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Strategies for novel control programmes via vaccination in coccidia
Symposium (C) I Parasitology
International
47 (Suppl.) (1998)
71-95
81
C-7. Coccidiosis in Domestic and Companion Animals s-c7-1
THE ROLE OF THE APICAL COMPLEX IN HOST CELL INVASfON BY COCCIDIA
Sasai. t$ Department of Veterinary University, Osaka, Japan
Medicine,
Osaka
Prefecture
The role of the apical complex in host-cell invasion by coccidia. Coccidia are ubiquitous protozoan parasites that require an intracellular site for growth and replication. There seems to be two mechanisms involved in sporozoite invasion into host cell. One is that the parasite may enter a cell by phagocytosis or engulfment without resulting its own death inside the cell. The other is that communication of the parasite’s apical pole and the host cell membrane may evoke a sequence of invasion steps different from that of phagocytosis. This invasion process initiated by the cooperation of the host cell and the parasite, follwed by a series of complicated steps such as the host cell recognition; parasite movements by means of a subpellicular microtubule cytoskeleton; cell to cell adhesion; regulated protein secretion from three distinct parasite organelles called micronemes, rhoptries, and dense granules; conoid penetration; induction of a parasitophorous vacuole; interiorization of the parasite. This invasion is an active, oriented and specific process depending on chemical factors such as energy sources, cations, as well as microviscosity and membrane structures. In this study, it is aimed to provide an up-to-date coverage of the role of the apical complex in host cell
s-c74
PROGRESS TOWARDS A VACCINE AGAINST POULTRY COCCIDIOSIS : THE POTENTIAL HARNESSING OF MATERNAL IMMUNITY
Smith University
of Technology,
Sydney, Australia
Several species within the genus, Eimeria, cause the disease known as coccidiosis in chickens. Immunity to these parasites is multifactorial and extremely effective. The primary means by which birds defend themselves against Eimeria is thought to be by generation of specific T cells and production of cytokines, most notably, interferon-gamma. However, antibodies are also able to inhibit Eimeria. This has been demonstrated by injecting antibodies from immune chickens into naive chickens with resultant concommitant resistance to infection; this resistance is dependent on the relative concentration of specific antibodies. In nature, a parallel situation exists, namely, the ability of hens to protect their hatchlings via transfer of maternal IgG antibodies through the egg yolk. This is an important primary defence against Eimeria for birds early in their life. These protective maternal antibodies have been used to identify antigens that may be useful components in a subunit vaccine against Eimeria in chickens. Paramount amongst these antigens are glycoproteins of 56, 82 and 230 kDa isolated from the macrogametocytes of Eimeria maxima, though promising antigens have also been identified in merozoites. These antigens, formulated in suitable adjuvants, can be injected into broiler breeder hens to stimulate a strong antibody response. These antibodies are subsequently passed on to broiler chicks to protect them against clinical coccidiosis caused by several species of Eimeria for up to seven weeks, making this a very economic means of parasite control. The goal of this immunoprophylactic strategy, based on maternal immunity, is to reduce oocyst contamination of broiler house litter and thereby inhibit transmission of the parasite. Transmission blocking vaccines for other Apicomplexan parasites, including Cryptosporidium and Plasmodium. are also conceivable and the principles established by studying poultry coccidiosis may be beneficial in devising strategies to control these other parasites.
invasion by coccidia. S-C7-2 DIAGNOSIS
SCORING
s-c7-4 OF
POULTRY
TO NUCLEOTIDE
EIMERIA:
FROM SEQUENCES
LESION
er BE*, Thebo PL*, Mattsson JG”, Tomley FM*‘, Shirley MW”. Uggla A* *Swedish University of Agriculrurai Sciences & National Veterinary Institute, Dept of Parasitology, Uppsala, Sweden; **Instimte for Animal Health, Compton Laboratory, UK Avian coccidiosis. caused by seven species of Eimerio is economically one of the most important diseases in the modem poultry industry. We the degree of pathogenicity of E. ncerwlinn, E. brunetti, E. maxima. E. mitis, E. necatrii and E. tenella is considered medium to high. E. praecox is only mildly pathogenic. Several species often occur concomitantly in their host. Accurate identification of Eimena species is indispensable for the development of any further control method but can be diicult and time consuming. Traditionally it implies consideration of biological features of the parasites, such as prepatent period. site of development within the intestine, clinical signs and morphological appearance of oocysts and endogenous stages in the mucosa of the intestine. The presence of parasites can therefore be confirmed by exammation of the host post mortem. However, a definitive identification requires more accurate laboratory investigations including methods such as isoenzyme analysis and techniques that detect variations in DNA. Our laboratories have performed a variety of studies for identification of and differentiation between species of poultry Eimeriu: Extensive isoenzyme analysis identified all seven species present in Sweden. Furthermore. a polymerase chain reaction (PCR)-based technique was applied by the development of species-specific primers based on their Internal Transcribed Spacer 1 (ITS 1) Regions. The primers were tested in vitro. with clinical samples as well as ‘on mixed/field samples Altemativly these primers were applied as probes in a Paper Chromatography Hybridisation Assay (DACHA) and each probe reliably detected its corresponding target DNA from pure as well as mlxed blotu-labelled PCR products.
STRATEGIES FOR NOVEL CONTROL PROGRAMMISS VIA VACCINATION IN COCCIDIA Tomlev F, Smith A and Shirley M Institute for Animal Health, Compton, Berkshire UK Coccidia sre the most widespread sad economically significant protozoan parasites that at?lict the intensive farming industry. They are of particular importance to the poultry farmer where seven species of the genus Einreria are capable of infecting chickens. The prophylactic use of anti-coccidial drugs is the main method of control but the continued global emergence of drugresistant strains and concerns about the need to eliminate residues in food now confront the use of drugs. Recently, novel live attenuated vaccines have been developed and these are having a major impact on the welfare of birds kept for egg production in many countries. The proof of principle for a safe comprehensive vaccination strategy has thus been clearly demonstrated. An important feature of the host response to infection with coccidial parasites is that a strong protective immunity develops quickly. This feature underpins the ongoing success with live vaccines and also supports the premise that other immunological strategies are an attainable goal. Studies that focus on the interactions between the host and the parasite continue to improve our understanding of the events that occur during the early stages of the parasite life-cycle, in particular they provide a detailed view of the processes by which the parasites enter the cells of the host, at both a structural and molecular level. The early stages of the developing parasite are the major targets of the response by the immune host and characterisation of the molecules and antigens displayed by the parasites during invasion will help to define targets for the host effector response
International
47 (Suppl.) (1998)
71-95
81
C-7. Coccidiosis in Domestic and Companion Animals s-c7-1
THE ROLE OF THE APICAL COMPLEX IN HOST CELL INVASfON BY COCCIDIA
Sasai. t$ Department of Veterinary University, Osaka, Japan
Medicine,
Osaka
Prefecture
The role of the apical complex in host-cell invasion by coccidia. Coccidia are ubiquitous protozoan parasites that require an intracellular site for growth and replication. There seems to be two mechanisms involved in sporozoite invasion into host cell. One is that the parasite may enter a cell by phagocytosis or engulfment without resulting its own death inside the cell. The other is that communication of the parasite’s apical pole and the host cell membrane may evoke a sequence of invasion steps different from that of phagocytosis. This invasion process initiated by the cooperation of the host cell and the parasite, follwed by a series of complicated steps such as the host cell recognition; parasite movements by means of a subpellicular microtubule cytoskeleton; cell to cell adhesion; regulated protein secretion from three distinct parasite organelles called micronemes, rhoptries, and dense granules; conoid penetration; induction of a parasitophorous vacuole; interiorization of the parasite. This invasion is an active, oriented and specific process depending on chemical factors such as energy sources, cations, as well as microviscosity and membrane structures. In this study, it is aimed to provide an up-to-date coverage of the role of the apical complex in host cell
s-c74
PROGRESS TOWARDS A VACCINE AGAINST POULTRY COCCIDIOSIS : THE POTENTIAL HARNESSING OF MATERNAL IMMUNITY
Smith University
of Technology,
Sydney, Australia
Several species within the genus, Eimeria, cause the disease known as coccidiosis in chickens. Immunity to these parasites is multifactorial and extremely effective. The primary means by which birds defend themselves against Eimeria is thought to be by generation of specific T cells and production of cytokines, most notably, interferon-gamma. However, antibodies are also able to inhibit Eimeria. This has been demonstrated by injecting antibodies from immune chickens into naive chickens with resultant concommitant resistance to infection; this resistance is dependent on the relative concentration of specific antibodies. In nature, a parallel situation exists, namely, the ability of hens to protect their hatchlings via transfer of maternal IgG antibodies through the egg yolk. This is an important primary defence against Eimeria for birds early in their life. These protective maternal antibodies have been used to identify antigens that may be useful components in a subunit vaccine against Eimeria in chickens. Paramount amongst these antigens are glycoproteins of 56, 82 and 230 kDa isolated from the macrogametocytes of Eimeria maxima, though promising antigens have also been identified in merozoites. These antigens, formulated in suitable adjuvants, can be injected into broiler breeder hens to stimulate a strong antibody response. These antibodies are subsequently passed on to broiler chicks to protect them against clinical coccidiosis caused by several species of Eimeria for up to seven weeks, making this a very economic means of parasite control. The goal of this immunoprophylactic strategy, based on maternal immunity, is to reduce oocyst contamination of broiler house litter and thereby inhibit transmission of the parasite. Transmission blocking vaccines for other Apicomplexan parasites, including Cryptosporidium and Plasmodium. are also conceivable and the principles established by studying poultry coccidiosis may be beneficial in devising strategies to control these other parasites.
invasion by coccidia. S-C7-2 DIAGNOSIS
SCORING
s-c7-4 OF
POULTRY
TO NUCLEOTIDE
EIMERIA:
FROM SEQUENCES
LESION
er BE*, Thebo PL*, Mattsson JG”, Tomley FM*‘, Shirley MW”. Uggla A* *Swedish University of Agriculrurai Sciences & National Veterinary Institute, Dept of Parasitology, Uppsala, Sweden; **Instimte for Animal Health, Compton Laboratory, UK Avian coccidiosis. caused by seven species of Eimerio is economically one of the most important diseases in the modem poultry industry. We the degree of pathogenicity of E. ncerwlinn, E. brunetti, E. maxima. E. mitis, E. necatrii and E. tenella is considered medium to high. E. praecox is only mildly pathogenic. Several species often occur concomitantly in their host. Accurate identification of Eimena species is indispensable for the development of any further control method but can be diicult and time consuming. Traditionally it implies consideration of biological features of the parasites, such as prepatent period. site of development within the intestine, clinical signs and morphological appearance of oocysts and endogenous stages in the mucosa of the intestine. The presence of parasites can therefore be confirmed by exammation of the host post mortem. However, a definitive identification requires more accurate laboratory investigations including methods such as isoenzyme analysis and techniques that detect variations in DNA. Our laboratories have performed a variety of studies for identification of and differentiation between species of poultry Eimeriu: Extensive isoenzyme analysis identified all seven species present in Sweden. Furthermore. a polymerase chain reaction (PCR)-based technique was applied by the development of species-specific primers based on their Internal Transcribed Spacer 1 (ITS 1) Regions. The primers were tested in vitro. with clinical samples as well as ‘on mixed/field samples Altemativly these primers were applied as probes in a Paper Chromatography Hybridisation Assay (DACHA) and each probe reliably detected its corresponding target DNA from pure as well as mlxed blotu-labelled PCR products.
STRATEGIES FOR NOVEL CONTROL PROGRAMMISS VIA VACCINATION IN COCCIDIA Tomlev F, Smith A and Shirley M Institute for Animal Health, Compton, Berkshire UK Coccidia sre the most widespread sad economically significant protozoan parasites that at?lict the intensive farming industry. They are of particular importance to the poultry farmer where seven species of the genus Einreria are capable of infecting chickens. The prophylactic use of anti-coccidial drugs is the main method of control but the continued global emergence of drugresistant strains and concerns about the need to eliminate residues in food now confront the use of drugs. Recently, novel live attenuated vaccines have been developed and these are having a major impact on the welfare of birds kept for egg production in many countries. The proof of principle for a safe comprehensive vaccination strategy has thus been clearly demonstrated. An important feature of the host response to infection with coccidial parasites is that a strong protective immunity develops quickly. This feature underpins the ongoing success with live vaccines and also supports the premise that other immunological strategies are an attainable goal. Studies that focus on the interactions between the host and the parasite continue to improve our understanding of the events that occur during the early stages of the parasite life-cycle, in particular they provide a detailed view of the processes by which the parasites enter the cells of the host, at both a structural and molecular level. The early stages of the developing parasite are the major targets of the response by the immune host and characterisation of the molecules and antigens displayed by the parasites during invasion will help to define targets for the host effector response