Cardiac Lesions of Natural and Experimental Infection by Parrot Bornaviruses.

Lymphoplasmacytic inflammation associated with bornavirus N protein occurs in the epicardial ganglia, myocardium and endocardium of birds diagnosed with proventricular dilatation disease (PDD). These pathological findings suggest that sudden death in psittacine birds might stem from cardiac compromise due to parrot bornavirus (PaBV) infection. Therefore, we investigated cardiac lesions in cases of PDD, searching databases from 1988 to 2019, and reviewed three experimental studies of PaBV infection. Fifty cases of PDD in birds infected naturally with PaBV and 27 cases of PDD in birds infected experimentally with PaBV (all having descriptions of inflammatory cardiac lesions) were reviewed. For each case, five regions of the heart were evaluated by light microscopy and immunohistochemistry (IHC). These regions were the epicardial ganglia/nerves, the endocardium, the myocardium, the Purkinje fibres and the great vessels. Sudden death was documented in 17/50 naturally infected cases, while 23/50 had digestive signs, and only 12/50 had neurological signs. Grossly, only five naturally-infected and five experimentally-infected cases had cardiomegaly or hydropericardium. Epicardial ganglioneuritis was the most consistent microscopical finding in natural (46/50) and experimental cases (26/27), followed by myocarditis (34/50) for naturally-infected and endocarditis for experimentally-infected birds (6/27). PaBV-2 antigen was detected most frequently by IHC in the epicardial ganglia (54/77) compared with the other tissues. This retrospective study demonstrates the presence of PaBV protein and inflammation in the heart of birds infected with PaBV and suggests a link between PaBV and cardiac disease and sudden death in psittacine birds.

Ancient T-independence of mucosal IgX/A: gut microbiota unaffected by larval thymectomy in Xenopus laevis.

Many studies address the influence of the gut microbiome on the immune system, but few dissect the effect of T cells on gut microbiota and mucosal responses. We have employed larval thymectomy in Xenopus to study the gut microbiota with and without the influence of T lymphocytes. Pyrosequencing of 16S ribosomal RNA genes was used to assess the relative abundance of bacterial groups present in the stomach, small and large intestine. Clostridiaceae was the most abundant family throughout the gut, while Bacteroidaceae, Enterobacteriaceae, and Flavobacteriaceae also were well represented. Unifrac analysis revealed no differences in microbiota distribution between thymectomized and unoperated frogs. This is consistent with immunization data showing that levels of the mucosal immunoglobulin IgX are not altered significantly by thymectomy. This study in Xenopus represents the oldest organisms that exhibit class switch to a mucosal isotype and is relevant to mammalian immunology, as IgA appears to have evolved from IgX based upon phylogeny, genomic synteny, and function.

Unusual and severe lesions of proventricular dilatation disease in cockatiels (Nymphicus hollandicus) acting as healthy carriers of avian bornavirus (ABV) and subsequently infected with a virulent strain of ABV.

A flock of 14 apparently healthy cockatiels, purchased from a single aviary, was tested for the presence of avian bornavirus (ABV). Twelve birds were found to be intermittently shedding ABV, predominantly genotype 4. Four of the cockatiels known to be shedding ABV4 were subsequently challenged with the tissue culture derived, virulent M24 strain of ABV4. The challenged birds remained in apparent good health until day 92 when one was found dead. The remaining three birds began to exhibit severe neurologic signs, ataxia and convulsions on day 110 and were euthanized. On necropsy, all four birds showed mild proventricular enlargement. In contrast, histopathological examination showed unusually severe and widespread tissue lesions. These included massive lymphocytic infiltration and lymphoid nodule formation within and around the ganglia throughout the gastrointestinal tract. There were similar lesions in the medullary cords of the adrenal gland, heart, spleen, liver, kidney, lungs, pancreas, testes and ovary. Immunohistochemistry demonstrated ABV P antigen not only in the cells of the central and autonomic nervous systems, but also within the mononuclear cells infiltrating the various organs. Two healthy cockatiels, one of which was a known ABV carrier, were inoculated with uninfected tissue culture cells and euthanized on day 150. These birds showed no gross lesions of proventricular dilatation disease but had a mild lymphocytic infiltration in their liver, spleen, and kidneys. Prior infection with ABV did not therefore confer significant immunity on these birds, and may have resulted in increased disease severity following challenge.

Histopathology and the detection of avian bornavirus in the nervous system of birds diagnosed with proventricular dilatation disease.

Avian bornavirus (ABV) is currently considered a probable etiologic agent of proventricular dilatation disease (PDD) of psittacines. We tested 24 stored avian brain samples, processed for histopathology and retained following their submission for necropsy or histopathology to the Schubot Exotic Bird Center diagnostic laboratory in 1992. Thirteen of these samples were from birds diagnosed at that time as suffering from PDD. The remaining 11 samples were diagnosed as suffering from diseases other than PDD. Immunohistochemistry was performed using an antiserum directed against the ABV nucleoprotein (N-protein). Stained slides were read by an investigator unaware of their prior histopathology results. Cells containing ABV N-protein were present in the nervous tissues of all 13 PDD cases. One bird not previously diagnosed with PDD also had ABV N-protein in its brain. A review of this bird's necropsy report indicated that it was, most probably, also suffering from PDD. The remaining 10 non-PDD birds had no detectable N-protein in their brains. The N-protein was present in the cerebrum, cerebellum and spinal cord. These findings support other studies that indicate that ABV is an etiological agent of PDD.

Humoral response to Mycobacterium avium subsp. avium in naturally infected ring-neck doves (Streptopelia risoria).

Creation of a reliable and easy to use serologic test would greatly improve ante mortem diagnosis of Mycobacterium avium subsp. avium and aid in the control of avian mycobacteriosis, particularly in captive birds. In order to determine whether serodiagnostics could be of value in testing ring-neck doves (Streptopelia risoria) for M. a. avium infection, Western blot analysis was used to assess the humoral response of ring-neck doves exposed to M. a. avium, and to evaluate whether an association could be made between the humoral response and necropsy findings, histopathology, culture, and PCR testing. Western blot results were examined for reactivity patterns associating humoral response with infection status, severity and type of lesions (diffuse vs. multifocal granulomatous inflammation) and phenotype (white vs. non-white). A sensitivity of 88.24% and a specificity of 100% were achieved utilizing Western blot analysis to detect M. a. avium infection in ring-neck doves, offering a negative predictive value of 93% and a positive predictive value of 100%. While Western blot analysis results did not reflect lesion severity, lesion type did partially correspond with the humoral response. The findings of the present study indicate that serologic testing can be used as a valuable ante mortem screening tool for identifying ring-neck doves infected with M. a. avium.

Isolation and characterization of structural components of Aloe vera L. leaf pulp.

The clear pulp, also known as inner gel, of Aloe vera L. leaf is widely used in various medical, cosmetic and nutraceutical applications. Many beneficial effects of this plant have been attributed to the polysaccharides present in the pulp. However, discrepancies exist regarding the composition of pulp polysaccharide species and an understanding of pulp structure in relation to its chemical composition has been lacking. Thus, we examined pulp structure, isolated structural components and determined their carbohydrate compositions along with analyzing a partially purified pulp-based product (Acemannan hydrogel) used to make Carrisyn hydrogel wound dressing. Light and electron microscopy showed that the pulp consisted of large clear mesophyll cells with a diameter as large as 1000 microm. These cells were composed of cell walls and cell membranes along with a very limited number of degenerated cellular organelles. No intact cellular organelles were found in mesophyll cells. Following disruption of pulp by homogenization, three components were isolated by sequential centrifugation. They were thin clear sheets, microparticles and a viscous liquid gel, which corresponded to cell wall, degenerated cellular organelles and liquid content of mesophyll cells based on morphological and chemical analysis. These three components accounted for 16.2% (+/-3.8), 0.70% (+/-0) and 83.1% of the pulp on a dry weight basis. The carbohydrate composition of each component was distinct; liquid gel contained mannan, microparticles contained galactose-rich polysaccharide(s) and cell walls contained an unusually high level of galacturonic acid (34%, w/w; Gal A). The same three components were also found in Acemannan Hydrogel with mannan as the predominant component. Thus, different pulp structural components are associated with different polysaccharides and thus may potentially be different functionally. These findings may help lay a basis for further studies and development of better controlled processing methods and applications for this well-accepted medicinal plant.

In situ detection and quantification of bursa of fabricius cellular proliferation or apoptosis in normal or steroid-treated neonatal chicks.

Apoptosis, or programmed cell death, is believed to be the mechanism for depletion of lymphocytes recognizing self-antigens following clonal expansion in the bursa of Fabricius. Although bursal apoptosis has previously been shown to increase following in vivo exposure to glucocorticoids, the microanatomical site of induced or normal apoptosis has not been unequivocally established. Presently, we adapted the existing terminal deoxynucleotidal transferase-mediated dUTP nick-end labeling (TUNEL) assay for use with neonatal bursae. Similar to previous reports, TUNEL revealed that normal apoptosis is preferentially, but not exclusively, ongoing in bursal follicular cortical cells. Administration of a single dose of a synthetic glucocorticoid (dexamethasone) or androgen (19-nortestosterone) did not significantly (P < 0.05) alter follicular lymphocyte numbers or apoptosis per unit of area at the time points evaluated post-administration (6 or 24 h). However, administration of 19-Nortestosterone increased the interfollicular epithelial thickness, a change usually associated with edema, within 6 h following treatment. Additionally, administration of the androgen 19-nortestosterone significantly decreased the number of proliferating cells as detected using mouse anti-proliferating cell nuclear antigen (PCNA) as a primary immunohistochemical antibody. In normal (control) bursal sections, occasional follicles consisting of predominantly apoptotic cells were observed (0.26% of follicles). Such follicles were consistently one-tenth the area of normal follicles. This incidental finding may suggest occasional occurrence of a common signal for deletion, such as a common integral or clonal mistake, viral infection, or an aberrant paracrine signal.

Plant-based vaccines: unique advantages.

Numerous studies have shown that viral epitopes and subunits of bacterial toxins can be expressed and correctly processed in transgenic plants. The recombinant proteins induce immune responses and have several benefits over current vaccine technologies, including increased safety, economy, stability, versatility and efficacy. Antigens expressed in corn are particularly advantageous since the seed can be produced in vast quantities and shipped over long distances at ambient temperature, potentially allowing global vaccination. We have expressed the B-subunit of Escherichia coli heat-labile enterotoxin and the spike protein of swine transmissible gastroenteritis virus at high levels in corn, and demonstrate that these antigens delivered in the seed elicit protective immune responses.

Specificity and prevalence of natural bovine anti-alpha galactosyl (Galalpha1-6Glc or Galalpha1-6Gal) antibodies.

Immunity against the carbohydrate components of microorganisms mediated by antibodies is an important part of host defenses. Humans and closely related primates, but not other mammals, possess natural anti-Galalpha1-3Gal antibodies which also, although less avidly, react with melibiose (Galalpha1-6Glc). Using an enzyme-linked immunosorbent assay (ELISA) with melibiose-bovine serum albumin as an antigen, we analyzed bovine anti-alpha galactosyl antibodies with respect to specificity and distribution in individual animals. Inhibition assays showed that melibiose was the strongest inhibitor, followed equally by stachyose (Galalpha1-6Galalpha1-6Glcbeta1-2Fru) and raffinose (Galalpha1-6Glcbeta1-2Fru) and then by Galbeta1-6Gal, Gal, and Galalpha1-2Gal. Others, including Galalpha1-3Gal and Galalpha1-4Gal, only exhibited minor inhibition. Thus, these bovine anti-alpha galactosyl antibodies appeared to preferentially react with Galalpha1-6Glc or Galalpha1-6Gal. The distinction of this specificity from that (Galalpha1-3Gal) of human antibodies was further demonstrated by the poor reaction of bovine serum to the Galalpha1-3Gal antigen in comparison to human serum. All 27 healthy bovine serum samples of the three age groups (newborn, calf, and adult) tested contained such antibodies with titers increasing with age. The antibodies purified by affinity chromatography using a melibiose-agarose column were mainly of the immunoglobulin G (IgG) isotype with a concentration of >23 microg/ml in most samples. IgG1 was found to be the primary antimelibiose IgG isotype in all age groups by isotype-specific ELISA, but a significant increase in IgG2, an isotype more related to innate immunity, was observed in calves and adults, compared to newborns. The purified antibodies reacted with the type II bovine strain of Streptococcus agalactiae, a common pathogen of bovine mastitis. Thus, these anti-Galalpha1-6Glc or Galalpha1-6Gal antibodies in cattle might be involved in defense against microbes bearing this or the related epitopes.

Specificity and prevalence of natural bovine antimannan antibodies.

Immune responses to the carbohydrate components of microorganisms, mediated both by antibodies and by lectins, are an important part of host defense. In the present experiments, the specificity and presence of natural bovine antibodies against mannan, a common fungal antigen, were examined by enzyme-linked immunosorbent assay (ELISA), using Saccharomyces cerevisiae mannan as an antigen. The results showed that all serum samples from animals of three age groups (newborn, calf, and adult) tested contained antimannan antibodies, and the titer of these antibodies increased significantly in adults. However, titers among individual adult cattle differed widely. Inhibition assays showed that yeast mannan was the strongest inhibitor. D-Mannose exhibited only a minor inhibitory effect at high concentrations. This suggests that most of these antibodies recognize an oligosaccharide-based epitope(s) different from those recognized by lectins. Cattle possess three serum C-type lectins (collectins) capable of recognizing mannan in a calcium-dependent manner. Addition of EDTA to the reaction did not reduce antibody binding, suggesting that the binding of these antibodies to mannan was not affected by the presence of collectin. The antibodies purified from either calf or adult serum by mannan-Sepharose affinity chromatography consisted of mainly immunoglobulin G (IgG) and a smaller amount of IgM. IgG1 was shown to be the dominant antimannan IgG isotype by isotype-specific ELISA. Together, these results demonstrate the production of natural antimannan antibodies in cattle in an age-dependent manner. These antibodies might be involved in defending the host against mannan-containing pathogens as a specific line of defense in conjunction with the innate response by lectins.

Grease, anthraxgate, and kennel cough: a revisionist history of early veterinary vaccines.

In conclusion, it is remarkable just how farsighted many of the early vaccine investigators were. Jenner was apparently very comfortable with contagion and even recognized that infectious agents could gradually change and adapt to a new species. Pasteur, long before his fowl cholera experiment, dreamed that attenuation could yield safe vaccines and it took him no time at all therefore to recognize the significance of that serendipitous experiment. The fact that two other investigators were also developing anthrax vaccines simultaneously is yet another example of how the times favor certain discoveries. Finally Ferry, while constrained by the fact that he had no idea that distemper was caused by a virus, recognized well the concept of secondary infection and rationalized, not unreasonably, that his vaccine might assist in controlling this. It is also clear that we must look skeptically at the accepted historical record. Thus, it is clear that Jenner used horse-derived material as a source of vaccine material and that vaccinia may in fact be the long-lost agent of horsepox. Certainly this would not be news to many nineteenth-century investigators and veterinarians. Individuals planning to use live vaccinia in recombinant vaccines may wish to keep this in mind. Who discovered anthrax vaccine? Burdon-Sanderson clearly recognized that he could attenuate the organism. Greenfield showed that this could protect against disease although he was far from developing an effective vaccine. Poor Henri Toussaint was probably the first to develop an effective product but did not publicize his results widely. It was left to Louis Pasteur to take the risks inherent in a high-profile public experiment and win. I believe that he richly deserves the prize. Finally, who deserves the credit for distemper vaccine? First, Carré deserves much more credit than hitherto for discovering that distemper was caused by a virus. Second, Ferry, although misled by his identification of B. bronchiseptica deserves credit for realizing that his vaccine could play a role in controlling secondary infections. The true discoverer of an effective distemper vaccine was the Italian, Puntoni, but once again the publicity went to others, Laidlaw and Dunkin. Thus a pattern emerges that prior discovery matters little in the face of aggressive publicity. If nobody knows you did the experiment you might as well have never done it in the first place. Publish or perish is by no means a new phenomenon.

Use of serologic testing to assess immune status of companion animals.

At the November 1997 meeting of the AVMA Council on Biologic and Therapeutic Agents, the Council recommended that the JAVMA publish an article on the current status of the use of serologic testing in an effort to assist practitioners who must make decisions regarding vaccination of companion animals (i.e., dogs, cats, and horses). It is anticipated that the peer-reviewed article provided here will be of benefit to veterinarians and will facilitate their attempts to maintain animal health through the knowledgeable use of vaccines.

Induction of apoptosis in a macrophage cell line RAW 264.7 by acemannan, a beta-(1,4)-acetylated mannan.

Acemannan is a polydispersed beta-(1,4)-linked acetylated mannan with antiviral properties. It is an immunomodulator, and studies in our laboratory have shown that it causes activation of macrophages. In the presence of IFNgamma, acemannan induced apoptosis in RAW 264. 7 cells. These cells exhibited chromatin condensation, DNA fragmentation, and laddering characteristic of apoptosis. The induction of apoptosis by acemannan and IFNgamma does not seem to be mediated by nitric oxide, since N-nitro-L-arginine methyl ester, the nitric oxide inhibitor, had no effect. Acemannan in the presence of IFNgamma also inhibited the expression of bcl-2. These results suggest that acemannan in the presence of IFNgamma induces apoptosis in RAW 264.7 cells through a mechanism involving the inhibition of bcl-2 expression.

Lectin-carbohydrate interaction in the immune system.

The immune system consists of various types of cells and molecules that specifically interact with each other to initiate the host defense mechanism. Recent studies have shown that carbohydrates and lectins (carbohydrate-binding proteins) play an essential role in mediating such interactions. Both lectins and carbohydrates are widely distributed in the mammalian tissues as well as in microorganisms. Carbohydrates, due to their chemical nature, can potentially form structures that are more variable than proteins and nucleic acids. Lectins can exist in either soluble or cell-associated form, and although overall structures vary, invariably possess carbohydrate-recognition domains (CRD) with various specificities. The interaction between lectins and carbohydrates have been shown to be involved in such activities as opsonization of microorganisms, phagocytosis, cell adhesion and migration, cell activation and differentiation, and apoptosis. The number of lectins identified in the immune system is increasing at a rapid pace. The development in this area has opened a new aspect in studying the immune system, and at the same time, provided new therapeutic routes for the treatment and prevention of disease.

Activation of a mouse macrophage cell line by acemannan: the major carbohydrate fraction from Aloe vera gel.

Acemannan is the name given to the major carbohydrate fraction obtained from the gel of the Aloe vera leaf. It has been claimed to have several important therapeutic properties including acceleration of wound healing, immune stimulation, anti-cancer and anti-viral effects. However, the biological mechanisms of these activities are unclear. Because of this wide diversity of effects, it is believed that they may be exerted through pluripotent effector cells such as macrophages. The effects of acemannan on the mouse macrophage cell line, RAW 264.7 cells were therefore investigated. It was found that acemannan could stimulate macrophage cytokine production, nitric oxide release, surface molecule expression, and cell morphologic changes. The production of the cytokines IL-6 and TNF-alpha were dependent on the dose of acemannan provided. Nitric oxide production, cell morphologic changes and surface antigen expression were increased in response to stimulation by a mixture of acemannan and IFN-gamma. These results suggest that acemannan may function, at least in part, through macrophage activation.

Acemannan, a beta-(1,4)-acetylated mannan, induces nitric oxide production in macrophage cell line RAW 264.7.

Acemannan is a polydispersed beta-(1,4)-linked acetylated mannan with antiviral properties. It is an immunomodulator, and studies in our laboratory have shown that it causes activation of macrophages. Inducible NO synthase is generally expressed after transcriptional induction and is known to mediate some of the cytotoxic action of activated macrophages. Acemannan, in the presence of interferon-gamma, greatly increased the synthesis of NO in RAW 264.7 cells. This increase was preceded by increased expression of mRNA for the inducible form of macrophage NO synthase. Preincubation with pyrrolidine dithiocarbamate inhibited the induction, indicating the involvement of nuclear factor-kappa B. These results suggest that acemannan causes the activation of macrophages by increasing the level of NO synthase at the level of transcription.

The effect of Acemannan Immunostimulant in combination with surgery and radiation therapy on spontaneous canine and feline fibrosarcomas.

Eight dogs and five cats with histopathologically confirmed fibrosarcomas were treated with Acemannan Immunostimulanta in combination with surgery and radiation therapy. These animals had recurring disease that had failed previous treatment, a poor prognosis for survival, or both. Following four to seven weekly acemannan treatments, tumor shrinkage occurred in four (greater than 50%; n = 2) of 12 animals, with tumors accessible to measurement. A notable increase in necrosis and inflammation was observed. Complete surgical excision was performed on all animals between the fourth and seventh week following initiation of acemannan therapy. Radiation therapy was instituted immediately after surgery. Acemannan treatments were continued monthly for one year. Seven of the 13 animals remain alive and tumor-free (range, 440+ to 603+ days) with a median survival time of 372 days. The data suggests that Acemannan Immunostimulant may be an effective adjunct to surgery and radiation therapy in the treatment of canine and feline fibrosarcomas.