Mary C. Smith

Application of Monoclonal Antibodies in Functional and Comparative Investigations of Heavy-Chain Immunoglobulins in New World Camelids

ABSTRACT Of the three immunoglobulin G (IgG) isotypes described to occur in camelids, IgG2 and IgG3 are distinct in that they do not incorporate light chains. These heavy-chain antibodies (HCAbs) constitute approximately 50% of the IgG in llama serum and as much as 75% of the IgG in camel serum. We have produced isotype-specific mouse monoclonal antibodies (MAbs) in order to investigate the roles of HCAbs in camelid immunity. Seventeen stable hybridomas were cloned, and three MAbs that were specific for epitopes on the γ chains of llama IgG1, IgG2, or IgG3 were characterized in detail. Affinity chromatography revealed that each MAb bound its isotype in solution in llama serum. The antibodies bound to the corresponding alpaca IgGs, to guanaco IgG1 and IgG2, and to camel IgG1. Interestingly, anti-IgG2 MAbs bound three heavy-chain species in llama serum, confirming the presence of three IgG2 subisotypes. Two IgG2 subisotypes were detected in alpaca and guanaco sera. The MAbs detected llama serum IgGs when they were bound to antigen in enzyme-linked immunosorbent assays and were used to discern among isotypes induced during infection with a parasitic nematode. Diseased animals, infected with Parelaphostrongylus tenuis, did not produce antigen-specific HCAbs; rather, they produced the conventional isotype, IgG1, exclusively. Our data document the utility of these MAbs in functional and physiologic investigations of the immune systems of New World camelids.

Eye Infections due to Listeria Monocytogenes in Three Cows and One Horse

A retrospective study was conducted to determine case histories, microbiological characteristics, and molecular subtypes associated with Listeria monocytogenes infections of the eye in large animals. For selected cases, environmental L. monocytogenes contamination patterns on case farms were also evaluated to probe for potential sources and spread of listerial eye infections. Records of 170 L. monocytogenes isolates from animal infections were reviewed to determine the fraction of isolates associated with eye infections (conjunctivitis, keratitis, and uveitis) of animals and to gather information on the clinical history of these cases. Overall, 4 of 170 Listeria monocytogenes isolates were associated with eye infections; 3 of these had occurred in cows and 1 in a horse. Molecular subtyping (by EcoRI ribotying) showed that 4 different L. monocytogenes subtypes were isolated from these 4 cases; the same ribotypes had previously been found among invasive animal listeriosis infections. Although a variety of L. monocytogenes subtypes were isolated from environmental sources, on 1 farm, the same ribotype associated with the eye infection was also isolated from a fecal sample of a healthy animal and from a soil sample. The data reported in this study further suggest that L. monocytogenes can be a cause of eye infections in several animal species. Listerial eye infections do not seem to require specific pathogen-related virulence characteristics but rather seem to be a function of environmental or host factors, such as direct exposure of the eyes of susceptible animals to high numbers of the pathogen. Although listerial eye infections are rarely diagnosed because of its ubiquitous nature, L. monocytogenes may have to be considered more commonly as a causative agent of eye infections in ruminants and horses.

Diagnosis of Borrelia‐associated uveitis in two horses

Borrelia burgdorferi, the etiologic agent of Lyme disease is a tick born spirochetal infection. Clinical signs of Lyme borreliosis are uncommon in horses, but when present they are often vague and nonspecific. In horses, Lyme borreliosis has been implicated in musculoskeletal, neurological, reproductive, and ocular disorders, including uveitis, but definitive diagnosis can be challenging as the causative agent is rarely isolated and serologic tests can be unreliable and do not confirm active disease. Here, we report two cases of equine uveitis associated with B. burgdorferi based on the identification of spirochetes within ocular fluids and confirmed with PCR testing. The two cases illustrate some of the challenges encountered in the recognition and diagnosis of equine Lyme borreliosis. Although only one of many possible causes of equine uveitis, Lyme disease should be considered a differential diagnosis, especially in endemic areas. Given the possibility for false negative results of serum tests during uveitis associated with B. burgdorferi and the failure of such tests to confirm active infection, a combination of cytologic assessment, antibody, and/or PCR testing of ocular fluids may be worthwhile if the clinical suspicion for Lyme uveitis is high.

Comparison of pregnancy diagnosis in dairy cattle by use of a commercial ELISA and palpation per rectum

OBJECTIVE To compare agreement between 2 pregnancy tests in dairy cattle. DESIGN Evaluation study. ANIMALS 976 and 507 cattle for phases 1 and 2, respectively. PROCEDURES Blood samples were collected, and palpation per rectum (PPR) was performed on cattle. Blood samples for the pregnancy-specific protein B (PSPB) ELISA were sent by courier to a commercial laboratory with results returned later. Results of PPR were extracted from herd records. Statistical comparison of results was performed by use of a mixed linear model and N analysis. RESULTS Of 571 cattle classified as pregnant by the PSPB ELISA in phase 1, 30 (5%) were nonpregnant by PPR. Mean +/- SE adjusted optical density (OD) of cattle classified pregnant by both tests was significantly higher (0.31 +/- 0.01), compared with the adjusted OD of cattle classified pregnant by the PSPB ELISA and nonpregnant by PPR (0.22 +/- 0.02). Of 255 cows classified pregnant by the PSPB ELISA in phase 2, 31 (12%) were nonpregnant by PPR. Mean +/- SE adjusted OD of cattle classified pregnant by both tests was significantly higher (0.26 +/- 0.01), compared with the adjusted OD of cattle classified pregnant by the PSPB ELISA and nonpregnant by PPR (0.21 +/- 0.01). The N value was 0.82 and 0.81 for phases 1 and 2, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Good agreement existed between the 2 tests, especially at longer intervals after insemination. Discrepant results appeared to be attributable to a nonviable fetus, embryonic loss, or fetal loss.

Skin diseases in the alpaca (Vicugna pacos): a literature review and retrospective analysis of 68 cases (Cornell University 1997–2006)

This retrospective study describes 68 alpacas with skin diseases investigated from 1997 through 2006 at Cornell University. During this time period, 40 of 715 (5.6%) alpacas presented to the university hospital had dermatological diseases. In addition, skin-biopsy specimens accounted for 86 of 353 (24.4%) of alpaca biopsy specimens submitted to the diagnostic laboratory, and of these 86 specimens, follow-up was available for 28 cases. The following diseases were most common: bacterial infections (22%); neoplasms, cysts and hamartomas (19%); presumed immunological disorders (12%); and ectoparasitisms (10%). Conditions described for the first time included intertrigo, collagen and hair follicle hamartomas, lymphoma, hybrid follicular cysts, melanocytoma, anagen defluxion, telogen defluxion, presumed insect-bite hypersensitivity, ichthyosis, and possible hereditary bilateral aural haematomas and chondritis. The results of the retrospective study are compared and contrasted with the results of a literature review.

Effector Functions of Camelid Heavy-Chain Antibodies in Immunity to West Nile Virus

ABSTRACT Three classes of IgG have been described for camelids. IgG1 has a conventional four-chain structure, while IgG2 and IgG3 do not incorporate light chains. The structures and antigen-binding affinities of the so-called heavy-chain classes have been studied in detail; however, their regulation and effector functions are largely undefined. The aim of this study was to examine the participation of conventional and heavy-chain IgG antibodies in the camelid immune defense directed against West Nile virus (WNV). We found that natural infection or vaccination with killed WNV induced IgG1 and IgG3. Vaccination also induced IgG1 and IgG3; IgG2 was produced during the anamnestic response to vaccination. When purified IgGs were tested in plaque-reduction neutralization titer (PRNT) tests, IgG3 demonstrated PRNT activities comparable to those of conventional IgG1. In contrast, IgG2 demonstrated only suboptimal activity at the highest concentrations tested. Flow cytometric analysis revealed that macrophages bound IgG1, IgG2, and IgG3. Furthermore, subneutralizing concentrations of all three isotypes enhanced WNV infection of cultured macrophages. Our results document distinctions in regulation and function between camelid heavy-chain isotypes. The reduced size and distinct structure of IgG3 did not negatively impact its capacity to neutralize virus. In contrast, IgG2 appeared to be less efficient in neutralization. This information advances our understanding of these unusual antibodies in ways that can be applied in the development of effective vaccines for camelids.

Treatment of Emergency Conditions in Sheep and Goats

The emergency treatment of small ruminant patients can be overwhelming for clinicians with limited experience with these species. This article outlines the diseases most frequently encountered in veterinary practice. Each section discusses clinical signs, causes, and treatment and/or procedures associated with small ruminant emergencies. Emphasis is placed on the treatment of critical patients, but practitioners should also be prepared to manage these conditions on a flock or herd level because most small ruminant emergencies stem from poor management.

Toxic Plants of the Northeastern United States

This article lists commonly encountered toxic plants that affect ruminants in the Northeastern United States. Livestock are at risk for ingestion of a large variety of toxic plants. Plant poisonings are likely to be underdiagnosed because tests for most plant toxins are not routinely available at veterinary diagnostic laboratories. Prevention of access to poisonous plants is usually more effective and economical than treatment of plant poisonings.

An investigation of blood selenium concentrations of goats in New York State

The goal of the current study was to determine the range of blood selenium concentrations in goats in New York State that were fed adequately supplemented diets. Blood samples from mature, juvenile, and neonatal goats from commercial farms, 2 dairy and 2 meat producers, were analyzed via graphite-furnace atomic absorption spectroscopy. Feed samples were analyzed by using inductively coupled argon plasma optical emission spectroscopy to confirm that dietary selenium concentrations were adequate. The ranges of blood selenium concentration obtained were 9.1–49.9 μg/dl for mature goats, 7.6–37.5 μg/dl for juveniles, and 9.7–40.7 μg/dl for neonates.

Gross and histological description of the epidermal membrane found on normal neonatal piglets.

The structure and composition of fetal and placental tissues vary among different species of placental mammals. Some mammals, including camelids and pigs, possess an epidermal membrane during the fetal stage, called the epithelion, that is absent from other domestic mammals. Because neonatal piglets are a common animal model for many research techniques, it is important that researchers correctly identify this tissue and recognize its lack of pathological consequence when working with fetal and neonatal piglets. Here, the authors describe gross and histological examinations of the epithelion, comparing this tissue with other extra-fetal tissues and coatings.