Biomedical subjects

H D Danforth

Publications and source records attributed to H D Danforth.

82 records · Page 5Linked to original sources

PubMedDate not supplied

The ultrastructural effect of amprolium medication on development of Eimeria adenoeides in turkeys.

The ultrastructural appearance of first-generation schizonts of Eimeria adenoeides was markedly altered in turkey poults fed 0.0125% amprolium-medicated feed. When compared with development seen in unmedicated control birds 48-72 hr postinoculation (PI), most of the schizonts present in the medicated birds were fragmented, contained enlarged nuclei, had swollen endoplasmic reticulum and Golgi apparatus, and showed no budding of merozoites. Other schizonts were almost completely degenerated and contained pyknotic nuclei, dense cytoplasm, and large intracytoplasmic vacuoles containing membrane whorls or lipid droplets. A few mature schizonts were seen in the medicated poults, and these did not appear to differ ultrastructurally from those seen in unmedicated control birds. Ultrastructurally normal second-generation schizonts and the sexual stages were also seen in small numbers in the medicated turkey poults 72-120 hr PI. Mature sexual stages were seen much earlier in medicated turkeys--at 96 hr PI--than in the unmedicated poults.

Amprolium↗

PubMedDate not supplied

Use of hybridoma antibodies and recombinant DNA technology in protozoan vaccine development.

The use of hybridoma antibodies developed against the sporozoite stage of avian coccidia, coupled with genetic-engineering techniques, has made it possible to begin bird-immunization studies utilizing an Escherichia coli-elicited coccidial protein. The coccidia are currently controlled in the poultry industry by use of anticoccidial compounds, but it now may be possible to use the bird's own immune system for defense against the parasitic infection. Since the sporozoite stage, which initiates the infection in poultry, is quite complex and is made up of hundreds of proteins or antigens, hybridoma antibodies were produced to identify specific antigens. These antigens, once identified, were found in such minute amounts that it became necessary to utilize genetic engineering in order to produce enough protein for immunization studies. One such protein, designated 5401, has been shown to stimulate an antibody response in immunized birds and to impart partial protection against a coccidial challenge infection. The results of these studies indicate that development of a vaccine against coccidial parasites may someday be possible.

Animals↗

PubMedDate not supplied

Development and use of hybridoma antibodies directed against Eimeria acervulina merozoites for cross-reactive and ferritin-labeling studies.

Hybridoma antibodies (Hab) were produced against Eimeria acervulina merozoites that had been separated from extraneous intestinal material by a fiber column technique before injection into mice. The Hab demonstrated three different immunofluorescent-antibody (IFA) patterns of tip, surface, or surface-internal fluorescence in or on the merozoites. Some Hab reacted with round immature schizonts, which were also present in the fiber-cleaned merozoite material. Variations in cross-reactivity were seen with a number of Hab tested by IFA with merozoites, sporozoites, and immature schizonts of different coccidial species. Certain Hab were species- and stage-specific, whereas others cross-reacted with some or all stages or species tested. One Hab apparently reacted with only a small percentage of the E. acervulina merozoites in the fiber-cleaned material. The ferritin (Fe)-labeling technique showed that with one Hab, which gave a surface-internal IFA pattern, there was an irregular clumping of the Fe label along the surface of the immature schizont. A heavier deposit of Fe label was seen on the area of the schizont where the merozoite was beginning to form. A heavy uniform labeling of Fe was seen on the surface of the pellicle of the mature merozoites. These results demonstrate that stage-specific and cross-reactive antigens are present in or on the merozoites of E. acervulina, and as shown with one Hab, surface antigens present on the immature schizont are incorporated onto the mature merozoite.

Animals↗

PubMedDate not supplied

A study of the dynamics of the invasion of immunized birds by Eimeria sporozoites.

The invasion of the intestinal epithelium of immunized and unimmunized turkeys and chickens by four species of Eimeria was quantitated. In unimmunized birds, E. adenoeides, E. acervulina, and E. tenella invaded primarily the areas in which first-generation schizonts subsequently developed. Eimeria meleagrimitis invaded a larger area of the intestine. Between 1 and 4 hr postinoculation, the numbers of intracellular sporozoites increased, but their location within the intestine was little changed. When birds were immunized with either of two lower intestinal species, E. adenoeides or E. tenella, and then challenged with the immunizing species, invasion was reduced by 36% to 55%. In contrast, immunizing and then challenging birds with either of two upper intestinal species, E. meleagrimitis or E. acervulina, did not reduce invasion: there were 44% more intracellular sporozoites in E. meleagrimitis-immunized turkeys and 11% more in E. acervulina-immunized chickens than in their unimmunized counterparts.

Animals↗

PubMedDate not supplied

Effects of hybridoma antibodies on invasion of cultured cells by sporozoites of Eimeria.

Hybridoma antibodies (Hab) produced against sporozoites or merozoites of four species of Eimeria were tested for the ability to inhibit the invasion of cultured primary avian kidney cells by sporozoites of Eimeria. Five of 16 Hab that were tested showed inhibitory activity. All five of these Hab were produced against sporozoites and reacted with sporozoite surface antigens or surface/internal antigens. Four Hab produced against merozoites of E. acervulina cross-reacted with sporozoite surface antigens but failed to inhibit invasion. Similarly, Hab reacting with sporozoite anterior tips or refractile bodies had little effect on invasion. Collectively, the data suggest that surface antigens or surface/internal antigens that are unique to the sporozoite stage may influence or be part of the invasion process. Indirect immunofluorescent-antibody tests and ferritin (Fe) labeling combined with electron microscopy indicated differences in binding of two of the Hab to the sporozoite surface membranes. For example, after exposure to Hab 43A6 and a fluorescein-antimouse IgG conjugate, extracellular sporozoites of E. meleagrimitis fluoresced brightly but intracellular sporozoites exhibited little fluorescent label. Sporozoites labeled with Hab 43A6 plus a ferritin-antimouse IgG conjugate that were observed in the process of cell invasion had ferritin on the extracellular portion of the parasite but not on the intracellular portion. Extracellular aggregates of ferritin were observed near the site of invasion. The data suggested that antigens of the sporozoite surface that are recognized by Hab 43A6 are "scraped off" during the invasion of cells. In contrast, after exposure to Hab E5, both extracellular and intracellular sporozoites of E. tenella fluoresced. However, ferritin label was not observed on viable sporozoites, even when they were fixed immediately after the labeling procedure. The antigens recognized by Hab E5 may be associated with parasite secretory products rather than with an integral part of the sporozoite surface membrane.

Animals↗

PubMedDate not supplied

Avian Eimeria: effects of gamma irradiation on development of cross-species immunity in foreign and natural host birds.

Repeated inoculation (immunization) of white leghorn chickens with oocysts of the turkey coccidium, Eimeria adenoeides, resulted in significantly improved weight gain and feed-conversion ratios (feed efficiency) after E. tenella challenge. However, the development E. tenella in the immunized chickens did not differ markedly from that in unimmunized chickens, and intestinal lesions remained severe (greater than 3.0). Apparently improved weight gain and feed efficiency can be maintained in the presence of extensive parasite development. The ability to elicit cross-protective immunity was abrogated when the E. adenoeides oocysts were exposed to 15 kRad of gamma irradiation before inoculation into the chickens. Sporozoites existing from irradiated oocysts of E. acervulina also failed to immunize the chickens against challenge with E. tenella but protected chickens almost completely against homologous challenge with E. acervulina. The results indicate that cross-species immunity is not elicited by all developmentally arrested sporozoites and that the ability to produce cross-species immunity can be destroyed by gamma irradiation of the immunizing species.

Animals↗

PubMedDate not supplied

Protective immunity against coccidiosis elicited by radiation-attenuated Eimeria maxima sporozoites that are incapable of asexual development.

Eimeria maxima oocysts were exposed to various doses of gamma radiation that did not affect sporozoite invasion of intestinal epithelium but did prevent subsequent merogonic development therein. Although merogony and oocyst formation were inhibited, parasites exposed to 12 kRad radiation induced a level of immunity against E. maxima challenge equivalent to that induced by non-irradiated oocysts. Chickens immunized per os with 20 kRad-treated E. maxima oocysts were not protected against coccidial challenge. Immunization of chickens with a single low dose (five oocysts) of non-irradiated (0 kRad) or irradiated (12 kRad) E. maxima was effective in preventing weight depression after coccidial challenge. Immunofluorescence staining of intestinal tissue from chickens infected with irradiated (12 or 20 kRad) or non-irradiated (0 kRad) E. maxima oocysts with developmental stage-specific monoclonal antibodies showed that sporozoite invasion was similar in all groups. However, merogonic development was not observed at any time postinfection in chickens infected with irradiated oocysts, unlike the case with chickens infected with non-irradiated parasites. These results suggest that sporozoite-infected host cells are capable of eliciting complete protection against E. maxima challenge.

Animals↗

PubMedDate not supplied

Eimeria tenella and E. acervulina: differences in ability to elicit cross-species protection as compared with the turkey coccidium, E. adenoeides.

Repeated oral inoculation of turkey poults with large doses (1 x 10(6) oocysts) of the chicken coccidia, Eimeria tenella or E. acervulina, failed to prevent weight loss, poor feed conversion, and intestinal pathology in turkeys challenged with the turkey coccidium, E. adenoeides. Invasion by E. tenella in turkeys was significantly greater than invasion by E. adenoeides in chickens; by 24 hr postinoculation (PI), the numbers of E. tenella and E. adenoeides sporozoites in the ceca had decreased markedly as compared with the numbers that initially invaded, and they did not differ significantly from each other. At 24 hr PI, however, transfer of cecal scrapings from chickens or turkeys inoculated with E. adenoeides produced infection in 53% of the recipient turkeys, but transfer of scrapings from either chickens or turkeys inoculated with E. tenella failed to produce infection in 20 attempts with recipient chickens. Cultured chicken peripheral blood monocytes (PBMs) that were inoculated with E. adenoeides sporozoites contained numerous vesicles that were recognized by the refractile body-specific monoclonal antibody 1209; the number of vesicles was markedly decreased in PBM cultures inoculated with gamma-irradiated E. adenoeides sporozoites. Very few vesicles were detected in the cytoplasm of turkey PBMs that contained E. tenella sporozoites, and none were detected in turkey PBMs containing E. adenoeides sporozoites. The survival of infective sporozoites, along with the secretion of refractile body antigen, may be more critical to the development of cross-species immunity than the number of sporozoites that initially invade the foreign host.

Animals↗

PubMedDate not supplied

Protection against coccidiosis in outbred chickens elicited by gamma-irradiated Eimeria maxima.

In an effort to develop an attenuated coccidiosis vaccine against coccidiosis, we exposed Eimeria maxima oocysts to an optimum dose of gamma irradiation (17 kRad) that does not affect sporozoite invasion of the intestinal mucosa but does prevent asexual parasite development. Irradiated E. maxima oocysts were suspended in gelatin slabs and placed in battery cages for ingestion by 1-day-old chickens. Separate groups of chickens were given gelatin slabs containing nonirradiated E. maxima oocysts or were inoculated per os with either irradiated or nonirradiated E. maxima oocysts. Chickens infected with irradiated or nonirradiated oocysts by either oral inoculation or gel delivery showed a dose-dependent protection against weight loss associated with E. maxima challenge compared with unimmunized controls. In general, nonirradiated oocysts elicited protective immunity at lower immunization doses compared with irradiated oocysts. These experiments were extended to a floor pen study wherein 1-day-old male and female broiler chickens were given irradiated or nonirradiated E. maxima oocysts in gelatin slabs in hatching boxes and challenged at 4 wk of age. A significant reduction (P < 0.05) in lesion scores was observed for chickens immunized with either irradiated or nonirradiated oocysts compared with unimmunized controls. Although no significant difference (P > 0.05) was observed in weight gain between these groups, both male and female chickens inoculated with irradiated E. maxima oocysts showed about a 10% greater weight gain than unimmunized controls. For both male and female chickens, average weights at challenge were greater in groups that were immunized with 17-kRad-irradiated E. maxima oocysts compared with those animals immunized with nonirradiated oocysts.

Administration, Oral↗

PubMedDate not supplied

Evaluation of the efficacy of Eimeria maxima oocyst immunization with different strains of day-old broiler and roaster chickens.

The performances of three different strains of male and female broiler or roaster chickens immunized at 1 day of age with a drug-resistant field isolate of Eimeria maxima were evaluated in battery and floorpen immunization trials. No difference in immunization potential was seen between these strains or sexes of day-old chickens immunized with 2500 oocysts/bird of E. maxima and challenged at 10 days of age with 25,000 oocysts/bird of the same isolate in two separate battery trials. All immunized birds showed significant protection for the parameters of weight gain and midintestinal lesion scores at 7 days post challenge (PC) when compared with nonimmunized challenged controls. In two separate floorpen trials, one broiler bird strain (designated strain 2) immunized by the same procedure and challenged at 21 days of age with the equivalent of 25,000 oocysts/bird of the same isolate showed significant protection for weight gain and lesion scores at 7 days PC when compared with nonimmunized controls. Birds in these same floorpen experiments immunized with E. maxima and then fed three different anticoccidial shuttle diets (narasin and nicarbazin 90 grams/ton (g/t) in starter feed and narasin 72 g/t + roxarsone 45.4 g/t in grower feed; nicarbazin 113 g/t in starter feed and narasin 72 g/t + roxarsone 45.4 g/t in grower feed; and monensin 100 g/t in starter and grower feed) showed no interference with elicited immunity with E. maxima challenge for the same parameters measured. No significant difference was seen between any floorpen immunized bird groups for total weight gain at trial terminations (49 days of age).

Animal Feed↗