J. R. Thurston

Recent studies on aspergillosis in turkey poults.

A review of the studies on aspergillosis in turkey poults at the National Animal Disease Center include limited field studies, pathogenicity studies, and vaccine development. Natural ventilation in turkey rearing houses was effective in reducing airborne propagules of four major fungal genera, but the effectiveness of ventilation appeared to be limited by the width of the building. Aspergillus fumigatus was more effective than A. flavus in producing mortalities in aerosol exposed poults. Toxigenicity of A. flavus did not enhance its pathogenicity, and no apparent aflatoxin production occurred during pathogenesis in infected turkey poults. Spores of A. fumigatus were disseminated quite rapidly in poults exposed to aerosols, and alveolar macrophages from respiratory lavages taken immediately after exposure contained spores of A. fumigatus. Vaccines produced from germlings of A. fumigatus and administered to turkey poults were the most efficacious of five vaccines tested against challenge exposure to aerosols of A. fumigatus spores.

Bovine sire effects on daughters' in vitro blood neutrophil functions, lymphocyte blastogenesis, serum complement and conglutinin levels

Blood neutrophil functions, lymphocyte blastogenic responses, serum complement, and serum conglutinin activity of 98 lactating Holstein cows from two genetic lines were evaluated. The genetic lines were produced in a selection experiment that created and perpetuated genetic differences in milk production for up to seven generations. No significant differences between the two genetic lines of cows were found for neutrophil function, lymphocyte blastogenic responses, serum complement levels, or serum conglutinin levels. Significant differences between sire progeny groups within lines were found for unstimulated and mitogen-stimulated lymphocyte blastogenesis (P less than 0.0001), and almost all neutrophil functions (antibody independent neutrophil cytotoxicity, antibody dependent neutrophil cytotoxicity, ingestion of bacteria, iodination, chemiluminescence, chemokinesis, and chemotaxis (P less than or equal to 0.05)). Sire progeny group differences (P less than or equal to 0.0001) within lines for serum complement and conglutinin activity were also found. Neutrophil chemiluminescence activity (positive relationship; P less than or equal to 0.001), concanavalin A-stimulated lymphocyte blastogenesis (positive relationship; P less than or equal to 0.004), and serum conglutinin activity levels (negative relationship; P less than or equal to 0.01) each had small but significant associations with the total milk somatic cell count. Cows seropositive for bovine leukosis virus had increased resting and mitogen-stimulated lymphocyte blastogenic activity and were associated with increased in vitro neutrophil random migration and production of superoxide anion. Estimates of genetic parameters of various immune cell functions, of serum complement and of conglutinin levels for daughters of 11 sires with 4-6 daughters in the data set were determined. In this report, genetic variation was demonstrated for nonspecific humoral and cellular immunity.

EFFECTS OF MYCOTOXINS ON IMMUNITY

ABSTRACT Mycotoxins induce a variety of effects on animal systems. Certain of the mycotoxins have definite effects on various immune phenomena and resistance to disease. The role that mycotoxins play in lowering resistance to disease, interfering with acquired immunity, affecting antibody production and cellular immunity, and interfering with mechanisms of defense such as phagocytosis by the mononuclear phagocyte system is discussed. The important economic effects of these mycotoxin activities are difficult to assess; however, the potential effects could be severely manifested in our livestock industry.

Effect of Aflatoxin on Complement Activity in Guinea Pigs

Summary Guinea pigs were dosed once daily with partially purifed aflatoxin in measured amounts per os for 20 days. A significant average depression of complement titers occurred in guinea pigs given a daily dose of aflatoxin equivalent to 0.03 mg or greater of fraction B1. Guinea pigs given a daily dose of aflatoxin equivalent to 0.01 5 mg or greater of fraction B1 had average weight significantly below that of control guinea pigs. Microscopic changes in the liver were detected mostly in guinea pigs given 0.03 mg or more of B1 equivalents. Considerable individual variation in complement titers, weights, and liver changes were noted among the guinea pigs.

Use of rats to compare atrophic rhinitis vaccines for protection against effects of heat-labile protein toxin produced by Pasteurella multocida serogroup D

Four bacterin-toxoid and three bacterin commercial vaccines against atrophic rhinitis were tested in rats for their capacity to immunize against the lethal and systemic effects of purified heat-labile protein toxin (D-toxin) produced by Pasteurella multocida serogroup D. Only one bacterin-toxoid vaccine stimulated sufficient immunity to prevent the death of all rats challenged with D-toxin. None of the vaccines prevented weight loss, leukocytosis or increases in serum complement titers in rats challenged with D-toxin. Rats provide an inexpensive animal model for testing the capacity of vaccines to generate antitoxic immunity against the lethal and systemic effects of D-toxin.

Detection of conglutinin in bovine serum by complement-dependent agglutination of Escherichia coli

Agglutination of Escherichia coli (ECA) by normal bovine serum was shown to be prevented by heating serum to 56 degrees C for 30 min, but restored by normal horse, swine, rabbit or guinea pig sera. Further investigation of the ECA reaction using techniques to distinguish between conglutination and immunoconglutination indicated ECA to be a conglutination reaction. Testing of 264 sera obtained from 22 normal cattle over a period of 5 months did not show individual or seasonal variation in ECA. Changes in ECA and conglutination were detected in sera of periparturient cows. The ECA reaction is a simple technique for detecting conglutinin in bovine serum.

Effects of mycotoxins on immunity and resistance of animals.

ABSTRACT Recognition of impaired immunogenesis among animals receiving dietary aflatoxin has added an important new parameter to the undesirable biological reactions caused by mycotoxin consumption. Experimental studies in laboratory animals, poultry, and swine have shown that moderate levels of aflatoxin (ca 0.25 ppm of feed or 0.07 mg/kg body weight B1 activity) consumed during the period of immunization impaired the establishment of actively acquired immunity in some, but not all model systems. At these levels, thymic hypoplasia and defective cell mediated immune responses with normal antibody production were observed; clinical signs of intoxication other than reduced rate of gain were generally absent. At very high levels of aflatoxin intake, some investigators have reported alterations in the quality and quantity of antibody in addition to the effects on cell mediated immune mechanisms. In addition to aflatoxin, ochratoxin, stachybotryotoxin, diacetoxyscirpenol, and T-2 toxin have been found to adversely affect the thymus and cell mediated immune activity. Aflatoxin has also reduced the effectiveness of the mechanisms of resistance to infection; this effect has been related to a number of actions and has been reported as the basis of field outbreaks of naturally occurring animal disease. The minimal levels of aflatoxin or other mycotoxins affecting immune responses and native resistance remain to be determined.

Electron microscopic examination of ribosome preparations from germinated spores of Aspergillus fumigatus

Ribosomes were isolated from germinated spores (germlings) of Aspergillus fumigatus and electron microscopy was used to determine qualitatively the extent of cellular contamination. After differential centrifugation, the initial crude preparation contained 80S ribosomes and numerous membrane contaminants in the form of membrane sheets, palisade aggregates, and vesicles 0.10–0.18 μm in size. Gel filtration chromatography of crude ribosomes in Sepharose CL-4B did not remove all of the membrane contamination. Homogenous ribosome suspensions, morphologically free of other cellular component contamination, were then obtained after gel filtration fractions were centrifuged through a 35% sucrose solution. The total ribosome yield from a germling preparation was approximately four times the yield of ribosomes from a comparable spore preparation. Gel diffusion precipitin patterns of germling ribosomes were identical to those of spore ribosomes with both germling and spore ribosomes antisera.

Isolation of 80S ribosomes from spores of Aspergillus fumigatus and their antigenicity in rabbits

Ribosomes were obtained from spores of Aspergillus fumigatus by mechanical disruption and differential centrifugation. The initial preparation (crude ribosomes) contained spore components which appeared to be broken fragments of plasmalemma with or without organelles. Purified ribosomes free of membranous material were prepared by gel filtration chromatography on Sepharose CL-4B. Monomeric 80S ribosomes consisting of 40% protein and 60% RNA, and morphologically characteristic of fungal ribosomes were isolated.Serological reactions in sera from rabbits injected with crude or purified ribosomes were similar indicating that the purification process did not change or eliminate antigens that stimulated antibody detectable either by indirect hemagglutination (IHA) or in gel precipitin tests.

Effects of pre-treatment with aflatoxin on a second aflatoxin treatment in guinea pigs

Two-hundred guinea pigs, weighing approximately 500 grams each, were placed in 8 groups, 4 of which received 20 μg/kg/day of partially purified aflatoxin for 7 days, followed by a 7 day recovery period. Paired groups then received 0,20,35 or 50 μg/kg/day of partially purified aflatoxin for 21 days. Animals were sacrificed periodically from all groups and blood was drawn for chemical and immunologic analysis. Weight gains were recorded and histopathologic studies were done on all animals. Pretreatment did not protect guinea pigs from a second exposure, and in fact enhanced mortality and liver toxicity as determined by histopathology. Serum chemistries and immunologic parameters of guinea pigs dosed twice were less conclusive, as neither high nor low doses differed from guinea pigs treated once. Glycocholic acid concentrations were more sensitive than traditional enzymes (aspartate and alanine amino transferase, alkaline phosphatase) for indicating hepatotoxicity.