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Field application of a subunit vaccine against an enteric protozoan disease.

Wallach MG, Ashash U, Michael A, Smith NC - PLoS ONE (2008)

Bottom Line: Progeny of immunized hens excreted significantly less oocysts of various species of Eimeria in their faeces than chicks from unvaccinated hens.These results demonstrate that a vaccine composed of antigens purified from the gametocytes of Eimeria can be used safely and effectively to prevent the deleterious effects of coccidiosis.It is the first subunit vaccine against any protozoan parasite to be successfully applied on a commercial scale.

View Article: PubMed Central - PubMed

Affiliation: Institute for the Biotechnology of Infectious Diseases, University of Technology Sydney, Broadway, Australia. michael.wallach@uts.edu.au

ABSTRACT

Background: Coccidiosis is a major global veterinary health problem in intensively reared chickens. It is caused by apicomplexan parasites of the genus Eimeria.

Principal findings: A subunit vaccine composed of purified antigens from the gametocytes of Eimeria maxima was used to stimulate the production and transfer of maternal antibodies between breeding hens and their hatchlings. The vaccine was injected into hens twice before they began laying eggs. Immunization had no adverse affects on egg laying or health of the hens and resulted in high antibody levels throughout the life of the hens. Progeny of immunized hens excreted significantly less oocysts of various species of Eimeria in their faeces than chicks from unvaccinated hens. Furthermore, the offspring of vaccinated hens developed stronger natural immunity to Eimeria, so that they were resistant to challenge infection even at 8 weeks of age, well after all maternal antibodies had left their circulation. Field trials were conducted in South Africa, Brazil and Thailand, involving at least 1 million progeny of vaccinated hens and at least 1 million positive control birds (raised on feed containing anticoccidial drugs or immunized with a live vaccine) in each country. Additionally, trials were carried out in Israel involving 60 million progeny of vaccinated hens and 112 million positive control birds. There were no significant differences in growth rate, feed conversion ratios or mortality in the offspring of vaccinated hens compared with the positive control chickens in any of these countries regardless of different management practices, different breeds of chickens or climate.

Conclusions: These results demonstrate that a vaccine composed of antigens purified from the gametocytes of Eimeria can be used safely and effectively to prevent the deleterious effects of coccidiosis. It is the first subunit vaccine against any protozoan parasite to be successfully applied on a commercial scale.

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Effect of immunization with purified gametocyte antigens of Eimeria maxima on gametocyte antigen-specific antibody levels in flocks of breeding hens.Commercial broiler breeder hens were vaccinated twice with purified gametocyte antigens (PGA) at 15 and 20 weeks of age. Sera (10–15 samples per flock) were collected at each time point post vaccination from 10 flocks of chickens (six from Israel, two from South Africa, and one each from Argentina and Thailand). The ELISA results are expressed as an S/P ratio, which is calculated as follows: (Sample optical density value – Negative control optical density value)/(Positive control optical density value – Negative control optical density value). Results show the average S/P±Standard Error for the ten flocks at different times post-vaccination. The average S/P for four control flocks from some of the same farms that were tested during the testing period are also shown.
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pone-0003948-g001: Effect of immunization with purified gametocyte antigens of Eimeria maxima on gametocyte antigen-specific antibody levels in flocks of breeding hens.Commercial broiler breeder hens were vaccinated twice with purified gametocyte antigens (PGA) at 15 and 20 weeks of age. Sera (10–15 samples per flock) were collected at each time point post vaccination from 10 flocks of chickens (six from Israel, two from South Africa, and one each from Argentina and Thailand). The ELISA results are expressed as an S/P ratio, which is calculated as follows: (Sample optical density value – Negative control optical density value)/(Positive control optical density value – Negative control optical density value). Results show the average S/P±Standard Error for the ten flocks at different times post-vaccination. The average S/P for four control flocks from some of the same farms that were tested during the testing period are also shown.

Mentions: Hens were bled and ELISA carried out at various time points post-vaccination. The commercial ELISA kit contains 96-well plates coated with affinity purified gametocyte antigens, as well as positive and negative control sera. The ELISA test results are recorded as an S/P ratio, calculated as follows: (Sample optical density value – Negative control optical density value)/(Positive control optical density value – Negative control optical density value). A cut-off S/P value of 0.4 has been determined by the manufacturers (ABIC Ltd, Israel) to indicate a sufficiently high antibody level to confer protective maternal immunity against coccidiosis and is used as a key parameter in the quality control of the commercial ELISA kit. As an example of our typical results, ten breeder flocks from various countries (six from Israel, two from South Africa, and one each from Argentina and Thailand) were monitored throughout their entire laying period (Figure 1). In these immunized flocks, the average ELISA S/P ratio was 0.8 or higher for the first 3 months post-immunization, dropped to 0.6 at 4 months and remained well above the ELISA kit cut-off S/P ratio of 0.4 throughout the hens' laying period. In contrast, control flocks had S/P values of less than 0.4 (0.18±0.1, average±S.D.) throughout the laying period of the hens' life, most often in the 0.1–0.2 range. We believe that the maintenance of the high specific IgG antibody levels in the vaccinated flocks is due to the boosting effect of oocysts that are naturally encountered in every chicken house worldwide. It is conceivable that, on some farms, natural exposure by itself can lead to increased maternal antibody levels, however, without vaccination, these natural titres are likely to be variable, unreliable and relatively non-specific.


Field application of a subunit vaccine against an enteric protozoan disease.

Wallach MG, Ashash U, Michael A, Smith NC - PLoS ONE (2008)

Effect of immunization with purified gametocyte antigens of Eimeria maxima on gametocyte antigen-specific antibody levels in flocks of breeding hens.Commercial broiler breeder hens were vaccinated twice with purified gametocyte antigens (PGA) at 15 and 20 weeks of age. Sera (10–15 samples per flock) were collected at each time point post vaccination from 10 flocks of chickens (six from Israel, two from South Africa, and one each from Argentina and Thailand). The ELISA results are expressed as an S/P ratio, which is calculated as follows: (Sample optical density value – Negative control optical density value)/(Positive control optical density value – Negative control optical density value). Results show the average S/P±Standard Error for the ten flocks at different times post-vaccination. The average S/P for four control flocks from some of the same farms that were tested during the testing period are also shown.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2596963&req=5

pone-0003948-g001: Effect of immunization with purified gametocyte antigens of Eimeria maxima on gametocyte antigen-specific antibody levels in flocks of breeding hens.Commercial broiler breeder hens were vaccinated twice with purified gametocyte antigens (PGA) at 15 and 20 weeks of age. Sera (10–15 samples per flock) were collected at each time point post vaccination from 10 flocks of chickens (six from Israel, two from South Africa, and one each from Argentina and Thailand). The ELISA results are expressed as an S/P ratio, which is calculated as follows: (Sample optical density value – Negative control optical density value)/(Positive control optical density value – Negative control optical density value). Results show the average S/P±Standard Error for the ten flocks at different times post-vaccination. The average S/P for four control flocks from some of the same farms that were tested during the testing period are also shown.
Mentions: Hens were bled and ELISA carried out at various time points post-vaccination. The commercial ELISA kit contains 96-well plates coated with affinity purified gametocyte antigens, as well as positive and negative control sera. The ELISA test results are recorded as an S/P ratio, calculated as follows: (Sample optical density value – Negative control optical density value)/(Positive control optical density value – Negative control optical density value). A cut-off S/P value of 0.4 has been determined by the manufacturers (ABIC Ltd, Israel) to indicate a sufficiently high antibody level to confer protective maternal immunity against coccidiosis and is used as a key parameter in the quality control of the commercial ELISA kit. As an example of our typical results, ten breeder flocks from various countries (six from Israel, two from South Africa, and one each from Argentina and Thailand) were monitored throughout their entire laying period (Figure 1). In these immunized flocks, the average ELISA S/P ratio was 0.8 or higher for the first 3 months post-immunization, dropped to 0.6 at 4 months and remained well above the ELISA kit cut-off S/P ratio of 0.4 throughout the hens' laying period. In contrast, control flocks had S/P values of less than 0.4 (0.18±0.1, average±S.D.) throughout the laying period of the hens' life, most often in the 0.1–0.2 range. We believe that the maintenance of the high specific IgG antibody levels in the vaccinated flocks is due to the boosting effect of oocysts that are naturally encountered in every chicken house worldwide. It is conceivable that, on some farms, natural exposure by itself can lead to increased maternal antibody levels, however, without vaccination, these natural titres are likely to be variable, unreliable and relatively non-specific.

Bottom Line: Progeny of immunized hens excreted significantly less oocysts of various species of Eimeria in their faeces than chicks from unvaccinated hens.These results demonstrate that a vaccine composed of antigens purified from the gametocytes of Eimeria can be used safely and effectively to prevent the deleterious effects of coccidiosis.It is the first subunit vaccine against any protozoan parasite to be successfully applied on a commercial scale.

View Article: PubMed Central - PubMed

Affiliation: Institute for the Biotechnology of Infectious Diseases, University of Technology Sydney, Broadway, Australia. michael.wallach@uts.edu.au

ABSTRACT

Background: Coccidiosis is a major global veterinary health problem in intensively reared chickens. It is caused by apicomplexan parasites of the genus Eimeria.

Principal findings: A subunit vaccine composed of purified antigens from the gametocytes of Eimeria maxima was used to stimulate the production and transfer of maternal antibodies between breeding hens and their hatchlings. The vaccine was injected into hens twice before they began laying eggs. Immunization had no adverse affects on egg laying or health of the hens and resulted in high antibody levels throughout the life of the hens. Progeny of immunized hens excreted significantly less oocysts of various species of Eimeria in their faeces than chicks from unvaccinated hens. Furthermore, the offspring of vaccinated hens developed stronger natural immunity to Eimeria, so that they were resistant to challenge infection even at 8 weeks of age, well after all maternal antibodies had left their circulation. Field trials were conducted in South Africa, Brazil and Thailand, involving at least 1 million progeny of vaccinated hens and at least 1 million positive control birds (raised on feed containing anticoccidial drugs or immunized with a live vaccine) in each country. Additionally, trials were carried out in Israel involving 60 million progeny of vaccinated hens and 112 million positive control birds. There were no significant differences in growth rate, feed conversion ratios or mortality in the offspring of vaccinated hens compared with the positive control chickens in any of these countries regardless of different management practices, different breeds of chickens or climate.

Conclusions: These results demonstrate that a vaccine composed of antigens purified from the gametocytes of Eimeria can be used safely and effectively to prevent the deleterious effects of coccidiosis. It is the first subunit vaccine against any protozoan parasite to be successfully applied on a commercial scale.

Show MeSH
Related in: MedlinePlus