on parasite dissemination following a live oral challenge with a complete strain of T. gondii (M4). Lambs were culled at 14, 28 and 42 days post challenge. Parasite DNA was detected at significantly (p < 0.0001) lower levels in samples from the vaccinated/challenged group (0% in heart and 5.9% in skeletal muscles), when compared to the non-vaccinated/challenged animals (75% heart, 87.9% skeletal muscle). S48 T. gondii DNA was found in muscle or lymph nodes until 42 days post infection, suggesting that parasite DNA or tachyzoites could persist longer after immunization than previously thought. Non-vaccinated/challenged animals showed more frequent lesions in muscles and central nervous system than the vaccinated animals. These results demonstrate that vaccination of lambs with the incomplete S48 T. gondii strain, can protect against establishment of tissue cysts following challenge with a complete strain of T. gondii. Consumption of undercooked meat containing T. gondii cysts is a major route of transmission to people, therefore vaccination of food animals may improve the safety of meat for human consumption.
    Veterinary Parasitology 07/2014; DOI:10.1016/j.vetpar.2014.07.003 · 2.46 Impact Factor
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    • "Toxovax is the only commercially accessible vaccine against Toxoplasma infection for sheep. It is a live attenuated vaccine produced of S48 strain of T. gondii (Buxton, 1993; Innes et al., 2009). To date, the production of vaccine against human toxoplasmosis was not successful. "
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    ABSTRACT: Excretory secretory antigens (ESAs) of Toxoplasma gondii are one of the candidates for immunization against toxoplasmosis. For evaluation of immunization, we determined the kinetics of the distribution of Toxoplasma and parasite load in different tissues of mice immunized by ESAs. In this experimental study, 36 mice in case (n=18) and control (n=18) groups were immunized with ESAs and PBS, respectively. After 2 weeks, mice were challenged intraperitoneally with Toxoplasma virulent RH strain. Blood and different tissues (brain, spleen, liver, heart, kidney, and muscle) were collected daily after challenge (1, 2, 3 and last day before death). Parasite load was calculated using Real time QPCR targeted at the B1 gene. ESAs as vaccine in different tissues showed various effects. However, infected mice which received the vaccine in comparison with control group, displayed a drastically decreasing in parasite burden, in their blood and tissues (P= 0.000). These results indicated that ESAs with reduction of parasite load in different tissues of host could be evaluable candidate for the development of immunization strategies against toxoplasmosis.
    Experimental Parasitology 05/2014; 143(1). DOI:10.1016/j.exppara.2014.05.008 · 1.64 Impact Factor
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