Immune response to Sarcocystis neurona infection in naturally infected horses with equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis (EPM) is one of the most common neurologic diseases of horses in the United States. The primary etiologic agent is Sarcocystis neurona. Currently, there is limited knowledge regarding the protective or pathophysiologic immune response to S. neurona infection or the subsequent development of EPM. The objectives of this study were to determine whether S. neurona infected horses with clinical signs of EPM had altered or suppressed immune responses compared to neurologically normal horses and if blood sample storage would influence these findings. Twenty clinically normal horses and 22 horses with EPM, diagnosed by the presence of S. neurona specific antibodies in the serum and/or cerebrospinal (CSF) and clinical signs, were evaluated for differences in the immune cell subsets and function. Our results demonstrated that naturally infected horses had significantly (P<0.05) higher percentages of CD4 T-lymphocytes and neutrophils (PMN) in separated peripheral blood leukocytes than clinically normal horses. Leukocytes from naturally infected EPM horses had significantly lower proliferation responses, as measured by thymidine incorporation, to a non-antigen specific mitogen than did clinically normal horses (P<0.05). Currently, studies are in progress to determine the role of CD4 T cells in disease and protection against S. neurona in horses, as well as to determine the mechanism associated with suppressed in vitro proliferation responses. Finally, overnight storage of blood samples appears to alter T lymphocyte phenotypes and viability among leukocytes.     

Campylobacteriosis in an aborted equine fetus

Abortion caused by Campylobacter fetus subsp fetus was diagnosed in a 7-month-old equine fetus. The fetus was small for its gestational age. Macroscopically, the proximal portion of the small intestine was hemorrhagic and its wall was thick. Histologically, the Brunner glands were distended with neutrophils, and the submucosa was thick, owing to fluid accumulation and/or cellular infiltrates. Curved bacteria were observed in the Brunner glands and intestinal glands. Campylobacter fetus subsp fetus was isolated from stomach contents, liver, and lungs, and was detected by dark-field microscopic examination of ocular fluid and stomach contents. Placenta was not available for examination.     

Toxoplasma-like sporozoa in an aborted equine fetus

Multifocal areas of necrosis and infiltrations of mononuclear cells were seen in lung specimens of an equine fetus aborted 2 months before term. Extracellular and intracellular protozoa were seen in the alveolar tissue. Individual organisms were 4 microns by 2.5 microns, and cyst-like structures were 25 microns by 18 microns. Organisms did not stain with periodic acid-Schiff or by use of the immunoperoxidase and peroxidase-antiperoxidase method for Toxoplasma gondii. Twelve days after abortion, the mare had serum antibody titer of less than 1:10 against T gondii.     

Isolation of equine herpesvirus-2 from the lung of an aborted fetus.

This study describes the isolation of equine herpesvirus-2 (EHV-2) from the lung of an aborted equine fetus in Argentina. The isolated virus was confirmed as EHV-2 by indirect immunofluorescence using a rabbit anti-EHV-2 polyclonal antiserum and by virus-neutralization test using an equine polyclonal antibody against EHV-2. Restriction endonuclease DNA fingerprinting with BamHI also confirmed the identity of the virus as EHV-2. Furthermore, viral nucleic acid was detected by polymerase chain reaction from the original lung sample and from the DNA obtained from cells infected with the virus isolate. This work constitutes the first reported isolation of EHV-2 from an aborted equine fetus. The presence of EHV-2 in the lung of the aborted fetus would indicate that this virus is capable of crossing the placental barrier. However, no cause-effect relationship was established between the EHV-2 isolate and the abortion.     

Immune responses to commercial equine vaccines against equine herpesvirus-1, equine influenza virus, eastern equine encephalomyelitis, and tetanus

Horses are commonly vaccinated to protect against pathogens which are responsible for diseases which are endemic within the general horse population, such as equine influenza virus (EIV) and equine herpesvirus-1 (EHV-1), and against a variety of diseases which are less common but which lead to greater morbidity and mortality, such as eastern equine encephalomyelitis virus (EEE) and tetanus. This study consisted of two trials which investigated the antigenicity of commercially available vaccines licensed in the USA to protect against EIV, EHV-1 respiratory disease, EHV-1 abortion, EEE and tetanus in horses. Trial I was conducted to compare serological responses to vaccines produced by three manufacturers against EIV, EHV-1 (respiratory disease), EEE, and tetanus given as multivalent preparations or as multiple vaccine courses. Trial II compared vaccines from two manufacturers licensed to protect against EHV-1 abortion, and measured EHV-1-specific interferon-gamma (IFN-gamma) mRNA production in addition to serological evidence of antigenicity. In Trial I significant differences were found between the antigenicity of different commercial vaccines that should be considered in product selection. It was difficult to identify vaccines that generate significant immune responses to respiratory viruses. The most dramatic differences in vaccine performance occurred in the case of the tetanus antigen. In Trial II both vaccines generated significant antibody responses and showed evidence of EHV-1-specific IFN-gamma mRNA responses. Overall there were wide variations in vaccine response, and the vaccines with the best responses were not produced by a single manufacturer. Differences in vaccine performance may have resulted from differences in antigen load and adjuvant formulation.     

Immune response to fungal infections

The immune mechanisms of defence against fungal infections are numerous, and range from protective mechanisms that were present early in evolution (innate immunity) to sophisticated adaptive mechanisms that are induced specifically during infection and disease (adaptive immunity). The first-line innate mechanism is the presence of physical barriers in the form of skin and mucous membranes, which is complemented by cell membranes, cellular receptors and humoral factors. There has been a debate about the relative contribution of humoral and cellular immunity to host defence against fungal infections. For a long time it was considered that cell-mediated immunity (CMI) was important, but humoral immunity had little or no role. However, it is accepted now that CMI is the main mechanism of defence, but that certain types of antibody response are protective. In general, Th1-type CMI is required for clearance of a fungal infection, while Th2 immunity usually results in susceptibility to infection. Aspergillosis, which is a disease caused by the fungus Aspergillus, has been the subject of many studies, including details of the immune response. Attempts to relate aspergillosis to some form of immunosuppression in animals, as is the case with humans, have not been successful to date. The defence against Aspergillus is based on recognition of the pathogen, a rapidly deployed and highly effective innate effector phase, and a delayed but robust adaptive effector phase. Candida albicans, part of the normal microbial flora associated with mucous surfaces, can be present as congenital candidiasis or as acquired defects of cell-mediated immunity. Resistance to this yeast is associated with Th1 CMI, whereas Th2 immunity is associated with susceptibility to systemic infection. Dermatophytes produce skin alterations in humans and other animals, and the essential role of the CMI response is to destroy the fungi and produce an immunoprotective status against re-infection. The resolution of the disease is associated with a delayed hypersensitive response. There are many effective veterinary vaccines against dermatophytoses. Malassezia pachydermatis is an opportunistic yeast that needs predisposing factors to cause disease, often related to an atopic status in the animal. Two species can be differentiated within the genus Cryptococcus with immunologic consequences: C. neoformans infects predominantly immunocompromised hosts, and C. gattii infects non-immunocompromised hosts. Pneumocystis is a fungus that infects only immunosupressed individuals, inducing a host defence mechanism similar to that induced by other fungal pathogens, such as Aspergillus.     

Physiological development of the equine fetus during late gestation

In many species, the pattern of growth and physiological development in utero has an important role in determining not only neonatal viability but also adult phenotype and disease susceptibility. Changes in fetal development induced by a range of environmental factors including maternal nutrition, disease, placental insufficiency and social stresses have all been shown to induce adult cardiovascular and metabolic dysfunction that often lead to ill health in later life. Compared to other precocious animals, much less is known about the physiological development of the fetal horse or the longer-term impacts on its phenotype of altered development in early life because of its inaccessibility in utero, large size and long lifespan. This review summaries the available data on the normal metabolic, cardiovascular and endocrine development of the fetal horse during the second half of gestation. It also examines the responsiveness of these physiological systems to stresses such as hypoglycaemia and hypotension during late gestation. Particular emphasis is placed on the role of the equine placenta and fetal endocrine glands in mediating the changes in fetal development seen towards term and in response to nutritional and other environmental cues. The final part of the review presents the evidence that the early life environment of the horse can alter its subsequent metabolic, cardiovascular and endocrine phenotype as well as its postnatal growth and bone development. It also highlights the immediate neonatal environment as a key window of susceptibility for programming of equine phenotype. Although further studies are needed to identify the cellular and molecular mechanisms involved, developmental programming of physiological phenotype is likely to have important implications for the health and potential athletic performance of horses, particularly if born with abnormal bodyweight, premature or dysmature characteristics or produced by assisted reproductive technologies, indicative of an altered early life environment.     

苦马豆素-BSA接种山羊的免疫学研究

疯草（Locoweed）是世界范围内危害草原畜牧业生产最严重的一类毒草，在我国主要分布于西部的广大草原，危害面积达1100万hm^2，并且日趋蔓延。动物采食疯草后不仅引起大量中毒死亡，更为重要的是导致母畜流产、不孕、胎儿畸形和公畜不育，同时疯草蔓延可促使草场退化，降低草场利用率，给草原畜牧业造成巨大的经济损失。国内外学者自1873年至今对动物疯草中毒做了大量的研究，现已确认的疯草毒素为吲哚兹啶生物碱-苦马豆素（swainsonine，SW）。疯草除含有毒素外，营养学研究也发现，其粗蛋白含量高达11％～12％，有着被作为优良饲草的潜力。     

Immune response to Encephalitozoon infection review

The microsporidia are emerging agents of infectious disease in both immunocompromised and immunocompetent mammals. Recently, there has been an increased interest in studying the immunobiology of microsporidiosis. This paper discusses the humoral and cell-mediated immune responses to Encephalitozoon spp. The T-cell-mediated responses appear to be most important in conferring resistance. This has become evident by the lethal effects of microsporidiosis in T-cell-deficient hosts. However, much still needs to be learned about the immunobiology of microsporidiosis regarding the specific T-cell responses and the cytokines that provide protective immunity and facilitate the macrophage-mediated killing of microsporidia. Such information will become important in developing immunotherapeutic strategies to control microsporidiosis in the future.     

Cryptococcal pneumonia and abortion in an equine fetus.

Cryptococcus neoformans was the causative agent of pneumonia in a 9-month-old equine fetus aborted by a healthy American Paint mare. Endometritis was diagnosed on biopsy, and vaginal specimens obtained for culture were Cryptococcus-positive 1 month following abortion but not 5 months after abortion. Infection resolved without treatment between 1 and 5 months after abortion, and the mare was bred the following year and delivered a live premature foal without evidence of Cryptococcus infection.     

Homeostasis of intracellular Ca2+ in equine chondrocytes: response to hypotonic shock

REASONS FOR PERFORMING STUDY: Ca2+ homeostasis in articular chondrocytes affects synthesis and degradation of the cartilage matrix, as well as other cellular functions, thereby contributing to joint integrity. Although it will be affected by mechanical loading, the sensitivity of intracellular Ca2+ concentration ([Ca2+]i) in equine articular chondrocytes to many stimuli remains unknown. HYPOTHESIS: An improved understanding of Ca2+ homeostasis in equine articular chondrocytes, and how it is altered during joint loading and pathology, will be important in understanding how joints respond to mechanical loads. METHODS: [Ca2+]i was determined using the fluorophore fura-2. We examined the effects of hypotonic shock, a perturbation experienced in vivo during mechanical loading cycles. We used inhibitors of Ca2+ transporters to ascertain the important factors in Ca2+ homeostasis. RESULTS: Under isotonic conditions, [Ca2+]i was 148 +/- 23 nmol/l, increasing by 216 +/- 66 nmol/l in response to reduction in extracellular osmolality of 50%. Resting [Ca2+]i, and the increase following hypotonic shock, were decreased by Ca2+ removal; they were both elevated when extracellular [Ca2+] ([Ca2+]o) was raised or following Na+ removal. The hypotonicity-induced rise in [Ca2+]i was inhibited by exposure of cells to gadolinium (Gd3+; 10 micromol/l), an inhibitor of mechanosensitive channels. [Ca2+]i was also elevated following treatment of cells with thapsigargin (10 micromol/l), an inhibitor of the Ca2+ pump of intracellular stores. CONCLUSIONS: A model is presented which interprets these findings in relation to Ca2+ homeostasis in equine articular chondrocytes, including the presence of mechanosensitive channels allowing Ca2+ entry, a Na+/Ca2+ exchanger for removal of intracellular Ca2+ and intracellular stores sensitive to thapsigargin. POTENTIAL RELEVANCE: A more complete understanding of Ca2+ homeostasis in equine chondrocytes may allow development of future therapeutic regimes to ameliorate joint disease.     

Immune response of cattle to respiratory mycoplasmas

M. bovis and M. dispar produce very different types of response in the calf lung. The immune response of the host plays a major role in the formation of the lesion induced by M. bovis and this response is predominantly Ig mediated. In contrast M. dispar produces a much milder reaction in the lung which may be related to an ability of the mycoplasma to inhibit the host's immune response. Recovery from infection appears to be primarily mediated by IgG present in the lung and functioning in conjunction with alveolar macrophages. The immunity following vaccination which is observed in experimental studies and field trials is also likely to be mediated by the same mechanism.     

Mesenchymal hamartoma of the liver in a late-term equine fetus

Mesenchymal hamartoma of the liver is a rare congenital disorder of biliary tract development. During the necropsy of a late-term equine fetus, a markedly enlarged liver of more than two times normal weight was found. Light microscopic review revealed that the normal hepatic parenchyma had been obliterated, replaced, and expanded by abnormal bile ducts surrounded by abundant, myxoid stroma. The lesion was diagnosed as a mesenchymal hamartoma. Small portions of the liver had bridging septa of fibrosis and proliferations of small-caliber abnormal bile ducts, resembling another congenital biliary abnormality termed congenital hepatic fibrosis.     

Chemotactic response of equine polymorphonuclear leucocytes to Streptococcus equi

Streptococcus equi infection in horses is characterised by intense infiltration of lymph nodes by polymorphonuclear leucocytes (PMNs) suggesting a potent chemotactic response to the organism or its products. Equine PMNs were separated using Ficoll-Hypaque medium and used in an assay of chemotaxis under agarose to study the components of S equi involved in this response. Results showed that complement-derived chemotactic factors generated by activation of the alternative complement pathway were important in chemotactic responses to S equi. Both whole bacteria and peptidoglycan preparations were potent complement activators, whereas purified M protein was less active. In contrast, S equi culture supernatant protein did not activate complement; instead it directly inhibited migration of PMNs. Moreover, PMNs, when incubated with culture supernatant of a non-haemolytic strain, showed signs of cellular degeneration suggesting the presence of a cytotoxin distinct from haemolysin.